SLIT VALVE DOOR ASSEMBLY

Related Application This application claims the benefit of U.S. Provisional Application No.

60/829,258 filed October 12, 2006, which is hereby incorporated herein by reference.

Field of the Invention The present invention relates generally to seal assemblies for valves and more particularly to slit valve door seal assemblies having particular use in forming a seal between chambers in vacuum equipment employed in the semiconductor industry for chip manufacture.

Background of the Invention

Vacuum systems for manufacturing integrated circuits on wafers are generally known. A vacuum processing system may typically have a centralized vacuum chamber, called a transfer chamber, which may be part of a mainframe, for transferring wafers from one process chamber or load lock chamber to the next. A vacuum processing system may also typically have some kind of subsystem, such as a mini-environment, for providing the wafers to the load locks and other chambers and for collecting them back in order to send them on to the next system for processing. This transfer chamber plus the peripheral chambers and staging areas are sometimes called a cluster tool. Between two vacuum chambers, such as the transfer chamber and one of the process chambers, is a slit valve. The slit valve includes an elongated rectangular opening for providing physical access between the two vacuum chambers. For example, when the slit valve is open, a robot in the transfer chamber may retrieve a wafer from one vacuum chamber and insert it into another vacuum chamber using a long, thin blade to hold the wafer.

After the wafer has been inserted into a vacuum chamber, the slit valve may be closed and sealed with a slit valve door. The slit valve door usually forms an airtight seal for the slit valve so that the pressure differential between

the two chambers will not cause a gas leak through the slit valve. A metal insert may be placed within the slit valve opening in order to form a better airtight seat for the slit valve door.

Slit valve doors have typically been made of metal. The metal-to-metal contact between a slit valve door and the metal insert may provide a very good seal, but metal-to-metal contact may create microscopic particles that scrape off of the metal and get into the otherwise relatively clean environment of the vacuum chambers. Such particles may land on the wafers in the chambers, thereby contaminating them. Such contamination is undesirable in the processing of wafers.

To reduce the contamination by particles from the slit valve, an O-ring has typically been placed in a groove in the slit valve door. Thus, metal-to-metal contact is avoided, so no particles are thereby generated, and the O-ring provides a satisfactory seal for the slit valve. Since the seal between the O-ring and the slit valve is not static, but rather is constantly being opened and closed such that there is rubbing and abrading on the O-ring from the slit valve insert, some particle generation, typically from the O-ring, still may occur.

A further problem with the O-rings used in the slit valve doors has been that the O-rings may stick to the slit valve seat, so that when the door opens, the O-ring may be partially pulled out of the dovetail groove, which can damage the O-ring, cause particle generation, and require early servicing of the chamber. Additionally, the amount of squeeze on the O-ring when metal-to-metal contact occurs can destroy the O-ring in short order due to over-compression and extrusion.

U.S. Patent No. 6,089,543 discloses a two piece slit valve door comprising a seal plate mounted on a mounting member. The seal plate, which actually contacts the slit valve, has a molded-in-place seal for making the contact and preventing metal-to-metal contact between the door and the valve. The seal may have a parabolic profile and may be adhesively bonded within a groove in the seal plate.

Semiconductor manufacturing processes, such as etch and deposition processes, utilize a wide variety of processing gases and substrate materials. Highly volatile process byproducts are typically removed from the processing chamber by application of vacuum. Less volatile byproducts may adhere to the interior surface of the processing chamber or may redeposit on the surface of the semiconductor substrate being processed. Most semiconductor manufacturers prefer to have redepositing byproducts deposit on processing chamber surfaces (rather than the substrate). The processing chamber surfaces are then periodically cleaned. Frequent chamber cleanings are expensive in terms of processing chamber downtime. The more redeposited byproducts which can be held by the processing chamber surfaces, the less frequent the cleaning requirement.

Interior surfaces of semiconductor processing chambers are frequently aluminum. One prior art semiconductor processing chamber includes anodized aluminum surfaces which have been lapped to have a surface roughness of only 4 Ra, which is essentially a mirror finish.

