Rotary indexer with additional rotation axis

Abstract

A rotary indexer is provided that can be rotated to move semiconductor wafers or other items between various stations arranged in a circular array; during such movement, the items being moved can be supported by the arms of the indexer. The rotary indexer can be further configured to also rotate the items being moved about other rotational axes to cause rotation of the items relative to the arms supporting them.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to U.S. Application No. 15 / 867,599, filed on January 10, 2018, entitled “ROTATIONAL INDEXER WITH ADDITIONAL ROTATIONAL AXES,” which is incorporated herein by reference for all purposes. Background Art

[0003] Some semiconductor processing tools process multiple wafers simultaneously in a common chamber and use a rotary indexer to move the wafers between processing stations in the chamber. In such semiconductor processing tools, the processing stations may generally be arranged so that the wafer center points are equally spaced along a circular path. A rotary indexer comprising a central hub and a plurality of arms radiating outward from the central hub may be used to move the wafers between stations; the ends of the arms may have some form of wafer support that may be used to support the wafers moved by the indexer. Using such a device to move wafers between stations is referred to as "indexing" the wafers. Typically, the number and angular spacing of the arms on the indexer will correspond to the number and angular spacing of the processing stations around the center point of the circular path. For example, in a four-station chamber, there may be four arms on the indexer, each at a 90° angle to the adjacent arm. The wafer may be placed on the arms, and the central hub and the arms connected thereto may be rotated as a unit around the center point of the circular path to move the wafer between stations. Summary of the invention

[0004] The details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, drawings, and claims.

[0005] In some embodiments, a device may be provided, comprising a base, a first motor, a second motor, and a first hub. The first motor may be configured to rotate the first hub around a central axis of the first hub and relative to the base, and the device may further comprise N indexer arm assemblies, each indexer arm assembly comprising a) a wafer support and b) an indexer arm having a proximal portion connected to the first hub and a distal portion rotatably connected to the wafer support. Each wafer support may be configured to rotate around a rotation axis of the wafer support relative to the indexer arm supporting it. N may be selected so that there are two or more indexer arm assemblies. The device may further comprise an actuating mechanism, the actuating mechanism may be configured to be actuated by the second motor, and may be further configured to rotate the wafer support of the indexer arm simultaneously around a corresponding rotation axis of the wafer support and relative to the indexer arm in response to rotation of the first motor, the second motor, or the first motor and the second motor.

[0006] In certain embodiments of the apparatus, the actuation mechanism may include a second hub configured to rotate about the central axis of the first hub in response to actuation of the second motor, and each indexer arm assembly may further include a pull rod having a proximal portion rotatably connected to the second hub via a first rotatable interface and a distal portion rotatably connected to the wafer support of the indexer arm assembly via a second rotatable interface. In such embodiments, the actuation mechanism and indexer arm assembly may be configured such that relative rotation between the first hub and the second hub about the first central axis causes the pull rod to translate in a generally radial manner relative to the first central axis, thereby causing each pull rod to rotate the wafer support to which the pull rod is rotatably connected to rotate relative to the indexer arm and about the rotation axis of the wafer support.

[0007] In some embodiments of the device, the first hub and the second hub can be configured to be rotatable relative to each other from a first relative rotational position to a second relative rotational position.

[0008] In some embodiments of the apparatus, the indexer arm, the pull rods, and the wafer support may be made of ceramic material.

[0009] In some embodiments of the device, each indexer arm assembly may include a third rotatable interface, which rotatably connects the wafer support for the indexer arm assembly with the indexer arm of the indexer arm assembly, and the first rotatable interface, the second rotatable interface and the third rotatable interface may all be ceramic ball bearings.

[0010] In some embodiments of the apparatus, there may be four indexer arm assemblies. Additionally, each of the wafer supports may be in a third relative rotational position relative to the first hub when the first hub and the second hub are in the first relative rotational position, and in a fourth relative rotational position relative to the first hub when the first hub and the second hub are in the second relative rotational position; in such embodiments, the third relative rotational position and the fourth relative rotational position may be 90° out of phase with each other.

[0011] In some embodiments of the device, the device may include a stop mechanism configured to limit relative rotational movement between the first hub and the second hub to between 90° and 95°.

[0012] In some embodiments of the device, the proximal end of each pull rod may have a highest surface directly above the first rotatable interface of the pull rod, each first rotatable interface may be horizontally spaced a first distance from the nearest other first rotatable interface, each pull rod may include an offset region extending between a first longitudinal distance from the rotation center of the first rotatable interface of the pull rod and a second longitudinal distance from the rotation center of the first rotatable interface of the pull rod, the first longitudinal distance may be less than the first distance and the second longitudinal distance may be greater than the first distance, and the offset region of each pull rod may have a lowest surface that is higher than the highest surface of the distal end of the pull rod from the adjacent indexer arm assembly, thereby allowing the distal end of the pull rod from the adjacent indexer arm assembly to pass under the pull rod when the first hub and the second hub are in the first relative rotational position.

[0013] In some embodiments of the apparatus, each of the wafer supports may be in a third relative rotational position relative to the first hub when the first hub and the second hub are in the first relative rotational position, and in a fourth relative rotational position relative to the first hub when the first hub and the second hub are in the second relative rotational position; in such embodiments, the third relative rotational position and the fourth relative rotational position may be 360° / N out of phase with each other.

[0014] In some embodiments of the device, the hub may include a separate mounting interface for each indexer arm assembly, each mounting interface may include a tensionable interface and three tapered recesses arranged around the tensionable interface. A sphere may be nested in each tapered recess, and each indexer arm may include a hole through which the tensionable interface protrudes, and the three recesses radiate outwardly relative to the hole. Each sphere of the corresponding mounting interface may also be nested in a corresponding recess of the indexer arm, and the tensionable interfaces may each be configured to compress the sphere between a corresponding one of the indexer arms and a corresponding one of the mounting interfaces.

[0015] In some embodiments of the device, the tensionable interface associated with each indexer arm can include a threaded component and a spring configured to press the indexer arm against the ball between the indexer arm and the mounting interface connecting the indexer to the first hub when the threaded component is tightened and in tension.

[0016] In some embodiments of the device, the device may further include a motor housing that accommodates the first motor and the second motor and supports the first hub via a first hub rotation interface, and may also include a z-axis drive system that is configured to cause the motor housing to translate along the vertical axis in response to actuation of the z-axis drive system.

[0017] In some embodiments of the apparatus, the apparatus may further include a semiconductor processing chamber housing having N processing stations, each processing station including a pedestal configured to support a semiconductor wafer.

