DEVICE AND WAFER MASS METROLOGY APPARATUS

Field of the Invention

The present invention relates to a device, for example a device for changing the temperature of a wafer, and to a wafer mass metrology apparatus comprising such a device.

Background

Microelectronic devices are fabricated on semiconductor (e.g. silicon) wafers using a variety of techniques, including deposition techniques and removal techniques. Semiconductor wafers may be further treated in ways that alter their mass, e.g. by cleaning, ion implantation, lithography and the like.

Measuring the change in mass of a wafer either side of a processing step is an attractive method for implementing product wafer metrology. The wafer in question is weighed before and after the processing step of interest. The change in mass is correlated to the performance of the production equipment and/or the desired properties of the wafer.

Processing steps carried out on semiconductor wafers can cause very small changes in the mass of the semiconductor wafer, which it may be desirable to measure with high accuracy. For example, removing a small amount of material from the surface of the semiconductor wafer may reduce the mass of the semiconductor wafer by a few milligrams, and it may be desirable to measure this change with a resolution of the order of ±1 OOpg or better.

At these high levels of measurement accuracy, errors in the measurement output caused by temperature variations in the semiconductor wafers being measured and/or in the temperature of the measurement apparatus may become significant.

The temperature of a semiconductor wafer immediately after it has been processed in a production line may be 400-500°C or higher. After processing, the semiconductor wafer may be loaded into a wafer cassette for transportation. When the wafer cassette arrives at a wafer mass metrology apparatus, the temperature of the semiconductor wafers may still be high, for example 70°C or higher. In contrast, the temperature of the wafer mass metrology apparatus may be approximately 20°C. Therefore, there may be a significant temperature difference between the semiconductor wafers and the wafer mass metrology apparatus.

This temperature difference may cause errors in the measurement output of the wafer mass metrology apparatus. For example, if the semiconductor wafer has a higher temperature than a measurement chamber of the wafer mass metrology apparatus, air currents (e.g. convection currents) may be generated in the air in the measurement chamber, which may affect the measurement output. In addition, the air in the measurement chamber may be heated, changing its density and pressure and therefore the buoyancy force exerted on the semiconductor wafer by the air. This may also affect the measurement output. W002/03449 describes a semiconductor wafer mass metrology method that aims to reduce errors in the measurement output caused by temperature variations in the wafer mass metrology apparatus or the semiconductor wafers being measured. In the method described in W002/03449, a semiconductor wafer is removed from a wafer cassette and placed on a passive thermal transfer plate that is thermally coupled to a chamber of a wafer mass metrology apparatus before it is placed on a measurement area of the wafer mass metrology apparatus. The passive thermal transfer plate equalises the temperature of the semiconductor wafer to the temperature of the chamber to within ±0.1 °C, thus avoiding or preventing the problems described above.

With such a thermal transfer plate, the wafer can be clamped to the surface of the thermal transfer plate using a vacuum clamping mechanism to ensure good thermal contact between the surface and the wafer. For example, the surface can be provided with a vacuum groove or channel from which gas such as air is sucked using a vacuum pump to generate a lower pressure or reduced pressure in the vacuum groove or channel. This lower pressure causes the wafer to be clamped to the surface of the thermal transfer plate, ensuring good thermal contact between the surface and the wafer. More specifically, a pressure difference between the lower pressure or reduced pressure in the vacuum groove or channel and the pressure of the gas above the wafer causes a force to act on the wafer towards the surface so as to hold the wafer against the surface. In addition, this force may also flatten the wafer against the surface, causing the wafer to conform to the surface.

However, difficulties with clamping the wafer to the surface can occur if the wafer is curved or bowed, which can occur particularly with thin wafers. In particular, if the wafer is curved or bowed, there may be poor contact between at least some parts of the wafer and the surface. This may mean that the wafer is not effectively clamped to the surface when gas is sucked from the vacuum groove or channel, because one or more parts of the wafer are too far away from the vacuum groove or channel due to the curve or bow of the wafer to be effectively clamped, which may mean that the thermal contact between the surface and the wafer is negatively affected. As a consequence, it may take longer to cause a desired or predetermined change in the temperature of the wafer, or if the wafer is placed in contact with the surface for a predetermined period of time the temperature change of the wafer during the predetermined period of time may be less than expected.

The present invention has been devised in light of the above considerations.

Summary of the Invention

According to a first aspect of the present invention there is provided a device comprising: a surface for supporting a wafer; a gas inlet in the surface; a plurality of suction devices for gripping the wafer above the surface and drawing or pulling the wafer towards the surface; a shared vacuum line in fluid communication with the gas inlet in the surface and the plurality of suction devices; and a flow restrictor in a flow path between the shared vacuum line and the gas inlet in the surface. The device according to the first aspect of the present invention has a plurality of suction devices, for gripping the wafer above the surface and drawing or pulling the wafer towards the surface, that are in fluid communication with the shared vacuum line. When a wafer is lowered towards the surface of the device it can first be contacted by the plurality of suction devices above the surface. When suction is applied to the plurality of suction devices using the shared vacuum line, the plurality of suction devices can grip the wafer. The plurality of suction devices can then be used to draw or pull the wafer (or move the wafer) towards the surface. This may at least partly flatten the wafer and/or cause the wafer to at least partly conform to the surface.

In addition, the device according to the first aspect of the present invention has one or more gas inlets in the surface that are connected to the shared vacuum line. Therefore, when a wafer is in contact with the surface, or adjacent to the surface, and suction is applied to the gas inlet using the shared vacuum line, a lower pressure or reduced pressure can be generated at least in parts between the surface and the wafer, so that the wafer is gripped by the surface or clamped to the surface. The lower pressure or reduced pressure may flatten, or substantially flatten, the wafer, and/or cause the wafer to conform, or substantially conform, to the surface.

This configuration is particularly advantageous when dealing with a wafer that is curved or bowed, which is more likely when dealing with thin wafers. In particular, when dealing with a curved or bowed wafer, a device having the gas inlet alone (i.e. not including the plurality of suction devices) may not be able to effectively clamp the wafer, due to the curved or bowed shape of the wafer, as discussed above. Where the device is for changing the temperature of the wafer, this may lead to poor or reduced thermal contact between the wafer and the surface.

As a consequence, it may take longer to change the temperature of the wafer to a desired temperature, for example to achieve thermal equilibrium between the wafer and the surface. This will reduce throughput of the device and is therefore undesirable. Alternatively a change in the temperature of the wafer achieved in a predetermined period of time may be less than expected. In this case, the temperature of the wafer when it is removed from the surface after the predetermined period of time may be different to a desired or expected temperature. As discussed above, this can cause errors in a mass metrology measurement performed on the wafer by a wafer mass metrology apparatus and is therefore also undesirable.

Problems can also occur when clamping a bowed or curved wafer to a surface for purposes other than to change the temperature of the wafer, for example when supporting the wafer for processing of an upper surface of the wafer. For example, processing of the upper surface of the wafer may not be correctly performed if the wafer is not correctly clamped, wherein an upper surface of the wafer remains bowed or curved. The present invention is therefore not limited to changing the temperature of the wafer and is more generally applicable to devices for supporting a wafer.

In contrast, with the present invention, the wafer can first be contacted by the plurality of suction devices above the surface of the wafer, and the plurality of suction devices can be used to grip the wafer and draw or pull (or move) the wafer towards the surface. Therefore, the plurality of suction devices may act to at least partly flatten a bowed or curved wafer. For example, the plurality of suction devices may cause the wafer to at least partly conform to a shape of the surface. This may allow the wafer to be more effectively gripped or clamped by the gas inlet. Where the device is for changing the temperature of the wafer, this may improve the thermal contact between the surface and the wafer. The gas inlet may alternatively or additionally act to flatten, or substantially flatten, the wafer.

Therefore, by including both the gas inlet and the plurality of suction devices of the present invention, better clamping of the wafer to the surface can be achieved for curved or bowed wafers. In particular, a curved or bowed wafer may be more effectively flattened by the combination of the plurality of suction devices and the gas inlet than by one or more gas inlets alone.

The present inventors have realised that with a configuration in which the gas inlet and the plurality of suction devices are in fluid communication with a shared vacuum line as in the first aspect of the present invention, it is possible that too much of the vacuum in the shared vacuum line may be lost through the open gas inlet in the surface when the wafer is in contact with the plurality of suction devices. This may mean that the plurality of suction devices may not be able to effectively or correctly grip the wafer or draw or pull the wafer sufficiently flat, because the suction or vacuum at the plurality of suction devices is insufficient. Therefore, the problems described above, for example caused by reduced thermal contact between the wafer and the surface, may still occur.

The present inventors have realised that this problem could be addressed by providing separate electronically controllable valves in flow paths to the gas inlet and the plurality of suction devices respectively. However, the present inventors have realised that such an arrangement would result in increased complexity, an increase in required electronic components and more complex control software.

Instead, the present inventors have realised that this problem can be addressed by providing the flow restrictor of the present invention in the flow path between the shared vacuum line and the gas inlet in the surface. In particular, the flow restrictor can sufficiently reduce the amount of vacuum lost through the gas inlet in the surface while the wafer is in contact with the plurality of suction devices that the plurality of suction devices can effectively grip the wafer and draw or pull the wafer sufficiently flat, while still allowing sufficient vacuum through the gas inlet to grip the wafer or clamp the wafer to the surface.

Therefore, with the present invention curved or bowed wafers can be more effectively clamped to the surface of the device, without a significant increase in the complexity of the device, the number of electronic components and the complexity of the control software. This can therefore reduce the cost and complexity of the device and of production of the device.

For example, where the device is for changing the temperature of the wafer, with the present invention curved or bowed wafers can be brought into good thermal contact with the thermal plate without a significant increase in the complexity of the device, the number of electronic components and the complexity of the control software.

