CN117484384A - Wafer conveying device - Google Patents

Abstract

The subject of the invention is to improve the conveying precision of a wafer relative to a polishing table. The solution of the present invention is that a wafer conveying device comprises: a first slider driven in a first direction by a first actuator; and a second slider driven in a second direction intersecting the first direction by a second actuator. The wafer transfer device has a transfer hand attached to the second slider and holds the wafer transferred to the polishing table. The wafer transfer apparatus includes a control system that controls the first actuator to move the transfer hand in the first direction by a target distance, and transfers the wafer to the polishing table. The wafer transfer apparatus includes a measuring device that is communicably connected to the control system and measures outer edge data of the wafer transferred to the polishing table.

Description

Wafer conveying device

Technical Field

The present invention relates to a wafer transfer apparatus for transferring a wafer to a polishing table.

Background

In the manufacturing process of semiconductor devices, electronic circuits are formed on wafers such as silicon wafers. The wafer of the semiconductor material is not only subjected to polishing processing for polishing the front surface of the wafer, but also subjected to polishing processing for polishing the outer edge of the wafer from the viewpoint of preventing chipping accompanying the processing (see patent document 1).

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2009-297842

Disclosure of Invention

Problems to be solved by the invention

In addition, when polishing the outer edge of the wafer, the wafer is sucked and fixed on the polishing table after the wafer is conveyed to the polishing table by the conveying device. Then, the wafer on the polishing table is pressed against the rotating polishing drum, and the outer edge of the wafer is polished by the polishing drum. Here, when the center of the polishing table is deviated from the center of the wafer, it is difficult to uniformly contact the polishing drum with the outer edge of the wafer, and there is a concern that the polishing quality of the wafer may be lowered. Therefore, it is required to improve the accuracy of transporting the wafer to the polishing table so that the center of the polishing table and the center of the wafer are close to each other.

The invention aims to improve the conveying precision of a wafer relative to a polishing table.

Means for solving the problems

The wafer transfer apparatus according to one embodiment is a wafer transfer apparatus for transferring a wafer to a polishing table for polishing an outer edge of the wafer, and includes: a first slider mounted to a first rail extending in a first direction and driven in the first direction by a first actuator; a second slider mounted on a second rail provided on the first slider and driven in a second direction intersecting the first direction by a second actuator; a carrier hand attached to the second slider and holding the wafer carried to the polishing table; a control system that moves the carrier hand in the first direction by a target distance by controlling the first actuator to carry the wafer to the polishing table; and a measuring device communicably connected to the control system for measuring outer edge data of the wafer transferred to the polishing table, wherein the control system calculates a center position of the wafer, that is, a center of the wafer, based on the outer edge data, and calculates an eccentric amount of the center of the wafer with respect to a center position of the polishing table, that is, a center of the table, and the control system controls the second actuator based on the eccentric amount and moves the transfer hand in the second direction when the eccentric amount is higher than a threshold value, and corrects the target distance when the wafer is transferred based on the eccentric amount.

Effects of the invention

According to an embodiment of the present invention, the control system controls the second actuator based on the eccentric amount and moves the carrier in the second direction when the eccentric amount is higher than the threshold value, and corrects the target distance when the wafer is carried based on the eccentric amount. This can improve the accuracy of wafer conveyance.

Drawings

FIG. 1 is a diagram showing a portion of a wafer production line;

fig. 2 is a diagram showing a conveyor device and a polishing device in a first polishing step;

fig. 3 is a view showing a part of the conveyor device and the polishing device in the first polishing step;

fig. 4 is a diagram showing an internal structure of a table unit constituting the polishing apparatus;

fig. 5 (a) is a diagram showing a conveying unit from the arrow 5A direction of fig. 2, and fig. 5 (B) is a diagram showing a conveying unit from the arrow 5B direction of fig. 2;

fig. 6 (a) to (C) are diagrams showing a conveyance state of a wafer;

fig. 7 (a) and 7 (B) are diagrams showing a measurement unit;

fig. 8 is a diagram showing an example of a control system;

FIG. 9 is a view showing a polishing table and a wafer;

fig. 10 is a flowchart showing an example of the execution procedure of the conveyance position correction control;

fig. 11 shows a conveyance device and a polishing device during conveyance position correction control.

