CN114905402A

CN114905402A - Grinding device for semiconductor wafer

Info

Publication number: CN114905402A
Application number: CN202111327652.2A
Authority: CN
Inventors: 川原龙之介; 关直树; 久保武之
Original assignee: Bbs Kim Myung Co Ltd
Current assignee: Bbs Kim Myung Co Ltd
Priority date: 2021-02-09
Filing date: 2021-11-10
Publication date: 2022-08-16
Also published as: JP7099757B1; JP2022121900A

Abstract

The invention relates to a polishing device for a semiconductor wafer, which can maintain the polishing precision of the outer periphery of the semiconductor wafer for a long time. A polishing device (10) is provided with: a column (17) provided with a chuck (21) for holding a semiconductor wafer (W); a reciprocating stage (14) mounted on the base member (13) so as to be capable of reciprocating; a polishing head (55) which rotatably supports a polishing pad (56); and a support table (48) on which a slide plate (54) of the polishing head (55) is mounted, wherein a pressing cylinder (41) of a pressing force applying member for applying a pressing force to the semiconductor wafer toward the polishing head (55) via the reciprocating table (14) is mounted on the base member (13), and a load cell (76) of an actual load measuring device for measuring an actual load applied to the semiconductor wafer by the pressing force applying member is mounted between the support table and the slide plate.

Description

Grinding device for semiconductor wafer

Technical Field

The present invention relates to a wafer polishing apparatus for polishing an outer peripheral portion of a semiconductor wafer.

Background

A semiconductor wafer, which is a material for a semiconductor integrated circuit, is generally made of single crystal silicon, which is called a silicon wafer. A silicon wafer is manufactured by slicing a cylindrical ingot from a raw material, and has a surface on which a plurality of circuit patterns such as wiring of a semiconductor integrated circuit and elements are formed. The silicon wafer on which the plurality of circuit patterns are formed is cut into individual semiconductor chips by dicing.

In order to express the crystal orientation, the outer peripheral portion of the semiconductor wafer is ground by a V-shaped notch called a notch for orientation or a straight portion called a flat surface for orientation. In a process of forming a circuit pattern on a semiconductor wafer, the orientation of the wafer is made uniform by a notch or a flat surface.

The notch and the flat surface for orientation, which are processed on the outer peripheral portion of the semiconductor wafer, are polished by a polishing apparatus. In the polishing process, a semiconductor wafer is held by a chuck, and patent document 1 describes a chuck for holding a semiconductor wafer. The chuck is attached to a reciprocating stage disposed on the base member so as to be capable of reciprocating, and a disk-shaped polishing pad for polishing the outer periphery of the semiconductor wafer is rotatably attached to a support stage. The semiconductor wafer held by the chuck is pressed against the polishing pad by the reciprocating stage.

Documents of the prior art

Patent literature

Patent document 1: japanese unexamined patent application publication No. 2006-114643

Disclosure of Invention

Technical problem to be solved by the invention

In order to apply a load necessary for polishing from the polishing pad to the outer peripheral portion of the semiconductor wafer, a pressing cylinder formed of a pneumatic cylinder is attached to the reciprocating stage. In order to measure a pressing force applied to a semiconductor wafer from a polishing pad during polishing, it is attempted to mount a load cell between a rod of a pressing cylinder and a reciprocating table.

The reciprocating stage provided with the chuck is movably attached to the base member, and sliding resistance is applied to the reciprocating stage with respect to the base member. A plurality of wires and pipes are connected to the chuck, and resistance of the wires and pipes is applied to the slide table. If these resistances change with time or with time, the actual polishing load applied from the polishing pad to the semiconductor wafer becomes unstable.

As described above, if the load cell is provided in the pressing cylinder in order to detect the pressing force applied to the semiconductor wafer from the polishing pad, the load cell monitors whether or not the pressing load of the pressing cylinder on the reciprocating stage is output in accordance with the command value. Therefore, if the sliding resistance applied to the reciprocating stage changes with time or with time, the actual load itself applied to the semiconductor wafer from the polishing pad cannot be monitored more accurately by the load cell. If an error occurs in the set value of the actual load with respect to the pressing force, the accuracy of the polishing process of the notch or the orientation flat in the outer peripheral portion of the semiconductor wafer is lowered.

The purpose of the present invention is to maintain the polishing accuracy of the outer peripheral portion of a semiconductor wafer with high accuracy over a long period of time.

