TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to apparatuses and methods for the transport of carriers with a magnetic levitation system, particularly carriers used for carrying large area substrates. More specifically, embodiments of the present disclosure relate to apparatuses and methods for the contactless transport of vertically oriented carriers in a substrate processing apparatus, e.g. in a vacuum deposition system. In particular, embodiments of the present disclosure relate to carrier transport systems, magnetic stabilization units, carriers, and methods for contactlessly transporting a carrier.

BACKGROUND

[0002] Techniques for layer deposition on a substrate include, for example, sputter deposition, physical vapor deposition (PVD), chemical vapor deposition (CVD), and thermal evaporation. Coated substrates may be used in several applications and in several technical fields. For instance, coated substrates can be used in the field of display devices. Display devices can be used for the manufacture of television screens, computer monitors, mobile phones, other hand-held devices, and the like for displaying information. Typically, displays are produced by coating a substrate with a stack of layers of different materials.

[0003] Substrates are typically coated in a vacuum deposition system with a plurality of deposition sources and other substrate processing apparatuses. The substrates are typically transported through the vacuum deposition system along a track assembly, e.g. from a first deposition module to a second deposition module and/or to other substrate processing apparatuses. The substrates may be transported through the vacuum system in an essentially vertical orientation.

[0004] A substrate is typically carried by a carrier, i.e. a carrying device for carrying the substrate. The carrier is typically transported through the vacuum deposition system using a carrier transport system, e.g. a magnetic levitation system in which the weight of the carrier is at least partially held by magnetic forces. The magnetic levitation system may be configured for conveying the carrier that carries a substrate along a track assembly that extends in a transport direction and defines a transportation path for the carrier.

[0005] An accurate and smooth transportation of carriers through a vacuum system is challenging, particularly if the carriers are vertically oriented during the transport. It is possible to support and/or move the carriers by rollers. However, particle generation due to friction between moving parts can cause a deterioration in the manufacturing process. Transporting the carriers with a magnetic levitation system can decrease the particle generation because the mechanical contact between moving parts is reduced. For example, a magnetic levitation system may include magnetic levitation units that generate a carrier levitation force, i.e. a magnetic force acting on the carrier in a vertical direction for holding the weight of the carrier.

[0006] The magnetic levitation units of a magnetic levitation system may be actively controlled. In other words, the upwardly directed levitation force generated by the magnetic levitation units may be actively controlled based on a measured gap width to continuously ensure a predetermined distance between the carrier and the actively controlled magnetic levitation units. However, actively controlled magnetic levitation units are typically expensive and complex, and considerable efforts may be necessary for providing a sufficient cooling of the large electromagnets used for generating the large magnetic levitation forces. Further, thermally induced expansion or retraction of the carrier during processing may make a reliable position control of the carrier challenging.

[0007] In view of the above, it would be beneficial to provide an improved carrier transport system for levitating and transporting carriers as well as improved methods of contactlessly transporting carriers in a vacuum system, which overcome at least some problems of the state of the art. Specifically, it would be beneficial to provide a carrier transport system that allows a contactless carrier transport with reduced efforts and an improved reliability.

SUMMARY

[0008] In light of the above, carrier transport systems for contactlessly transporting a carrier along a track assembly in a vacuum chamber, magnetic stabilization units for a carrier transport system, carriers for being transported by a carrier transport system, and methods for contactlessly transporting a carrier according to the independent claims are provided. Further aspects, advantages, and features are apparent from the dependent claims, the description, and the accompanying drawings.

[0009] According to one aspect, a carrier transport system for contactlessly transporting a carrier along a track assembly in a transport direction is provided. The carrier transport system includes a passive magnet arrangement for generating a carrier levitation force counteracting the weight force of the carrier; and an actively controlled, bidirectional magnetic stabilization unit configured to exert a magnetic stabilization force on the carrier selectively in an upward direction and a downward direction for keeping the carrier at a predetermined vertical position in a carrier transportation space.

[0010] In some embodiments, the magnetic stabilization unit is arranged at a first vertical coordinate, and a first permanentmagnetic levitation unit of the passive magnet arrangement is arranged at a second vertical coordinate different from the first vertical coordinate, e.g., having a distance of 1 m or more from the first vertical coordinate.

[0011 ] According to one aspect, a magnetic stabilization unit for a carrier transport system is provided, particularly for a carrier transport system as described herein. The magnetic stabilization unit includes at least one electromagnet for acting on a first magnetic unit of the carrier arranged in a guiding space between the two poles of the at least one electromagnet; a set of permanent magnets that generate a magnetic field having opposite directions in an upper and a lower area of the guiding space; a gap sensor; and a controller configured to control the at least one electromagnet based on a signal of the gap sensor. The magnetic stabilization unit is actively controlled and configured to exert a magnetic stabilization force on the carrier selectively in an upward direction and a downward direction for keeping the carrier at a predetermined vertical position in a carrier transportation space.

[0012] According to one aspect, a carrier for being transported by a carrier transport system is described, particularly by any of the carrier transport systems described herein. The carrier includes a holding section for carrying an object to be transported at the carrier in an essentially vertical orientation; a first magnetic unit protruding laterally from the carrier at a first vertical coordinate and configured to magnetically interact with an actively controlled, bidirectional magnetic stabilization unit; and a second magnetic unit arranged at the carrier at a second vertical coordinate and configured to magnetically interact with a first permanentmagnetic levitation unit generating a carrier levitation force. The object to be transported can be, for example, a substrate or a mask.

[0013] The carrier may optionally further include any of a third magnetic unit arranged at the carrier at a third vertical coordinate and configured to interact with a drive unit configured to move the carrier along a track assembly in a transport direction; and a fourth magnetic unit arranged at the carrier at a fourth vertical coordinate and configured to magnetically interact with a second permanentmagnetic levitation unit generating a carrier levitation force.

[0014] According to one aspect, a vacuum deposition system for depositing a material on a substrate in a vacuum chamber is provided. The vacuum deposition system includes a vacuum chamber; a carrier transport system according to any of the embodiments described herein; and a deposition source arranged in the vacuum chamber. Optionally, also the carrier according to any of the embodiments described herein may be a part of the vacuum deposition system.