Fig. 12 (a) and 12 (B) are diagrams showing the polishing table unit and the measurement unit during the conveyance position correction control;

fig. 13 shows an example of the displacement of the outer edge measured by the laser displacement meter.

Fig. 14 (a) and 14 (B) show the position of the wafer center with respect to the stage center.

Description of the reference numerals

23: conveying device (wafer conveying device)

27: conveying device (wafer conveying device)

28: conveying hand

30: grinding table

32: conveying hand

34: laser displacement meter (measuring machine)

71: first slider

72: guides (first guide)

75: mobile motor (first actuator)

81: guides (second guide)

82: second slider

83: adjustment actuator (second actuator)

93: containing box (case)

120: control system

W: wafer with a plurality of wafers

E: outer edge

X: x direction (first direction)

Y: y direction (second direction)

D1: target distance of movement (target distance)

And Cw: wafer center

Cs: workbench center

Alpha: eccentric amount

X2: critical value of

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same or substantially the same components or elements are denoted by the same reference numerals, and overlapping description thereof is omitted.

[ wafer production line ]

Fig. 1 is a diagram showing a part of a wafer manufacturing line 10 for processing wafers such as silicon wafers. By using the illustrated wafer production line 10, polishing or the like is performed on a wafer, which is a material of semiconductor devices. As shown in fig. 1, the wafer production line 10 includes a first notch step Pn1 and a second notch step Pn2 for forming notches in a wafer, and a first polishing step Pp1 and a second polishing step Pp2 for polishing the outer edge of the wafer.

The first notch step Pn1 is provided with a polishing device 13 composed of a polishing table unit 11 for fixing a wafer and a polishing machine 12 for polishing a notch in the wafer. As indicated by arrow a1, a conveyor 15 that conveys the wafer from the cassette 14 to the polishing table unit 11 is provided in the first notch step Pn 1. Similarly, in the second notch step Pn2, a polishing device 18 composed of a polishing table unit 16 for fixing a wafer and a polishing machine 17 for polishing a notch in the wafer is provided. As indicated by an arrow a2, the second notch step Pn2 is provided with a conveyor 19 for conveying the wafer from the polishing table unit 11 to the polishing table unit 16 in the previous step.

The first polishing step Pp1 is provided with a polishing apparatus 22 comprising a polishing table unit 20 for fixing a wafer and a polishing machine 21 for polishing the outer edge of the wafer. As indicated by an arrow a3, the first polishing step Pp1 is provided with a conveyor 23 for conveying the wafer from the polishing table unit 16 to the polishing table unit 20 in the previous step. Similarly, in the second polishing step Pp2, a polishing apparatus 26 including a platen unit 24 for fixing the wafer and a polishing machine 25 for polishing the outer edge of the wafer is provided. As indicated by an arrow a4, the second polishing step Pp2 is provided with a conveyor 27 for conveying the wafer from the polishing table unit 20 to the polishing table unit 24 in the previous step.

The carrier hand 28 provided in the carrier device 27 of the second polishing step Pp2 has a function of reversing the front and back sides of the wafer. That is, the outer edge is polished from the front surface side of the wafer in the first polishing step Pp1, and the outer edge is polished from the back surface side of the wafer in the second polishing step Pp2. In the first and second polishing steps Pp1 and Pp2, the outer edge may be polished simultaneously from both the front surface side and the back surface side of the wafer. In this case, the wafer inverting mechanism can be reduced from the carrier hand 28 of the carrier device 27. The process of polishing the outer edge of the wafer is not limited to the two polishing processes Pp1 and Pp2, and the outer edge of the wafer may be polished by one polishing process or may be polished by three or more polishing processes.