The approach taken in the present invention may also lead to faster clamping of a wafer to the surface, since there is no need to control the vacuum to the suction devices to firstly clamp the wafer with the suction devices and to then control the vacuum to the gas inlet to clamp the wafer with the gas inlet. Instead, since a vacuum is applied to both the gas inlet and the plurality of suction devices simultaneously, as soon as the plurality of suction devices have drawn or pulled (or moved) the wafer towards the surface the gas inlet will be able to clamp the wafer without any delay.

Improving the speed of the clamping of the wafer to the surface will improve the throughput of wafers through the device, which may also improve the throughput of a corresponding wafer mass metrology apparatus that subsequently performs mass metrology measurements on the wafers.

The device according to the first aspect of the present invention may have any one, or, where compatible, any combination of the following optional features.

There may be one or more of the gas inlets.

The device may be for supporting a wafer, or configured or adapted to support a wafer.

The device may be for changing the temperature of a wafer, and the surface may be for exchanging heat with the wafer.

Changing the temperature of the wafer may comprise cooling the wafer.

Changing the temperature of the wafer may comprise reducing the temperature of the wafer.

Changing the temperature of the wafer may comprise bringing the wafer into thermal equilibrium, or substantially into thermal equilibrium, with the surface.

The device may be for controlling the temperature of the wafer, or for changing the temperature of the wafer to be a predetermined temperature.

The wafer may be a semiconductor wafer.

The wafer may have a diameter of 200mm, or 300mm, or 450mm, for example.

The device may be for supporting a wafer, or changing the temperature of a wafer, having a predetermined diameter, or configured to support a wafer, or change the temperature of a wafer, having a predetermined diameter. The predetermined diameter may be 200mm, or 300mm, or 450mm.

The device may be configured or adapted to change the temperature of the wafer.

The surface may be configured to support the wafer.

The surface being for supporting the wafer may mean that the surface is configured to support some or all of the weight of the wafer.

The surface being for supporting the wafer may mean that the surface is configured to contact the wafer.

The surface may be configured to contact a majority of the surface of the wafer.

The surface may be configured to exchange heat with the wafer. The surface being for exchanging heat with the wafer may mean that the surface and the wafer will exchange heat when the wafer is supported by the surface if there is a temperature difference between the surface and the wafer.

Exchanging heat with the wafer may comprise performing heat transfer with the wafer or transferring heat with the wafer.

Exchanging heat with the wafer may comprise receiving heat from the wafer.

Exchanging heat with the wafer may comprise exchanging or transferring thermal energy with the wafer.

Exchanging heat with the wafer may comprise receiving thermal energy from the wafer.

Exchanging heat with the wafer may comprise conduction of heat between the surface and the wafer.

Exchanging heat with the wafer may comprise conduction of heat from the wafer to the surface.

The surface may be a surface of a body of the device. The device may therefore comprise a body having the surface.

The surface may be a top surface of the body of the device.

The surface may comprise a thermally conductive material.

The surface may comprise aluminium.

The body may comprise aluminium.

The gas inlet may be for generating a lower pressure or reduced pressure between the surface and the wafer, at least in parts.

The gas inlet may be configured to, or adapted to, generate a lower pressure or reduced pressure between the surface and the wafer, at least in parts.

The gas inlet may be for vacuum clamping the wafer to the device (to the surface of the device).

The gas inlet may be configured to, or adapted to, vacuum clamp the wafer to the device (to the surface of the device).

A gas inlet may mean any type or shape or inlet or opening or hole or space through which gas can be sucked by a vacuum source such as a vacuum pump via the vacuum line.

There may be one, or only one, gas inlet.

There may be more than one gas inlet. For example, there may be a plurality of gas inlets, which in combination may fulfil one or more of the functions of the gas inlet described above.

The gas inlet may instead be referred to as a vacuum inlet.

The plurality of suction devices may be configured to, or adapted to, or operable to, grip the wafer above the surface. The plurality of suction devices may be configured to, or adapted to, or operable to, draw or pull (or move) the wafer towards the surface.

The plurality of suction devices may be configured to, or adapted to, retract or compress to draw or pull (or move) the wafer towards the surface.

Gripping the wafer may comprise gripping the wafer using suction and/or gripping the wafer using a vacuum.

Gripping the wafer may comprise gripping a surface of the wafer.

Gripping the wafer may mean engaging or holding or clamping a surface of the wafer.

The suction devices may alternatively be referred to as vacuum gripping devices or vacuum clamping devices.

Gripping the wafer above the surface may mean that the plurality of suction devices contact the wafer and grip the wafer while the wafer is spaced apart from the surface.

The plurality of suction devices may grip the underside of the wafer.

Drawing or pulling the wafer towards the surface may mean that the suction devices apply a force to the wafer to draw or pull the wafer towards the surface.

Drawing or pulling the wafer towards the surface may comprise moving the wafer towards the surface and/or flattening the wafer against the surface.

Drawing or pulling the wafer towards the surface may mean or comprise the wafer experiencing a force towards the surface due to a difference in pressure between a pressure of gas above the wafer and a lower or reduced pressure in the suction device.

Drawing or pulling the wafer towards the surface may comprise making or rendering the wafer more planer, or less non-planar.

The plurality of suction devices may therefore be for making the wafer flatter and/or more planar and/or less non-planar.

Drawing or pulling the wafer towards the surface may comprise deforming and/or bending the wafer.

Drawing or pulling the wafer towards the surface may mean moving or guiding the wafer towards the surface.

The plurality of suction devices may be configured to draw or pull the wafer towards the surface so as to at least partly flatten a curved or bowed wafer.

The plurality of suction devices may be configured to draw or pull the wafer towards the surface so as to at least partly conform a curved or bowed wafer to a shape of the surface.

The plurality of suction devices may be provided in, or at least partly in, the surface.

The shared vacuum line may be a pipe or tube or passageway or flow path along which gas can flow. The shared vacuum line may be referred to as a common vacuum line, or a single vacuum line.

The shared vacuum line may be for applying or supplying or providing a vacuum or suction to the gas inlet and the plurality of suction devices.

The shared vacuum line may be connected, directly or indirectly, to the gas inlet and the plurality of suction devices.

The shared vacuum line may be in gas communication with the gas inlet in the surface and the plurality of suction device.

The vacuum line being shared means that the same vacuum line provides a vacuum to both the gas inlet and the plurality of suction devices. In other words, the shared vacuum line is shared by or between the gas inlet and the plurality of suction devices.

Providing a vacuum may mean providing suction.

The shared vacuum line may simultaneously provide a vacuum or suction to both the gas inlet and the plurality of suction devices.

A flow restrictor may mean a device, or element, or part for restricting the flow of gas through the flow path.

Restricting the flow of gas may mean reducing or inhibiting or decreasing the flow of gas.

Restricting the flow of gas may mean reducing or inhibiting or decreasing the flow of gas without preventing or stopping the flow of gas.

The flow path may be a gas flow path.

The flow path may be a vacuum flow path.

The flow path may be a suction flow path.

The flow path may connect, directly or indirectly, the shared vacuum line to the gas inlet.

The flow restrictor may comprise a fixed restriction. In other words, the restriction may not be adjustable.

Alternatively, the flow restrictor may comprise an adjustable restriction. In other words, an amount or degree to which the flow restrictor restricts the flow of gas through the flow path may be adjustable or changeable.

The flow restrictor may be passive. In other words, the flow restrictor may not be actively controllable and/or electronically controllable.

The flow restrictor may be non-controllable.

The flow restrictor may be non-electronically controllable.

The flow restrictor may be non-remotely controllable.

The flow restrictor may not have any electronic parts or components. The flow restrictor may comprise a narrowing or aperture in the flow path, for example a fixed or nonvariable narrowing or aperture in the flow path.

The device may comprise a body having the surface.

The flow restrictor may be in the flow path inside the body. In other words, the flow restrictor may be located inside the body.

Alternatively, the flow restrictor may be in the flow path outside the body. In other words, the flow restrictor may be located outside the body. For example, the flow restrictor may be located in a pipe or tube that connects the shared vacuum line to the body.

The gas inlet in the surface may comprise a vacuum groove or channel in the surface.

The vacuum groove or channel may be for vacuum clamping the wafer to the surface.

There may be one or more holes or openings in the vacuum groove or channel in fluid communication with the shared vacuum line through which gas can be sucked form the vacuum groove or channel to cause a lower pressure or reduced pressure in the vacuum groove or channel.

The vacuum groove or channel may comprise or have a shape of a segment or arc of a circle.

Alternatively, or in addition, the gas inlet in the surface may comprise a hole or opening in the surface.

There may be a plurality of such holes or openings in the surface. Each of the plurality of holes or openings may be in fluid communication with the shared vacuum line.

The plurality of holes or openings may be arranged in the shape of a segment or arc of a circle.

The plurality of holes or openings may be distributed across a majority of the surface.

The gas inlet may comprise a channel or passageway below the surface and a plurality of holes or openings in the surface connected to the channel or passageway. Therefore, when vacuum or suction is applied to the channel or passageway, vacuum or suction is simultaneously applied to all of the holes or openings in the surface connected to the channel or passageway.

There may be a plurality of gas inlets in the surface, each of which is in fluid communication with the shared vacuum line.

The flow restrictor may be in a flow path between the shared vacuum line and the plurality of gas inlets.

The flow restrictor may be in a flow path between the shared vacuum line and all of the plurality of gas inlets. In other words, all of the plurality of gas inlets may have their flow restricted by a single flow restrictor.