[0018] In some embodiments of the apparatus, the processing station may be configured to perform a semiconductor processing operation selected from the group consisting of a deposition operation, an etching operation, a curing operation, and a thermal treatment operation.

[0019] In some embodiments of the apparatus, the apparatus may further include a controller having a memory and one or more processors. The memory and the one or more processors may be communicatively connected, the one or more processors may be configured to control the first motor and the second motor, and the memory may store computer executable instructions for controlling the one or more processors to selectively actuate the first motor, the second motor, and one or more of the first motor and the second motor to cause: the first hub and the indexer arm assembly to rotate so that each wafer support moves from a corresponding one of the processing stations to an adjacent one of the processing stations; a first relative rotational motion between the first hub and the second hub so that during movement between processing stations, the wafer support moves between the first and second hubs; each wafer support rotates a first amount in a first direction about the rotation axis of the wafer support and relative to the first hub while the wafer support resides at each processing station, or during movement between processing stations and while the wafer support resides at each processing station; and a second relative rotational motion between the first hub and the second hub such that each wafer support rotates a first amount in a second direction opposite to the first direction about the rotation axis of the wafer support and relative to the first hub while the wafer support resides at each processing station, or during movement between processing stations and while the wafer support resides at each processing station.

[0020] In some embodiments of the apparatus, N may be equal to 4, and the memory may store additional computer executable instructions for controlling the one or more processors to cause the first motor to rotate the first hub 90° in the first direction while the second hub remains stationary.

[0021] In some embodiments, a method can be provided, the method comprising: a) picking up a plurality of wafers from a corresponding plurality of pedestals using an indexer having a corresponding plurality of wafer supports, each wafer support rotatably mounted to a distal end of an indexer arm of the indexer, and each indexer arm mounted to a hub of the indexer, wherein the wafer is supported by the wafer support; b) rotating the hub and the indexer arm about a first rotational axis to move each wafer support from a position above each of the pedestals to a position above an adjacent one of the pedestals; c) placing the wafer on the pedestal after (b); and d) rotating the wafer support relative to the indexer arm and about the rotational axis of the wafer support between (a) and (c).

[0022] In some embodiments of the method, the indexer may have four indexer arms, and (b) may include rotating the hub and the indexer arms 90°, and (d) may include rotating the wafer support 90° relative to the indexer arms.

[0023] Other features, aspects, and advantages will become apparent from the description, drawings, and claims.Please note that the relative dimensions of the following drawings may not be drawn to scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Various embodiments disclosed herein are illustrated by way of example and not limitation in the figures of the accompanying drawings in which like reference numerals refer to similar elements.

[0025] FIG. 1 is a schematic diagram illustrating rotation of a wafer in a conventional rotary indexer.

[0026] Figure 2 is a schematic diagram illustrating wafer rotation supported by a rotary indexer having an additional axis of rotation as discussed herein.

[0027] Figure 3 Depicted is a top view of a portion of an exemplary semiconductor processing tool having a rotary indexer, which is an example of one type of rotary indexer discussed herein.

[0028] Figure 4 Depicted Figure 3 A partially exploded perspective view of an exemplary rotary indexer of FIG.

[0029] Figure 5 Depicted Figure 3 Another partially exploded perspective view of an exemplary rotary indexer of FIG.

[0030] Figure 6 Depicted Figure 3 A side cross-sectional view of an exemplary rotary indexer.

[0031] Figure 7 Depicted Figure 3 Detail view of the center of an exemplary rotary indexer with some additional components removed.

[0032] Fig. 9 Depicted is a detailed top view of a portion of an exemplary second hub and tie rod, showing the overlap between the two tie rods in a particular configuration.

[0033] Figure 8 Depicted is a detailed top view of another exemplary second hub and portion of a tie rod, illustrating an alternative tie rod design.

[0034] Fig.10 Depicted Figure 3 A partially exploded perspective view of an exemplary rotary indexer of FIG. 1 , showing the bottom side of the exemplary rotary indexer.

[0035] Figures 11-A to 11-EThe various actuation states of the rotatable wafer support at the distal end of the indexer arm are shown. Figure 3 An exemplary rotary indexer of .

[0036] Fig.12 A partial cross-sectional view of an exemplary rotary indexer having internal purge gas flow passages is depicted.

[0037] Fig.13 is a flow chart of an exemplary technique for operating a rotary indexer according to some examples described herein.

[0038] Fig.14 Describes the use Figure 3 System diagram of an exemplary controller for a rotary indexer.

[0039] Figures 3 to 12 Each of the figures is drawn to scale, although the scale varies from figure to figure. The drawings depict only examples of the concepts discussed herein, and it will be readily appreciated that the concepts discussed herein may be implemented in numerous alternative embodiments, all of which are considered to be within the scope of the present disclosure. DETAILED DESCRIPTION

[0040] Importantly, the concepts discussed herein are not limited to any single aspect or embodiment discussed herein, nor are they limited to any combination and / or permutation of such aspects and / or embodiments. Moreover, each aspect of the present invention and / or its embodiments may be used alone or in combination with one or more other aspects and / or its embodiments. For the sake of brevity, many of these permutations and combinations will not be discussed and / or illustrated separately herein.

[0041] The rotary indexers disclosed herein with additional axes of rotation differ from conventional rotary indexers in that they have an additional degree of rotational freedom at the distal ends of the indexer arms. For example, in conventional indexers, the only rotation provided is that of the entire hub / arm structure about the central axis of the indexer—as a result, as the hub / arm structure rotates, the items carried at the ends of each arm rotate in the same manner about the same axis of rotation. This allows items such as semiconductor wafers to maintain the same orientation relative to the axis of rotation—for example, the same portion of each item will always be closest to the central axis of rotation.

[0042] This can be seen in FIG. 1 , which is a schematic diagram illustrating the rotation of wafers in a conventional rotary indexer. Three indexer positions are shown—a starting position at the top, an intermediate position in the middle, and an ending position at the bottom (this is a single set of wafer movements from the position shown at the top to the position shown at the bottom). Each wafer 108 has a short line / mark at the outermost edge; the indexer 102 is then rotated, and all four wafers 108 are rotated about the axis of rotation of the indexer 102. As a result, the edge of the wafer 108 with the line / mark remains the edge of the wafer farthest from the axis of rotation of the indexer 102 throughout the rotational motion. In other words, the orientation of each wafer relative to the arm supporting it remains unchanged.