During semiconductor processing procedures, byproducts can be formed that are not sufficiently volatile to be removed by the vacuum system of the processing chamber. In many instances, it is desirable to provide a surface inside the processing chamber on which these byproducts are capable of adhering, so that they will not fall upon semiconductor workpieces during processing, causing contamination.

One method of improving the adhesion of semiconductor processing byproducts to an aluminum surface within a semiconductor processing chamber is to provide a roughened surface to which byproducts generated during processing can stick. Typically, aluminum semiconductor chamber surfaces have been roughened by bead blasting.

The provision of a slit valve door with a molded-in-place seal and bead- blasted or otherwise treated door surface presents a manufacturing challenge, since the surface treatment may damage a previously molded-in-place seal or the molding of the seal can damage a previously processed door surface. Consequently, care would have to be taken to protect a previously molded seal

during surface processing or protect the processed surface during molding of the seal.

Another issue is controlling the size of the gap between the door and chamber to eliminate dynamic metal-to-metal scrubbing of the door to the chamber. Limiting the size of this gap protects the seal from excessive exposure to the harsh chemicals that are used. This can involve tedious adjustment of the door.

Summary of the Invention The present invention provides a slit valve door assembly comprising a door having a recess in a front face and an annular seal peripherally bounding the recess, and an insert disposed in the recess and having a front face processed separately from the door.

The door and insert may be manufactured separate from one another. During manufacture, the door may undergo various process steps utilizing different tools in order, for example, to effectively vulcanize the seal into the door. Such procedures can be performed even if they would have been detrimental to the insert surfaces that may be sensitive to abrasion, staining and/or contamination, inasmuch as the insert can be processed separately. Manufacture of the insert as a separate piece also removes the insert from exposure to the labor intensive vulcanization process which may damage the sensitive surfaces of the insert. Likewise, the seal and door need not be exposed to processes and treatments applied to the insert, such as those used to form the typically hard anodized and polished peripheral surface region of the front face of the insert, or the roughening, for example by bead blasting, of the central region or pocket on the face of the insert.

Subsequently, the insert may be assembled to the door, as by bonding the insert in the recess in the door using a suitable bonding agent. The insert can be adjusted relative to the door for precisely controlling the size of a gap with an opposing sealing surface that protects the seal from excessive exposure to harsh chemicals. The insert may be adjusted in a direction perpendicular to its front face to vary the position of such surface relative to the front face of the

door. The insert can then be secured at such adjusted position, as by means of an adhesive or any other suitable means, such as set screws. Preferably the insert is closely constrained laterally in the recess in the door, such that the primary adjustment direction is perpendicular to the front face of the insert. The front face of the insert may have a peripheral smooth region surrounding a roughened central region of the front face.

The insert may be removably secured in the recess.

The insert may be bonded to the door.

The slit valve door assembly may be used in combination with a slit valve having an opposed sealing surface against which the annular seal sealingly engages when the door is closed.

The front face of the insert may have a peripheral region forming a gap with the opposed sealing surface.

The insert may be adjustable in the door to vary the size of the gap. The peripheral region of the front face of the insert is a polished surface.

The front face of the insert may have a central roughened region.

The annular seal may be vulcanized in an annular groove in a front face of the door.

The annular seal may be closely laterally spaced from the insert. According to another aspect of the invention, an insert for a slit valve door assembly has a front face with a peripheral polished region surrounding a pocket region.

The pocket region may have a roughened surface.

According to a further aspect of the invention, a method of forming a slit valve door assembly, comprises forming a door with a recess in a front face thereof and an insert separately from one another, and then assembling the insert into the recess.

The door and insert may be subjected to different processes.

An annular seal may be vulcanized to the door prior to assembly of the insert into the recess.

The insert may be adjustably positioned in the door to provide a desired gap when the door is closed against a slit valve surface.

The foregoing and other features of the invention are more particularly described in the following detailed description when considered in conjunction with the drawings.

