Wafer positioning device
By using a combination of ranging sensors and rotary jaws in the wafer positioning device, the problem of misjudgment and correction time of wafer positioning in the prior art is solved, and more efficient and accurate wafer positioning and correction are achieved.
Patent Information
- Application Number
- CN202421864781.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-02
- Publication Date
- 2025-06-03
- Estimated Expiration
- 2034-08-02
AI Technical Summary
The existing wafer positioning technology overlaps the gap and the jaw during wafer load transfer, resulting in sensor misjudgment, increasing correction time, especially for thin wafers to be easily irregularly deformed and misjudgment.
Using a combination of a stage, lifting jaws, rotating jaws, ranging sensors and control modules, the relative distance change is sensed along the edge of the wafer through the distance sensor, accurately judge the gap position, and rotate the wafer to a predetermined position by rotating jaws.
It effectively avoids sensor misjudgment, reduces the time to readjust the wafer position, improves the accuracy and efficiency of wafer correction, and avoids wafer deformation and misjudgment.
Smart Images
Figure CN222939899U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a semiconductor device, in particular to a wafer positioning device. Background Art
[0002] With the advancement of science and technology and the improvement of people's living standards, semiconductor electronic products have been widely used in various fields of society and life, and have become an indispensable part of modern life. Before the semiconductor wafer enters the process equipment, the wafer needs to be positioned so that the pre-set notch on the wafer faces a specific position, so as to facilitate subsequent processing of the wafer after positioning.
[0003] Specifically, the general wafer positioning method is to place the wafer on a tray through a robotic arm. The controller controls the rotation of the tray and detects the notch of the wafer through a sensor to quickly position and eccentricity correct the wafer. Among them, the prior art uses a reference sensor to determine the notch, but because the wafer is in an uncalibrated state when it is transferred to the equipment, when the wafer is grasped by the device's clamp for calibration, the notch of the wafer often overlaps with the clamp, causing the reference sensor to be unable to correctly determine the position of the notch. Therefore, in practice, it is often necessary to readjust the wafer position to allow the notch to be staggered with the clamp, thereby increasing the wafer calibration time. In addition, when the wafer is thin, in addition to being prone to irregular deformation and warping due to the gripping of the clamp, it is also easy to misjudge the position of the notch. Utility Model Content
[0004] The utility model provides a wafer positioning device, which can efficiently determine the notch position of the wafer and meet the required positioning and calibration effect.
[0005] The utility model discloses a wafer positioning device, comprising a carrier, a lifting claw, a rotating claw, a distance measuring sensor and a control module. The lifting claw can be lifted and lowered on the carrier. The rotating claw can be rotatably arranged on the carrier. The lifting claw and the rotating claw are coaxial and staggered relative to the carrier. The distance measuring sensor is arranged beside the carrier. The control module electrically connects the lifting claw, the rotating claw and the distance measuring sensor. The control module drives the lifting claw to lift and lower relative to the carrier so that the wafer is transferred between the lifting claw and the rotating claw. When the wafer is located on the rotating claw, the control module drives the rotating claw to rotate relative to the carrier, and drives the distance measuring sensor to sense the change of relative distance along the edge of the wafer to determine the position of the notch of the wafer.
[0006] In an embodiment of the utility model, an in-position detector is further included, which is arranged beside the carrier and electrically connected to the control module. The control module determines whether the wafer is located on the lifting clamp or on the rotating clamp through the in-position detector.
[0007] In an embodiment of the present utility model, the in-position detector includes a first detection unit and a second detection unit, which are electrically connected to the control module respectively. The first detection unit is located beside the lifting gripper, and the second detection unit is located above the rotating gripper.
[0008] In an embodiment of the present utility model, the carrier has a central axis. A plurality of first gripper units of the lifting gripper are symmetrically arranged with respect to the central axis, and a plurality of second gripper units of the rotating gripper are symmetrically arranged with respect to the central axis, and the plurality of first gripper units and the plurality of second gripper units are staggered with each other.
[0009] In an embodiment of the present utility model, the distance of the first gripper unit with respect to the central axis is equal to the distance of the second gripper unit with respect to the central axis.
