Wafer clamping device

Abstract

The invention discloses a wafer clamping device which comprises a chuck base, a plurality of clamping pieces, a transmission wheel disc, a wheel disc driving piece, a power piece and a first elastic piece. The chuck base comprises a bearing panel, a back plate and an internal space; the transmission wheel disc is used for driving the multiple clamping pieces to rotate to any position between the opening position and the closing position. The transmission wheel disc is driven to rotate; two ends of the first elastic piece are respectively connected with the transmission wheel disc and the chuck base; the chuck base further comprises an outlet formed in the back plate and a first telescopic sealing piece used for sealing the outlet. The wheel disc driving piece comprises a power input part moving up and down, the power piece is used for driving the power input part to move up and down, and one end of one of the power piece and the power input part penetrates through the outlet in the telescopic sealing piece. Efficient and stable opening and closing of the clamping part are achieved through the gear pair, and the service life of the driving part and other parts in the internal space of the chuck base is prolonged by arranging the first telescopic sealing part.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor equipment manufacturing equipment, and in particular to a wafer clamping device. Background Art

[0002] In wafer processing processes (such as wafer cleaning processes), a wafer chuck is often required. Specifically, a wafer is fixed on a rotatable wafer chuck, which drives the wafer to rotate to achieve uniform cleaning and rapid drying after cleaning.

[0003] The wafer chuck requires a clamp to secure the wafer. When the robot transfers the wafer into the cleaning chamber, the clamp needs to be in the open position to place the wafer in the clamping space on the wafer chuck. Once the wafer is placed, the clamp needs to be in the closed position to clamp the wafer so that it is fixed relative to the wafer chuck. When the cleaning process is completed, the clamp needs to be opened again, and then the robot removes the cleaned wafer. This shows that in the wafer processing process using a wafer chuck, the clamp of the wafer chuck needs to be opened and closed frequently.

[0004] Existing wafer chucks typically use a drive wheel to drive the self-rotation of the clamping parts to open and close. Multiple clamping parts are mounted on the chuck base, and the drive wheel and the chuck base are rotatably superimposed. A clamping space for the wafer is formed between the multiple clamping parts. A transmission gear is provided on the circumferential edge of the drive wheel, and a pinion is provided at the bottom of the clamping part. The transmission gear and the pinion mesh with each other. Driven by a driving component, the drive wheel rotates, which in turn drives the pinion, which in turn rotates the clamping parts to clamp or release the wafer.

[0005] On the one hand, this places high demands on the drive components' efficiency, precision, and stability. On the other hand, in some wafer processing processes, such as wafer cleaning, the presence of corrosive gases (e.g., acidic gases emitted by acidic cleaning fluids) within the process chamber can affect the lifespan of the drive components. Therefore, providing a wafer chuck with an efficient, stable, and corrosion-resistant clamping mechanism has become a technical challenge that needs to be addressed. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a wafer clamping device for solving the problems of how to improve the efficiency, stability and corrosion resistance of the opening and closing structure of the clamping parts of the wafer chuck in the prior art.

[0007] To achieve the above-mentioned and other related purposes, the present invention provides a wafer clamping device, comprising a chuck base, a plurality of clamping members, a transmission wheel, a wheel driving member, a power member and a first elastic member; the chuck base comprises a bearing panel and a back plate, and an internal space formed between the bearing panel and the back plate; the plurality of clamping members are arranged on the chuck base, and a clamping space for clamping a wafer is formed between the plurality of clamping members; the transmission wheel is in transmission connection with the plurality of clamping members, and is used to drive the plurality of clamping members to rotate to any position between an open position and a closed position; the The wheel drive is at least partially arranged in the internal space for driving the transmission wheel to rotate; the two ends of the first elastic member are respectively connected to the transmission wheel and the chuck base; the chuck base further includes an outlet arranged on the back plate and a first retractable sealing member for sealing the outlet; the wheel drive includes a power input part that moves up and down, and the power member is arranged outside the internal space for driving the power input part to move up and down, wherein one end of the power member and the power input part passes through the outlet inside the first retractable sealing member.