[0043] However, an indexer according to the present disclosure is capable of providing additional degrees of rotational movement such that the orientation of the wafer relative to the arm can be changed during, before, and / or after the rotational movement of the indexer. As a result, the edge of the wafer or portion of that edge that is closest to the indexer's axis of rotation can be changed so that a different side of the wafer can be closest to the indexer's center of rotation at each station. Thus, such an indexer can not only "index" a wafer between different positions, but can also "rotate" the wafer during, before, or after such "indexing" movement.

[0044] This can be Figure 2 Seen in Figure 2 is a schematic diagram showing wafer rotation supported by a rotary indexer having an additional axis of rotation as discussed above and elsewhere herein. Figure 2 1, there are three positions of the rotating indexer 202, and the wafers 208 shown. From the highest position, it can be seen that the short lines / marks along the outer edge of the wafer 208 are all farthest from the center of rotation of the indexer 202, and are generally aligned with the arms of the indexer 208. In the intermediate position, the indexer 202 has been rotated 45° clockwise, but the wafers 208 have also been rotated the same amount in the counterclockwise direction. As a result, the orientation of each wafer 208 relative to the arm supporting it changes, with the wafer 208 being rotated 90° relative to the arm in the lower position. This results in the same Figure 2 The top position in FIG. 2 is farthest from the center of rotation of the indexer 202 than the different edges of the wafer 208 .

[0045] Figure 3 Depicted is a top view of a portion of an exemplary semiconductor processing tool having a rotary indexer, which is an example of the rotary indexers discussed herein. Figure 3, a semiconductor processing tool 300 is shown having a processing chamber 306 containing four semiconductor processing stations 304, each having a base 310. The semiconductor processing stations 304 are arranged in a radial or circular array around a central axis, and a rotary indexer 302 is provided, which is configured to rotate around the central axis. The rotary indexer 302 can have a plurality of indexer arms 340, for example, four indexer arms in this example, which are attached to a first hub 330 at a proximal end 342, so that when the first hub 330 is rotated around the central axis (see Fig.10 The distal end 344 of the indexer arm 340 may be provided with a wafer support 338, each of which may be configured to be rotatable relative to the indexer arm 340 supporting it and around a rotation axis located at the distal end 344 (such a rotation axis is located at the distal end 344). Figure 5 Each wafer support 338 may be configured to support a wafer 308 during movement of the wafer 308 between processing stations 304 (the wafer 308 is shown in dashed outline to allow components of the indexer arm to be more easily seen).

[0046] Figure 4 Depicted Figure 3 A partially exploded perspective view of an exemplary rotary indexer of FIG. Figure 4 As can be seen in FIG. 1 , one of the indexer arm assemblies 336 is shown in exploded form; the other indexer arm assemblies 336 are shown in their assembled state, as they would be arranged when secured to the first hub 330 (only one indexer arm assembly 336 is numbered). For reference, one of the indexer arm assemblies is shown supporting a wafer 308, which is shown as partially transparent and having dashed edges so as not to obscure the features of the indexer arm assemblies 336. Each indexer arm assembly 336 may include an indexer arm 340 having a proximal end portion 342 that is directly or indirectly connected to the first hub 330. Each indexer arm assembly 336 may also include a wafer support 338 rotatably mounted to a distal end portion 344 of the indexer arm 340. The wafer support may be, for example, a small plate or platform configured to support a semiconductor wafer. The wafer support 338 may be rotatable relative to the indexer arm 340 that supports it, about a rotational axis of the wafer support (eg, an axis passing through the center of the semiconductor wafer that the wafer support 338 is designed to support).

[0047] In general, the first hub 330 and the indexer arm assembly 336 attached thereto may be rotatable about the rotation axis of the first hub 330 to move the wafer 308 between stations. In addition to such rotation, the indexer 302 may also include an actuation mechanism that may be configured to simultaneously rotate all of the wafer supports 338 relative to the indexer arm 340 and about respective rotation axes located in the distal end 344 of the indexer arm 340. The actuation mechanism may further be configured to simultaneously rotate all of the wafer supports 338 in response to a single mechanical input. For example, a common rotating drive shaft located at the center of the rotary indexer 302 may be connected to a drive shaft extending along each indexer arm 340 via a bevel gear or other type of gear; each drive shaft may in turn cause the wafer support 338 to rotate in response to the rotation of the drive shaft. In an alternative embodiment, a flexible belt, such as a thin stainless steel belt, may be looped between pulleys attached to each wafer support 338 and a common rotating drive shaft so that rotation of the drive shaft relative to the indexer arm 340 causes the wafer support 338 to also rotate relative to the indexer arm 340.

[0048] In some embodiments, the actuation mechanism may utilize an array of movable tie rods to rotate the wafer support 338 relative to the indexer arm 340 . Figure 3 and Figure 4 The exemplary rotary indexer 302 in includes such a mechanism. Figure 4 3, the actuation mechanism of the rotary indexer 302 includes a second hub 332. The second hub 332 can be configured to rotate about an axis of rotation, which is the axis of rotation about which the first hub 330 is configured to rotate. The first hub 330 and the second hub 332 can be independently rotatable so that the first hub 330 and the second hub 332 can be placed in a variety of different angular orientations relative to each other.

[0049] In such an actuation mechanism, each indexer arm assembly 336 may further include a tie rod 346 extending along the length of the corresponding indexer arm 340. Each tie rod 346 may have a proximal end portion 348 rotatably connected to the second hub 332 via a first rotatable interface 356 and a distal end portion 350 rotatably connected to the corresponding wafer support 338 via a second rotatable interface 358 (see Figure 5 ). The first rotatable interface 356 and the second rotatable interface 358 can be positioned at a distance from the central axis 352 and the rotation axis 354, respectively, so as to define a moment arm about each axis. The rotation axis 354 can be, for example, the rotation axis of the third rotatable interface 360, which can rotatably couple the wafer support 338 to their respective indexer arms 340.

[0050] When relative rotational motion about the central axis 352 is induced between the first hub 330 and the second hub 332, the tie rods 346 move in a generally radial manner (with some tangential motion as the tie rods 346 move away from and then toward the adjacent indexer arm 340), which causes the wafer support 338 to which they are rotatably connected to rotate about the rotation axis 354 relative to the indexer arm 340 to which the wafer support 338 is attached. When there is no relative rotational motion between the first hub 330 and the second hub 332, then the wafer support 338 will remain in a fixed position relative to the indexer arm 340.