[0010] In an embodiment of the present utility model, each of the first gripper unit and the second gripper unit includes a seat body and a friction plate. The seat body has an inclined guiding surface. The friction plate is located on the seat body. By abutting against the edge of the wafer and being guided by the inclined guiding surface, the wafer falls onto the seat body and contacts the friction plate.
[0011] In an embodiment of the present utility model, the first gripper unit includes a seat body and a telescopic member. The telescopic member is arranged on the side surface of the carrier, and the telescopic direction of the telescopic member is parallel to the central axis. The seat body is arranged on the telescopic member to move up and down relative to the carrier along with the telescopic movement of the telescopic member.
[0012] In an embodiment of the present utility model, the height of the rotating gripper on the carrier is between the lifting strokes of the lifting gripper relative to the carrier.
[0013] In an embodiment of the present utility model, the rotating gripper includes a rotating seat and a plurality of second gripper units. The rotating seat is rotatably arranged on the carrier along the central axis of the carrier, and the plurality of second gripper units are arranged on the rotating seat to rotate relative to the carrier along with the rotating seat.
[0014] In an embodiment of the present utility model, it further includes an attitude sensor, which is electrically connected to the control module. The attitude sensor includes a light emitting unit and a receiving unit. The light emitting unit is arranged beside one of the first gripper units, and the receiving unit is arranged beside another first gripper unit. The light emitting unit provides a light beam projected onto the receiving unit, and the control module determines the attitude of the wafer on the rotating gripper according to whether the receiving unit receives the light beam.
[0015] Based on the above, the wafer positioning device enables the wafer to be smoothly transferred between the two through the interactive action of the lifting gripper and the rotating gripper on the carrier. In particular, the lifting gripper is only used for wafer transfer, so as to transfer the wafer to the rotating gripper or take out the wafer from the rotating gripper, and the wafer only senses the notch above the rotating gripper.
[0016] More importantly, the wafer positioning device senses the relative distance change of the edge of the wafer through a distance measuring sensor. In other words, it can determine the position of the notch because it senses that the relative distance changes at the notch, and then the rotating gripper can further and accurately rotate the wafer to a predetermined position, which is conducive to the subsequent process. This effectively avoids the possible misjudgment of the existing sensor. Especially when the notch of the wafer overlaps with the gripper, the distance measuring sensor can avoid the interference of the aforementioned situation, reduce the time spent on repositioning the wafer, and thus improve the accuracy and efficiency of the sensing process.
[0017] To make the above features and advantages of the present invention more obvious and understandable, specific embodiments are hereinafter given and described in detail in conjunction with the accompanying drawings as follows. Brief Description of the Drawings
[0018] Figure 1 is a schematic diagram of a wafer placed on a wafer positioning device according to an embodiment of the present invention;
[0019] Figure 2 is a schematic diagram of the wafer positioning device;
[0020] Figure 3 is Figure 2 a top view of the wafer positioning device;
[0021] Figure 4 is an electrical connection relationship diagram of related components in the wafer positioning device;
[0022] Figure 5 is Figure 2 a side view of the wafer positioning device;
[0023] Figure 6 is an operation flow chart of the wafer positioning device;
[0024] Figure 7 is Figure 2 a partial simple schematic diagram of the wafer positioning device. Detailed Description of the Embodiment
[0025] Figure 1 is a schematic diagram of a wafer placed on a wafer positioning device according to an embodiment of the present invention. Figure 2 is a schematic diagram of the wafer positioning device. Figure 3 is Figure 2 a top view of the wafer positioning device. Figure 4 is an electrical connection relationship diagram of related components in the wafer positioning device. Please first refer to Figure 1 , Figure 2 and Figure 4, in this embodiment, the wafer positioning device 100 includes a stage 110, a lifting jaw 120, a rotating jaw 130, a distance measuring sensor 140, a in-position detector 150, and a control module CM. The lifting jaw 120 is disposed on the side surface F2 of the stage 110 in a liftable manner. The rotating jaw 130 is rotatably disposed on the top surface F1 of the stage 110. The lifting jaw 120 and the rotating jaw 130 are coaxially and staggeredly disposed with respect to the central axis CX of the stage 110. The distance measuring sensor 140 is disposed beside the stage 110, and includes a housing 142 and a sensing unit 141 disposed within the housing 142. As Figure 1 shown, the in-position detector 150 includes a first detection unit 151 and a second detection unit 152, which are respectively disposed beside the stage 110, wherein the first detection unit 151 is located beside the lifting jaw 120, and the second detection unit 152 is located above the rotating jaw 130.