[0015] According to one aspect, a method for contactlessly transporting a carrier is provided. The method includes generating a carrier levitation force that counteracts a weight force of the carrier with a passive magnet arrangement that may include a first permanentmagnetic levitation unit arranged at a second vertical coordinate; stabilizing a predetermined vertical positioning of the carrier in a carrier transportation space by exerting a magnetic stabilization force on the carrier selectively in an upward direction and a downward direction with an actively controlled, bidirectional magnetic stabilization unit arranged at a first vertical coordinate; and moving the carrier in the transport direction with a drive unit arranged at a third vertical coordinate.

[0016] Embodiments are also directed at apparatuses for carrying out the disclosed methods and include apparatus parts for performing each described method aspect. These method aspects may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, embodiments according to the disclosure are also directed at methods for operating the described apparatus and method of manufacturing the apparatuses and devices described herein. The methods for operating the described apparatus include method aspects for carrying out every function of the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following:

[0018] FIG. 1 shows a schematic sectional view of a carrier transport system and a carrier according to embodiments described herein;

[0019] FIG. 2 shows a schematic side view of a carrier transport system and a carrier according to embodiments described herein;

[0020] FIG. 3 shows a schematic perspective view of a magnetic stabilization unit according to embodiments described herein;

[0021] FIG. 4 shows a top view of the magnetic stabilization unit of FIG. 3; [0022] FIG. 5A shows a side view of the magnetic stabilization unit of FIG. 3 in a first control state (I);

[0023] FIG. 5B shows a side view of the magnetic stabilization unit of FIG. 3 in a second control state (II); and

[0024] FIG. 6 shows a flowchart of a method for contactlessly transporting a carrier in a transport direction according to embodiments described herein.

DETAILED DESCRIPTION OF EMBODIMENTS

[0025] Reference will now be made in detail to the various embodiments of the disclosure, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the disclosure and is not meant as a limitation of the disclosure. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations.

[0026] A carrier transport system is configured for transporting a carrier in a vacuum environment, particularly in a vacuum chamber or in a vacuum system including a plurality of vacuum chambers arranged next to each other. The carrier transport system may provide one, two or more transport paths, and the carrier can be moved or conveyed along the one or more transport paths in a transport direction (T) along a track assembly.

[0027] The carrier transport system described herein can be a part of a vacuum processing system, particularly a vacuum deposition system configured for depositing a material on a substrate carried by a carrier. The carrier transport system may be configured to move the carrier along the track array by a distance of 5 m or more or 10 m or more. [0028] As used herein, the “transport direction T” is a direction along which the carrier can be transported by the carrier transport system. A track assembly 105 extending in the transport direction T may be provided, and the carrier can be transported along the track assembly 105 by the carrier transport system 100. The transport direction T is typically a horizontal direction or an essentially horizontal direction (horizontal direction +/-10 ⁰ ). As used herein, the “vertical direction V” corresponds to the direction of gravity, i.e., the weight force of the carrier is directed downwardly in the vertical direction. In order to counteract the weight force of the carrier, such that the carrier can be contactlessly held in a floating state, a magnetic levitation unit is configured to exert a carrier levitation force FL on the carrier that is directed upwardly in the vertical direction V. As used herein, the “lateral direction L” is a direction transverse to the transport direction T and transverse to the vertical direction V. The lateral direction L is typically an essentially horizontal direction perpendicular to the transport direction T.

[0029] In some embodiments, the carrier may have an essentially vertical orientation during the transport. In other words, the orientation of the carrier, and of the substrate that is carried by the carrier, may be substantially vertical during the transport (vertical +/- 10°). The substrate may be a large area substrate, particularly a large area glass substrate, e.g. for display manufacturing. In some embodiments, the substrate may be a semiconductor substrate, e.g., a wafer, and the vacuum system may be a semiconductor processing system.

[0030] A “carrier transportation space 102” may be understood as a space in which the carrier is contactlessly held by the carrier transport system 100 and through which the carrier is contactlessly transported by the carrier transport system. The magnets of the carrier transport system may apply magnetic forces on the carrier that hold the carrier contactlessly in the carrier transportation space 102, i.e. the carrier does not escape from the carrier transportation space 102.

[0031] FIG. 1 is a schematic sectional view of a carrier transport system 100 for contactlessly transporting a carrier 10 along a track assembly in the transport direction T as described herein. The carrier 10 may carry a substrate 11, e.g. a large area substrate having a surface area of 1 m ² or more, at a holding section of the carrier 10. Alternatively, the carrier can carry another object to be transported at the holding section, for example a mask. The holding section may include a holding mechanism, e.g. a mechanical, electrostatic or magnetic chucking device for holding the object at the holding section. Specifically, an angle enclosed between the vertical direction V and the main surface of the substrate or the other object may be 10° or less during the carrier transport.

[0032] The carrier transport system 100 includes a passive magnet arrangement 120 for generating a carrier levitation force FL that counteracts the weight force of the carrier 10, such that the carrier can be held in a floating state relative to the track assembly 105 in the carrier transportation space 102. A “passive” magnet arrangement may be understood as including passive magnets for the generation of the carrier levitation force that are not actively controlled. For example, the passive magnet arrangement 120 may include a permanentmagnetic levitation unit for generating the carrier levitation force FL and/or an electromagnet or an electropermanent magnet that generates a magnetic field whose strength is not controlled depending on a current carrier position. Accordingly, a “passive magnet arrangement” is different from an “actively controlled magnet arrangement” that generates a magnetic field that is varied depending on an input parameter, such as a gap width between the carrier and the track assembly.

[0033] In some embodiments, the carrier levitation force FL is an attractive magnetic force exerted on the carrier 10 that pulls the carrier upwardly toward the passive magnet arrangement 120. Specifically, the passive magnet arrangement 120 includes levitation magnets, e.g. permanent magnets, configured to exert an attractive force on the carrier for pulling the carrier upwardly. For example, levitation magnets of the passive magnet arrangement may be arranged above the carrier transportation space 102, such as to pull the carrier upwardly toward the levitation magnets, as it is schematically depicted in FIG. 1.