As described above, the illustrated wafer production line 10 is provided with four conveying devices 15, 19, 23, and 27. Among these conveying apparatuses 15, 19, 23, and 27, the conveying apparatuses 23 and 27 provided in the polishing steps Pp1 and Pp2 are wafer conveying apparatuses according to an embodiment of the present invention. Since the conveyors 23 and 27 have the same configuration, the conveyor 23 of the first polishing step Pp1 will be described below, and the conveyor 27 of the second polishing step Pp2 will be omitted.

[ first polishing step ]

Fig. 2 is a diagram showing the conveyor 23 and the polishing device 22 in the first polishing step Pp1, and fig. 3 is a diagram showing a part of the conveyor 23 and the polishing device 22 in the first polishing step Pp 1. In each drawing, the X direction indicated by an arrow X is a direction along a rail 72 described later. The Z direction indicated by the arrow Z is a direction orthogonal to the X direction, and the Y direction indicated by the arrow Y is a direction orthogonal to both the X direction and the Z direction.

As shown in fig. 2 and 3, a polishing device 22 including a polishing table unit 20 (hereinafter referred to as a table unit 20) and a polishing machine 21 is provided in the first polishing step Pp 1. The table unit 20 is provided with a polishing table 30 for fixing the wafer W, and the polishing machine 21 is provided with a polishing drum 31 for polishing the outer edge E of the wafer W. The first polishing step Pp1 is provided with a conveyor 23 including a conveyor unit 33 and a measuring unit 35. The carrying unit 33 is provided with a carrying hand 32 for holding the wafer W, and the measuring unit 35 is provided with a laser displacement meter 34 for measuring the outer edge data of the wafer W.

[ polishing apparatus ]

Fig. 4 is a diagram showing an internal structure of the table unit 20 constituting the polishing apparatus 22. As shown in fig. 4, the table unit 20 has: a base frame 40 provided with a table lifting motor 39; a lifting section 42 provided with a table rotation motor 41; and a polishing table 30 mounted rotatably with respect to the lifting/lowering portion 42. The polishing table 30 is coupled to a hollow shaft 44 having a movable gear 43. The table rotation motor 41 is coupled to a reduction mechanism 45, and the reduction mechanism 45 is provided with a drive gear 46 that meshes with the gear 43. That is, the polishing table 30 and the table rotating motor 41 are coupled to each other, and the polishing table 30 can be rotated by the table rotating motor 41. The lifting portion 42 is provided with a support plate 48, and the support plate 48 is provided with a sleeve 47 rotatably supporting the hollow shaft 44. The support plate 48 is provided with a bearing portion 50 via a connecting rod 49, and the bearing portion 50 is provided with a hollow screw shaft 51 extending in the Z direction.

The nut 52 engaged with the screw shaft 51 is rotatably provided on the base frame 40 of the table unit 20. A steel ball, not shown, is inserted between the screw shaft 51 and the nut 52, and the screw shaft 51 and the nut 52 form a ball screw. A moving gear 53 is fixed to a nut 52 provided rotatably with respect to the base frame 40, and a drive gear 54 engaged with the moving gear 53 is provided to the table lifting motor 39. By rotating the table lifting motor 39, the nut 52 of the base frame 40 can be rotated, and the screw shaft 51 of the lifting portion 42 can be moved up and down in the Z direction. That is, by rotating the table lifting motor 39, the lifting portion 42 and the polishing table 30 supported thereby can be moved up and down in the Z direction.

A through passage 55 is formed in the polishing table 30 and the hollow shaft 44, and the through passage 55 is connected to a negative pressure pipe 56. The negative pressure pipe 56 is connected to a negative pressure chamber 58 through a solenoid valve 57, and the negative pressure chamber 58 is connected to a negative pressure pump 59. The solenoid valve 57 is operable in an adsorption state in which the through passage 55 and the negative pressure chamber 58 are connected to each other and in a release state in which the through passage 55 and the atmosphere opening port 60 are connected to each other. By controlling the solenoid valve 57 to the suction state, the through flow path 55 and the negative pressure chamber 58 can be connected, and the pressure in the through flow path 55 can be reduced to suck the wafer W onto the polishing table 30. On the other hand, by controlling the solenoid valve 57 to the released state, the through flow path 55 and the atmosphere opening port 60 can be connected, and the pressure in the through flow path 55 can be increased to release the adsorption of the wafer W.