[0026] The control module CM is electrically connected to the lifting jaw 120, the rotating jaw 130, the distance measuring sensor 140, and the first detection unit 151 and the second detection unit 152 of the in-position detector 150. The control module CM drives the lifting jaw 120 to lift relative to the stage 110 (i.e., move along a direction parallel to the central axis CX) so as to transfer the wafer 200 between the lifting jaw 120 and the rotating jaw 130. When the wafer 200 is located on the rotating jaw 130, the control module CM drives the rotating jaw 130 to rotate relative to the central axis CX of the stage 110, and drives the distance measuring sensor 140 to sense the relative distance along the edge of the wafer 200, and determines the position of the notch 210 of the wafer 200 according to the change of the relative distance.
[0027] Please refer to Figure 2 and Figure 3 , specifically, the lifting jaw 120 of this embodiment includes a plurality of first jaw units A1, A2, A3, A4 (taking 4 as an example here), and is symmetrically configured with respect to the central axis CX, and the rotating jaw 130 includes a plurality of second jaw units B1, B2, B3, B4 (taking 4 as an example here), and is symmetrically configured with respect to the central axis CX, wherein the first jaw units A1 - A4 and the second jaw units B1 - B4 are staggered with each other. Furthermore, as Figure 3 shown, the distance of the first jaw units A1 - A4 with respect to the central axis CX is equal to the distance of the second jaw units B1 - B4 with respect to the central axis CX, so that the lifting jaw 120 and the rotating jaw 130 can each carry wafers 200 of the same size, wherein the distance with respect to the central axis CX represents the radius of the carried wafer 200.
[0028] In addition, as Figure 2As shown, taking the first clamping jaw unit A3 of the lifting clamping jaw 120 as an example (the other first clamping jaw units A1, A2, and A4 are also composed of the same components and will not be repeated here), the first clamping jaw unit A3 includes a seat body A31, a friction plate A32, a base A33 and an inclined guide surface A35, wherein the base A33 is arranged on the side surface F2 of the carrier 110, the seat body A31 is located on the base A33, the friction plate A32 is configured on the seat body A31, and the upper protruding structure of the seat body A31 has two inclined guide surfaces A35. When the wafer 200 is carried on the first clamping unit A1-A4 of the lifting clamp 120, the edge of the wafer 200 is actually supported on the seat A31 and the bottom surface contacts the friction plate A32 to maintain the position of the wafer 200 on the lifting clamp 120, and the inclined guide surface A35 is provided for the edge of the wafer 200 to abut against when the wafer 200 falls into the lifting clamp 120, thereby providing a guiding and positioning effect.
[0029] like Figure 2 As shown, the rotating jaw 130 further includes a rotating seat 131, which is rotatably disposed on the top surface F1 of the carrier 110 along the central axis CX of the carrier 110, and the aforementioned second jaw units B1-B4 are respectively disposed on the rotating seat 131 to rotate relative to the carrier 110 along with the rotating seat 131. Similarly, the plurality of second jaw units B1-B4 of the rotating jaw 130 also each have a component composition similar to that of the first jaw units A1-A4, and the second jaw unit B4 is taken as an example here, and the other second jaw units B1-B3 also have the same component composition and are not repeated. In this embodiment, the second clamping jaw unit B4 includes a seat body B41, a friction plate B42, a base B43 and an inclined guide surface B45, wherein the base B43 extends radially from the rotating seat 131 and away from the central axis CX, the seat body B41 is located at the end of the base B43, the friction plate B42 is disposed on the seat body B41, and the upper protruding structure of the seat body B41 has two inclined guide surfaces B45. The wafer 200 is supported on the seat body B41 so that the bottom surface contacts the friction plate B42. The inclined guide surface B45 is also used for the edge of the wafer 200 to abut and provide a guiding and positioning effect when the wafer 200 falls into the rotating clamping jaw 130.