Alternatively, the device may comprise a respective flow path between each of the plurality of gas inlets and the shared vacuum line, and a respective flow restrictor in each of the flow paths. Therefore, suction or vacuum through each of plurality of gas inlets may be individually or separately or independently restricted by the respective flow restrictors. For example, the device may comprise a plurality of vacuum grooves or channels in the surface, each of which has a respective flow path with a respective flow restrictor.

Alternatively, the device may comprise a plurality of flow paths, each of which is between a respective plurality of the gas inlets and the shared vacuum line, and a respective flow restrictor in each of the flow paths. In other words, a group or set of gas inlets may be connected to the same flow path.

Different groups or sets of the plurality of gas inlets may be connected to the shared vacuum line by respective flow paths, such that vacuum or suction is applied to a particular group or set of gas inlets simultaneously via a single flow path. A respective flow restrictor may be provided for each of the flow paths. Therefore, suction or vacuum through each of the groups or sets of gas inlets may be individually or separately or independently restricted by the respective flow restrictors.

There may be a plurality of gas inlets in the surface that are connected together by a channel or passageway beneath the surface. Therefore, vacuum or suction can be simultaneously provided to each of the gas inlets by providing vacuum or suction to the channel or passageway.

The plurality of suction devices may each comprise a compressible bellows that is configured to be compressed when the suction device grips the wafer, so as to draw the wafer closer to the surface. A distal end of the bellows may be configured or arranged to contact a bottom surface of the wafer to engage or grip the bottom surface of the wafer.

The plurality of suction devices may each be changeable between a first configuration in which the distal end of the bellows is positioned a predetermined distance above the surface, and a second configuration in which the distal end of the bellows is closer to the surface than in the first configuration.

The distal end of the bellows may be referred to as a wafer contact portion or wafer contact part of the bellows.

The distal end of the bellows may comprise a pad or cup, such as a suction pad or suction cup.

The bellows may be a bellows suction cup.

The plurality of suction devices may each comprise a pad or cup that is configured to contact the wafer. References to pad below may be replaced with references to cup, or suction pad or suction cup, unless incompatible.

The pad may be removable and/or detachable from the suction device.

The pad may be replaceable.

The pad may be detachably connected to the suction device.

For example, the pad may be removable for cleaning, or to replace the pad with a pad made of a different material, for example for a different specific application.

For example, the pad may be removable and/or replaceable so that a pad can be included that meets different materials requirements, for example regarding cleanliness, lower particle and metal contamination risk, conductivity of the pad, and/or minimising contact of the lower or backside of the wafer with other parts of the suction devices such as the bellows mentioned below, which may be a contamination risk.

The pad may be an elastomeric pad.

The pad may be resiliently deformable.

The pad may be configured to engage the wafer and/or to grip the wafer, or a surface of the wafer.

The pad may be configured to engage the wafer and/or grip the wafer by suction.

The pad may be a suction pad or a suction cup.

The pad may comprise a recess on an upper surface of the pad that faces the wafer and a flow path through which gas can be sucked from the recess so as to generate a lower pressure or reduced pressure in the recess below the wafer.

The recess may be resiliently deformable or resiliently compressible.

The pad may be configured to be compressed when the suction device grips the wafer, so as to draw the wafer closer to the surface.

The plurality of suction devices may each be changeable between a first configuration in which the pad, or a top or upper surface of the pad, is positioned a predetermined distance above the surface, and a second configuration in which the pad, or a top or upper surface of the pad, is closer to the surface than in the first configuration.

In the first configuration the suction devices protrude or extend from or above the surface.

The pad may change from the first configuration to the second configuration while gripping the wafer so as to draw or pull the wafer closer to the surface.

In the second configuration the pad may be flush, or substantially flush, with the surface. Therefore, in the second configuration a wafer gripped by the suction devices may be in contact with the surface.

Each of the suction devices may comprise a compressible bellows that is configured to be compressed when the suction device grips the wafer, so as to draw the wafer closer to the surface.

For example, the vacuum applied to the suction device by the shared vacuum line may cause the bellows to be compressed when the suction device grips the wafer.

The pad may be integral to the bellows, for example formed as one piece with the bellows or non- detachably connected to the bellows. Alternatively, the pad may be removable and/or detachable from the bellows. For example, the pad may be detachably connected to the bellows.

The device may comprise a sensor for detecting a position of the wafer while it is gripped by the suction devices, to verify correct functioning or operation of the suction devices, for example for safety and/or to prevent damage to the wafer. Alternatively, or in addition, the device may comprise one or more sensors for detecting a position and/or configuration of one or more of the suction devices to verify correct functioning or operation of the suction devices, for example for safety and/or to prevent damage to the wafer.

The device may comprise a controller that is configured to control an operation of the device based on an output of the one or more sensors mentioned above. For example, the controller may be configured to control a suction or vacuum applied to the shared vacuum line based on an output of the one or more sensors mentioned above.

Each of the suction devices may comprise a base that is housed in an opening or hole or space in the surface, the base may be connected to the pad by the bellows, and gas may be sucked from above the pad through the pad, bellows and base.

Alternatively, the bellows may comprise an integral base that forms part of the bellows, wherein the base of the bellows is housed or received in an opening or hole or space in the surface.

The bellows may comprise a flow path that extends from above the pad, through the pad, bellows and base, to below the base.

The bellows may be integral with the pad, for example formed as one piece.

The base, bellows and pad may be integral, for example formed as one piece.

The base and pad may form lower and upper surfaces of the bellows respectively.

The bellows and pad may be formed of resilient material, for example rubber, for example nitrile rubber, or silicone rubber.

The bellows, pad and base may be formed of resilient material, for example rubber, for example nitrile rubber or silicone rubber.

The device may comprise a locator and/or connector in an opening or hole or space in the surface for locating a base of the bellows on the surface and/or for connecting to the base of the bellows.

The locator and/or connector may comprise a protrusion or barb.

The bellows may be positioned and/or mounted on the device by the locator and/or connector.

The bellows may be positioned and/or mounted on the locator and/or connector.

The locator and/or connector (for example protrusion or barb) may comprise a flow path or passageway that is connected to a flow path or passageway through the base, bellows and pad when the bellows is positioned or mounted on the locator and/or connector.

The bellows may comprise a wavey or ridged or undulating or corrugated shape that is resiliently compressible in a longitudinal direction of the bellows.

In some embodiments a suction pad or suction cup may be provided without a bellows. Therefore, a base of the suction pad or suction cup may be directly housed or received in an opening or hole or space in the surface, for example in the same manner as described above. As above, the base of the suction pad or suction cup may be positioned or mounted on a locator and/or connector located or provided in an opening or hole or space in the surface.

Alternatively, each of the suction devices may comprise a lifting pin having the pad.

A lifting pin may mean a pin or rod or member that extends substantially perpendicular to the surface and can be moved longitudinally relative to the surface to lift or lower the pin relative to the surface.

The device may comprise one or more lifting mechanisms for lifting the lifting pins relative to the surface.

The one or more lifting mechanisms may also be for lowering the lifting pins relative to the surface.

The lifting pins may be movable between a first configuration in which the pad is a predetermined distance above the surface and a second configuration in which the pad is closer to the surface, for example flush or substantially flush with the surface.

In the second configuration the lifting pin may be entirely, or substantially entirely, received in a hole in the device through the surface of the device.

Each of the lifting pins may have a flow path along which gas can be sucked from above the pad. The flow path may be a vacuum flow path or gas flow path. The flow path may be longitudinal.

The device may comprise a plate or block having the surface.

The device may comprise a thermal transfer plate, or thermal plate, orthermalisation plate having the surface.

The plate may be made of a material having a high conductivity.

The plate may be made of a metal such as aluminium.

The device may be for passively cooling the wafer. In other words, the device may not have any active cooling devices or means such as a Peltier device.

Alternatively, the device may be for actively cooling the wafer. In other words, the device may comprise an active cooling means such as a Peltier device.

The device may further comprise a vacuum source or suction source such as a vacuum pump in fluid communication with the shared vacuum line.

The device may comprise a valve for controlling the vacuum or suction in or through the shared vacuum line. For example, the valve may be openable to allow flow of gas through the shared vacuum line so that vacuum or suction is applied to the gas inlet and plurality of suction devices by the vacuum source or suction source, and closable to prevent flow of gas through the shared vacuum line so that vacuum or suction is not applied to the gas inlet and plurality of suction devices by the vacuum source or suction source.

The valve may be operable to fluidly connect the gas inlet and plurality of suction devices to the vacuum source or suction source and to fluidly disconnect the gas inlet and plurality of suction devices from the vacuum source or suction source. The valve may comprise a solenoid. For example, the valve may be a solenoid valve.

The valve may be electronically controllable, for example by a controller of the device.

Each of the suction devices may have a respective flow path connecting the suction device to the shared vacuum line, and a respective flow restrictor may be included in each of the flow paths. Therefore, each of the suction devices may be provided with a respective flow restrictor.

According to a second aspect of the present invention there is provided an apparatus comprising the device according to the first aspect of the present invention and a vacuum source or suction source such as a vacuum pump in fluid communication with the shared vacuum line of the device.

The apparatus according to the second aspect of the present invention may have any one or more of the features of the first aspect of the present invention described above, unless incompatible.

According to a third aspect of the present invention there is provided a wafer mass metrology apparatus comprising the device according to the first aspect of the present invention.

The apparatus according to the third aspect of the present invention may have any one or more of the features of the first aspect of the present invention described above, unless incompatible.

The mass metrology apparatus may be for measuring a mass or the wafer, or may be configured to measure the mass of the wafer.

The mass metrology apparatus may comprise a measurement chamber.

The measurement chamber may be a weighing chamber and/or mass measurement chamber.

The device may be thermally coupled to the measurement chamber.

The device may be thermally coupled to an outside of the measurement chamber.

The device may be mounted on the measurement chamber, for example mounted on an outside of the measurement chamber.