As shown in fig. 2, the polishing apparatus 22 includes a polishing machine 21 for polishing an outer edge E of a circular wafer W. The polishing machine 21 is provided with a polishing drum 31 disposed above the polishing table 30, and a drum rotation motor 62 connected to the polishing drum 31 by a belt mechanism 61. When polishing the outer edge E of the wafer W carried on the polishing table 30, the polishing drum 31 is rotated by the drum rotation motor 62, and the polishing table 30 is raised to a predetermined position in the Z direction. Thus, the outer edge E of the wafer W can be brought into contact with the polishing pad 31a provided on the polishing drum 31, and the outer edge E of the wafer W can be polished by the polishing drum 31. When polishing the wafer W by the polishing drum 31, the table rotation motor 41 is driven to rotate the polishing table 30, that is, the wafer W, in order to uniformly polish the outer edge E of the wafer W. The rotation center of the polishing table 30 and the rotation center of the polishing drum 31 are coincident with each other.

[ conveying device ]

Fig. 5 (a) is a diagram showing the conveying unit 33 from the arrow 5A direction in fig. 2, and fig. 5 (B) is a diagram showing the conveying unit 33 from the arrow 5B direction in fig. 2. Fig. 5 (a) and 5 (B) show partial cross-sectional views of the transport unit 33 in order to show the internal structure of the transport unit 33.

As shown in fig. 2 and 5, a rail (first rail) 72 extending in the X direction (first direction) is provided on the mount 70, and the first slider 71 is movably attached to the rail 72. The mount 70 is provided with a screw shaft 73 extending in the X direction, and the first slider 71 is provided with a nut 74 engaged with the screw shaft 73. A steel ball, not shown, is inserted between the screw shaft 73 and the nut 74, and the screw shaft 73 and the nut 74 form a ball screw. The first slider 71 is provided with a conveying motor (first actuator) 75 that is a motor for driving the nut. The nut 74 and the conveying motor 75 are connected to each other by a belt mechanism 76. The first slider 71 can be moved along the screw shaft 73 and the guide rail 72 by rotating the nut 74 by driving the conveyance motor 75. That is, the first slider 71 driven in the X direction by the conveying motor 75 is provided in the conveying unit 33.

The first slider 71 is provided with a rail (second rail) 81 extending in the Y direction (second direction), and the second slider 82 is movably attached to the rail 81. As shown in fig. 5a, the first slider 71 is provided with an adjustment actuator (second actuator) 83 including a telescopic rod 83a, and the telescopic rod 83a of the adjustment actuator 83 is coupled to the second slider 82 via a bracket 84. The illustrated adjustment actuator 83 is an electric actuator that expands and contracts the expansion and contraction rod 83a by an unillustrated motor. The second slider 82 can be moved along the guide rail 81 by expanding and contracting the expansion and contraction rod 83a of the adjustment actuator 83. That is, the conveyance unit 33 is provided with a second slider 82 driven in the Y direction by an adjustment actuator 83.

The second slider 82 is provided with a lift lever 85 extending in the Z direction. The upper end of the lifting lever 85 is connected to a lifting actuator 86 including a telescopic lever 86a via an adapter 87. The illustrated lift actuator 86 is an electric actuator that extends and contracts a telescopic rod 86a by a motor 88. The lower end of the lift lever 85 is connected to the carrier hand 32 for holding the wafer W. The carrier hand 32 has a first arm 89 and a second arm 90 for holding the wafer W. Further, the first arm 89 can be moved in the Y direction and the second arm 90 can be moved in the Y direction by an actuator not shown. In this way, the conveying unit 33 is provided with the conveying hand 32 attached to the second slider 82.

By using such a transfer unit 33, the wafer W can be transferred to the polishing table 30. Here, (a) to (C) of fig. 6 show the conveyance state of the wafer W. Fig. 6 (a), 6 (B), and 6 (C) show a state in which the wafer W is conveyed toward the polishing table 30 in this order.