Brief Description of the Drawings

In the annexed drawings:

Fig. 1 is a top schematic view of a prior art vacuum system including a transfer chamber and a lid;

Fig. 2 is a perspective view of a transfer chamber with the lid off; Fig. 3 is a plan view of the face of a seal plate;

Fig. 4 is a perspective view of an exemplary slit valve door assembly according to the invention;

Fig. 5 is a perspective view, partly shown in cross-section, of the slit valve door assembly of Fig. 4; and Fig. 6 is a cross-sectional view of the slit valve door assembly shown in closed relationship to a mating sealing surface of a slit valve.

Detailed Description

Referring now in detail to the drawings and initially to Fig. 1 , an exemplary prior art vacuum processing system is generally indicated at 10. The system 10 comprises a series of vacuum chambers 14 attached to a central vacuum transfer chamber 12. A pair of vacuum load lock chambers 16 provide a passageway to a mini-environment 18. Pod loaders 20 are shown attached to the mini-environment 18. This system is an example of a cluster tool. The vacuum chambers 14 may be connected to the transfer chamber 12 at an airtight seal which permits wafers to pass between the chambers 12, 14 and 16 without losing the vacuum in the chambers. The pod loaders 20 are attached to the mini-environment 18 and may be loaded with wafer cassettes (wafer holders) by a person or by an automated machine that is part of the over-all automated manufacturing system of the manufacturing plant or building that houses the vacuum processing system 10. A robot (not shown) within the mini-environment 18 may move the wafers or cassettes from the pod loaders 20

to the load lock chambers 16 and back again. A robot (not shown) with an arm and a blade for moving wafers within transfer chamber 12 may move the wafers from one of the load lock chambers 16 to the process chambers 14 and back to one of the load lock chambers 16. The vacuum chambers 14 may be any of several types of process chambers, such as a chemical vapor deposition (CVD) chamber, a physical vapor deposition (PVD) chamber, an etch chamber, etc., for performing on a wafer some type of process in a series of many processes for manufacturing integrated circuits on wafers. In Fig. 2 the transfer chamber 12 is shown with its lid removed so that the interior of the transfer chamber 12 is visible. Several slit valves with openings 24 can be seen, as can slit valve inserts 28, 30, 32 and 34. Circular opening 36 supports a robot with an arm for moving wafers inside the transfer chamber 12, but the robot is not shown in this drawing so other details of the transfer chamber 12 may be visible. Openings 38 provide access for an actuating cylinder for manipulating a slit valve door, the face of which is shown in Fig. 3. The actuating cylinder and the slit valve door are not shown so that other features in the transfer chamber 12 may be visible. An example of a slit valve door and actuating cylinder is shown and described in U.S. Pat. No. 5,226,632, which is incorporated herein by reference.

Fig. 3 shows the front face plate of the slit valve door 40. On front face 48 of seal plate 42 is a molded-in-place seal 50 for contacting with a slit valve insert 28, 30, 32, 34, or a seat portion formed thereon. The molded-in-place seal 50 is molded into a groove 58 formed around the periphery of front face 48. The seal may be vulcanized to the seal plate 42. Thus, in the manufacturing of seal plate 42, the seal 50 may be permanently attached to the seal plate 42. The seal 50 may be adhesively bonded to the metal surface of groove 58.

The molded-in-place seal 50 helps overcome problems associated with O-ring seals on slit valve doors, such as short seal life, poor sealing, particle generation, and O-ring extraction. It also eliminates problems with metal-to-metal contact, seal/door gland abrasion, O-ring retention, and O-ring installation.