The device may be attached to the measurement chamber, for example attached to an outside of the measurement chamber.

The apparatus may further comprise a measurement device for measuring the weight and/or mass of the wafer that is inside the measurement chamber.

The measurement device may be for generating measurement output indicative of the weight and/or mass of the wafer.

The measurement device may comprise a support such as a pan for supporting the wafer during the measurement.

The apparatus may further comprise a robotic arm having an end effector for transporting the wafer.

The end effector may be configured to support the wafer from beneath when the end effector is used to transport the wafer. According to a fourth aspect of the present invention there is provided a bellows assembly comprising a bellows and a bellows insert received in an end portion of the bellows.

The bellows assembly according to the fourth aspect of the present invention may have any one, or, where compatible, any combination of the following optional features.

The bellows assembly may be used in a suction device in any of the other aspects of the present invention described above.

The bellows insert may be configured to contact a wafer when the wafer is brought into contact with a distal end of the bellows assembly. In other words, the bellows insert may provide or form a wafer contact surface of the bellows assembly.

In one example a main body of the bellows insert may comprise or be made of PEEK (polyether ether ketone).

The bellows insert may comprise a material that has been selected for suitability for contact with wafers such as semiconductor wafers.

For example, a portion or portions of the insert that is configured to come into contact with a wafer may comprise or be made of a fluorinated elastomer or a perfluorinated elastomer. In a specific example, the portion or portions may comprise or be made of Perlast ®.

Providing the insert means that the bellows does not need to be made of a material that has been selected for suitability for contact with wafers, because only the bellows insert contacts the wafer. This means that the bellows may be made of a material that is cheaper, or that is more suitable for use in a bellows, for example.

The end portion of the bellows may be a distal end portion of the bellows, or a top end portion of the bellows.

An external shape of a main body of the bellows insert may conform to an internal shape of the end portion of the bellows. In other words, an external shape of the main body of the bellows insert may match or correspond to an internal shape of the end portion of the bellows.

An external shape of the main body of the bellows insert may be substantially frustoconical.

A surface of the bellows insert may provide a contact surface of the bellows assembly at a distal end of the bellows assembly. The surface may be a main surface or main face of the bellows insert, for example.

The surface may be substantially flat, for example.

The bellows insert may comprise a removable element in the surface of the bellows insert.

The removeable element may protrude from, or above, or extend above, the surface of the bellows insert.

The removable element may be configured to contact a wafer when a wafer is brought into contact with the distal end of the bellows assembly. Since it is the removable element that comes into contact with the wafer, only the removable element may need to be made of a material that is suitable for contacting the wafer. A main body of the bellows insert may therefore be made of a different material, for example a cheaper material.

As mentioned above, the main body of the bellows insert may comprise, or be made of, PEEK (polyether ether ketone), for example.

The removable element may comprise, or be made of, a fluorinated elastomer or a perfluorinated elastomer. In a specific example, the removable element may be made of Perlast ®.

The removable element may comprise an O-ring received in a groove in the surface of the bellows insert.

The material that comes into contact with the wafer may therefore easily be selected or changed by selecting or changing the removable element (such as an O-ring) to be a removable element made of a suitable material.

The bellows insert may comprise a retaining portion for retaining the bellows insert in the bellows.

The retaining portion may removably retain the bellows insert in the bellows.

The bellows may have an undulating or corrugated shape, the retaining portion may have a width that is larger than a narrowing in the undulating or corrugated shape, and the retaining portion may be positioned on an opposite side of the narrowing to the main body when the bellows insert is received in the bellows.

Therefore, when the bellows insert is inserted into the bellows, the retaining portion may deform the bellows by stretching the undulating or corrugated shape so that the retaining portion passes through the narrowing and is positioned on the opposite side of the narrowing.

A portion of the bellows insert above or adjacent to the retaining portion may be narrower than the retaining portion, so that the bellows subsequently returns to its original shape after the bellows insert has been inserted, with the retaining portion of the bellows insert located on the opposite side of the narrowing to the main body of the bellows insert.

The retaining portion may be located at a narrower end of a frustoconical main body of the bellows insert.

In this manner, the bellows insert may be removably retained in the bellows.

The bellows insert may comprise one or more passageways extending through the bellows insert that allow air to flow through the bellows insert into the bellows. Therefore, a vacuum can be applied through the bellows through the bellows insert.

As mentioned above, the bellows assembly of the fourth aspect of the present invention may be used in a suction device in the device according to any of the other aspects of the present invention discussed above.

According to a fifth aspect of the present invention there is provided a bellows insert configured to be received in an end portion of a bellows. The bellows insert according to the fifth aspect of the present invention may have any one, or, where compatible, any combination of the following optional features.

The bellows insert may also have any of the features of the bellows insert in the fourth aspect of the present invention discussed above.

The end portion of the bellows may be a distal end portion of the bellows.

An external shape of a main body of the bellows insert may be substantially frustoconical.

A surface of the bellows insert may be configured to provide a contact surface at a distal end of the bellows when the bellows insert is received in the bellows. The surface may be a main surface or main face of the bellows insert.

The bellows insert may comprise a removable element in the surface of the bellows insert.

The removable element may comprise an O-ring received in a groove in the surface of the bellows insert.

The bellows insert may comprise a retaining portion for retaining the bellows insert in the bellows.

The retaining portion may comprise a portion having increased width relative to an adjacent portion of the bellows insert.

The retaining portion may comprise a portion having increased width that is located at a narrower end of a frustoconical main body of the bellows insert.

The bellows insert may comprise one or more passageways extending through the bellows insert that allow air to flow through the bellows insert.

Bellows insert means an insert for use in a bellows.

The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.

Summary of the Figures

Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

Figure 1 is a schematic illustration of a top view of a device according to an embodiment of the present invention.

Figure 2 is a schematic illustration of a side view of the device of Figure 1.

Figure 3 is a schematic illustration of a side view of the device of Figure 1. Figure 4 is a schematic illustration of a suction assembly that can be used in embodiments of the present invention.

Figure 5 is a schematic illustration of a top view of the suction assembly of Figure 4.

Figure 6A and 6B are schematic illustrations of a further suction assembly that can be used in embodiments of the present invention.

Figure 7A and 7B are schematic illustrations of a further suction assembly that can be used in embodiments of the present invention.

Figure 8A is a schematic illustration of a side view of a device according to an embodiment of the present invention.

Figure 8B is a schematic illustration of a side view of a device according to an embodiment of the present invention.

Figure 9 is a schematic illustration of a side view of a device according to an embodiment of the present invention.

Figures 10A and 10B are schematic illustrations of flow restrictors that can be used in embodiments of the present invention.

Figure 11 is a schematic illustration of a device according to an embodiment of the present invention.

Figure 12 is a schematic illustration of a suction lift pin that can be used in embodiments of the present invention.

Figure 13 is a schematic illustration of a top view of the suction lift pin of Figure 12. Figure 14 is a schematic illustration of a top view of a device according to an embodiment of the present invention.

Figure 15 is a schematic illustration of an apparatus according to an embodiment of the present invention.

Figure 16 is a schematic illustration of a bellows insert according to an embodiment of the present invention.

Figure 17 is a schematic illustration of a sectional view of a bellows assembly according to an embodiment of the present invention.

Detailed Description of the Invention

Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

A device 1 for changing the temperature of a wafer according to a first embodiment of the present invention is illustrated in Figures 1 to 3.

Specifically, the device 1 is for cooling semiconductor wafers, such as silicon wafers.

The device 1 in this embodiment is for passively cooling a wafer. In other words, the device 1 in this embodiment does not include any powered cooling means/devices, such as a Peltier device. However, in other embodiments the device 1 may be for actively cooling a wafer, for example using a powered cooling means/device such as a Peltier device.

In alternative embodiments, the device 1 may be for heating a wafer rather than cooling a wafer.

The device 1 may comprise or be a thermal transfer plate, or thermal plate, orthermalisation plate, for example.

The device 1 comprises a plate or block 3. The plate or block 3 is made of, or comprises, a material having a high thermal mass and high thermal conductivity. The plate or block 3 may be made of, or comprise, a metal, such as aluminium.

As illustrated in Figures 1 to 3, the plate or block 3 has a surface 5 that is configured to support a wafer when the wafer is placed on the plate or block 3 on the surface 5. The surface 5 is an upper surface of the plate or block 3, and therefore an upper surface of the device 1 . The surface 5 is configured to support the wafer by contacting an underside of the wafer so as to support the weight of the wafer.

The surface 5 is configured to contact the wafer to support the wafer and to exchange heat or thermal energy with the wafer to change the temperature of the wafer. In other words, the surface 5 is for performing heat transfer with the wafer to change the temperature of the wafer.

In particular, the surface 5 is configured to provide good thermal contact with the wafer so that heat can efficiently and/or effectively be transferred from the wafer to the surface 5 by conduction.

The surface 5 may be referred to as a heat transfer surface of the plate or block 3 or the device 1.

The device 1 may be for changing the temperature of a wafer having a predetermined diameter, for example 200mm, or 300mm, or 450mm. The surface 5 may therefore be configured to support a wafer having the predetermined diameter.

The device 1 comprises a vacuum clamping mechanism or suction mechanism for clamping the wafer to the surface 5 of the device 1 . In particular, the plate or block 3 comprises a vacuum groove or channel 7 in the surface 5 of the plate or block 3 from which gas such as air can be sucked using a vacuum source so as to generate a lower pressure or reduced pressure in the vacuum groove or channel 7 beneath the wafer, so as to clamp the wafer to the surface 5 and/or so as to grip the wafer.