As shown in fig. 6 (a), when the wafer W on the polishing table unit 16, which is not shown, is held by the carrier hand 32, the carrier motor 75 and the lifting actuator 86 are controlled, and the carrier hand 32 moves toward the polishing table 30 as shown by an arrow b 1. That is, as shown by an arrow D1 in fig. 1, the conveyance motor 75 is controlled at a predetermined target rotation angle, so that the conveyance hand 32 is moved in the X direction by a predetermined target movement distance (target distance) D1.

Next, when the wafer W is conveyed to the polishing table 30 as indicated by an arrow B2 in fig. 6 (B), the first arm 89 and the second arm 90 move as indicated by an arrow B3, and the wafer W is separated from the carrier 32. In fig. 6 (B), negative pressure is supplied to the through flow path 55 of the polishing table 30, and therefore the wafer W is sucked and fixed to the polishing table 30. Then, when the first arm 89 and the second arm 90 are separated from the wafer W on the polishing table 30, the conveyance motor 75 and the lift actuator 86 are controlled to move the conveyance hand 32 toward the predetermined standby position as indicated by an arrow b4 in fig. 6 (C).

As described above, the conveyor 23 is provided with the measuring means 35 for measuring the outer edge data of the wafer W. Here, (a) of fig. 7 and (B) of fig. 7 represent the measurement unit 35. In fig. 7 (a) and 7 (B), a partial cross-sectional view of the measuring unit 35 is shown in order to show the internal structure of the measuring unit 35.

As shown in fig. 7 (a), the measurement unit 35 has: a base plate body 95 to which a housing case 93 and a cylinder 94 are attached; and a lifting table 96 connected to the telescopic rod 94a of the cylinder 94. The elevating table 96 is provided with: a setting table 97 provided with a laser displacement meter (measuring machine) 34; and a waterproof cover 98 that covers the laser displacement meter 34. In order to drive the cylinder 94 connected to the lift table 96, the cylinder 94 is connected to two supply/discharge pipes 99 and 100. These supply and discharge pipes 99 and 100 are connected to an air chamber 102 via an electromagnetic valve 101, and the air chamber 102 is connected to an air pump 103.

The solenoid valve 101 can be operated in a lowered state in which the elevating table 96 is lowered and in a raised state in which the elevating table 96 is raised. By controlling the solenoid valve 101 to a lowered state, the supply and discharge pipe 99 and the air chamber 102 are connected to each other, and the supply and discharge pipe 100 and the exhaust port 104 are connected to each other. As a result, as shown in fig. 7 (a), the telescopic rod 94a of the cylinder 94 can be shortened, and the elevating table 96 can be lowered so that the laser displacement meter 34 is accommodated in the accommodation box 93. On the other hand, by controlling the solenoid valve 101 to the raised state, the supply and discharge pipe 99 and the exhaust port 105 are connected to each other, and the supply and discharge pipe 100 and the air chamber 102 are connected to each other. Thus, as shown in fig. 7 (B), the telescopic rod 94a of the air cylinder 94 can be extended, and thus the elevating table 96 can be lifted up to let the laser displacement meter 34 come out of the housing box 93.

In this way, the laser displacement meter 34 provided to the measuring unit 35 can be moved to the storage position accommodated in the accommodation box 93 and the measuring position out of the accommodation box 93. As shown in fig. 7 (B), the laser displacement meter 34 is moved to the measurement position, whereby the laser displacement meter 34 is disposed radially outward of the wafer W on the polishing table 30. Thus, the laser beam is irradiated from the laser beam displacement meter 34 toward the outer edge E of the wafer W, and the position of the outer edge E of the wafer W can be measured by the laser beam displacement meter 34. The laser displacement meter 34 is communicably connected to a control unit 116 constituting a control system 120 described later.