[0051] Thus, such a rotary indexer can be driven to provide: rotation of the wafer support 338 relative to the indexer arm 340 without any corresponding rotation of the indexer arm 340 (by rotating the second hub 332 while holding the first hub 330 stationary); rotation of the indexer arm 340 about the central axis 352 without any corresponding rotation of the wafer support 338 relative to the indexer arm 340 [by rotating the first hub 330 and the second hub 332 synchronously (by the same amount)]; and rotation of the indexer arm 340 about the central axis 352 with simultaneous rotation of the wafer support 338 relative to the indexer arm 340 (by rotating the first hub 330 asynchronously with the second hub 332, for example by rotating the first hub 330 about the central axis 352 while holding the second hub 332 stationary, or by rotating the first hub 330 and the second hub 332 about the central axis 352 at different rates).

[0052] In some embodiments, such as in the depicted example, the distance between each of the first rotatable interfaces 356 and the central axis 352 can be equal to the distance between each of the second rotatable interfaces 358 and the corresponding rotation axis 354, so that the moment arms defined by the tie rods 346 are the same. In such embodiments, the relative rotation between the wafer support 338 and the indexer arm 340 can be the same as the relative rotation between the first hub 330 and the second hub 332. Such an embodiment can be particularly effective because it allows each wafer to be maintained in the same absolute orientation (e.g., relative to the semiconductor processing tool) regardless of which processing station the wafer is moved to by the rotary indexer 302, as each wafer is transferred between stations by rotating only the first hub 330 while keeping the second hub 332 stationary.

[0053] Figure 6 Depicted Figure 3 A side cross-sectional view of an exemplary rotary indexer. Figure 6As shown, the rotary indexer 302 can include a base 312 that can be mounted in the semiconductor processing tool 300. The base 312 can house various systems that can be used to actuate the rotary indexer 302. For example, the base 312 can have a motor housing 322 that can house a first motor 318 and a second motor 320. The first motor 318 can be connected to the first hub 330 via a first shaft 314, and the second motor 320 can be connected to the second hub 332 via a second shaft 316. Therefore, the first motor 318 can be actuated to rotate the first hub 330, and the second motor can be actuated to rotate the second hub 332.

[0054] In some embodiments, the rotary indexer 302 may also be configured for vertical movement. For example, a z-axis drive system 324 may be provided to drive the motor housing 322, the first motor 318, the second motor 320, the first hub 330 and the second hub 332 vertically upward and downward, thereby causing the indexer arm 340 to move vertically. In some embodiments, the z-axis drive system 324 may include a third motor 3102 configured to rotate a threaded shaft 328 through a ball screw 326 attached to the motor housing 322, thereby causing vertical movement when the third motor 3102 is actuated.

[0055] In an embodiment having an actuation mechanism as discussed above, in which the wafer support 338 rotates relative to the indexer arm 340 about the axis 354 by the same amount that the first hub 330 and the second hub 332 rotate relative to each other, during such relative rotation between the first hub 330 and the second hub 332, the first rotatable interface 356 linking the pull rod 346 to the second hub 332 can be moved so as to be in the same position as the adjacent first rotatable interface was prior to such rotation. Figure 7 Depicted Figure 3 Detailed view of the center of an exemplary rotary indexer of (which is an example of such a rotary indexer) with some additional components removed, for example, the indexer arm assembly 336, the first hub 330 are removed, and various other components are omitted.

[0056] like Figure 7As shown, the tie rod 346 may further include an offset region 364. The offset region 364 may extend a certain distance along the length of the tie rod 346 (i.e., in the longitudinal direction). Each offset region 364 may be considered to start at a position that is a first longitudinal distance 368 away from the rotational center axis of the first rotatable interface 356 of the tie rod 346 of the offset region, and may be considered to end at a position that is a second longitudinal distance 370 away from the rotational center axis of the first rotatable interface 356 of the tie rod 346 of the offset region. Generally speaking, the first longitudinal distance 368 and the second longitudinal distance 370 may be selected to be smaller and larger than the first distance 366 between the rotational center axes of adjacent first rotatable interfaces 356, respectively. As shown in FIG. Figure 7 As shown, the first rotatable interface 356 is represented by a dashed outline and depicts the column 3100 connected to the missing first rotatable interface 356 (in this example, the first rotatable interface 356 is a rotatable bearing assembly, such as a ball bearing, roller bearing or other similar device).

[0057] Each offset region 364 can be configured such that during rotational movement as described above, i.e., when each first rotatable interface 356 is positionally advanced to the position last occupied by the adjacent first rotatable interface 356, the tie rod 346 of which the offset region 364 is a part does not contact or collide with the proximal end portion 348 of the adjacent tie rod 346. Thus, the tie rod 346 can include an inching or other deviation from the overall shape of the tie rod 346 in the offset region 364.

[0058] For example, in Figure 7 In the illustrated embodiment, the offset region 364 includes a lowermost surface 390 (at Figure 7 Not shown, but see Fig.10 ), which surface is located at a certain height, when the rotary indexer is positioned with the central axis 352 oriented vertically and the base 340 is below the indexer arm 340, the height is higher than the highest surface 362 of the proximal end portion 348 of the adjacent tie rod 346 directly above the first rotatable interface 356 of the adjacent tie rod 346. This allows the proximal end portion 348 of the tie rod 346 to pass under the offset area 364 of the adjacent tie rod 346 (the tie rods 346 do not have any contact with each other) when each first rotatable interface 356 is advanced in position to the position last occupied by the adjacent first rotatable interface 356. Figure 8 3 is a detailed view showing how the proximal end 348 of a tie rod 346 passes under the offset region 364 of another tie rod 346 .

[0059] The offset zone concept can also be used in a "horizontal" rather than a "vertical" way. For example, Fig. 9As can be seen, the offset region 864 is offset from the nominal centerline of the tie rod 846 (the dashed line in the figure) by a distance D, which can be selected so that the proximal end 848 of the adjacent tie rod 346 can move to the position shown without contacting the Figure 8 Tie rod 846 is shown having an offset region 864 .

[0060] The rotary indexer disclosed herein with an additional axis of rotation may be particularly advantageous when used in certain types of semiconductor processing equipment, For example, in a multi-station deposition or etch processing tool, there may be process non-uniformities in the wafer that are biased toward the center of the array of processing stations (e.g., toward the central axis 352).

[0061] If a conventional rotary indexer is used to move wafers between stations in such a semiconductor processing tool, the wafer may experience such non-uniformity in the same manner at each processing station, as the same edge of the wafer is closest to the central axis 352 at each station. However, if a rotary indexer having such an additional axis of rotation is used to move wafers between stations in such a semiconductor processing tool as disclosed herein, the wafer may be rotated between stations such that a different edge of the wafer, or portion of the edge, may be closest to the central axis 352 at each station. This may help eliminate or mitigate the non-uniformity, thereby improving wafer processing quality.