In particular, the vacuum groove or channel 7 is connected to a gas flow path or vacuum flow path via one or more holes or openings in the vacuum groove or channel 7, for example in a base of the vacuum groove or channel 7, so that gas is sucked from the vacuum groove or channel 7 via the one or more holes or openings when suction is applied to the gas flow path. The vacuum groove or channel 7 and/or the one or more holes or openings therefore correspond to a gas inlet in the surface 5 through which gas can be sucked using a vacuum or suction applied to the gas flow path. The gas flow path may comprise a pipe, or tube, or passageway, or channel for conveying gas.

In an alternative arrangement the vacuum groove or channel 7 may be replaced with a channel or passageway below the surface 5 that has a plurality of holes or openings extending from the channel or passageway to the surface 5 (a so-called buried channel or passageway). Vacuum or suction may therefore be applied to the plurality of holes or openings simultaneously by applying vacuum or suction to the channel or passageway below the surface 5.

In addition, the device 1 further comprises a plurality of suction assemblies 9 (or suction devices, or vacuum assemblies or vacuum devices) for gripping the wafer and drawing or pulling (for example moving) the wafer towards the surface 5.

Each of the plurality of suction assemblies 9 is configured to grip the wafer using suction or a vacuum and to pull or draw (or move) the wafer towards the surface 5 so as to at least partly flatten the wafer and so that the wafer can then be clamped to the surface 5 using the vacuum groove or channel 7.

The plurality of suction assemblies 9 are positioned on or in the surface 5 of the plate or block 3. In Figure 1 the plurality of suction assemblies 9 are arranged outside of the vacuum groove or channel 7, for example closer to a periphery of the surface 5 than the vacuum groove or channel 7. The plurality of suction assemblies 9 are therefore configured to grip the wafer radially outwards of where the wafer is gripped or clamped by the vacuum groove or channel 7. However, one or more suction assemblies may also be provided inside of the vacuum groove or channel 7 on the surface 5, for example at or adjacent to a centre of the surface 5. This may facilitate clamping wafers that are bowed or curved upwards in the centre away from the surface 5.

The plurality of suction assemblies 9 are configured to grip the wafer at a plurality of discrete locations on the wafer, corresponding to the locations of the suction assemblies 9.

The plurality of suction assemblies 9 are operable to at least partly flatten the wafer and/or at least partly conform the wafer to the surface 5.

As illustrated in Figure 2 for example, the plurality of suction assemblies 9 have a first configuration in which the plurality of suction assemblies 9 extend from or above (or protrude from or above) the surface 5 so as to contact or engage the wafer above the surface 5.

Furthermore, as illustrated in Figure 3 for example, the plurality of suction assemblies 9 have a second configuration in which the plurality of suction assemblies do not extend from (or protrude above) the surface 5. In the second configuration, top surfaces of the suction assemblies 9 may be flush, or substantially flush, with the surface 5.

An example of a suitable suction assembly 9 that may be used in embodiments of the present invention is schematically illustrated in Figures 4 and 5. Further examples of suitable suction assemblies 9 that may be used in embodiments of the present invention are schematically illustrated in Figures 6A and 6B and 7A and 7B and are described below. Of course, other suction assemblies can be used instead of those illustrated in Figures 4 to 7B.

As illustrated in Figure 4, the suction assembly 9 comprises a base 11 for mounting the suction assembly 9 on the plate or block 3. For example, the base 11 may be positioned in a correspondingly shaped recess, hole or opening in the surface 5 of the plate or block 3. The base 11 forms a lower or bottom side of the suction assembly 9.

The base 11 has an opening or through hole 13 or vacuum inlet through which gas such as air can be sucked, for example using one or more vacuum pumps.

The suction assembly 9 further comprises a pad 15 that is positioned above the base 11 and opposite to the base 11 . The pad 15 forms an upper or top side of the suction assembly 9.

The pad 15 also has an opening or through hole 17 or vacuum inlet through which gas such as air can be sucked, for example using one or more vacuum pumps.

The pad 15 may be referred to as a suction pad or suction cup, for example.

The pad 15 may be made of, or substantially made of a polyimide, for example. An underside (or bottom side or surface) of the pad 15 is connected to an upper side (or top side or surface) of the base 11 by a bellows 19. The base 11 , pad 15 and bellows 19 define a space or volume 21 . For example, the base 11 , pad 15 and bellows 19 may enclose or partly or substantially enclose the space or volume 21.

The bellows 19 is compressible or collapsible so as to reduce a size of the space or volume 21 . The bellows 19 may be resiliently compressible or collapsible, for example so that the bellows 19 returns to a predetermined configuration when a compressive force on the bellows is removed. Alternatively, the pad 15 may be biased apart from the base 11 using an additional resilient element or member, for example a spring.

Compression of the bellows 19 reduces a spacing between the base 11 and the pad 15 and therefore a size of the space or volume 21 .

The bellows 19 may be made of, or substantially made of, stainless steel, for example,

The pad 15 comprises a recess 23 in a top surface of the pad 15. In particular, the recess 23 is defined by a raised rim or lip or edge 25 around a periphery of the top surface of the pad 15.

When a wafer 27 is lowered onto the device 1 , for example as illustrated in Figure 2, the wafer initially comes into contact with the pads 23 of the suction assemblies 9, which are in the first configuration in which they extend above the surface 5. In particular, a lower surface of the wafer 27 comes into contact with a top surface of the raised rim or lip or edge 25 around the periphery of the top surface of the pad 15.

When a wafer is in contact with the pad 15 in this manner, a second space or volume is defined by the recess 23 and the lower surface of the wafer 27.

When a vacuum or suction is applied to the opening or through hole 13 in the base 11 , gas is sucked from the space or volume 21 through the opening or through hole 13. This generates a lower pressure or reduced pressure in the space or volume 21 , which causes gas to be sucked from the recess 23 into the space or volume 21 through the opening or through hole 17 in the pad 15.

When a wafer 27 is in contact with the pad 15 as described above, gas sucked from the recess 23 through the opening or through hole 17 in the pad 15 generates a lower pressure or reduced pressure in the second space or volume between the lower surface of the wafer 27 and the recess 23, so as to grip the wafer 27. The wafer 27 is therefore held against the top surface of the pad 15 by a force caused by a pressure difference between the lower pressure or reduced pressure in the second space or volume and a pressure of gas above the wafer 27.

Once the wafer 27 has been gripped by the pad 15, a pressure difference exists between the gas above the wafer 27 and the lower pressure or reduced pressure generated in the space or volume 21 by the suction through the opening or through hole 13 in the base 11 . This pressure difference causes a force on the pad 15 towards the base 11 . Put another way, the lower pressure or reduced pressure in the space or volume 21 sucks the pad 15 towards the base 11 . This force causes compression of the bellows 19 so that the pad 15 moves towards the base 11 , pulling or drawing the wafer with it. Therefore, the wafer 27 gripped by the pad 15 is pulled or drawn closer (moved closer) to the surface 5 by the suction assembly 9. In other words, the wafer 27 is moved or drawn downwards towards the surface 5 by the compression of the bellows 19 in the suction assemblies 9.

This may cause the wafer to be at least partly flattened and/or to at least partly conform to the surface 5.

As illustrated in Figure 3, the suction assemblies 9 are recessed or housed in the surface 5 so that when the bellows 19 are compressed as described above, tops of the pads 15 are flush, or substantially flush, with the surface 5. Therefore, when the bellows 19 are compressed as described above, the wafer 27 is in contact with, or adjacent to, the surface 5. For example, each of the suction assemblies 9 may be received in a recess, hole or opening in the surface having a depth that is equal to, or substantially equal to, a height of the suction assembly 9 when the bellows 19 is compressed by a predetermined amount.

In addition, vacuum or suction is also applied to the vacuum groove or channel 7 so that gas such as air is sucked from the vacuum groove or channel 7. When the wafer 27 is brought into contact with, or moved closer to, the surface 5 by the suction assemblies 9, a lower pressure or reduced pressure is generated in a space or volume defined by the lower surface of the wafer 27 and the vacuum groove or channel 7. This lower pressure or reduced pressure sucks the wafer 27 towards the surface 5 so that the wafer 27 is clamped to the surface 5. In particular, a pressure difference between the pressure of gas above the wafer 27 and the lower pressure or reduced pressure in the vacuum groove or channel 7 below the wafer causes a force on the wafer 27 towards the surface 5.

The arrangement described above is particularly advantageous for clamping curved or bowed wafers. In particular, when a wafer is curved or bowed, the vacuum clamping mechanism or suction mechanism comprising the vacuum groove or channel 7 alone may not be able to correctly clamp the wafer to the surface 5, because the lower surface of the wafer may not be close enough to the surface 5 in one or more places to sufficiently seal the space or volume in the vacuum groove or channel 7 due to the curvature or bowing of the wafer.

If the wafer is not correctly clamped to the surface 5, heat exchange between the wafer and the surface 5 may be less effective, because there may be poor contact between at least some parts of the wafer and the surface 5, such that the temperature of the wafer is not correctly controlled. As discussed above, this may lead to subsequent errors in a mass metrology measurement performed on the wafer. Alternatively, or in addition, if the wafer is not correctly clamped to the surface 5 an amount of time required to achieve a desired or predetermined change in the temperature of the wafer may be increased, because the heat transfer is less effective.

In contrast, with the arrangement described above, a curved or bowed wafer will first be gripped at discrete locations by the suction assemblies 9 while the wafer is spaced apart from the surface 5. When the suction assemblies 9 pull/draw/move the wafer towards the surface 5 as described above, the curved or bowed wafer may be at least partly flattened. Therefore, when the wafer is brought into contact with, or moved closer to, the surface 5 by the suction assemblies 9, the wafer may be less curved or bowed than originally, and there may therefore be better suction between the wafer and the surface 5. This may improve clamping of the wafer by the vacuum clamping mechanism or suction mechanism comprising the vacuum groove or channel 7 as described above.