Technical scheme for solving technical problem

A polishing apparatus for a semiconductor wafer comprises: a column provided with a chuck holding a semiconductor wafer; a reciprocating stage mounted on the base member to be capable of reciprocating, and on which the column is mounted; a polishing head that rotatably supports a polishing pad having a rotation center axis perpendicular to a reciprocating direction of the reciprocating stage, and that polishes an outer peripheral portion of the semiconductor wafer; a support table that supports the slide plate to which the polishing head is attached so as to be movable in the same direction as the direction in which the reciprocating stage moves; a pressing force applying member attached to the base member and applying a pressing force to the semiconductor wafer toward the polishing head via the reciprocating stage; and an actual load measuring device which is installed between the support table and the slide plate and measures an actual load applied to the polishing pad and the semiconductor wafer by the pressing force applying member.

Effects of the invention

Since the pressing force applied from the polishing pad to the outer peripheral portion of the semiconductor wafer, that is, the actual load can be set with high accuracy, the polishing accuracy of the outer peripheral portion of the semiconductor wafer can be maintained for a long period of time.

Drawings

Fig. 1 is a perspective view showing a polishing apparatus for a semiconductor wafer.

Fig. 2 is a front view of fig. 1.

Fig. 3 is a right side view of fig. 2.

Fig. 4a is a plan view showing a semiconductor wafer having a notch for orientation.

FIG. 4b is a plan view of a semiconductor wafer with a plane for orientation processing.

Fig. 5 is an enlarged perspective view of the chuck driving unit shown in fig. 1.

Fig. 6 is a front view of fig. 5.

Fig. 7 is an enlarged front view illustrating the pad driving unit of fig. 1.

Fig. 8 is a perspective view showing the back side of fig. 7.

Fig. 9 is a perspective view showing an upper side portion of fig. 7.

Fig. 10 is a pneumatic circuit for supplying compressed air to the pressing cylinder.

Fig. 11 is a block diagram showing a control circuit of the polishing apparatus.

Fig. 12a is a schematic view showing the principle of measuring the pressing force of the polishing pad of the present invention.

Fig. 12b is a schematic view showing the principle of measuring the pressing force of the polishing pad as a comparative example.

Description of the reference numerals

10: a grinding device; 11: a chuck driving unit; 12: a pad driving unit; 13: a base member; 14: a reciprocating stage; 17: a column; 19: a swing arm; 21: a chuck; 26: a space; 31: a drive box; 41: a pressing cylinder (pressing force applying member); 45: a support table; 48: a support table; 54: a sliding plate; 55: a grinding head; 66: a polishing pad; 68: a press-in amount measuring device; 76: a load cell (actual load cell).

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The polishing apparatus 10 for a semiconductor wafer shown in fig. 1 to 3 performs polishing processing on a notch for orientation previously processed in the outer peripheral portion of the semiconductor wafer W. The polishing apparatus 10 can perform polishing not only on the notch but also on the orientation flat surface. Fig. 4a shows a semiconductor wafer W as a workpiece having a notch V for orientation formed in the outer peripheral portion thereof, and fig. 4b shows a semiconductor wafer W having a flat surface F formed thereon.

As shown in fig. 1 to 3, the polishing apparatus 10 includes a chuck drive unit 11 that drives a chuck holding a semiconductor wafer W as a workpiece, and a pad drive unit 12 that drives a polishing pad that performs polishing on a notch V or a flat surface F previously machined in an outer peripheral portion of the workpiece W.

(chuck drive unit)

As shown in fig. 5 and 6, the chuck drive unit 11 includes a reciprocating stage 14 attached to a base member 13 provided in a horizontal direction so as to be capable of reciprocating in a linear direction. A guide block 15 is attached to the shuttle 14, the guide block 15 is movably attached along a guide rail 16 fixed to the base member 13, and the shuttle 14 is guided by the guide rail 16 to move. The moving direction of the reciprocating stage 14 is the X-axis direction shown in fig. 1 and 6, and if the surface of the chuck drive unit 11 shown in fig. 6 is the front surface, the moving direction of the reciprocating stage 14 is the left-right direction. In fig. 1 and 5, the base member 13 is not shown.