The slit valve door 40 may be actuated in a direction perpendicular to the plane in which its front face 48 is held by an actuating cylinder that protrudes out of opening 38. The seal 50 may match angular face 54 of the inner portion 31 of insert 28. The actuating cylinder protruding out of opening 38 pushes slit valve door 40 up against slit valve insert 28 such that the molded-in-place seal 50 engages surface 54 making an airtight seal all around opening 56. Thus, when slit valve opening 24 is closed by slit valve door 40, the pressure in either the transfer chamber 12 or the process chamber 14 may change as needed without leakage between the two chambers. Referring now to Figs. 4-6, a valve door assembly according the present invention is designated generally by reference numeral 60. Fig. 6 is a sectional view taken along the plane 62 in Fig. 4. The valve door assembly comprises a door 64 and a door insert 66 secured in a recess 68 in the front face 70 of the door. The assembly further comprises an annular seal 72 that preferably is molded into an annular groove 74 in the front face of the door. The molded-in-place seal 72 may have a bottom contour that matches the contour of the groove 74 as best seen in Fig. 6. As shown, the groove may have upwardly curving edges or sides that end almost vertical, or perpendicular, to front face 70. The groove surface may have a suitable roughness to enhance the adhesion between the seal material and the groove.

The seal 72 may be made of any suitable material that preferably does not generate many, if any, particles under the dynamic loading experienced by the seal, such as a variety of fluorocarbon and perfluoro elastomers that suit the requirements of wafer processing. Suitable seal materials are well known in the art. The seal may additionally or alternatively be bonded to the door by use of a suitable bonding agent.

The seal may have the cross-sectional shape illustrated in Figs. 5 and 6. In Fig. 6, the seal 72 would normally be compressed between the opposed/mating sealing surface 80 of the slit valve and the front face 70 of the door. Thus, the configuration would be different than that schematically depicted in Fig. 6. For instance, the seal may undergo compression as described in U.S. Patent No. 6,089,543, which is hereby incorporated herein by

reference. It is noted that a gap 82 (Fig. 6) will be formed between the opposing sealing surfaces 70 and 80.

In accordance with the invention, a portion of the door assembly interiorly of the seal is formed by the insert 66, that typically will be made of metal such as aluminum. As is preferred, the outer peripheral edge of the insert is spaced closely inwardly from the seal 72 as shown in Fig. 6. This spacing may be on the same order of size as the gap 82.

The front face of the insert 66 may be processed to provide a lapped/polished surface 86 that is overlapped by the opposing surface 80 to form the gap 82, or at least that portion of the gap interiorly of the seal 72. Alternatively or additionally, the insert may have a roughened surface 88 to which byproducts generated during processing can stick. The roughened surface 88 may form a shallow pocket 90 in the front face of the insert, and may be peripherally bounded by the lapped or gap-forming surface. As will be appreciated, the door 64 and insert 66 may be manufactured separate from one another. During manufacture, the door may undergo various process steps utilizing different tools in order, for example, to effectively vulcanize the seal into the door. Such procedures can be performed even if they would have been detrimental to the insert surfaces that may be sensitive to abrasion, staining and/or contamination, inasmuch as the insert can be processed separately. Manufacture of the insert as a separate piece also removes the insert from exposure to the labor intensive vulcanization process which may damage the sensitive surfaces of the insert.

Likewise, the seal 72 and door 64 won't be exposed to processes and treatments applied to the insert, such as those used to form the typically hard anodized and polished peripheral surface region 86 of the front face of the insert, or the roughening, for example by bead blasting, of the central region or pocket 90 on the face of the insert.

Subsequently, the insert may be assembled to the door, as by bonding the insert in the recess in the door using a suitable bonding agent. A suitable bonding agent should be resistant to the conditions to which the door assembly will be exposed. Preferably, the door is removably assembled in the door such

that it can be replaced without having to replace the entire door, or cleaned separately from the door.

A further benefit is that the insert can be adjusted relative to the door for precisely controlling the size of the gap 82 which protects the seal from excessive exposure to harsh chemicals. The insert may be adjusted in a direction perpendicular to its front face to vary the position of such surface relative to the front face of the door. The insert can then be secured at such adjusted position, as by means of an adhesive or any other suitable means, such as set screws. Preferably the insert is closely constrained laterally in the recess in the door, such that the primary adjustment direction is perpendicular to the front face of the insert.

Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a "means") used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.