Therefore, with the present invention the wafer can be correctly clamped to the surface 5 and the temperature of the wafer can be correctly controlled, and/or more efficiently controlled.

Figures 6A and 6B and 7A and 7B illustrate alternative examples of suction assemblies 9 that can be used in embodiments of the present invention instead of the suction assembly 9 described above with reference to Figures 4 and 5.

As shown in Figures 6A and 6B, in one embodiment the suction assemblies 9 may each comprise a bellows 24 having an integral suction cup 26 at a first (top or upper) end of the bellows 24. In particular, a distal end of the bellows 24 provides or forms a suction cup 26. The bellows 24 may be made of a resilient material such as rubber, for example nitrile rubber, or silicone rubber, for example.

The bellows 24 may be referred to as a bellows suction cup, for example.

The bellows 24 is resiliently compressible.

The bellows 24 comprises a wavey or ridged or undulating or corrugated shape that is resiliently compressible in a longitudinal direction of the bellows 24.

The bellows 24 comprises a through hole or flow path or passageway 28 that extends along a longitudinal length of the bellows 24 from the suction cup 26 to a second (bottom or lower) end 30 of the bellows 24. The second end 30 is a base of the bellows 24.

The second end 30 (or base) of the bellows 24 may be substantially cylindrical, for example.

The second end 30 (or base) of the bellows 24 forms or comprises an integral base of the bellows 24.

In use, the second end 30 (or base) of the bellows 24 is positioned in a hole or opening or recess in the surface 5. The hole or opening or recess comprises a locator and/or connector, for example a protrusion or barb, that is configured to be received in the through hole or flow path 28 in the second end 30 (or base) of the bellows 24. This facilitates positioning and/or mounting of the bellows 24 in or on the surface 5.

The protrusion or barb comprises a flow path or passageway that is connected to the through hole or flow path 28 of the bellows 24 when the bellows 24 is positioned and/or mounted on the protrusion or barb. Therefore, vacuum or suction can be applied to the suction assembly 9 by applying vacuum or suction to the flow path or passageway in the protrusion or barb.

When the bellows 24 is mounted in this way, the bellows 24 is vertical with the suction cup 26 positioned upwards and spaced apart from the surface 5. In other words, the bellows 24 protrudes out of the hole or opening or recess in the surface 5 to a position above the surface 5.

When a wafer is brought into contact with the suction cup 26, for example by being lowered as described above, and suction or vacuum is applied to the through hole or flow path 28, the wafer is gripped by the suction cup 26. In particular, a pressure difference between a lower pressure or reduced pressure in the suction cup 26 and a pressure of gas such as air above the wafer causes the wafer to experience a force towards the suction cup 26.

Since the suction cup 26 is formed of resilient material, this force causes the suction cup 26 to compress an/or flatten.

Continued vacuum or suction applied to the through hole or flow path 28 causes the bellows 24 to be compressed longitudinally, thereby drawing or pulling or moving the wafer towards the base 30 of the bellows 24, i.e. towards the surface 5.

The second end 30 (or base) of the bellows is located in the hole or opening or recess in the surface 5 such that when the bellows is compressed in this manner an upper surface of the suction cup 26 is flush, or substantially flush, with the surface 5.

Therefore, the suction assembly 9 can be used to grip the wafer above the surface and to draw or pull or move the wafer towards the surface in a similar manner to that described above.

Figures 7A and 7B show an alternative example of a suction assembly 9 that includes a suction cup 26 similar to the suction cup 26 described above. The suction cup 26 may have any of the features of the suction cup 26 described above.

The suction cup 26 has a base 30 that corresponds to the second end 30 (or base) described above, and that may have any of the features of the second end 30 (or base) described above.

The suction cup 26 also has a through hole or flow path 28 that extends from an upper side of the suction cup 26 through the suction cup 26 to a lower side of the suction cup 26 through the base 30 of the suction cup 26. The through hole or flow path 28 may have any of the features of the through hole or flow path 28 described above.

The suction assembly 9 in this embodiment therefore differs from the suction assembly 9 of Figures 6A and 6B in that the bellows 24 is omitted, and instead the suction cup has an integral base that is mounted to the locator and/or connector in the hole or opening or recess in the surface 5.

In use, the base of the suction cup 26 is positioned in a hole or opening or recess in the surface 5. The hole or opening or recess comprises a locator and/or connector, for example a protrusion or barb, that is configured to be received in the through hole or flow path 28 in the base 30 of the suction cup 26. This facilitates positioning and/or mounting of the suction cup in or on the surface 5.

The protrusion or barb comprises a flow path or passageway that is connected to the through hole or flow path 28 of the suction cup 26 when the suction cup 26 is positioned and/or mounted on the protrusion or barb. Therefore, vacuum or suction can be applied to the suction assembly 9 by applying vacuum or suction to the flow path or passageway in the protrusion or barb.

When the suction cup 26 is mounted in this way, the suction cup 26 is vertical with a top surface of the suction cup 26 positioned upwards and spaced apart from the surface 5. In other words, the suction cup 26 protrudes from the hole or opening or recess in the surface 5 so that a top surface of the suction cup 26 is located above the surface 5. When a wafer is brought into contact with the suction cup 26, for example by being lowered as described above, and suction or vacuum is applied to the through hole or flow path 28, the wafer is gripped by the suction cup 26. In particular, a pressure difference between a lower pressure or reduced pressure in the suction cup 26 and a pressure of gas such as air above the wafer causes the wafer to experience a force towards the suction cup 26.

Since the suction cup 26 is formed of resilient material, this force causes the suction cup 26 to compress an/or flatten, thereby drawing or pulling or moving the wafer towards the base 30 of the suction cup 26, and therefore towards the surface 5.

The base 30 of the suction cup 26 is located in the hole or opening or recess in the surface 5 such that when the suction cup 26 is compressed in this manner an upper surface of the suction cup 26 is flush, or substantially flush, with the surface 5.

Therefore, the suction assembly 9 can be used to grip the wafer above the surface and to draw or pull or move the wafer towards the surface in a similar manner to that described above.

Figures 8A, 8B and 9 illustrated how vacuum or suction can be applied to the vacuum groove or channel 7 and the suction assemblies 9 in embodiments of the present invention.

As shown in Figures 8A, 8B and 9, the vacuum groove or channel 7 and the suction assemblies 9 are connected to the same vacuum or suction line 29, either directly or indirectly. The vacuum groove or channel 7 and the suction assemblies 9 are therefore in fluid (i.e. gas) communication with the shared vacuum or suction line 29. The shared vacuum or suction line 29 is connected to a vacuum or suction source 31 . For example, the vacuum or suction source 31 may comprise a pump, such as a vacuum pump.

The shared vacuum or suction line 29 may comprise a pipe or tube for conveying gas.

Therefore, gas such as air can simultaneously be sucked through both the vacuum groove or channel 7 and the suction assemblies 9 by the vacuum or suction source 31 through the shared vacuum or suction line 29.

As discussed above, the present inventors have realised that if the vacuum groove or channel 7 and the suction assemblies 9 are connected to the same vacuum or suction line 29 as described above, the vacuum or suction may be lost through the vacuum groove or channel 7 before the suction assemblies 9 pull or draw the wafer towards the surface 5 and sufficiently flatten the wafer for it to be effectively clamped by the vacuum groove or channel 7. This could lead to ineffective clamping of the wafer to the surface 5 and therefore incorrect adjustment of the temperature of the wafer, or a long time being required to achieve a desired or predetermined temperature of the wafer.

In order to address this problem, the embodiments of the present invention include a flow restrictor 33 in a flow path between the shared vacuum or suction line 29 and the vacuum groove or channel 7, to restrict flow of gas from the vacuum groove or channel 7 to the shared vacuum or suction line 29. In particular, since the flow of gas from the vacuum groove or channel to the shared vacuum or suction line 29 is restricted by the flow restrictor 33, a sufficient lower pressure or reduced pressure may be maintained in the suction assemblies 9 for the suction assemblies 9 to pull or draw the wafer towards the surface 5 and at least partly flatten the wafer, without the vacuum or suction being lost through the vacuum groove or channel 7.

The flow restrictor 33 provides a narrowing or aperture in a flow path (a gas flow path or vacuum flow path) between the shared vacuum or suction line 29 and the vacuum groove or channel 7. For example, the flow restrictor 33 may comprise an aperture having a smaller diameter or cross-sectional area than adjacent or other parts of the flow path. In particular, the flow restrictor 33 may comprise a fixed restriction such as a fixed aperture.

The flow path may be a pipe or tube or passageway or conduit for conveying gas.

The flow restrictor 33 may be a passive flow restrictor.

The flow restrictor 33 may not be an electronically controllable flow restrictor.

The flow restrictor may be a non-controllable flow restrictor, for example a non-electronically and/or non- remotely controllable flow restrictor.

The flow restrictor 33 may be adjustable, for example manually adjustable, to adjust an amount of restriction provided by the flow restrictor 33.

As shown in Figure 8A, in some embodiments the flow restrictor 33 may be located in the plate or block 3.

For example, the plate or block 3 may comprise one or more first flow paths 35 (such as gas flow paths or vacuum flow paths) that are connected to the vacuum groove or channel 7 and to the shared vacuum or suction line 29, through which gas can be sucked from the vacuum groove or channel 7 to the shared vacuum or suction line 29. The flow restrictor 33 may be located in or on one of the one or more first flow paths 35 in the plate or block 3. The first flow path may comprise a pipe, or tube, or passageway, or channel along which gas can flow in the plate or block 3.

The plate or block 3 may also comprise one or more second flow paths 37 that are connected to the suction assemblies 9 and to the shared vacuum or suction line 29, through which gas can be sucked from the suction assemblies 9 to the shared vacuum or suction line 29. The second flow paths 37 may comprise a pipe, or tube, or passageway, or channel along which gas can flow in the plate or block 3.