[ control System ]

As shown in fig. 1, in the wafer production line 10, a plurality of control units 110 to 118 are provided for controlling the polishing devices 13, 18, 22, 26, the conveying devices 15, 19, 23, 27, and the like. The wafer production line 10 includes control units 110 to 113 for controlling the polishing devices 13, 18, 22, and 26, and control units 114 to 117 for controlling the conveying devices 15, 19, 23, and 27. A main control unit 118 for integrally controlling these control units is provided as a control unit of the wafer production line 10. The control units 110 to 118 are communicably connected to each other via a wired or wireless communication network 119. Each of the control units 110 to 118 provided in the wafer production line 10 has a microcontroller in which a processor, a main memory, and the like are assembled. A predetermined program is stored in the main memory, and an instruction set of the program is executed by the processor. The control units 110 to 118 are provided with an input circuit, a driving circuit, an external memory, and the like.

In order to control the wafer carrier apparatus 23 according to the embodiment of the present invention, the control system 120 is configured by the two control units 112 and 116. Fig. 8 is a diagram showing an example of the control system 120. As shown in fig. 8, the control system 120 is constituted by a control unit 112 that controls the polishing apparatus 22 and a control unit 116 that controls the conveying apparatus 23. The control unit 112 can control the table rotation motor 41, the table lifting motor 39, the solenoid valve 57, the drum rotation motor 62, and the like. The control unit 116 can control the conveyance motor 75, the adjustment actuator 83, the lifting actuator 86, the first arm 89, the second arm 90, the laser displacement meter 34, the solenoid valve 101, and the like.

[ control of conveying position correction ]

Fig. 9 is a diagram showing the polishing table 30 and the wafer W. As described above, in the first polishing step Pp1, the wafer W is carried onto the polishing table 30, and the outer edge E of the wafer W is polished by the polishing drum 31. Here, as shown in the enlarged portion of fig. 9, when the center position of the wafer W, that is, the wafer center Cw, is deviated from the table center Cs, that is, the center position of the polishing table 30, it is difficult to uniformly polish the outer edge E of the wafer W. Therefore, when the wafer center Cw is deviated from the table center Cs, the control system 120 executes the conveyance position correction control for correcting the conveyance position of the wafer W by the conveyance unit 33.

Fig. 10 is a flowchart showing an example of the execution procedure of the conveyance position correction control. Fig. 11 is a diagram showing the conveyance device 23 and the polishing device 22 during conveyance position correction control, and fig. 12 (a) and 12 (B) are diagrams showing the table unit 20 and the measuring unit 35 during conveyance position correction control. Fig. 12 (a) shows a top view of the table unit 20 and a top view of the measurement unit 35 from which the waterproof cover 98 has been removed. Fig. 12 (B) shows a side view of the table unit 20 and a side view of the measuring unit 35 to which the waterproof cover 98 is attached.

As shown in fig. 10, in step S10, it is determined whether or not the wafer W has been conveyed to the polishing table 30 by the conveying unit 33. In step S10, if it is determined that the wafer W has been transferred to the polishing table 30, the process proceeds to step S11, the process proceeds to step S12, and it is determined whether or not the number of transfers C1 is higher than the predetermined number X1, by executing the process of counting the number of transfers C1. In step S12, when it is determined that the number of times of conveyance C1 is higher than the predetermined number of times X1, the process proceeds to step S13, the reset process of the number of times of conveyance C1 is executed, and the process proceeds to step S14, and the laser displacement meter 34 is moved to the measurement position. That is, as shown in fig. 11 and 12, by raising the lift table 96 of the measuring unit 35, the laser displacement meter 34 comes out of the housing box 93 and moves to the measuring position located radially outward of the wafer W. Further, an arrow r1 shown in fig. 12 indicates a radial direction of the wafer W.

When the laser displacement meter 34 is moved to the measurement position in this way, the process proceeds to step S15, and the position (outer edge data) of the outer edge E of the wafer W is measured by the laser displacement meter 34 while rotating the polishing table 30 by 360 °. That is, as shown in fig. 12 (a), the table rotating motor 41 is used to rotate the polishing table 30, i.e., the wafer W, in the direction of arrow r 2. As shown by a one-point chain line L in fig. 12 (a), the laser beam is irradiated from the laser displacement meter 34 toward the outer edge E, and the laser beam reflected from the outer edge E enters the laser displacement meter 34. As a result, as shown in an enlarged portion of fig. 12 (a), the positions of the plurality of measurement points Pm set on the outer edge E of the wafer are measured by the laser displacement meter 34.