[0008] Optionally, the first retractable sealing member further includes a first transmission plate, which is fixed to the lower end of the power input part and is configured to be pushed by the power member to move upward to drive the power input part to move upward.

[0009] Optionally, the power member further includes a second retractable sealing member and a push actuator, the push actuator is used to push the first transmission plate to move upward, and the second retractable sealing member is used to seal the push actuator.

[0010] Optionally, the pushing actuator further includes a second transmission plate, which is fixed to the upper end of the second retractable sealing member; and the power member is configured to push the first transmission plate to move upward by driving the second transmission plate.

[0011] Optionally, the first retractable sealing member further includes a second elastic member that is retractable in a vertical direction.

[0012] Optionally, the first retractable seal further includes a first guide sleeve, and the first guide sleeve and the power input part form a first sliding pair.

[0013] Optionally, the second retractable sealing member further includes a second guide sleeve, and the second guide sleeve and the push actuator form a second sliding pair.

[0014] Optionally, the first retractable seal and / or the second retractable seal comprises a bellows.

[0015] Optionally, the wheel drive includes a power output gear and a motion conversion gear arranged on the same gear shaft, the motion conversion gear and the power input part constitute a first motion pair, which is used to convert the up and down movement of the power input part into a rotation along the axis of the gear shaft, and the power output gear and the transmission wheel are engaged with each other to drive the transmission wheel to rotate along the axis of the transmission wheel.

[0016] Optionally, the motion conversion gear includes a spur gear, the power input part includes a rack, the first motion pair includes a gear rack pair consisting of the spur gear and the rack; the power output gear includes a first bevel gear, and the transmission wheel includes a bevel gear part meshing with the first bevel gear.

[0017] Optionally, the bevel gear portion includes part or all of a bevel gear coaxial with the transmission wheel.

[0018] As described above, the present invention provides a wafer clamping device having the following beneficial effects:

[0019] 1) By providing a retractable seal, the service life of the wheel drive and other components inside the chuck base is effectively extended;

[0020] 2) The drive gear pair composed of the wheel drive member and the transmission wheel drives the transmission wheel, thereby driving the clamping member to rotate, effectively improving the driving efficiency and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Shown is a front view of a wafer clamping device according to a preferred embodiment of the present invention;

[0022] Figure 2 Display as Figure 1 Perspective view at A in the middle;

[0023] Figure 3 Display as Figure 2 A partial enlarged view of point B in the middle;

[0024] Figure 4 It is a three-dimensional diagram of a wafer clamping device according to a preferred embodiment of the present invention, wherein the back plate and the power member are omitted;

[0025] Figure 5 It is a bottom view of a wafer clamping device according to a preferred embodiment of the present invention, wherein the power member is omitted;

[0026] Figure 6 Display as Figure 5 A cross-sectional view along line AA; and

[0027] Figure 7Shown is a top view of a transmission pulley in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] In the description of this application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, vertical, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of this application; the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0030] For ease of description, spatially relative terms, such as "on," "above," and "under," may be used herein to describe the spatial positional relationship of one device or feature to other devices or features as shown in the figures. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures.

[0031] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0032] It should be noted that the illustrations provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Although the illustrations only show components relevant to the present invention and are not drawn according to the number, shape, and size of components in actual implementation, the form, quantity, and proportion of each component in actual implementation may be varied arbitrarily, and the component layout may be more complex. Similar reference numerals and letters represent similar items in the following figures. Therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0033] See Figures 1 to 4 ,in, Figure 1 It is a front view of a wafer holding device according to a preferred embodiment of the present invention. Figure 2 Display as Figure 1 The structural diagram at A in the middle, Figure 3 Display as Figure 2 A partial enlarged view of point B in the middle. Figure 4 A perspective view of a wafer clamping device according to a preferred embodiment of the present invention is shown, with the backing plate and power element omitted. The wafer clamping device comprises a chuck base 1, multiple clamping members 2, a transmission wheel 3, a wheel drive member 5, a power element 6, and a first elastic member 7. The chuck base 1 includes a support panel 11 and a backing plate 12, forming an internal space between the support panel 11 and the backing plate 12.