A column 17 is attached to the reciprocating stage 14, a swing shaft 18 is rotatably provided on the column 17, and a tip end of the swing shaft 18 protrudes from a front surface of the column 17. The swing shaft 18 has a swing center axis O extending in the Y-axis direction perpendicular to the X-axis direction, and a swing arm 19 is provided on the swing shaft 18. The swing arm 19 is provided with a chuck 21 for holding the semiconductor wafer W. The chuck 21 is swingable within a range of an angle θ in the vertical direction around the swing shaft 18 as shown in fig. 5 and 6, and in the case shown in the figure, is swung within a range of 70 ° in the vertical direction with respect to the horizontal position.

The chuck 21 has a drive case 22 attached to the swing arm 19, and a holding member 23 is provided on one side of the drive case 22 and a movable holding member 24 is provided on the other side. The holding member 23 includes two holding rods 25 extending in the X-axis direction, and two claw portions 25a that contact the outer peripheral surface of the workpiece W are provided at the distal ends of the holding rods 25. As shown in fig. 5, a space 26 for polishing is formed between the two claw portions 25 a. On the other hand, the holding member 24 extends in a direction perpendicular to the holding rod 25, and two claw portions 24a that contact the outer peripheral surface of the workpiece W are provided at both end portions. The intervals of the two claw portions 24a are separated by a wider interval than the space 26. Each of the

claw portions

25a, 24a is formed of a material having appropriate elasticity and chemical resistance, such as fluororubber.

An air cylinder, not shown, is incorporated in the drive case 22, and the holding member 24 is attached to a rod 27 of the air cylinder. The claw portions 24a of the holding member 24 are reciprocated by the air cylinders in the direction approaching and separating from the claw portions 25a of the holding member 23, and the workpiece W is supported by the chuck 21 by the contact of the

claw portions

25a, 24a with the outer periphery of the workpiece W. The four

claw portions

25a and 24a form a support surface for supporting the workpiece W, and the support surface swings about the swing center axis O within the range of the angle θ. The swing center portion of the support surface, i.e., the swing center portion of the workpiece W, is the position of the swing center axis O in the space 26 between the two claw portions 25 a.

As shown in fig. 3, a pipe 28 including a hose or the like for supplying/discharging compressed air to/from the internal cylinder is attached to the drive case 22. A wiring 29 including a signal cable or the like for transmitting a control signal for controlling the driving of the air cylinder is also attached to the drive box 22. The piping 28 and the wiring 29 are connected to an external control device, and wiring and piping, not shown, are provided between the control device and the column 17.

A drive case 31 is fixed to the lower surface of the column 17, and the drive case 31 protrudes downward from the base member 13 through a through hole 32 formed in the base member 13. An electric motor 33 for swinging the workpiece is attached to the front surface of the drive case 31, a pulley 34 provided on the main shaft of the electric motor 33 is provided in the drive case 31, a pulley 35 provided on the swing shaft 18 is provided in the column 17, and a belt 36 is stretched between the two

pulleys

34, 35. The rotation of the spindle of the electric motor 33 is transmitted to the chuck 21 via the belt 36, and the workpiece W is driven by the electric motor 33 around the swing center portion.

(Driving of column)

As shown in fig. 6, a guide rail 37 is attached to the lower surface of the base member 13 so as to extend in the X-axis direction, and an electric motor 38 for positioning is attached to the guide rail 37. A slider 39 mounted on the guide rail 37 is screw-coupled to a ball screw rotationally driven by a main shaft of the electric motor 38, and the slider 39 is reciprocated in the X-axis direction by the electric motor 38.

A pressing cylinder 41 formed of a pneumatic cylinder is attached to the slider 39 via a bracket 42, and a piston rod 43 of the pressing cylinder 41 penetrates through an attachment table 67 fixed to the drive box 31 and is pressed against the connecting block 44. Thus, if the piston rod 43 of the pressing cylinder 41 is driven in the protruding direction, the column 17 is driven in the left direction in fig. 2. The piston rod 43 is provided with a contact member 43a such as a nut that contacts the inner surface of the mount table 67, and when the piston rod 43 moves backward, the contact member 43a contacts the mount table 67, and the column 17 is driven rightward in fig. 2. In this way, the chuck 21 is reciprocated by the electric motor 38 between the machining position shown in fig. 2 and 6 and the workpiece mounting position on the right side in fig. 6 than the machining position.

(pad driving unit)

As shown in fig. 7, the pad driving unit 12 includes a support base 45. As shown in fig. 7 to 9, two guide rails 46 are attached to the support table 45 so as to extend in the Y-axis direction, and a support table 48 is attached to a slider 47 attached to each guide rail 46. A mount 49 is attached to the support base 45, an electric motor 51 for oscillation is attached to the mount 49, and a feed screw 52 attached to a spindle of the electric motor 51 is screwed to a nut of a nut assembly 53 fixed to the support table 48. Therefore, the support table 48 is moved in the Y-axis direction by the electric motor 51. In fig. 1, 8, and 9, the support base 45 is not shown.