[0030] Figure 5 yes Figure 2 The side view of the wafer positioning device is shown in which the first clamping unit A1 of the lifting clamping jaw 120 and the second clamping unit B1 of the rotating clamping jaw 130 are partially enlarged, and the movement mode of the first clamping unit A1 is shown with a dotted line. Here, the first clamping unit A1 has a lifting stroke d1, and the height of the second clamping unit B1 relative to the carrier 110 is located within the lifting stroke d1. This means that during the lifting process of the lifting clamping jaw 120, the wafer 200 can be smoothly and effectively transferred to the rotating clamping jaw 130 or taken out from the rotating clamping jaw 130.
[0031] Here, the first jaw unit A1 further includes a telescopic member A14, which is disposed on the side surface F2 of the stage 110 and the telescopic direction of the telescopic member A14 is parallel to the central axis CX. The seat body A11 is disposed on the telescopic member A14 and is lifted and lowered relative to the base A13 provided on the stage 110 as the telescopic member A14 expands and contracts. Accordingly, during the process of the seat body A11 descending through the telescopic member A14, the wafer 200 originally placed on the lifting jaw 120 can be made to rest on the second jaw unit B1 of the rotating jaw 130 when the lifting jaw 120 passes by the second jaw unit B1 of the rotating jaw 130. Here, the second jaw unit B1 also includes a base B13, a seat body B11, and a friction plate B12. Here, the seat body B11 rests on the end of the base B13, and the friction plate B12 is disposed on the seat body B11. After the wafer 200 is transferred from the first jaw unit A1 to the second jaw unit B1, the side edge of the wafer 200 abuts against the inclined guiding surface B15 and smoothly falls onto the friction plate B12. Conversely, during the process of the seat body A11 ascending through the telescopic member A14, the wafer 200 can be pushed upward and taken out from the rotating jaw 130. This enables the wafer 200 in this case to be alternately carried by the lifting jaw 120 and the rotating jaw 130, avoiding the possibility of the wafer 200 being bent and deformed due to continuous clamping by a single jaw.
[0032] Figure 6 is the operation flowchart of the wafer positioning device. Please refer to Figure 6 and respectively correspond to the foregoing Figures 1 to 5 so as to clearly understand the positioning process performed by the wafer positioning device 100 on the wafer 200. Here, in the figure, the symbol Y represents affirmation, and the symbol N represents negation.
[0033] First, in step S1, the lifting jaw 120 is driven by the control module CM to be in the transfer position. Here, please refer to Figure 5 , the transfer position corresponds to the position shown by the dashed line of the seat body A11 of the first jaw unit A1, which is conducive to the insertion and removal of the wafer 200. Next, in step S2, the wafer 200 is placed into the lifting jaw 120, as shown by the dashed line in the figure. Next, in step S3, the control module CM senses and detects the lifting jaw 120 through the first detection unit 151 (as shown in Figure 1 ) to confirm that the wafer 200 is correctly carried by the lifting jaw 120. If it is sensed at this time that the wafer 200 is not placed in the lifting jaw 120, then step S12 is performed, that is, the wafer positioning device 100 is stopped to wait for the wafer 200 to be indeed placed in the lifting jaw 120. It should be noted that here, there is no limit to the upper device for placing the wafer 200 into the lifting jaw 120.
[0034] In addition, it should be mentioned in this embodiment that in step S3, in addition to confirming whether the wafer 200 is in place by the first detection unit 151, the attitude of the wafer when it is in place can be further confirmed. Figure 7 Yes Figure 2 A partial simple schematic diagram of the wafer positioning device, which is simply shown from a side view perspective. Please refer to Figures 2 to 4 Any one of Figure 7 , in this embodiment, the wafer positioning device 100 further includes an attitude sensor 160, which is electrically connected to the control module CM. The attitude sensor 160 includes a light emitting unit 161 and a receiving unit 162. The light emitting unit 161 is disposed beside one of the first jaw units (taking the first jaw unit A3 as an example here, but not limited thereto), and the receiving unit 162 is disposed beside another first jaw unit (taking the first jaw unit A2 as an example here, but not limited thereto). The light emitting unit 161 provides a light beam 161a (shown in Figure 3 and Figure 7 ) and projects it onto the receiving unit 162. The control module CM determines the attitude of the wafer 200 on the lifting jaw 120 according to whether the receiving unit 162 receives the light beam 161a.