As shown in Figure 9, alternatively, or in addition, the flow restrictor 33 may be located outside of the plate or block 3.

For example, the flow restrictor 33 may be located in or on a pipe or tube that is external to the plate or block 3 and that connects the shared vacuum or suction line 29 to the one or more first flow paths 35. There may also be a second pipe that is external to the plate or block 3 and that connects the shared vacuum or suction line 29 to the one or more second flow paths 37. Of course, in some embodiments there may be more than one vacuum groove or channel 7, or other gas inlets, in the surface 5 to which vacuum or suction is applied. In particular, in other embodiments there may be a plurality of gas inlets, for example a plurality of vacuum grooves or channels 7.

In such embodiments, each of the plurality of gas inlets may have a respective flow path that connects the gas inlet to the shared vacuum or suction line 29, and a respective flow restrictor 33 may be provided in each of the flow paths.

For example, in one embodiment there may be two or more vacuum grooves or channels 7 in the surface, wherein each of the two or more vacuum grooves or channels is connected to the shared vacuum or suction line 29 by a respective flow path, and wherein a respective flow restrictor 33 is provided in each of the flow paths.

Therefore, suction or vacuum through each of the plurality of gas inlets may be individually or separately or independently restricted by the respective flow restrictors.

In alternative embodiments, different groups or sets of gas inlets may be connected to the shared vacuum or suction line 29 by respective flow paths, such that vacuum or suction is applied to a particular group or set of gas inlets simultaneously via a single flow path. A respective flow restrictor may be provided for each of the flow paths.

Therefore, suction or vacuum through each of the groups or sets of gas inlets may be individually or separately or independently restricted by the respective flow restrictors.

For example, a group or set of gas inlets may comprise a plurality of holes or openings in the surface 5 that are each connected to a single channel or passageway below the surface, which is connected to the shared vacuum or suction line 29. A single flow restrictor may be provided in a flow path to the single channel or passageway. Of course, there may be more than one such channel or passageway, each with a respective group or set of gas inlets, respective flow path and respective flow restrictor.

In some embodiments, a flow restrictor may also be provided in a respective flow path to each of the suction assemblies 9. This may facilitate simultaneous or synchronous operation of the suction assemblies 9.

For example, without such individual flow restrictors, the suction assemblies 9 may be compressed in stages and/or one at a time as a vacuum or suction to each of the suction assemblies 9 varies depending on a changing resistance to compression of each of the suction assemblies 9 during compression of each of the suction assemblies 9.

The vacuum may be switched by a 3-way valve 34 (e.g. a solenoid as depicted in Fig. 8B). The 3-way valve may be connected to ambient atmosphere through ambient line 36 so to switch suction line 29 from vacuum to ambient pressure in order to release the wafer from vacuum gripping. A filter 38 may be provided to ensure that only clean air is drawn into the vacuum system when the wafer is released.

Figures 10A and 10B illustrate some non-exhaustive examples of the flow restrictor 33 that can be used in embodiments of the present invention. As shown in Figure 10A, in some embodiments the flow restrictor 33 may comprise a fixed narrowing or aperture in the flow path.

As shown in Figure 10B, in other embodiments the flow restrictor 33 may comprise an adjustable narrowing or aperture in the flow path. For example, the flow restrictor 33 may comprise a valve such as a needle valve that can be adjusted to adjust a size of the narrowing or aperture in the flow path.

The flow restrictor 33 may therefore be adjustable, but not electronically controllable.

The flow restrictor 33 may be manually adjustable.

Of course, in other embodiments a shape of the vacuum groove or channel 7 may be different to that illustrated in Figure 1 . For example, the vacuum groove or channel does not have to be in the form of a circle, and for example may instead comprise a segment or arc of a circle. In addition, or alternatively, in other embodiments there may be more than one of the vacuum groove or channel 7.

As mentioned above, in some embodiments the channel 7 may be located or housed or enclosed below the surface 5, and there may be a plurality of holes or openings through the surface 5 to the channel 7. Therefore, when vacuum or suction is applied to the channel 7, the vacuum or suction is applied to the holes or openings through the surface. A single flow restrictor may be provided for the channel 7, so that the flow thorough all of the plurality of openings is restricted simultaneously by the single flow restrictor.

Of course, there may be more than one such channel 7 located or housed or enclosed below the surface, and a separate flow path and flow restrictor may be provided for each of the channels 7.

In addition, or alternatively, in other embodiments the number and/or positioning of the suction assemblies 9 may be different to that illustrated in Figure 1 . For example, there may be more than three of the suction assemblies 9, and/or the positioning of the suction assemblies 9 may be different. As mentioned above, in embodiments of the present invention there may also be one or more suction assemblies 9 at or adjacent to a centre of the surface 5, and/or inside or radially inwards of the vacuum groove or channel 7.

There may be three of more of the suction assemblies 9.

In addition, in other embodiments the structure of the suction assemblies 9 may be different to that illustrated in Figures 4, 5, 6A, 6B, 7A and 7B.

In alternatively embodiments a different type of vacuum inlet or gas inlet may be provided in the surface instead of, or in addition to, the vacuum groove or channel 7.

Figures 11 to 13 illustrate an alternative embodiment of the present invention in which the suction assemblies 9 of the previous embodiment are replaced with different suction assemblies or devices 39.

The device 41 illustrated in Figures 11 to 13 may include any of the features of the device 1 illustrated in Figures 1 to 10 and described above, unless incompatible. The device 41 differs from the device 1 in that the suction assemblies 9 in the device 1 are replaced with suction assemblies or devices 39. The other features of the device 1 described above may be unchanged and therefore included in the device 41 .

The suction assemblies or devices 39 have the same function as the suction assemblies 9 of gripping the wafer above the surface 5 and then pulling/moving/drawing the wafer towards the surface 5 so as to at least partly flatten the wafer.

The suction assemblies or devices 39 each comprise a lifting pin 42 that can be lifted and/or moved relative to the plate or block 3 to protrude above the surface 5 of the plate or block 3, or lowered relative to the plate or block 3 so that the lifting pin 42 is received inside the plate or block 3 with a top surface of the lifting pin 42 flush or substantially flush with the surface 5.

In particular, each of the lifting pins 42 is located in a hole or opening in the surface 5.

The device 41 further comprises one or more lifting mechanisms, for example one or more electronic actuators, that can be operated to lift or lower the lifting pins 42 relative to the plate or block 3.

As illustrated in Figure 12, each of the lifting pins 42 has a longitudinal passageway or flow path 43 through which gas such as air can be sucked, for example using one of the arrangements illustrated in Figures 8A, 8B or 9 and described above.

In addition, each of the lifting pins 42 has a pad 45 at a top end of the lifting pin 42. The pad 45 includes a recess 47 in a top surface of the pad 45 that is connected to (in fluid communication with) the longitudinal passageway or flow path 43. Therefore, when suction is applied to the longitudinal passageway or flow path 43, gas is sucked from the recess 47 in the pad 45.

The pad 45 may be a suction pad.

The pad 45 may be made of flexible material.

The lifting pins may be referred to as vacuum pins or suction pins.

When a wafer is lowered towards the surface 5 of the device 41 , and the lifting pins 42 are lifted above the surface 5, the wafer will first come into contact with the pads 45 at the top ends of the lifting pins 42, similarly to the arrangement illustrated in Figure 2. The lower side of the wafer will define a space or volume with the recess 47 in the top surface of the pad 45. When suction is applied to the longitudinal passageway or flow path 43 and gas is sucked from the recess 47, a lower pressure or reduced pressure will be generated in space or volume in the recess 47. This lower pressure or reduced pressure will cause the lower surface of the wafer to be gripped by the pads 45. Then, when the lifting pins 42 are subsequently lowered while gripping the wafer, the wafer will be pulled or drawn towards the surface 5 by the lifting pins and will be at least partly flattened and brought into contact with the surface 5, or closer to the surface 5. Then, the wafer can be clamped to the surface 5 by the suction applied through the vacuum groove or channel 7 as described above. As illustrated in Figure 11 , the lifting pins 42 are configured so that when the lifting pins 42 are fully lowed relative to the plate or block 3, tops of the lifting pins 42 are flush, or substantially flush, with the surface 5 of the plate or block 3.

Figure 14 illustrates an alternative embodiment of the present invention. This embodiment may have any of the features of the embodiments described above, unless incompatible.

The device 49 in this embodiment differs from the first embodiment described above in that the vacuum groove or channel 7 is replaced by a plurality of holes or openings 51 in the surface 5. The other features of the device 1 described above may be unchanged and therefore included in the device 49.

Similarly to the arrangements illustrated in Figures 8A, 8B and 9, one or more first flow paths 35 may be connected to the plurality of holes or openings 51 in the surface 5 and to the shared vacuum or suction line 29, so that gas can be sucked from the holes or openings 51 in the surface 5 similarly to the manner described above.

When a wafer is in contact with the surface 5, or adjacent to the surface 5, and gas is sucked from the holes or openings 5 a lower pressure or reduced pressure will be generated between the surface 5 and the wafer, at least in parts. The wafer will therefore be clamped to the surface 5 and/or gripped by the surface 5 in a similar manner to that described above.

In some embodiments, each of the plurality of holes or openings 51 may have a respective flow path with a respective flow restrictor, such that flow thorough each of the plurality of holes or openings 51 is independently and/or separately restricted.

Alternatively, different groups or sets of the plurality of holes or openings 51 may each comprise a respective flow path having a respective flow restrictor, so that flow through the plurality of holes or openings 51 in a particular group or set is restricted by a single flow restrictor. As mentioned above, the plurality of holes or openings 51 in a particular group or set may be connected together via a channel or passageway below the surface 5, i.e. enclosed by the surface 5.