Here, fig. 13 is a diagram showing an example of the displacement of the outer edge E measured by the laser displacement meter 34. When the wafer center Cw is deviated from the table center Cs, as shown in fig. 13, the laser displacement meter 34 detects the displacement, which is the position of the outer edge E, which varies according to the rotation angle of the polishing table 30. The laser displacement meter 34 may measure the position of the outer edge E at every predetermined rotation angle, or may continuously measure the position of the outer edge E. That is, the measurement points Pm set on the outer edge E of the wafer may be set in the circumferential direction at predetermined intervals or may be set continuously in the circumferential direction. As shown in fig. 10, when the position of the outer edge E of the wafer is measured by the laser displacement meter 34 in step S15, the process proceeds to step S16, and the lift table 96 of the measuring unit 35 is lowered to move the laser displacement meter 34 to the storage position in the storage box 93.

Next, in step S17, the center coordinates (Xa, ya) of the wafer W with the center coordinates of the polishing table 30 as the origin are calculated based on the position of the outer edge E of the wafer measured by the laser displacement meter 34. That is, profile data of the wafer W is generated from the position data of the outer edge E of the wafer, and the center coordinates (Xa, ya) of the wafer W are calculated from the profile data of the wafer W. In step S17, as shown in fig. 9, a distance α between the table center Cs and the wafer center Cw, that is, an eccentric amount α of the wafer center Cw with respect to the table center Cs is calculated. In other words, the amount α of eccentricity of the wafer center Cw with respect to the stage center Cs refers to a distance in the XY plane between a center axis passing through the stage center Cs and a center axis passing through the wafer center Cw. The XY plane is a plane orthogonal to the Z direction.

Next, in step S18, it is determined whether or not the eccentricity α is higher than a predetermined threshold value X2. If it is determined in step S18 that the eccentricity α is higher than the threshold value X2, the process proceeds to step S19, where the adjustment actuator 83 of the conveyance unit 33 is controlled so that the wafer center Cw approaches the table center Cs. That is, the second slider 82 is moved in the Y direction by a predetermined distance by adjusting the actuator 83 so that the Y coordinate of the wafer center Cw becomes "0". Next, in step S20, the target movement distance D1 of the first slider 71 used for wafer conveyance is corrected so that the wafer center Cw coincides with the stage center Cs. That is, the target movement distance D1 of the first slider 71 by the conveyance motor 75 is corrected so that the X coordinate of the wafer center Cw becomes "0".

In step S10, when it is determined that the wafer is not transferred to the polishing table 30 or when it is determined that the number of times of transfer C1 is equal to or less than the predetermined number X1 in step S12, the routine is exited without performing control of the adjustment actuator 83 or correction of the target movement distance D1. In step S18, when it is determined that the eccentric amount α is equal to or smaller than the threshold value X2, the routine is exited without performing control of the adjustment actuator 83 or correction of the target movement distance D1.

Here, fig. 14 (a) and 14 (B) are diagrams showing the position of the wafer center Cw with respect to the stage center Cs. Fig. 14 (a) shows a state before the correction of the conveyance position, and fig. 14 (B) shows a state after the correction of the conveyance position. As shown in fig. 14 (a), when the eccentricity α of the wafer center Cw with respect to the table center Cs is higher than the critical value X2, the coordinates (Xa, ya) of the wafer center Cw with respect to the table center Cs are calculated. Then, the second slider 82 is moved in the Y direction by a predetermined distance by adjusting the actuator 83 so that the Y coordinate of the wafer center Cw becomes "0". Then, the target movement distance D1 of the first slider 71 by the conveyance motor 75 is corrected so that the X coordinate of the wafer center Cw becomes "0".