[0062] If the rotary indexer with additional rotation axes discussed herein is used in certain circumstances, such as in a deposition or etching process semiconductor processing tool, it may be advantageous to include other features in addition to the above features in certain such circumstances. For example, in some embodiments, the indexer arm 340, the pull rod 346, and / or the wafer support 338 may be made of a ceramic material (e.g., alumina) having a low coefficient of thermal expansion (e.g., about 8 μm / m / C) and generally resistant to corrosion or chemical attack. Deposition and etching operations may involve elevated temperatures or large temperature fluctuations, which may cause the rotary indexer to heat up and experience thermal expansion. Due to the length of the indexer arm 340, this thermal expansion (or contraction, if there is cooling) may cause the wafer supported by the indexer arm to be slightly misaligned with the rotation axes 354 of the wafer support 338, which may in turn cause the wafer to be further misaligned when rotating about those rotation axes 354. Although some degree of misalignment is acceptable, the use of ceramics or other materials with low coefficients of thermal expansion can reduce, minimize, or otherwise maintain such misalignment at an acceptable level. In some cases, additional components in the indexer arm assembly 336 may also be made of similar materials. For example, the first rotatable interface 356, the second rotatable interface 358, and the third rotatable interface 360 ​​may be ceramic ball bearings, ceramic roller bearings, or ceramic thrust bearings made of ceramic materials, such as bearings having inner and outer races and rolling elements. Other elements of the indexer arm assembly 336 may also be made of ceramic materials, such as screws, bearing caps, retainer cups, etc. The first hub 330 and the second hub 332 may also be made of ceramic materials, but in many embodiments, are made of stronger and easier to manufacture materials (such as stainless steel or aluminum). Such metal-based materials may be more susceptible to chemical attack, but due to the fact that the first hub 330 and the second hub 332 can remain in the center of the processing chamber housing 306 and do not pass through the processing station 304 whenever they undergo rotational motion, such metal-based materials can also be more isolated from active substances used in semiconductor processing.

[0063] In such an embodiment, the indexer arm assembly 336 can be connected to the first hub 330 via a corresponding number of mounting interfaces. Such mounting interfaces can enable the indexer arm assembly 336 to be easily installed, aligned with the central axis 352 and fixed in position relative to the first hub 330.

[0064] Figure 5 Depicted Figure 3 Another partially exploded perspective view of an exemplary rotary indexer of FIG. Fig.10 Depicted Figure 3 A partially exploded perspective view of an exemplary rotary indexer of FIG. 1 , showing the bottom side of the exemplary rotary indexer. Figure 5 and 10, details of an exemplary mounting interface are depicted (such features are Figure 4 is also visible in ).

[0065] exist Figure 5 and Fig.10 In the embodiment, a mounting plate 374 may be provided that includes a plurality (e.g., three) tapered recesses 378 arranged around a central mounting location (e.g., a threaded hole). In the depicted example, the depicted three tapered recesses 378 are arranged in a uniformly spaced circular pattern around the central mounting location.

[0066] Each conical recess 378 may have a spherical bearing 380 nested therein; the spherical bearings may be made of the same material as the indexer arm 340 or mounting plate 374, or may be made of a different material if desired.

[0067] The indexer arm 340 may include an aperture 382 (see Figure 4 ), the hole 382 can be configured to accommodate a tensionable interface 376 that can be connected to the mounting plate 374. The tensionable interface 376 can be tightened to pull the indexer arm 340 closer to the mounting plate 374, thereby compressing the ball 380 between the two components. The tensionable interface 376 can, for example, include a threaded component 386 (e.g., a screw or bolt) and a spring 388 (e.g., a Belleville washer), as well as a potential adapter (as shown) to transfer the compressive force generated by the threaded component 386 to the spring 388. Therefore, when the threaded component 386 is screwed into the mounting plate 374, the spring 388 can be compressed, thereby exerting a compressive force on the indexer arm 340. Of course, in some embodiments, the spring 388 may not be used. Although its presence can reduce the risk of over-tightening, it can also help to distribute the compressive load to the indexer arm. This can be particularly advantageous for a ceramic indexer arm 340 because it can reduce the risk of initiating cracks in the ceramic component.

[0068] To help properly align the indexer arm assembly 336 relative to the mounting plate, the bottom side of the indexer arm 340 that contacts the ball 380 can include a plurality of grooves 384 that can be configured to accommodate the ball 380 when the assembly is tethered together. Each groove 384 for a particular indexer arm 340 can, for example, follow a radial path extending outward from the center of the hole 382, ​​so that during thermal expansion or contraction of the mounting plate 374 relative to the indexer arm 340, the ball 380 can slide radially inward or outward along the groove from a common point (the center of the hole 382) without binding the indexer arm 340 or causing the indexer arm 340 to move off-center, such as off-center of the tensionable interface. For example, since in some embodiments the mounting plate 374 can be made of aluminum or stainless steel, and in such embodiments the indexer arm 340 can be made of a ceramic material, an interface such as the groove / ball / conical notch interface described above can allow such components to experience different thermal expansion behaviors (due to different coefficients of thermal expansion during operation) without causing misalignment or undue stress. Such a kinematic mount can be constructed using a ceramic sphere so that if there is sliding motion between the sphere 380 and the groove 384, there is no or little motion between the sphere 380 and the conical recess 378 [the conical recess 378 has a larger contact area with the sphere 380 than with the groove 384, and thus has a typically higher friction load relative to the conical recess 378 than to the groove 384 (assuming the coefficients of friction are approximately equal)], thereby preventing sliding / abrasive movement between ceramic and non-ceramic (e.g., metal) parts.

[0069] In the depicted example, the indexer arm assembly 336 can be mounted to the mounting plate 374, and the resulting assembly can then be mounted to the first hub 330. Before the bolts securing the mounting plate 374 to the first hub 330 are tightened, the fixture can be mounted to the rotary indexer 302. For example, the fixture can have a centering feature that allows it to be centered on the first hub 330 or the second hub 332, as well as an arm or other structure that extends outward at least a certain distance along the indexer arm 340. The fixture can be secured to the rotary indexer 302 in a centered position, and then each indexer arm assembly 336 can be adjusted so that the alignment features (e.g., holes) on the indexer arm assembly 336 meet with corresponding alignment features on the fixture. After each indexer arm assembly 336 has been aligned with the fixture, the mounting plate 374 for that indexer arm assembly can be clamped in place by tightening the fasteners securing it to the first hub 330. Once all of the indexer arm assemblies 336 are installed and secured in place, the securing device is removed prior to using the rotary indexer 302. In other embodiments, other types of mounting interfaces may be used to secure the indexer arm assemblies 336 to the first hub 330.