[0034] Multiple clamping members 2 are mounted on the chuck base 1, forming a clamping space for holding the wafer 4 between the multiple clamping members 2. Specifically, this embodiment includes six clamping members 2, each of which is divided into an upper portion and a lower portion. The upper portion of the clamping members 2 protrudes upward from the support panel 11, forming a clamping space for holding the wafer 4 between the upper portions of the clamping members 2; the lower portion of the clamping members 2 is positioned within the interior space of the chuck base 1 and includes a clamping member gear 21.

[0035] The transmission wheel 3 is in transmission connection with the multiple clamping members 2, and is used to drive the multiple clamping members 2 to rotate to any position between the open and closed positions. Specifically, in this embodiment, a transmission gear 31 is provided on the circumferential edge of the transmission wheel 3. The transmission gear 31 meshes with the clamping member gear 21 to form a pair of gears, which realizes the transmission connection between the transmission wheel 3 and the multiple clamping members 2. When the transmission wheel 3 rotates, it drives the six clamping members 2 to rotate through the gear pair, thereby changing the positional relationship between the upper portion of the clamping member 2 and the wafer 4, allowing the clamping member 2 to be positioned anywhere between the open and closed positions.

[0036] It should be understood that being in the open position means that the clamping member 2 is in the open state, at which time the clamping member 2 has no clamping force on the wafer 4, so that the wafer 4 can be placed in the clamping space or the wafer 4 can be removed; being in the closed position means that the clamping member 2 is in the clamping state, and the clamping space formed by multiple clamping members 2 is closed, so that the wafer 4 is fixed to the chuck base 1.

[0037] It should be understood that the present invention does not impose any particular limitation on the specific clamping structure of the upper portion of the clamping member 2 .

[0038] The wheel drive 5 is at least partially disposed within the interior space of the chuck base 1, forming a drive gear pair with the drive wheel 3 to drive the drive wheel 3 to rotate. The first elastic member 7 has two ends connected to the drive wheel 3 and the chuck base 1, respectively. The chuck base 1 further includes an outlet 13 disposed on the back plate 12 and a first retractable seal 14 for sealing the outlet 13. The wheel drive 5 includes a power input portion 51 that moves vertically. The power member 6 is disposed outside the interior space and is used to drive the power input portion 51 to move vertically. One end of either the power member 6 or the power input portion 51 extends through the outlet 13 within the first retractable seal 14. (See Reference.) Figure 2 In this embodiment, the lower portion of the power input portion 51 extends from the outlet 13 into the interior space of the chuck base 1. The upper end of the first retractable seal 14 is mounted on the lower surface of the back plate 12 and extends downward from the outlet 13 to seal the outlet 13 and the lower portion of the power input portion 51. In other possible embodiments, the first retractable seal 14 may also extend upward from the outlet 13 to seal the outlet 13, and the lower end of the first retractable seal 14 may be mounted on the upper surface of the back plate 12, mirroring the first retractable seal 14 in this embodiment. In this case, the wheel drive member 5 is entirely disposed within the interior space of the chuck base 1. When it is necessary to drive the power input portion 51 upward, the upper end of the power member 6 passes through the outlet 13 within the first retractable seal 14 and extends into the interior space of the chuck base 1 to drive the power input portion 51 upward.

[0039] The working principle of the wafer clamping device provided by this embodiment is described in detail below: In the initial state, the chuck base 1 and the six clamping members 2 provided on the chuck base 1 are stationary, the first elastic member 7 is in a certain tension state, and the clamping members 2 are in the initial position.