[0035] As Figure 7 shown in the upper drawing above, when the receiving unit 162 successfully receives the light beam 161a provided by the light emitting unit 161, it means that the wafer 200 is horizontally carried on the lifting jaw 120 at this time. That is to say, the light beam 161a provided by the light emitting unit 161 is horizontal, and if the wafer 200 is also horizontal, the light beam 161a can smoothly travel along the upper surface of the wafer 200 until it is received by the receiving unit 162. On the contrary, if as Figure 7 shown in the lower drawing below, since the posture of the wafer 200 has blocked the travel of the light beam 161a, the wafer 200 is obviously not smoothly carried on the lifting jaw 120. Therefore, it is regarded that the wafer 200 is not on the lifting jaw 120, and the aforementioned step S12 needs to be performed.
[0036] Next, when it is indeed detected in step S3 that the wafer 200 has been placed on the lifting jaw 120, step S4 is performed. The control module CM drives the lifting jaw 120 to descend, that is Figure 5 as shown, the lifting jaw 120 descends a stroke d1 from the position shown by the dotted line and reaches the position shown by the solid line. Since the rotating jaw 130 is located within the moving stroke of the lifting jaw 120, the wafer 200 can be smoothly transferred from the lifting jaw 120 to the rotating jaw 130. Then, as shown in step S5, the control module CM passes through the second detection unit 152 (such as Figure 1as shown) to sense whether the wafer 200 has successfully fallen into the rotating gripper 130. If the second detection unit 152 does not sense that the wafer 200 is placed in the rotating gripper 130, steps S11 and S12 are sequentially executed, that is, the control module CM first raises the lifting gripper 120 to the initial position (step S11, the lifting gripper 120 returns to Figure 5 the position shown by the dashed line), and then step S12 is executed, that is, the wafer positioning device 100 is stopped to wait for the wafer 200 to be indeed placed in the lifting gripper 120.
[0037] On the contrary, if it is confirmed that the wafer 200 has been placed in the rotating gripper 130, step S6 is continued, that is, the control module CM drives the rotating gripper 130 to rotate the wafer 200, and at the same time drives the ranging sensor 140 to sense the edge of the wafer 200 to sense the presence or absence of the notch 210 of the wafer 200 through the change of the relative distance. Then, if the notch 210 of the wafer 200 is sensed, the control module CM executes step S7 to rotate the wafer 200 to a specific position, and then executes step S9. The control module CM drives the lifting gripper 120 to rise to transfer the wafer 200 from the rotating gripper 130 to the lifting gripper 120 and raise the lifting gripper 120 to the transfer position, as Figure 5 the position shown by the dashed line in the figure, waiting for the upper device to take out the wafer 200. Similarly, the upper device is not limited here.
[0038] On the contrary, if the ranging sensor 140 does not sense the notch 210 of the wafer 200, an error situation that the second detection unit 152 cannot detect may occur in the position where the wafer 200 is placed on the rotating gripper 130. Therefore, steps S9 and S10 are continued. Before step S9, the control module CM drives the lifting gripper 120 to rise to transfer the wafer 200 from the rotating gripper 130 to the lifting gripper 120, and then in step S10, the control module CM drives the rotating gripper 130 to rotate to change its relative position with the lifting gripper 120 and the wafer 200 thereon. Then, step S4 is executed again, that is, the lifting gripper 120 is driven to descend again to let the wafer 200 be placed in the rotating gripper 130 again, and then the subsequent steps are continued as described above. At this point, the wafer positioning device 100 can successfully obtain the location of the notch 210 of the wafer 200 through the mutual cooperation of the rotating gripper 130 and the lifting gripper 120, and rotate the wafer 200 to a specific position accordingly to facilitate the subsequent process.
[0039] In summary, in the above embodiments of the present utility model, the wafer positioning device enables the wafer to be smoothly transferred between the lifting jaws and the rotating jaws through the interactive action of the lifting jaws and the rotating jaws. In particular, the lifting jaws are only used for wafer transfer, so as to transfer the wafer to the rotating jaws or take out the wafer from the rotating jaws, and the wafer is only sensed for the notch above the rotating jaws. Furthermore, the above interactive action enables the wafer to naturally fall into the center of the jaws of the lifting jaws or the rotating jaws, which is beneficial to the position holding and center positioning effect of the wafer. In addition, the telescopic characteristics of the jaws can also increase the range of wafers applicable thereto.