[0034] In some implementations, the passive magnet arrangement 120 may also stabilize the carrier in the lateral direction L. In other words, the magnetic forces applied on the carrier by the passive magnet arrangement may prevent that the carrier inadvertently leaves the carrier transportation space 102 in the lateral direction L. In the embodiment shown in FIG. 1, the carrier is magnetically attracted by the passive magnet arrangement 120 and, therefore, does not try to laterally escape. Other types of passive magnet arrangements 120 are possible. Optionally, a magnetic stabilization unit for stabilizing the carrier in the lateral direction L may be additionally provided that may be active or passive.

[0035] The carrier transport system 100 further includes an actively controlled magnetic stabilization unit 140 configured to exert a magnetic stabilization force Fs on the carrier 10 in an upward direction and in a downward direction for holding the carrier 10 at a predetermined vertical position in a carrier transportation space 102. Since the magnetic stabilization unit can exert an upwardly directed stabilization force and a downwardly directed stabilization force on the carrier, the magnetic stabilization unit is also referred to herein as being “bi-directional”. Specifically, if a current carrier position is determined to be too low, the magnetic stabilization unit 140 can generate the magnetic stabilization force acting in the upward direction and pulling the carrier upwardly, and if a current carrier position is determined to be too high, the magnetic stabilization unit 140 can generate the magnetic stabilization force acting in the downward direction and pulling the carrier downwardly, such as to maintain a predetermined vertical positioning of the carrier.

[0036] As a consequence of Earnshaw’s theorem, a carrier cannot be held contactlessly in a floating state only by passive magnetic units that generate constant magnetic fields. For example, without an active control exerted by a magnetic stabilization unit or another stabilization force, the carrier would move towards and bump into a passive levitation unit that exerts an attractive force on the carrier from above, or the carrier would laterally escape from a passive levitation unit that exerts a repulsive force on the carrier from below. According to embodiments described herein, the carrier can be continuously contactlessly held in the carrier transportation space due to the actively controlled magnetic stabilization unit that ensures a predetermined distance between the carrier and the passive magnet arrangement. In other words, the carrier can be stabilized at a predetermined vertical distance from the passive magnet arrangement due to the magnetic stabilization force exerted on the carrier by the magnetic stabilization unit 140. [0037] The carrier transport system described herein is beneficial as compared to other magnetic levitation systems for the following reasons:

[0038] Other magnetic levitation systems that rely on a passive magnet arrangement for generating the carrier levitation force FL use mechanical elements such as rollers or spacer elements that at least temporarily contact the carrier for ensuring that the carrier can be held at a predetermined position and does not bump into or escape from the passive magnet arrangement. However, rollers or spacer elements in contact with the moving carrier generate small particles due to frictional forces which can negatively affect the deposition quality on the substrate carried by the carrier. The carrier transport system described herein can transport the carrier completely contactlessly, i.e. without a contacting stabilization element, due to the magnetic stabilization force exerted by the actively controlled magnetic stabilization unit.

[0039] Still other magnetic levitation systems rely on actively controlled levitation magnets for exerting the magnetic levitation force on the carrier. Strong magnetic forces need to be generated by such levitation magnets in order to counteract the weight force of the carrier. This means that large coils and complex cooling systems are typically provided for actively controlled levitation magnets. Further, actively controlled levitation magnets typically control the strength of the carrier levitation force based on a distance signal measured by a gap sensor that measures a vertical gap between the carrier and the levitation magnets with the aim to keep the gap width constant. However, it may be challenging to keep the gap width (which is typically as small as several millimeters or less) constant, e.g. when the carrier thermally expands or retracts. For example, the height of a vertically oriented carrier may considerably increase during thermal processing which may lead to a decreasing gap width and therefore to problems in the active control of the levitation units and/or problems related to maintaining a constant gap width of a linear motor.

[0040] In contrast, in the carrier transport systems described herein, the magnetic levitation units are passive units that are provided separately and at a vertical distance from the actively controlled magnetic stabilization unit. Accordingly, a comparatively small magnetic stabilization force generated by the magnetic stabilization unit is sufficient which may fluctuate around a force value of zero, since the (considerably larger) carrier levitation force is generated passively by the passive magnet arrangement that is arranged at a different position. Accordingly, a small and compact actively controlled magnetic stabilization unit can be provided, and cooling efforts can be reduced. Further, the magnetic stabilization unit can be placed at a position spaced apart from the magnetic levitation unit, e.g. at a position where thermally induced carrier deformations do not play a role or do not negatively affect the control of the magnetic stabilization force and/or of the drive force.

[0041] Still other magnetic levitation systems rely on a plurality of active stabilization units arranged at different positions around the carrier transportation space and configured to generate stabilization forces in different directions. Such magnetic levitation systems are complex and costly, and it is challenging to coordinate a plurality of active stabilization units. In contrast, the magnetic stabilization unit 140 of the carrier transport system 100 described herein is bi-directional, i.e. is able to generate both an upwardly and a downwardly directed stabilization force and is arranged at a first vertical coordinate. Accordingly, two or more stabilization units arranged at different vertical coordinates (such as above and below the carrier) may not be necessary. Accordingly, the control of the carrier positioning is simplified and a more reliable and smoother contactless carrier transport can be obtained.

[0042] In some embodiments, the passive magnet arrangement 120 includes a first permanentmagnetic levitation unit 121 arranged at a second vertical coordinate V2 different from the first vertical coordinate VI where the magnetic stabilization unit 140 is arranged. The first permanentmagnetic levitation unit 121 may include permanent magnets configured to exert an upwardly directed carrier levitation force on the carrier, and the carrier 10 may include a magnetic counter-unit (referred to herein as a second magnetic unit 15), e.g. a ferromagnetic track or a permanent magnet fixed at the carrier, that is attracted by the first permanentmagnetic levitation unit 121. Alternatively or additionally, the passive magnet arrangement may include one or more coils or a ferromagnet that is attracted by permanent magnets provided at the carrier. [0043] The first permanentmagnetic levitation unit 121 may be arranged above the carrier transportation space 102 and may be configured to magnetically interact with the second magnet unit 15 that may be arranged at a head part of the carrier. Specifically, the second vertical coordinate V2 where the first permanentmagnetic levitation unit 121 is arranged may be provided above the first vertical coordinate VI where the magnetic stabilization unit 140 is arranged. Specifically, the first permanentmagnetic levitation unit 121 may be configured to magnetically interact with the second magnetic unit 15 provided at the head part of the carrier, and the magnetic stabilization unit 140 may be configured to magnetically interact with a first magnetic unit 14 provided at a bottom part of the carrier. In some embodiments, the first magnetic unit 14 of the carrier may be a ferromagnetic element, e.g. a ferromagnetic track, that may be provided at a side of the carrier and may protrude from the carrier toward the magnetic stabilization unit.