As a result, as shown in fig. 14 (B), the wafer W can be transported by using the transport unit 33 so that the wafer center Cw coincides with the table center Cs at the next transport. That is, the accuracy of transporting the wafer W to the polishing table 30 can be improved, and the polishing table 30 and the center of the wafer W can be aligned with each other, so that the polishing accuracy of the outer edge E of the wafer W can be improved. In the wafer production line 10, since the eccentric amount α of the wafer center Cw with respect to the table center Cs is periodically determined, polishing failure due to positional deviation of the wafer W can be significantly reduced.

The laser displacement meter 34 measures the outer edge data of the wafer W, and thus the outer edge data can be measured without touching the wafer W. Thus, the outer edge data can be obtained without impairing the quality of the wafer W. Furthermore, the measuring machine, that is, the laser displacement meter 34, can be moved to a storage position accommodated in the accommodation box 93 and a measuring position out of the accommodation box 93. Thus, when polishing the wafer W by the polishing drum 31, the laser displacement meter 34 can be moved to the storage position, and therefore the laser displacement meter 34 can be appropriately protected from the polishing liquid scattered during the polishing process.

Of course, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit and scope thereof. For example, in the above description, the control system 120 is configured by two control units 112 and 116, but the present invention is not limited thereto, and the control system 120 may be configured by one control unit, or the control system 120 may be controlled by three or more control units. In the illustrated example, the X direction in which the first slider 71 moves and the Y direction in which the second slider 82 moves are orthogonal to each other, but the present invention is not limited thereto, and the X direction and the Y direction may intersect with each other. For example, the angle between the X-direction and the Y-direction may be less than 90 °, and the angle between the X-direction and the Y-direction may be greater than 90 °. Further, a servomotor may be used as the conveyance motor 75 that drives the first slider 71, and a servomotor may be used as a motor that is assembled to the adjustment actuator 83 that drives the second slider 82.

In the above description, the laser displacement meter 34 using a laser is used as the measuring device, but the present invention is not limited thereto, and any device may be used as long as the outer edge data of the wafer W can be obtained in a noncontact manner. For example, an ultrasonic displacement meter may be used as the measuring device, a capacitance displacement meter may be used, or an eddy current displacement meter may be used. Further, for example, a camera that captures the outline of the outer edge E of the wafer may be used as the measuring device. In the case of using a camera as the measuring machine, the contour data of the wafer W can be detected as the outer edge data of the wafer W, and the wafer center Cw can be calculated from the contour data of the wafer W. In the above description, the notch is formed in the wafer W, but the notch is not limited to this, and the orientation flat may be formed in the wafer W.

Claims (4)

1. A wafer transfer apparatus for transferring a wafer to a polishing table for polishing an outer edge of the wafer, comprising:

a first slider mounted to a first rail extending in a first direction and driven in the first direction by a first actuator;

a second slider mounted on a second rail provided on the first slider and driven in a second direction intersecting the first direction by a second actuator;

a carrier hand attached to the second slider and holding the wafer carried to the polishing table;

a control system that moves the carrier hand in the first direction by a target distance by controlling the first actuator to carry the wafer to the polishing table; and

a measuring machine communicably connected to the control system for measuring an outer edge data of the wafer transferred to the polishing table,

the control system calculates a center position of the wafer, i.e., a wafer center, based on the outer edge data, and calculates an eccentric amount of the wafer center with respect to a center position of the polishing table, i.e., a table center,

the control system controls the second actuator based on the eccentric amount and moves the carrier in the second direction when the eccentric amount is higher than a threshold value, and corrects the target distance when the wafer is carried based on the eccentric amount.

2. The wafer carrier apparatus according to claim 1, wherein the measuring device measures positions of a plurality of measurement points set on an outer edge of the wafer as the outer edge data.

3. The wafer carrier apparatus according to claim 2, wherein the measuring machine measures the position of the measurement point in a state where the polishing table rotates.

4. A wafer handling device according to any of claims 1 to 3, wherein said measuring machine is movable to a storage position accommodated in a bin and a measuring position out of said bin and measuring said peripheral data.