[0040] More importantly, the wafer positioning device senses the relative distance change of the edge of the wafer through the distance measuring sensor. In other words, it can determine the position of the notch because the relative distance is sensed to change at the notch, and then the rotating jaws can further and accurately rotate the wafer to a predetermined position, which is beneficial to the subsequent process. This effectively avoids the possible misjudgment of the existing sensors. Especially when the notch of the wafer overlaps the jaws, the distance measuring sensor can avoid the interference of the foregoing situation, reduce the time spent on repositioning the wafer, and thus improve the accuracy and efficiency of the sensing process.
[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present utility model, rather than to limit them; although the present utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present utility model.
Claims
1. A wafer positioning device, characterized in that: include: Carrier; A lifting clamp, which is liftably disposed on the platform; A rotating clamping jaw is rotatably disposed on the carrier, wherein the lifting clamping jaw and the rotating clamping jaw are coaxial and staggered relative to the carrier; A distance measuring sensor is arranged beside the platform; as well as A control module electrically connects the lifting jaw, the rotating jaw and the distance measuring sensor, The control module drives the lifting claw to move up and down relative to the carrier so that the wafer can be transferred between the lifting claw and the rotating claw. When the wafer is located on the rotating jaw, the control module drives the rotating jaw to rotate relative to the carrier, and drives the distance measuring sensor to sense the change of relative distance along the edge of the wafer to determine the position of the notch of the wafer.
2. The wafer positioning device according to claim 1, characterized in that: It also includes an in-situ detector, which is arranged beside the carrier and electrically connected to the control module. The control module determines whether the wafer is located on the lifting clamp or on the rotating clamp through the in-situ detector.
3. The wafer positioning device according to claim 2, characterized in that: The in-position detector includes a first detection unit and a second detection unit, which are electrically connected to the control module respectively. The first detection unit is located beside the lifting clamp, and the second detection unit is located above the rotating clamp.
4. The wafer positioning device according to claim 1, characterized in that: The carrier has a central axis, the multiple first clamping units of the lifting clamping jaws are symmetrically arranged relative to the central axis, the multiple second clamping units of the rotating clamping jaws are symmetrically arranged relative to the central axis, and the multiple first clamping units and the multiple second clamping units are staggered with each other.
5. The wafer positioning device according to claim 4, characterized in that: The distance between the first clamping jaw unit and the central axis is equal to the distance between the second clamping jaw unit and the central axis.
6. The wafer positioning device according to claim 4, characterized in that: The first clamping unit and the second clamping unit each include a seat body and a friction plate, wherein the seat body has an inclined guide surface, and the friction plate is located on the seat body. The wafer falls onto the seat body and contacts the friction plate by abutting against the edge of the wafer and being guided by the inclined guide surface.
7. The wafer positioning device according to claim 4, characterized in that: The first clamping claw unit includes a seat body and a telescopic member, wherein the telescopic member is arranged on the side of the platform and the telescopic direction of the telescopic member is parallel to the central axis, and the seat body is arranged on the telescopic member to rise and fall relative to the platform with the telescopic movement of the telescopic member.
8. The wafer positioning device according to claim 1, characterized in that: The rotating clamp is located at a height of the platform between the lifting and lowering strokes of the lifting clamp relative to the platform.
9. The wafer positioning device according to claim 1, characterized in that: The rotating clamp comprises a rotating seat and a plurality of second clamp units. The rotating seat is rotatably arranged on the carrier along the central axis of the carrier. The plurality of second clamp units are arranged on the rotating seat to rotate relative to the carrier along with the rotating seat.
10. The wafer positioning device according to claim 1, characterized in that: It also includes a posture sensor electrically connected to the control module, wherein the posture sensor includes a light-emitting unit and a receiving unit, the lifting clamp has a plurality of first clamp units, the light-emitting unit is arranged next to one of the first clamp units, and the receiving unit is arranged next to another first clamp unit, the light-emitting unit provides a light beam to be projected to the receiving unit, and the control module determines the posture of the wafer on the rotating clamp according to whether the receiving unit receives the light beam.