[0044] In some implementations, a distance DI between the first vertical coordinate VI and the second vertical coordinate V2 may be 1 m or more, particularly 2 m or more, more particularly 3 m or more, or even 4 m or more. For example, in a carrier transport system configured to transport a vertically oriented carrier, the passive magnet arrangement 120 may be provided at a top rail 106 of the track assembly 105, and the magnetic stabilization unit 140 may be provided at a bottom rail of the track assembly 105. It may be sufficient to accurately control the vertical carrier positioning relative to the bottom rail where the magnetic stabilization unit 140 is arranged, whereas a less accurate carrier positioning relative to the top rail (where only passive magnetic units may be provided) may be acceptable. Accordingly, thermally induced carrier deformations that may lead to a vertical movement of the head part of the carrier do not negatively affect the control of the magnetic stabilization force and do not impair the carrier transport by the linear motor.

[0045] The head part of a vertically oriented carrier may be understood as a carrier part above the substrate holding section that interacts with the top rail 106, and the bottom part may be understood as a carrier part below the substrate holding section that interacts with the bottom rail. A distance between the head part and the bottom part of the carrier may be 1 m or more, particularly 2 m or more, more particularly 3 m or more, or even 4 m or more. In some embodiments, the first permanentmagnetic levitation unit 121 may be configured to magnetically interact with the head part of the carrier, and the magnetic stabilization unit 140 may be configured to magnetically interact with the bottom part of the carrier. Specifically, the first permanentmagnetic levitation unit 121 may be arranged at the top rail 106 of the track assembly, particularly above the carrier transportation space 102, and the magnetic stabilization unit 140 may be arranged at the bottom rail of the track assembly. It may be sufficient to accurately monitor and maintain the carrier positioning relative to the bottom rail where the magnetic stabilization unit 140 and drive unit 150 may be provided.

[0046] In some embodiments, which can be combined with other embodiments described herein, the passive magnet arrangement 120 further includes a second permanentmagnetic levitation unit 122 arranged at a fourth vertical coordinate V4. The first permanentmagnetic levitation unit 121 may be configured to counteract a first portion of the weight force of the carrier and the second permanentmagnetic levitation unit 122 may be configured to counteract a second portion of the weight force of the carrier.

[0047] Similar to the first permanentmagnetic levitation unit 121, also the second permanentmagnetic levitation unit 122 may include permanent magnets or electromagnets for exerting the upwardly directed passive magnetic levitation force FL on the carrier. In FIG. 1, the north poles of the permanentmagnetic levitation units are shaded, whereas the south poles are shown in white. Since a south pole of the second permanentmagnetic levitation unit 122 is directed toward and facing a north pole of a magnetic counter-unit of the carrier (referred to herein as a fourth magnetic unit 17) arranged below the second permanentmagnetic levitation unit 122, an upwardly directed levitation force is exerted on the carrier. The fourth magnetic unit 17 of the carrier can be a ferromagnetic unit or a permanent magnet. In other embodiments, the orientation, the arrangement or the shape of the permanentmagnetic levitation units can be different, as long as an upwardly directed levitation force is exerted on the carrier.

[0048] In some embodiments, the first portion of the weight force of the carrier that is counteracted by the first permanentmagnetic levitation unit 121 may be 20% or more of the total weight force, particularly about 30% or more, more particularly 40% or more. The second portion of the weight force of the carrier that is counteracted by the second permanentmagnetic levitation unit 122 may be 50% or more of the total weight force, particularly about 80% or more, more particularly 90% or more.

[0049] By providing two or more magnetic levitation units at two or more different vertical coordinates (optionally with an offset in the lateral direction L) that generate a respective portion of the carrier levitation force FL, a smoother and more stable carrier transport can be obtained. For example, the first permanentmagnetic levitation unit 121 may be arranged at the top rail 106 of the track assembly and may be configured to magnetically interact with the head part of the carrier, and the second permanentmagnetic levitation unit 122 may be arranged at a bottom rail of the track assembly and configured to magnetically interact with the bottom part of the carrier. A distance between the second vertical coordinate V2 and the fourth vertical coordinate V4 may be 1 m or more, particularly 2 m or more, more particularly 3 m or more or 4 m or more. A distance between the first vertical coordinate V 1 and the fourth vertical coordinate V4 may be 30 cm or less.

[0050] Both the second permanentmagnetic levitation unit 122 and the magnetic stabilization unit 140 may be arranged at the bottom rail of the track assembly 105. For example, the second permanentmagnetic levitation unit 122 may be arranged below the magnetic stabilization unit 140 at the bottom rail and be configured to magnetically interact with the fourth magnetic unit 17 that is arranged at the carrier.

[0051] The sum of the first portion and the second portion may be 100% or more of the weight force of the carrier, particularly 120% or more, more particularly about 130%, or more than that. In other words, the first and second permanentmagnetic levitation units in combination may carry the full weight of the carrier (or may generate an even stronger force).

[0052] The reason for a carrier levitation force corresponding to more than 100% of the weight force of the carrier may be the presence of at least one further downwardly directed force component that acts on the carrier during the carrier transport. For example, a linear motor arranged below the carrier typically may not only exert a transport force FT in the transport direction T on the carrier, but additionally also a downwardly directed force component Fc that may correspond to 20% or more of the weight force of the carrier. The passive magnet arrangement 120 may counteract also the latter force component that pulls the carrier downwardly.