[0040] When the clamping member 2 needs to be opened to place or remove the wafer 4, the power input portion 51 moves upward a certain distance, causing the wheel drive 5 to drive the transmission wheel 3 to rotate a certain angle in a first direction (for example, clockwise), and the first elastic member 7 is further stretched. When the transmission wheel 3 rotates, the motion is transmitted through the clamping gear pair composed of the transmission gear 31 and the clamping member gear 21, thereby driving the clamping member 2 to rotate a certain angle, so that the clamping member 2 is in the open state. The power input portion 51 is maintained in its current position under the action of the power member 6, so that the driving force of the wheel drive 5 is balanced with the pulling force of the first elastic member 7, and the open state of the clamping member 2 is maintained, so that the robot or other wafer transfer device can place the wafer 4 in the clamping space formed between the clamping members 2 or remove the wafer 4 from the clamping space.

[0041] After the wafer 4 is placed, the power input part 51 no longer needs to be maintained in the current position, and the power part 6 no longer transmits power to the power input part 51. The transmission wheel 3 rotates a certain angle under the pulling force of the first elastic part 7, that is, it rotates a certain angle in the second direction opposite to the first direction, so that the transmission wheel 3 drives the clamping part 2 to rotate to the closed position to clamp the placed wafer 4. Accordingly, the power input part 51 is driven by the transmission wheel 3 to fall back a certain distance downward; or, after the wafer 4 is taken away, the power input part 51 no longer needs to be in the current position, and the transmission wheel 3 rotates a certain angle under the pulling force of the first elastic part 7, that is, it rotates a certain angle in the second direction opposite to the first direction, so that the transmission wheel 3 drives the clamping part 2 to rotate to the initial position. Accordingly, the power input part 51 is driven by the transmission wheel 3 to fall back a certain distance downward.

[0042] On the one hand, the drive gear pair formed by the wheel drive 5 and the transmission wheel 3 drives the transmission wheel 3 to rotate, which has high drive efficiency and stability, and the gear drive precision is also high. On the other hand, during the wafer 4 processing process, such as the wafer cleaning process, the wafer clamping device is often exposed to a corrosive gas atmosphere, which can easily cause corrosion to the transmission wheel 3 and the wheel drive 5, affecting both the transmission efficiency and stability of the transmission wheel 3 and the wheel drive 5 and the service life of the transmission wheel 3 and the wheel drive 5. In this embodiment, by providing a first retractable seal 14 to seal the outlet 13 of the chuck base 1 and disposing the wheel drive 5 in the interior space of the chuck base 1, the movement of the transmission wheel 3 and the wheel drive 5 is not affected, and the interior space of the chuck base 1 is isolated from the corrosive gas atmosphere, effectively protecting the transmission wheel 3, the wheel drive 5 and other components within the interior space of the chuck base 1.

[0043] See Figure 2 and Figure 3 Preferably, in this embodiment, the first telescopic seal 14 further includes a first transmission plate 141, which is located at the lower end of the first telescopic seal 14 and is fixedly connected to the lower part of the power input part 51. The first transmission plate 141 is configured to be pushed by the power member 6 to move upward, thereby driving the power input part 51 to move upward. Figure 3 The first transmission plate 141 is fixed to the lower end of the first telescopic seal 14 by screws 1411 and is fixedly connected to the lower portion of the power input portion 51 by screws 1412. It should be understood that in other embodiments, the fixing method of the first transmission plate 141 to the first telescopic seal 14 and the fixed connection with the lower portion of the power input portion 51 can also be achieved through other possible methods.

[0044] More preferably, see Figure 2The power member 6 further includes a second retractable seal 64, which is used to seal the push actuator 61 of the power member 6. The second retractable seal 64 further includes a second transmission plate 641, which is fixed to the upper end of the second retractable seal 64 and fixedly connected to the push actuator 61 of the power member 6. The power member 6 is configured to drive the second transmission plate 641 through the push actuator 61 to push the first transmission plate 141 upward. In this embodiment, the second transmission plate 641 is fixed to the upper end of the second retractable seal 64 by screws and is connected to the push actuator 61 by screws. In other embodiments, the fixed connection can also be achieved through other possible connection methods.

[0045] In this embodiment, the power member 6 is a cylinder, and the push actuator 61 is a piston rod of the cylinder. In other possible embodiments, the power member 6 can also be a linear motor or a power component that can output linear motion.