[0070] exist Figure 5 and Fig.10 Also visible is a stop mechanism which may include, for example, a stop 394 and an arcuate groove or notch 392. The stop mechanism may allow the first hub 330 and the second hub 332 to rotate only a predetermined amount relative to each other, such as 90° to 95° in the case of a four-arm indexer, to prevent over-rotation which may cause binding or damage to the actuator mechanism.

[0071] Figures 11-A to 11-E The various actuation states of the rotatable wafer support at the distal end of the indexer arm are shown. Figure 3 FIG. 1 is an exemplary rotary indexer of FIG. 1. In this example, the first hub 330 remains stationary and the second hub 332 rotates in a clockwise manner (22.5° between each pair of consecutive figures). In each of the previous figures, the position outlines of the moving parts are shown in dashed or broken lines. It will be appreciated that if the first hub 330 is rotated while the second hub 332 remains stationary, the wafer support 338 will rotate in exactly the same manner relative to the indexer arms 340 while all of the indexer arms 340 rotate about the central axis 352. Thus, a wafer supported by the wafer support 338 can be moved between stations during each such movement while rotating so that the absolute angular orientation of the wafer relative to the world coordinate system remains the same.

[0072] In some embodiments, particularly embodiments for rotary indexers used in semiconductor processing equipment performing deposition operations, additional features can be provided to direct purge gas (e.g., argon, helium, or nitrogen) to the various rotatable interfaces. By allowing purge gas to flow through each rotatable interface, process gases that might otherwise cause deposits on bearings can be flushed out or away from the rotatable interface, thereby preventing deposits on the surfaces of such components and extending the useful life of the rotatable interfaces.

[0073] Fig.12 Depicted is a portion of a rotary indexer with sections of some of the components cut away. Fig.12 In the second axis (not numbered, but see Figure 6) can be hollow and can serve as a conduit to direct the purge gas to the second hub 332 at position 333. The second hub 332 can have one or more conduits or gas passages 335, 337 that can fluidly connect (or otherwise deflect the purge gas to) various ports or gas flow channels. For example, the column 3100 that can connect the second hub 332 to the first rotational interface 356 can have an opening in it that is fluidly connected to the purge gas flow path. This can allow the purge gas to flow upward through the column 3100 and into the proximal end 348 of the tie rod 346, where some of the purge gas can flow through the first rotational interface 356 (e.g., between the balls or rollers of the bearing), and the remainder of the purge gas flowing through the column 3100 can flow into the channel 331 inside the tie rod 336. The passages 331 in the tie rod 336 may extend along the entire length of the tie rod 336 until they enter the distal end 350 of the tie rod 336, thereby allowing the purge gas to flow through the second rotatable interface 358 as well. Fig.12 In the figure, thick black lines and arrows are used to show the representative flow path of the purge gas; dashed lines are used in some locations to show the overall flow path direction where the flow path itself has left the cutting plane.

[0074] The indexer arm 340 may also have an internal gas flow passage 331' to which a purge gas may be provided via passages or channels in the first and second hubs 330 and 332. This purge gas may flow to the third rotatable interface 360 ​​at the distal end 344 of the indexer arm 340 in order to protect the third rotatable interface 360 ​​from unwanted deposits.

[0075] It should be understood that other arrangements of air flow channels and conduits may be used and are considered to be within the scope of the present disclosure.

[0076] Fig.13 An exemplary flow chart of a technique for controlling a rotary indexer having an additional axis of rotation is depicted; the rotary indexer in question includes N equally spaced indexer arms, where N is an integer greater than one. Fig.13 The technique in represents the actions taken to sequentially advance a group of wafers from one station to another in a semiconductor processing tool using such a rotary indexer. The technique can be repeated to perform further wafer advancement.

[0077] In block 1302, the wafers on each pedestal may be lifted from their respective pedestals, such as by activating a lift pin system in which pins within each pedestal move upward, or the pedestal moves downward, to lift the wafer from the upper surface of the pedestal to allow the wafer support of the rotary indexer to move beneath the wafer.

[0078] In block 1304, the first motor and the second motor may be actuated to rotate both of them +180° / N (or to rotate the first hub by that amount); assuming that each indexer arm is stowed midway between each station so as not to interfere with wafer handling operations when the rotary indexer is not in use. This rotation may cause the indexer arm and its wafer support to move to a position where the wafer support is below the wafer.

[0079] In block 1306, the lift pins may be lowered (or the rotary indexer may be raised) such that the wafer is lifted from the lift pins by the wafer support of the rotary indexer.

[0080] In block 1308, the first motor may be actuated to rotate the first hub 360° / N while the second motor is inactive or otherwise non-actuated. As a result, the indexer arms may rotate to move wafers from their stations to the next adjacent stations, while the wafer support may rotate the same amount in the same direction relative to the indexer arms to hold the wafers in the same absolute angular orientation.

[0081] In block 1310, the wafer may be lifted from the wafer support using lift pins (or a rotary indexer may be lowered to allow the wafer to rest on the lift pins and be lifted from the wafer support).

[0082] In block 1312, the first motor may be actuated to rotate the first hub 180° / N in the opposite direction to the previous rotation, while the second motor may be actuated to rotate the second hub 180° / N in the same direction as the previous rotation. Thus, the relative rotational movement between the first and second hubs will be -360° / N, which may cause the wafer supports to rotate to the same angular position relative to the indexer arms in which they are located (between blocks 1302 and 1304), effectively resetting their positioning. At the same time, the indexer arms may be moved to their midway "stowed" position between each pair of processing stations.

[0083] Once the indexer arm has cleared the processing station, block 1314 may be executed to lower the wafer onto the pedestal for further semiconductor processing operations. As described above, this process may be repeated as needed to continue advancing the wafer through the array of processing stations.

[0084] It should be understood that, as previously discussed, there are many ways to control the rotary indexer to transfer wafers between stations. The first hub and the second hub can be driven to move simultaneously, sequentially, at different rates and / or in different directions, etc. It should be understood that all of these different combinations of actuating the motors used to operate the rotary indexer described herein are considered to be within the scope of the present application.