[0053] In some embodiments, (i) the carrier levitation force FL of the passive magnet arrangement 120, (ii) the weight force of the carrier, and (iii) the downwardly directed force component Fc exerted on the carrier by a drive unit 150 add up to essentially zero during the carrier transport if the carrier is arranged exactly at a predetermined position in the carrier transportation space 102. Therefore, the average magnetic stabilization force Fs exerted by the magnetic stabilization unit 140 on the carrier may be essentially zero as well. For example, the magnetic stabilization force Fs exerted by the magnetic stabilization unit 140 on the carrier may continuously fluctuate around a zero force (e.g., the exerted stabilization force integrated over time may be essentially zero). The magnetic stabilization force may only be provided for stabilizing and keeping the carrier at the predetermined vertical position where the above forces (i), (ii), (iii) (and/or other optional forces acting on the carrier) add up to essentially zero. Since no large magnetic forces are to be exerted on the carrier by the magnetic stabilization unit 140, the magnetic stabilization unit can be kept small and compact, and the cooling efforts for the respective coils can be reduced.

[0054] The carrier levitation force FL generated by the passive magnet arrangement 120 may correspond to 100% or more of the weight force of the carrier, particularly 120% or more, more particularly 130% or more. Accordingly, the entire carrier levitation force may be passively generated (for example, by the first and/or second permanentmagnetic levitation units), and the actively controlled magnetic stabilization unit may only be provided for preventing that the carrier can escape from a predetermined position relative to the track assembly in the carrier transportation space 102.

[0055] In some embodiments, which can be combined with other embodiments described herein, the carrier transport system 100 further includes a drive unit 150, particularly a linear motor, for moving the carrier along the track assembly 105 in the transport direction T. The drive unit 150 may be arranged at a third vertical coordinate V3, particularly below a magnetic counterpart of the carrier (referred to herein as a third magnetic unit 16). Specifically, the drive unit 150 may be arranged below the carrier transportation space 102 and may be configured to magnetically interact with a bottom part of the carrier, particularly with the third magnetic unit 16 that is arranged at the bottom part of the carrier.

[0056] In some embodiments, a distance D2 between the first vertical coordinate VI, where the magnetic stabilization unit 140 is arranged, and the third vertical coordinate V3, where the drive unit 150 is arranged, may be 30 cm or less, particularly 20 cm or less, or even 10 cm or less. In particular, the magnetic stabilization unit 140 and the drive unit 150 may be arranged at a close vertical distance to each other, e.g. both at the bottom rail of the track assembly. The drive unit 150 (that may be a linear motor) may rely on an accurate and small gap width relative to the third magnetic unit 16 of the carrier. Accordingly, if the magnetic stabilization unit 140 that ensures a predetermined vertical carrier positioning is arranged in close proximity to the drive unit 150, said gap width can be accurately maintained even if the carrier should suffer from thermally induced deformations.

[0057] Specifically, if the carrier should expand, the head part of the carrier may move upwardly toward the top rail of the track assembly, but the bottom part, where the first magnetic unit 14 and also the third magnetic unit 16 of the carrier are arranged, may maintain the predetermined vertical positions. Accordingly, it is beneficial to arrange the magnetic stabilization unit in close vicinity to the drive unit. Problems related to a large distance between a linear motor and an actively controlled levitation unit can be avoided by arranging the actively controlled magnetic stabilization unit 140 in close vicinity to the drive unit 150, whereas the passive magnet arrangement can be arranged at different positions, e.g. at the top rail 106. No actively controlled levitation units are necessary at the top rail.

[0058] According to some embodiments, the magnetic stabilization unit 140 is arranged laterally on one side of the carrier transportation space 102. In particular, the magnetic stabilization unit 140 may be arranged laterally on only one side of the carrier, not on two opposite sides. By providing a magnetic stabilization unit 140 that is arranged on one side of the carrier and is able to bi-directionally control and stabilize the carrier position, the control can be simplified and it may not be necessary to coordinate several controllers of active units that are responsible for the carrier stabilization in different directions.

[0059] The magnetic stabilization unit 140 may define a guiding space 148 for a first magnetic unit 14 that protrudes laterally from the carrier into the guiding space 148. The first magnetic unit 14 may be a ferromagnetic element, e.g. a ferromagnetic track, that protrudes laterally from a side surface of the carrier toward the magnetic stabilization unit, particularly into the guiding space 148 that is defined by the magnetic stabilization unit 140. For example, the magnetic stabilization unit 140 may be a coil with a magnetic core shaped such that the magnetic core partially surrounds the guiding space 148, particularly at three sides thereof. The two magnet poles of the coil may be directed toward the guiding space 148 from two opposite sides, such that both poles are directed toward the first magnetic unit 14 when the first magnetic unit 14 is arranged in the guiding space 148.

[0060] The guiding space 148 may allow for a reliable guiding of the first magnetic unit 14 of the carrier that moves in the transport direction T in the guiding space while the magnetic field of the magnetic stabilization unit extends through the guiding space 148. Further, the guiding space enables stabilization forces in two opposite vertical directions to be applied on the first magnetic element 14 by the magnetic stabilization unit.

[0061] In some embodiments, which can be combined with other embodiments described herein, the magnetic stabilization unit 140 includes at least one electromagnet 141 for acting on the first magnetic unit 14 arranged in the guiding space 148, a gap sensor 146, and a controller 145 configured to control the at least one electromagnet 141 based on a signal of the gap sensor 146. The gap sensor 146 may be configured to measure a vertical positioning of the carrier, e.g. by measuring a gap width between the carrier and the magnetic stabilization unit (or another stationary component of the track assembly), and to forward the measured position value to the controller. The controller may be configured to control the magnetic stabilization unit to exert an upwardly directed stabilization force on the carrier (e.g., if the carrier position is too low) or a downwardly directed stabilization force on the carrier (e.g., if the carrier position is too high). Accordingly, a bi-directional magnetic stabilization unit is provided.

[0062] In some embodiments, the magnetic stabilization unit 140 may have a permanentmagnetic bias. Details of a specific example of a bi-directional magnetic stabilization unit will be described below with reference to figures 3, 4, 5 A, and 5B.

[0063] FIG. 2 shows a schematic side view of a carrier transport system 100 that contactlessly holds a carrier 10 according to embodiments described herein. The carrier transport system 100 and the carrier 10 may have some features or all the features of the embodiment shown in FIG. 1, such that reference can be made to the above explanations, which are not repeated here.