In any of the embodiments described above, the device may further comprise a plurality of lifting pins that are configured to receive a wafer that is being lowered onto the device and to lower the wafer towards the surface of the device. Where included, these lifting pins do not grip the wafer. The device may further comprise one or more lifting mechanisms for lifting or lowering the plurality of lifting pins.

When loading the wafer onto the device, the wafer may initially be supported from beneath by an end effector of a robotic arm that is used to pick the wafer up from a wafer cassette. The end effector may be used to lower the wafer towards the surface of the device until the wafer comes into contact with the lifting pins and is supported by the lifting pins. The end effector may then be laterally withdrawn from beneath the wafer. The lifting pins may then be used to lower the wafer until the wafer comes into contact with the suction assemblies or lifting pins described above.

Alternatively, these additional lifting pins may be omitted and the wafer may be directly lowered onto the suction assemblies or lifting pins described above. Figure 15 is an example of a wafer mass metrology apparatus according to the present invention that includes any of the devices described above.

The wafer mass metrology apparatus 53 comprises a device 55 for measuring the weight and/or mass of a wafer. The device 55 comprises a support 57 or pan for supporting the wafer during a weight and/or mass measurement performed on the wafer by the device 55. The device 55 is configured to provide measurement output indicative of the weight and/or mass of a wafer loaded on the support 57, or a change in the weight and/or mass of the wafer, or a difference between the weight and/or mass of the wafer and a reference weight and/or mass.

The device 55 is located within a measurement chamber 59, which forms an enclosed environment around the device 55. For example, the measurement chamber 59 may maintain a substantially uniform air density, air pressure and/or air temperature of the air around the device 55. The measurement chamber 59 has an opening (not shown), e.g. a suitably sized slot in a side-wall of the measurement chamber 59, to allow a wafer to be transported into the measurement chamber 59, by an end effector of a robotic arm, and positioned on the support 57. When not in use, the opening may be covered by an openable door or covering (not shown) to allow the measurement chamber 59 to be substantially closed or sealed when performing measurements using the device 55.

A temperature changing part 61 for changing a temperature of the wafer is positioned on top of the measurement chamber 59.

The temperature changing part 61 may correspond to, or be, the device according to any of the embodiments described above. The temperature changing part 61 may therefore have any of the features of the device according to any of the embodiments described above.

The temperature changing part 61 is positioned directly on top of the measurement chamber 59, so that there is a good thermal contact between the temperature changing part 61 and the measurement chamber 59. The temperature changing part 61 is in direct physical contact with the measurement chamber 59. The temperature changing part 61 may be attached or fixed to the measurement chamber 61 , for example using one or more bolts (not shown) and/or a thermally conductive bonding layer (not shown).

As a result of the good thermal contact between the temperature changing part 61 and the measurement chamber 59, the temperature changing part 61 may be substantially in thermal equilibrium with the measurement chamber 59 and therefore may have substantially the same temperature as the measurement chamber 59 (when a heat load on the temperature changing part 61 is low). The device 55 may also be in thermal equilibrium with the measurement chamber 59 and therefore may also have substantially the same temperature as the measurement chamber 59. As such, the temperature changing part 61 may be substantially in thermal equilibrium with the device 55 and therefore may have substantially the same temperature as the device 55 (when a heat load on the temperature changing part 61 is low). In use, a wafer to be measured is firstly positioned on the temperature changing part 61 to reduce its temperature. As discussed above, the temperature changing part 61 may correspond to, or be, the device according to any of the embodiments described above, and therefore may include the suction assemblies or devices 9 or 39 and the groove of channel or holes or openings 7 or 51 among other features described above.

Therefore, the wafer may be effectively clamped to the surface 5 of the temperature changing part 61 so that a good thermal contact is achieved between the temperature changing part 61 and the wafer, even when dealing with curved or bowed wafers. Thermal equilibrium between the wafer and the temperature changing part 61 may be achieved in a short time period, for example less than 0.01 °C temperature difference between the temperature changing part 61 and the wafer within 20 seconds.

The wafer may be positioned on the temperature changing part 61 for a predetermined period of time sufficient to achieve thermal equilibrium between the wafer and the temperature changing part 61 . Usually the temperature changing part 61 and the measurement chamber 59 are in thermal equilibrium with each other (when a heat load on the temperature changing part 61 is low), such that the wafer is brought to the same temperature as the temperature of the measurement chamber 59.

Typically, the temperature of the wafer is higher than the temperature of the temperature changing part 61 and the temperature of the measurement chamber 59, and therefore typically the temperature changing part 61 cools the wafer (reduces the temperature of the wafer).

After the wafer has been cooled by the temperature changing part 61 , it is transported from the temperature changing part 61 into the measurement chamber 59 and positioned on the support 57 of the device 55, for measurement.

The device 55 is used to perform a weight and/or mass measurement on the wafer. For example, the device 55 may measure a weight and/or mass of the wafer.

The apparatus 53 is configured to perform a calculation to calculate the mass of the wafer based on the result of the weight and/or mass measurement. The calculation may comprise performing a buoyancy correction to correct for a buoyancy force on the wafer from the air in the measurement chamber 59. For example, the measurement chamber 59 may comprise one or more sensors for detecting a temperature and/or pressure and/or humidity of the air in the measurement chamber 59, in order to calculate a buoyancy force on the wafer.

Of course, in other embodiments the temperature changing part 61 may be located in a different position relative to the measurement chamber 59 than that illustrated in Figure 15. For example, in another embodiment the temperature changing part 61 may not be mounted on the measurement chamber 59 and instead may be positioned to a side of the measurement chamber 59 and/or located separately to the measurement chamber 59. In such an alternative embodiment the temperature changing part 61 may or may not be thermally coupled to the measurement chamber 59 and therefore may or may not be substantially in thermal equilibrium with the measurement chamber 59. In addition, or alternatively, in other embodiments the temperature changing part 61 may have its temperature actively controlled using an active heating or cooling element, for example a Peltier device.

Figures 16 and 17 illustrate a bellows insert 63 according to another embodiment. Figure 17 is a sectional view illustrating the bellows insert 63 received in a bellows 65 to form a bellows assembly 66.

The bellows 65 may correspond to any of the bellows described above, for example, and the configuration of the bellows 65 is not limited to the specific configuration illustrated in Figure 17.

The bellows insert 63 may be used in any of the bellows of any of the apparatuses discussed above and illustrated in Figures 1 to 15, for example.

The bellows insert 63 is configured to be removably or detachably received or retained in the bellows 65. In particular, the bellows insert 63 is configured to be retained in at least a distal end portion of the bellows 65, which may correspond to a pad or wafer contact portion 67 of the bellows 65.

More specifically, an outer shape of the bellows insert 63 corresponds to, or matches, an inner shape of the distal end portion 67 of the bellows 65.

In this embodiment, the bellows insert 63, or a main body of the bellows insert 63, has a substantially frustoconical shape, wherein a sloped outer surface of the frustoconical shape corresponds to, or matches, a sloped inner surface of the distal end portion 67 of the bellows 65.

The bellows insert 63 has a substantially planar main face or surface 69 which is configured to be located at a distal end of the bellows 67 when the bellows insert 63 is retained in the bellows 63. The main face or surface 69 is configured to contact a wafer when a wafer is brought into contact with the bellows 67.

The bellows insert 63 comprises a plurality of through-holes or apertures 71 through which air can be sucked into the bellows 67 from above the main face or surface 69 of the bellows insert 63 when the bellows insert 63 is retained in the bellows 67. Specifically, each of the through holes is a channel through the bellows insert 63.

The bellows insert 63 comprises a groove or channel 73 in the main face or surface 69 of the bellows insert 63 in which an O-ring 75 is received. The O-ring protrudes from the groove or channel 73 above the main face or surface 69, so that a top surface of the O-ring contacts a wafer when a wafer is brought into contact with the bellows 67.

Therefore, the material of the bellows insert that is brought into contact with the wafer may be changed by changing a material of the O-ring, for example to optimise one or more properties of the material for a specific material of the wafer.

For example, the O-ring may comprise, or be made of, a fluorinated elastomer or a perfluorinated elastomer. In a specific example, the O-ring may comprise or be made of Perlast ®.

The main body of the bellows insert 63 may be made of PEEK, for example.

The bellows insert 63 further comprises a retaining portion or part 77 that is configured to removably retain the bellows insert 63 in the bellows 65 when the bellows insert 63 is received in the bellows 65. In particular, the bellows 65 has an undulating or corrugated shape, wherein an internal width of the bellows 65 varies between a minimum width at an inner vertex of the undulating or corrugated shape and a maximum width at an outer vertex of the undulating or corrugated shape.

The retaining portion 77 of the bellows insert 63 has a width that is larger than a narrowing in the undulating or corrugated shape of the bellows 65 in the distal portion of the bellows 65 and that is configured to be located on an opposite side of the narrowing to the main body of the bellows insert 63 when the bellows insert 63 is received in the bellows 65.

The retaining portion 77 is positioned at the narrower end of the frustoconical shape of the main body of the bellows insert 63, and the narrower end has a width that is substantially equal to the narrowing in the undulating or corrugated shape of the bellows 65.

Therefore, when the bellows insert 63 is inserted into the bellows 65, the retaining portion 77 may deform the bellows by stretching the undulating or corrugated shape so that the retaining portion 77 passes through the narrowing and is positioned on the opposite side of the narrowing to the main body.

The bellows may then return to its original shape with the narrowing positioned around the narrower end of the frustoconical main body of the bellows insert 63, with the retaining portion 77 on the opposite side of the narrowing to the main body. In this manner, the bellows insert 63 may be removably retained in the bellows 65.

The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example +/- 10%.