[0046] Specifically, when the clamping member 2 needs to be opened to place or remove the wafer 4, the piston rod of the cylinder moves upward to drive the second transmission plate 641 to move upward, and the second transmission plate 641 contacts the first transmission plate 141 and pushes the first transmission plate 141 to move upward, thereby driving the power input part 51 to move upward for a certain stroke. In order to maintain the open state of the clamping member 2, the piston rod maintains the upward movement trend under the lifting of the cylinder at this time, so that the power input part 51 continues to maintain the upward movement trend.

[0047] After the wafer 4 is placed or taken away, the piston rod falls back, the first transmission plate 141 disengages from the second transmission plate 641, and the transmission wheel 3 rotates a certain angle under the pulling force of the first elastic member 7, that is, rotates a certain angle in the second direction opposite to the first direction, so that the transmission wheel 3 drives the clamping member 2 to rotate to the closed position or the initial position. Correspondingly, the power input part 51 is driven by the transmission wheel 3 to fall back a certain distance.

[0048] Preferably, see Figure 2 and Figure 3 In this embodiment, the first retractable seal 14 further includes a second elastic member 143 that is retractable in the vertical direction. When the power input portion 51 moves upward for a certain distance or maintains its current position after moving upward for a certain distance, the second elastic member 143 is compressed. Therefore, when the power input portion 51 needs to fall back, the second elastic member 143 can provide a certain amount of assistance.

[0049] Preferably, in this embodiment, the first telescopic seal 14 further includes a first guide sleeve 142, which forms a first sliding pair with the power input portion 51. The second telescopic seal 64 further includes a second guide sleeve 642, which forms a second sliding pair with the piston rod of the cylinder. The provision of the first guide sleeve 142 and the second guide sleeve 642 can improve the stability of the power input portion 51 and the piston rod during movement, respectively.

[0050] Preferably, in this embodiment, the first telescopic seal 14 and the second telescopic seal 64 are both bellows. In other possible embodiments, the first telescopic seal 14 or the second telescopic seal 64 may also be other types of telescopic seals.

[0051] In order to improve the stability, opening and closing accuracy and efficiency of the clamping member 2, the present application further provides a wheel drive member 5. Figure 2 as well as Figures 4 to 7 , Figure 5 It is a bottom view of a wafer clamping device according to a preferred embodiment of the present invention, wherein the power member is omitted; Figure 6 Display as Figure 5 A cross-sectional view along line AA; and Figure 7 The top view of the transmission wheel in a preferred embodiment of the present invention is shown. The wheel drive member 5 includes a gear shaft 9 (refer to Figure 6 The power output gear 53 and the motion conversion gear 52 on the gear shaft 9) constitute a first motion pair with the power input part 51, which is used to convert the up and down motion of the power input part 51 into rotation along the axis of the gear shaft. The power output gear 53 is engaged with the transmission wheel 34 to drive the transmission wheel 34 to rotate along the normal of the transmission wheel 34 itself.

[0052] In this embodiment, for example, the motion conversion gear 52 is a spur gear, the power input part 51 is a rack, and the first motion pair is a gear rack pair consisting of a spur gear and a rack. Preferably, the power output gear 53 is a first bevel gear, the transmission wheel 3 includes a bevel gear portion 34, and the first bevel gear and the bevel gear portion 34 mesh with each other to form a bevel gear pair. Figure 6 As shown, the flat gear is arranged at one end of the gear shaft 9, and the first bevel gear is arranged at the other end of the gear shaft 9. The gear shaft 9 is rotatably fixed in a mounting bracket 8, and the mounting bracket 8 is fixed to the bottom surface of the bearing panel 11 of the chuck base 1.

[0053] Specifically, when it is necessary to open the clamping member 2 to place or remove the wafer 4, the rack moves upward, driving the flat gear to rotate, and the gear shaft 9 rotates accordingly, thereby driving the first bevel gear on the gear shaft 9 to rotate; the first bevel gear and the bevel tooth portion 34 at the bottom of the transmission wheel 3 constitute a bevel gear pair, so when the first bevel gear rotates, it can drive the transmission wheel 3 to rotate.