[0064] The carrier 10 is configured to be transported by the carrier transport system 100 described herein. The carrier 10 includes a holding section for carrying an object, such as a substrate 11 to be processed, particularly in an essentially vertical orientation. A carrier part above the holding section is also referred to herein as a head part, and a carrier part below the holding section is also referred to herein as a bottom part. The carrier 10 further includes a first magnetic unit 14 protruding laterally from the carrier at a first vertical coordinate and configured to magnetically interact with an actively controlled, bidirectional magnetic stabilization unit 140 as described herein. The first magnetic unit 14 may be a ferromagnetic element, e.g. a metal track, extending along the transport direction T on a side of the carrier and protruding from the carrier in the lateral direction L. The first magnetic unit 14 may be provided at the bottom part of the carrier, i.e. below the substrate holding section.

[0065] The magnetic stabilization unit 140 is schematically indicated in FIG. 2 for illustration purposes in a rotated position. The magnetic stabilization unit 140 is actually arranged such that the guiding space 148 that is defined between the magnet poles thereof is open toward the carrier, such that the first magnetic unit 14 can laterally protrude into the guiding space 148, as it is shown in FIG. 1. Several magnetic stabilization units 140 may be provided at the first vertical coordinate VI along the transport direction T, e.g. at predetermined intervals, such that the first magnetic unit 14 of the carrier that is also provided at the first vertical coordinate VI always protrudes into at least one magnetic stabilization unit during the movement along the track assembly, particularly always protrudes into at least two magnetic stabilization units during the movement along the track assembly. It is beneficial that the first magnetic unit 14 of the carrier protrudes into two magnetic stabilization units at the same time, such that the vertical position of the carrier and the pitch of the carrier (i.e., the rotational position of the carrier with respect to the lateral direction L) can be stabilized. Hence, the carrier can be vertically stabilized at various positions along the track assembly during the transport in the transport direction.

[0066] The carrier 10 further includes a second magnetic unit 15 arranged at the carrier at a second vertical coordinate and configured to magnetically interact with a passive magnet arrangement 120 that exerts a carrier levitation force FL on the second magnetic unit 15, particularly with the first permanentmagnetic levitation unit 121 described herein. The second magnetic unit 15 may include a permanentmagnetic track or a ferromagnetic track, e.g. a metal track. The second magnetic unit 15 may be provided at the head part of the carrier, e.g. 1 m or more above the first magnetic unit 14. In particular, the second magnetic unit 15 may be arranged at the top surface of the carrier.

[0067] In some embodiments, the carrier 10 further includes a third magnetic unit 16 arranged at the carrier at a third vertical coordinate and configured to interact with the drive unit 150 configured to move the carrier along a track assembly in the transport direction T. The third magnetic unit 16 may include a plurality of permanent magnets provided at a bottom surface of the carrier. Specifically, the third magnetic unit 16 may be the moving part of a linear motor that can be driven into movement by the linear motor. The third magnetic unit 16 may be arranged at the bottom part of the carrier, particularly at the bottom surface of the carrier. A vertical distance between the first magnetic unit 14 and the third magnetic unit 16 may be 30 cm or less. A gap width between the drive unit 150 and the third magnetic component 16 of the carrier may be 5 mm or less, particularly 3 mm or less, during the carrier transport.

[0068] According to some embodiments, the drive unit 150 may comprise a linear motor configured to apply a magnetic force on the carrier for contactlessly moving the carrier along the track assembly in the transport direction T. The drive unit 150 may include a plurality of linear motors provided at the track assembly, e.g. at predetermined intervals along the transport direction T.

[0069] The linear motor of the drive unit 150 may be configured to couple with the third magnetic unit 16 of the carrier to provide a driving force in the transport direction T. The drive unit that creates the driving force in the transport direction T is contactless and accordingly does not generate particles during the transport. In some implementations, the drive unit 150 may include a synchronous linear motor. In other embodiments, the drive unit 150 may include an asynchronous linear motor.

[0070] In some embodiments, the carrier 10 further includes a fourth magnetic unit 17 arranged at the carrier at a fourth vertical coordinate and configured to magnetically interact with a second permanentmagnetic levitation unit generating a carrier levitation force FL. The fourth magnetic unit 17 may include a permanentmagnetic track or a ferromagnetic track, e.g. a metal track. The fourth magnetic unit 17 may be provided at the bottom part of the carrier, e.g. 1 m or more below the second magnetic unit 15. In some implementations, the fourth magnetic unit 17 is arranged at the bottom part of the carrier between the first magnetic unit 14 and the third magnetic unit 16.

[0071] In some embodiments, the second magnetic unit 15 is arranged at the head part of the carrier above the holding section, and the first magnetic unit 14, the third magnetic unit 16, and/or the fourth magnetic unit 17 are arranged at the bottom part of the carrier below the holding section during the carrier transport. In particular, the first, third, and fourth magnetic units may be arranged at the bottom part.

[0072] The carrier depicted in FIG. 2 is particularly suitable for being transported with the carrier transport system 100 described herein. A smooth and reliable contactless carrier transport is possible, even if the carrier expands or retracts in a vertical direction during thermal processing due to the above arrangement of magnetic units.

[0073] In the following, the magnetic stabilization unit 140 of the carrier transport system according to embodiments of the present disclosure will be described in further detail with reference to figures 3, 4, 5 A, and 5B. FIG. 3 shows a schematic perspective view of the magnetic stabilization unit 140. FIG. 4 shows a top view of the magnetic stabilization unit 140. FIG. 5A shows a side view of the magnetic stabilization unit 140 in a first control state (I), and FIG. 5B shows a side view of the magnetic stabilization unit 140 in a second control state (II).

[0074] The magnetic stabilization unit 140 is actively controlled and can apply a magnetic stabilization force F _s in both an upward direction and a downward direction to a first magnetic unit 14. The first magnetic unit 14 may be a ferromagnetic carrier track of the carrier that is arranged in a guiding space 148 provided by the magnetic stabilization unit 140. The magnetic stabilization unit 140 includes at least one electromagnet 141, particularly a coil, for exerting the magnetic stabilization force Fs on the first magnetic unit 14, a gap sensor, and a controller (shown in FIG. 1) configured to control the at least one electromagnet 141 based on a signal of the gap sensor. The gap sensor may measure a vertical gap width between the carrier and a stationary component of the track assembly, e.g. between the at least one electromagnet 141 and the first magnetic unit 14.