[0085] As mentioned above, in some embodiments, a controller can be part of the rotary indexer system discussed herein. Fig.14 A schematic diagram of an exemplary controller 14104 having one or more processors 14106 and memory 14108 is depicted, which may be integrated with electronics for controlling the operation of the first motor 318, the second motor 320, and the third motor 3102 (if present) during wafer transfer operations. Depending on the processing requirements and / or the type of system, the controller may be programmed to control any of the processes disclosed herein, such as processes for controlling a rotary indexer, as well as other processes or parameters not discussed herein, such as the delivery of process gases, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, position and operation settings, wafer entry and exit chambers, and other transfer tools and / or load locks connected to or interfaced with a particular system.

[0086] Broadly speaking, a controller can be defined as an electronic device with various integrated circuits, logic, memory, and / or software that receives instructions, issues instructions, controls operations, enables cleaning operations, enables endpoint measurements, etc. The integrated circuits can include chips in the form of firmware that stores program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and / or one or more microprocessors, or microcontrollers (e.g., software) that execute program instructions. The program instructions can be instructions transmitted to the controller in the form of various individual settings (or program files) that define operating parameters for performing specific processing on or for a semiconductor wafer or system. In some embodiments, the operating parameters can be part of a recipe defined by a process engineer to complete one or more processing steps during the manufacture of a die of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or wafers.

[0087] In some embodiments, the controller can be part of or coupled to a computer that is integrated with the system, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller can be in the "cloud" or all or part of a Fab host computer system, which can allow remote access to wafer processing. The computer can enable remote access to the system to monitor the current process of a manufacturing operation, check the history of past manufacturing operations, check trends or performance indicators from multiple manufacturing operations, change parameters of the current process, set processing steps that follow the current process, or start a new process. In some examples, a remote computer (e.g., a server) can provide a process recipe to the system via a network that can include a local area network or the Internet. The remote computer can include a user interface that enables parameters and / or settings to be entered or programmed, and then the parameters and / or settings are transmitted from the remote computer to the system. In some examples, the controller receives instructions in the form of data that specify parameters for each processing step to be performed during one or more operations. It should be understood that the parameters can be specific to the type of process to be performed and the type of tool that the controller is configured to interact with or control. Thus, as described above, controllers may be distributed, for example, by including one or more discrete controllers that are networked together and work toward a common purpose (e.g., process and control as described herein). An example of a distributed controller for this purpose would be one or more integrated circuits on a chamber that communicate with one or more integrated circuits located remotely (e.g., at a platform level or as part of a remote computer) that combine to perform process control of the chamber.

[0088] Without limitation, an exemplary rotary indexer according to the present disclosure may be installed in or as part of a semiconductor processing tool having a plasma etching chamber or module, a deposition chamber or module, a spin rinse chamber or module, a metal plating chamber or module, a cleaning chamber or module, a bevel etching chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etching (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing system that may be associated with or used in the fabrication and / or manufacture of semiconductor wafers.

[0089] As described above, depending on the one or more processing steps to be performed by the tool, the controller may communicate with one or more of the following: other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools throughout the factory, a host computer, another controller, or a tool for material transportation that moves wafer containers to and from tool locations and / or load ports in a semiconductor manufacturing facility.

[0090] It should be understood that the term "group", unless further qualified, refers to a group of one or more items - unless there is further language suggesting that there are multiple items, there is no requirement that multiple items exist. For example, "a group of two or more items" will be understood to have at least two items therein. Conversely, "a group of one or more items" will be understood to potentially have only one item therein. In a similar manner, it should be understood that the term "each" can be used herein to refer to each member of a group, even if the group contains only one member. The term "each" can also be used in the same manner as an implied group (e.g., where the term group is not used but other language suggests that there is a group). For example, "each item in one or more items" should be understood to be equivalent to "each item in one or more items of the group."

[0091] It should be understood that the above disclosure, while focused on one or more specific exemplary embodiments, is not limited to the examples discussed, but is also applicable to similar variations and mechanisms, and such similar variations and mechanisms are also considered to be within the scope of the present disclosure.

Claims

1. An apparatus for transferring wafers between stations in a multi-station semiconductor processing chamber, the apparatus comprising: A rotary indexer for simultaneously moving a plurality of wafers along a circular path between equally spaced positions when the wafers are placed on the rotary indexer and the rotary indexer is actuated, the rotary indexer comprising: Pedestal; First Motor; Second motor; First Hub; N indexer arm assemblies, each indexer arm assembly comprising: a) a wafer support, and b) an indexer arm having a proximal end fixedly connected to the first hub and a distal end rotatably connected to the wafer support; as well as An actuating mechanism, wherein: The first motor is configured to rotate the first hub about a central axis of the first hub and relative to the base, The second motor is configured to provide a rotational input to the actuation mechanism, N is an integer greater than or equal to 2, Each wafer support is configured to rotate relative to the indexer arm of a corresponding indexer arm assembly and about a rotational axis of the wafer support, the rotational axis of each wafer support being positioned to pass through a center of a corresponding one of the wafers when the wafer support is supporting the wafers, and The actuation mechanism is configured to rotate the wafer support of the indexer arm in the same rotational direction relative to the indexer arm and simultaneously by the same amount about the corresponding rotational axis of the wafer support in response to: rotation of the first motor without rotation of the second motor; rotation of the second motor without rotation of the first motor; or rotation of the first motor and the second motor, so that the actuation mechanism is actuated.

2. The device according to claim 1, wherein: The actuation mechanism includes a second hub configured to rotate about the central axis of the first hub in response to actuation of the second motor, and Each indexer arm assembly further includes a pull rod having a proximal end rotatably connected to the second hub via a first rotatable interface and a distal end rotatably connected to the wafer support of the indexer arm assembly via a second rotatable interface, wherein the actuation mechanism and the indexer arm assembly are configured such that relative rotation between the first hub and the second hub about the central axis causes the pull rod to translate in a generally radial manner relative to the central axis, thereby causing each pull rod to rotate the wafer support to which the pull rod is rotatably connected relative to the indexer arm and about the rotational axis of the wafer support. 3 . The device of claim 2 , wherein the first hub and the second hub are configured to be rotatable relative to each other from a first relative rotational position to a second relative rotational position.

4. The apparatus of claim 2, wherein the indexer arm, the pull rods, and the wafer support are made of a ceramic material.

5. The device according to claim 4, wherein: each indexer arm assembly includes a third rotatable interface rotatably connecting the wafer support of the indexer arm assembly with the indexer arm of the indexer arm assembly, and The first rotatable interface, the second rotatable interface and the third rotatable interface are all ceramic ball bearings.