[0054] Through the combination of the rack gear pair and the bevel gear pair, the clamping member 2 can be opened and closed efficiently, accurately and stably.

[0055] Combine Figure 4 and Figure 7 In this embodiment, the bevel tooth portion 34 is a portion of the bevel gear coaxial with the transmission wheel 3. In other possible embodiments, for the sake of processing convenience, the bevel tooth portion 34 can also be the entire bevel gear coaxial with the transmission wheel 3, that is, the bevel tooth portion 34 is a complete bevel gear.

[0056] It should be understood that the application scenarios of the wafer clamping device provided by the present invention are not limited to the wafer picking and placing scenarios described in the above embodiments. In other scenarios, such as when debugging the accuracy of wafer picking and placing by a wafer robot, opening and closing the clamping member is also required, and the wafer clamping device provided by the present invention can also be used.

[0057] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A wafer clamping device, characterized in that: include: A chuck base, a plurality of clamping members, a transmission wheel, a wheel drive member, a power member and a first elastic member; The chuck base includes a bearing panel and a back plate, and an internal space formed between the bearing panel and the back plate; The plurality of clamping members are arranged on the chuck base, and a clamping space for clamping the wafer is formed between the plurality of clamping members; the transmission wheel is in transmission connection with the plurality of clamping members, and is used to drive the plurality of clamping members to rotate to any position between the open position and the closed position; The wheel drive member is at least partially disposed in the internal space and is used to drive the transmission wheel to rotate; Two ends of the first elastic member are respectively connected to the transmission wheel and the chuck base; The chuck base further includes an outlet disposed on the back plate and a first retractable seal for sealing the outlet; The wheel drive component includes a power input part that moves up and down. The power component is arranged outside the internal space and is used to drive the power input part to move up and down, wherein one end of the power component and the power input part passes through the outlet inside the first retractable seal.

2. The wafer clamping device according to claim 1, wherein: The first retractable sealing member further includes a first transmission plate, which is fixed to the lower end of the power input portion and is configured to be pushed by the power member to move upward to drive the power input portion to move upward.

3. The wafer clamping device according to claim 2, wherein: The power member further includes a second retractable sealing member and a push actuator, wherein the push actuator is used to push the first transmission plate to move upward, and the second retractable sealing member is used to seal the push actuator.

4. The wafer holding device according to claim 3, wherein: The second telescopic sealing member further includes a second transmission plate fixed to the upper end of the second telescopic sealing member; the power member is configured to push the first transmission plate to move upward by driving the second transmission plate.

5. The wafer holding device according to claim 1, wherein: The first retractable sealing member further includes a second elastic member that is retractable in a vertical direction.

6. The wafer holding device according to claim 2, wherein: The first retractable sealing element further includes a first guide sleeve, and the first guide sleeve and the power input part form a first sliding pair.

7. The wafer holding device according to claim 3, wherein: The second telescopic sealing member further includes a second guide sleeve, and the second guide sleeve and the push actuator form a second sliding pair.

8. The wafer holding device according to claim 3, wherein: The first retractable seal and / or the second retractable seal may comprise a bellows.

9. The wafer holding device according to claim 1, wherein: The wheel drive component includes a power output gear and a motion conversion gear arranged on the same gear shaft. The motion conversion gear and the power input part constitute a first motion pair, which is used to convert the up and down movement of the power input part into rotation along the axis of the gear shaft. The power output gear and the transmission wheel constitute a driving gear pair, which is used to drive the transmission wheel to rotate along the axis of the transmission wheel.

10. The wafer holding device according to claim 9, wherein: The motion conversion gear includes a spur gear, the power input part includes a rack, the first motion pair includes a gear rack pair consisting of the spur gear and the rack; the power output gear includes a first bevel gear, and the transmission wheel includes a bevel gear portion meshing with the first bevel gear.

11. The wafer holding device according to claim 10, wherein: The bevel gear portion includes a portion or the entirety of a bevel gear coaxial with the transmission wheel.

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