[0075] The at least one electromagnet 141 may include a first pole 181 and a second pole 182 arranged above one another and facing each other, and the guiding space 148 for the first magnetic unit 14 of the carrier is provided between the first pole

181 and the second pole 182. For example, the at least one electromagnet 141 may include a coil with a core that is bent such that the first pole 181 and the second pole

182 provided at the core ends are facing each other, defining the guiding space 148 therebetween.

[0076] The magnetic stabilization unit 140 may further include a permanentmagnetic bias provided by at least one set of permanent magnets 175, as it is explained in further detail below.

[0077] In some embodiments, the magnetic stabilization unit 140 can switch between a first control state (I) (illustrated in FIG. 5A) in which the magnetic stabilization force Fs is exerted on the carrier in the upward direction and a second control state (II) (illustrated in FIG. 5B) in which the magnetic stabilization force Fs is exerted on the carrier in the downward direction. Switching may be done by reversing the magnetic polarities of the first and second poles of the at least one electromagnet 141, e.g. by reversing the direction of the current flowing through the coil. Further, by controlling the current that flows through the coil via the controller, the absolute value of the force can be varied. Accordingly both the direction and the absolute value of the magnetic stabilization force can be set as appropriate for holding the carrier at a predetermined vertical position.

[0078] In some embodiments, which can be combined with other embodiments described herein, the at least one electromagnet 141 includes a first electromagnet 171, a second electromagnet 172, and optionally a third electromagnet 173 (and optionally yet further electromagnets) arranged side by side in the transport direction and respectively partially surrounding the guiding space 148. The second electromagnet 172 is arranged in the transport direction T next to the first electromagnet 171, and optionally between the first electromagnet 171 and the third electromagnet 173. For the exertion of the magnetic stabilization force Fs on the carrier, the controller controls these electromagnets such that the first electromagnet 171 (and the optional third electromagnet 173, i.e., the outer electromagnets) are poled inversely in relation to the second electromagnet (i.e., the center electromagnet). Accordingly, the magnetic field lines generated by the first electromagnet 171 (and the optional third electromagnet 173) extending through the guiding space 148 have opposite directions to the magnetic field lines 192 generated by the second electromagnet 172 extending through the guiding space 148, as it is schematically depicted in FIG. 5 A and FIG. 5B. If the at least one electromagnet 141 includes more than three electromagnets arranged side by side in the transport direction, two adjacent electromagnets are respectively inversely poled, such that a linear array of alternately poled electromagnets is provided.

[0079] In particular, in the first control state (I) that is schematically depicted in FIG. 5 A, the magnetic field lines 192 generated by the second electromagnet 172 extend through the guiding space 148 in a downward direction, and the magnetic field lines generated by the first electromagnet 171 (and by the optional third electromagnet 173) extend through the guiding space 148 in the upward direction. In the second control state (II) that is schematically depicted in FIG. 5B, the magnetic field lines 192 generated by the second electromagnet 172 extend through the guiding space 148 in the upward direction and the magnetic field lines generated by the first electromagnet 171 (and by the optional third electromagnet 173) extend through the guiding space 148 in the downward direction. A “symmetric” arrangement of three or more electromagnets that are inversely poled in an alternate arrangement, as it is depicted in FIG. 5A, can reduce undesired force components exerted on the carrier by the magnetic stabilization unit. Specifically, a stabilization force that is directed accurately in the upward or downward direction (e.g. in the vertical direction V or a direction enclosing an angle of 10° or less relative to the vertical direction V) can be provided.

[0080] In some embodiments, which can be combined with other embodiments described herein, the magnetic stabilization unit 140 includes a permanentmagnetic bias. In particular, the magnetic stabilization unit 140 includes a set of permanent magnets 175 that generate a magnetic field in the guiding space 148 that superimposes the magnetic field generated by the at least one electromagnet 141.

[0081] The magnetic field lines 191 of the magnetic field generated by the set of permanent magnets 175 may have opposite directions in at least one upper area 178 and at least one lower area 179 of the guiding space 148. For example, first two permanent magnets with same poles directed toward each other may be arranged above the guiding space 148, and second two permanent magnets with same poles directed toward each other may be arranged on the other side of the guiding space below the first two permanent magnets. Such an arrangement of permanent magnets generates oppositely directed magnetic field lines 191 in upper and lower areas of the guiding space, as it is schematically depicted in FIG. 5 A and FIG. 5B. Alternatively, the set of permanent magnets 175 may include one pair of permanent magnets arranged above and below the guiding space such as to generate oppositely directed magnetic field lines 191 in upper and lower areas of the guiding space. For example, a first permanent magnet may be arranged between the first and second electromagnets above the guiding space, and a second permanent magnet may be arranged between the first and second electromagnets below the guiding space.

[0082] In some embodiments, the set of permanent magnets 175 may be arranged between the first and second electromagnets, and optionally between the second and third electromagnets. In particular, a first pair of permanent magnets may be arranged between the first and second electromagnets above and below the guiding space 148, and an optional second pair of permanent magnets may be arranged between the second and third electromagnets above and below the guiding space 148. Such an arrangement of permanent magnets generates oppositely directed magnetic field lines 191 in the upper and the respective lower areas between the poles of the first, second, and third electromagnets, as it is schematically depicted in FIG. 5A and FIG. 5B.

[0083] In the first control state (I) that is schematically depicted in FIG. 5 A, the set of permanent magnets 175 generates magnetic field lines 191 having essentially same directions as the magnetic field lines 192 generated by the first and second electromagnets (and the optional third electromagnet) in upper areas 178 of the guiding space. Accordingly, an upwardly directed magnetic force acts on the first magnetic unit 14 in the upper areas 178 of the guiding space (see the three upper areas 178 that are encircled in FIG. 5A for illustration purposes). Further, the set of permanent magnets 175 generates magnetic field lines 191 having essentially opposite directions to the magnetic field lines 192 generated by the first and second electromagnets (and the optional third electromagnet) in the lower areas of the guiding space. Accordingly, no net magnetic force or only a small net magnetic force acts on the first magnetic unit 14 in the lower areas of the guiding space (see respective oppositely directed arrows in the lower areas in FIG. 5 A). Hence, the carrier is pulled upwardly in FIG. 5 A.