6. The device according to claim 3, wherein: There are four indexer arm assemblies, When the first hub and the second hub are in the first relative rotational position, each of the wafer supports is in a third relative rotational position relative to the first hub, each of the wafer supports is in a fourth relative rotational position relative to the first hub when the first hub and the second hub are in the second relative rotational position, The third relative rotational position and the fourth relative rotational position are 90° out of phase with each other.

7. The device of claim 6, further comprising a stop mechanism, wherein the stop mechanism is configured to limit relative rotational movement between the first hub and the second hub to between 90° and 95°.

8. The device according to claim 6, wherein: The proximal end of each tie rod has a highest surface directly above the first rotatable interface of the tie rod, Each first rotatable interface is horizontally spaced a first distance from another first rotatable interface nearest to it, Each tie rod includes an offset region extending between a first longitudinal distance from a center of rotation of the first rotatable interface of the tie rod and a second longitudinal distance from the center of rotation of the first rotatable interface of the tie rod, The first longitudinal distance is smaller than the first distance, and the second longitudinal distance is larger than the first distance, and The offset region of each tie rod has a lowest surface that is higher than the highest surface of the distal end of the tie rod from the adjacent indexer arm assembly, thereby allowing the distal end of the tie rod from the adjacent indexer arm to pass under the tie rod when the first hub and the second hub are in the first relative rotational position.

9. The device according to claim 3, wherein: When the first hub and the second hub are in the first relative rotational position, each of the wafer supports is in a third relative rotational position relative to the first hub, each of the wafer supports is in a fourth relative rotational position relative to the first hub when the first hub and the second hub are in the second relative rotational position, The third relative rotational position and the fourth relative rotational position are 360° / N out of phase with each other.

10. The device according to claim 1, wherein: The hub includes a separate mounting interface for each indexer arm assembly; Each mounting interface comprises a tensionable interface and three conical recesses arranged around the tensionable interface; A sphere is nested in each conical recess; as well as Each indexer arm contains: a hole through which the tensionable interface passes, and and three grooves radiating outwardly relative to the hole, wherein each ball of the corresponding mounting interface is also nested in the corresponding groove of the indexer arm, and wherein the tensionable interfaces are each configured to compress the ball between a corresponding one of the indexer arms and a corresponding one of the mounting interfaces.

11. The apparatus of claim 10, wherein the tensionable interface associated with each indexer arm comprises a threaded member and a spring configured to press the indexer arm against the ball between the indexer arm and the mounting interface connecting the indexer arm to the first hub when the threaded member is tightened and in tension.

12. The apparatus of claim 11, wherein for each indexer arm: a corresponding hole is located in the distal end of the indexer arm, The indexer arm is fixedly connected to the first hub via a corresponding mounting interface, Each mounting interface fixedly connects a corresponding indexer arm with the first hub such that a) the corresponding indexer arm and the first hub can experience different amounts of thermal expansion without direct sliding contact between the indexer arm and the first hub; and b) the corresponding indexer arm is at least partially fixedly held in position relative to the first hub by a compressive force exerted on the indexer arm by the threaded component of the tensionable interface of the corresponding mounting interface and the spring.

13. The apparatus according to claim 1, further comprising: a motor housing containing the first motor and the second motor and supporting the first hub via the first hub rotation interface; as well as A z-axis drive system is configured to translate the motor housing along a vertical axis in response to actuation of the z-axis drive system.

14. A system for processing a semiconductor wafer, the system comprising: The device according to claim 1; as well as A semiconductor processing chamber housing having N processing stations, wherein: Each processing station includes a pedestal configured to support a semiconductor wafer, and The apparatus is configured to transfer semiconductor wafers between pedestals within the semiconductor processing chamber housing.

15. The system of claim 14, wherein the processing station is configured to perform a semiconductor processing operation selected from the group consisting of a deposition operation, an etching operation, a curing operation, and a thermal treatment operation.

16. The system of claim 14, further comprising a controller having a memory and one or more processors, wherein: The memory is communicatively connected to the one or more processors, The one or more processors are configured to control the first motor and the second motor, and The memory stores computer executable instructions for controlling the one or more processors to cause the first motor, the second motor, and one or more of the first motor and the second motor to be selectively actuated to cause: the first hub and the indexer arm assembly rotate so that each wafer support moves from a corresponding one of the processing stations to an adjacent one of the processing stations, a first relative rotational movement between the first hub and the actuation mechanism such that each wafer support rotates a first amount in a first direction about the wafer support's rotational axis and relative to the first hub during movement between processing stations and while the wafer support resides at each processing station, or during movement between processing stations and while the wafer support resides at each processing station, and A second relative rotational movement between the first hub and the actuation mechanism causes each wafer support to rotate a first amount about the rotational axis of the wafer support and relative to the first hub in a second direction opposite to the first direction during movement between processing stations and while the wafer support resides at each processing station, or during movement between processing stations and while the wafer support resides at each processing station.

17. The system of claim 16, wherein N=4, and the memory stores additional computer executable instructions for controlling the one or more processors to cause the first motor to rotate the first hub 90° in the first direction without rotating the actuation mechanism.

18. A method for transporting a wafer in a semiconductor processing apparatus, the method comprising: a) picking up a plurality of wafers from a corresponding plurality of pedestals using an indexer having a corresponding plurality of wafer supports, each wafer support being rotatably mounted to a distal end of an indexer arm of the indexer, and each indexer arm being fixedly mounted to a hub of the indexer, wherein the wafers are supported by the wafer supports; b) rotating the hub and the indexer arm about a first rotational axis to move each wafer support from a position over each of the pedestals to a position over an adjacent one of the pedestals; c) placing the wafer on the pedestal after (b); as well as d) rotating the wafer supports relative to the indexer arms and about a wafer support's rotational axis between (a) and (c), wherein the rotational axis of each wafer support passes through a center of the wafer supported by the wafer support when the wafer is supported by the wafer support.

19. The method of claim 18 wherein the indexer has four indexer arms, and (b) comprises rotating the hub and the indexer arms 90°, and (d) comprises rotating the wafer support 90° relative to the indexer arms.

20. The method of claim 18, wherein each indexer arm is fixedly mounted to the hub of the indexer via a mounting interface such that a) the corresponding indexer arm and the hub can experience different amounts of thermal expansion without direct sliding contact between the indexer arm and the hub; and b) the corresponding indexer arm is at least partially fixedly held in position relative to the hub by a compressive force exerted on the indexer arm by a threaded component of a tensionable interface of the corresponding mounting interface and a spring.

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