[0084] In the second control state (II) that is schematically depicted in FIG. 5B, the set of permanent magnets 175 generates magnetic field lines 191 having essentially same directions as the magnetic field lines 192 generated by the first and second electromagnets (and the optional third electromagnet) in the lower areas 179 of the guiding space. Accordingly, a downwardly directed magnetic force acts on the first magnetic unit 14 in the lower areas 179 of the guiding space (see the three lower areas 179 that are encircled in FIG. 5B for illustration purposes). Further, the set of permanent magnets 175 generates magnetic field lines 191 having essentially opposite directions to the magnetic field lines 192 generated by the first and second electromagnets (and the optional third electromagnet) in the upper areas of the guiding space. Accordingly, no net magnetic force or only a small net magnetic force acts on the first magnetic unit 14 in the upper areas of the guiding space (see respective oppositely directed arrows in the upper areas in FIG. 5B). Hence, the carrier is pulled downwardly.

[0085] Accordingly, a bi-directional magnetic stabilization unit is provided that can switch between an upwardly directed force and a downwardly directed force exerted on the carrier by inverting the poles of the at least one electromagnet 141, particularly by inverting the poles of each of first, second, and optional third (or further) electromagnets. Further, the stabilization force can be controlled by controlling the current that flows through the at least one electromagnet 141, particularly through the first, second, and optional third electromagnets. One or more stabilization units arranged along the transport direction T at predetermined intervals therebetween at one vertical coordinate and having one common controller or a respective number of controllers is sufficient for bi-directionally stabilizing the carrier in the vertical direction. Accordingly, a simple and reliable arrangement is provided according to embodiments described herein.

[0086] The first electromagnet, the second electromagnet, and the optional third electromagnet may be controlled via the same control circuit and be connected to the same controller. Specifically, the same current (or currents that are varied in a corresponding way) may flow through the first, second, and third coils during the carrier transport in alternate directions, as it is schematically depicted in FIG. 4, such that the magnetic field of the second electromagnet is inverse to the magnetic field of the first and third electromagnets.

[0087] The magnetic stabilization unit may be configured to generate a maximum magnetic stabilization force of +/-400 N or less, particularly +/-300 N or less, more particularly about +/-200 N.

[0088] FIG. 6 is a block diagram that illustrates a method for contactlessly transporting a carrier in a transport direction T along a track assembly, e.g. through a vacuum chamber of a vacuum deposition system. The transport method may be carried out with a carrier transport system as described herein that contactlessly holds a carrier as described herein, such that reference can be made to the above explanations, which are not repeated here. [0089] In box 610, a carrier levitation force is generated with a passive magnet arrangement that counteracts the weight force of the carrier. The passive magnet arrangement may include a first permanentmagnetic levitation unit 121 arranged at a second vertical coordinate V2, and optionally a second permanentmagnetic levitation unit 122 arranged at a fourth vertical coordinate V4.

[0090] In box 620, a predetermined vertical positioning of the carrier in a carrier transportation space is stabilized by exerting a magnetic stabilization force on the carrier. The magnetic stabilization force is exerted on the carrier with an actively controlled, bidirectional magnetic stabilization unit 140 as described herein that is able to exert the magnetic stabilization force on the carrier in the upward direction and in the downward direction. In a first control state (I), an upwardly directed magnetic stabilization force is exerted on the carrier, e.g. if it is detected that the carrier position is too low and/or that the carrier is sinking downwardly. In a second control state (II), a downwardly directed magnetic stabilization force is exerted on the carrier, e.g. if it is detected that the carrier position is too high and/or that the carrier is rising upwardly. The position of the carrier may be controlled in a closed loop control.

[0091] In box 630, the carrier is moved in the transport direction T along the track assembly with a drive unit arranged at a third vertical coordinate V3, particularly with a linear motor that exerts a magnetic transport force FT on the carrier.

[0092] The levitation of box 610, the stabilization of box 620, and the movement of box 630 may happen simultaneously, enabling a smooth and stable contactless carrier transport in a vacuum system with a compact magnetic levitation system including an active control that is not negatively affected by thermally caused deformations of the carrier.

[0093] In some embodiments, which can be combined with other embodiments, the carrier is essentially vertically oriented during the transport. A distance between the first vertical coordinate VI and the second vertical coordinate V2 may be larger than a distance between the first vertical coordinate VI and the third vertical coordinate V3. The gap width between the linear motor 150 and the third magnetic unit 16 can therefore be accurately maintained through the control by the magnetic stabilization unit (e.g., maintaining a gap width of 3 mm or less), even if the head part of the carrier should “extend away” from the bottom part due to thermally induced deformations.

[0094] During the carrier levitation and transport, (i) the carrier levitation force FL exerted by the passive magnet arrangement, (ii) the weight force of the carrier, and (iii) a vertical force component Fc exerted on the carrier by the drive unit add up to essentially zero during the carrier transport, such that the average magnetic stabilization force Fs exerted by the magnetic stabilization unit 140 on the carrier is essentially zero as well because the stabilization force fluctuates around a net force of zero. This allows the magnetic stabilization unit to be compact and comparatively small.

[0095] In some implementations, the carrier and the substrate that is carried by the carrier are oriented essentially vertically. The substrate may be a large-area substrate having a surface area of 1 m ² , particularly 3m ² or more. The carrier may have a vertical dimension of 1 m or more, particularly 2 m or more.

[0096] The first permanentmagnetic levitation unit 121 may magnetically interact with a head part of the carrier, the magnetic stabilization unit 140 may magnetically interact with a bottom part of the carrier, and the drive unit 150 may interact with the bottom part of the carrier.

[0097] While the foregoing is directed to embodiments, other and further embodiments may be devised without departing from the basic scope, and the scope is determined by the claims that follow.