The slide plate 54 is attached to the support table 48 to be movable in the same direction as the reciprocating stage 14, i.e., in the X-axis direction, and a polishing head 55 is attached to the lower surface of the slide plate 54 in the vertical direction, i.e., in the Z-axis direction. The polishing head 55 is formed of a hollow columnar case member, and protrudes below the support table 45 through a through hole 56 formed in the support table 48 and a through hole 57 formed in the support table 45. A pulley 61 on the driving side is rotatably attached to the front side of the support plate 58 fixed perpendicular to the upper surface of the slide plate 54. A polishing shaft 62 is rotatably attached to a lower end portion of the polishing head 55, and a pulley 63 attached to a driven side of the polishing shaft 62 is disposed in the polishing head 55 and projects toward a rear surface side of the polishing head 55. A belt 64 is stretched between the two

pulleys

61, 63. As shown in fig. 8 and 9, an electric motor 65 for polishing is attached to the back surface side of the support plate 58, and the driving pulley 61 is attached to a spindle of the electric motor 65. A power supply line for supplying electric power to the electric motor 65 is connected to a control device fixed to the outside.

(polishing pad)

Two disk-shaped polishing pads 66 are attached to the polishing shaft 62, and the polishing pads 66 are rotationally driven by an electric motor 65 via a belt 64. The rotation center axis P of the polishing pad 66 is the Y-axis direction, is perpendicular to the X-axis direction, which is the reciprocating direction of the reciprocating stage 14, and is parallel to the support table 48. The polishing surface of the outer peripheral portion of the polishing pad 66 rotating about the rotation center axis P is rotationally moved in a direction crossing the outer peripheral portion of the workpiece W, and the outer peripheral portion of the workpiece W is polished. Since the polishing head 55 is provided with a plurality of polishing pads 66, the polishing of the notch V can be performed by any of the polishing pads 66. After one polishing pad 66 is worn, the notch V of a new workpiece W can be machined by the other polishing pad 66. This can extend the time required to replace the polishing pad 66 with a new polishing pad 66.

(pressing force of polishing pad)

When the outer peripheral portion of the semiconductor wafer W is polished by the polishing pad 66, a pressing force toward the polishing pad 66 is applied to the workpiece W by the pressing cylinder 41 via the connecting block 44, the driving box 31, the column 17, and the chuck 21. When a pressing force is applied from the semiconductor wafer W to the polishing pad 66, the pressing force is applied from the polishing pad 66 to the outer peripheral portion of the semiconductor wafer W as a reaction force. In this manner, the pressing cylinder 41 constitutes a pressing force applying member that applies a pressing force to the semiconductor wafer W toward the polishing pad 66. The pressing force applying member is not limited to the pressing cylinder 41, and the pressing force may be applied through the connecting block 44 by an electric motor that drives a feed screw, a compression coil spring, or the like.

As shown in fig. 6, a press-in amount measuring instrument 68 for detecting the press-in stroke of the press cylinder 41 is provided on a mounting table 67 fixed to the drive case 31. When the slider 39 is driven in the left direction in fig. 2 by the electric motor 38, the drive case 31 is driven in the left direction via the mount table 67 by the pressing cylinder 41 as described above.

Fig. 10 shows an air pressure circuit for supplying compressed air to the pressure cylinder 41, and a pipe 72 connecting an air pressure supply source 71, which is constituted by a compressor or the like, and the pressure cylinder 41 is provided with a pressure regulating valve 73 for regulating the pressure of the compressed air discharged from the air pressure supply source 71, and an on-off valve 74 for switching between a state of supplying compressed air to the pressure cylinder 41 and a state of cutting off the supply. In this way, the pressing force applied to the outer peripheral surface of the semiconductor wafer W is set by the pressure regulating valve 73 and is set by the compressed air of the pressure supplied to the pressurizing chamber of the pressurizing cylinder 41.

(measurement of actual load of pressing force)

As shown in fig. 7 to 9, the bracket 75 is fixed to the support table 48, and the load cell 76 is attached to the bracket 75 as an actual load measuring device. On the other hand, a pressing rod 78 is attached to a bracket 77 attached to the slide plate 54, and when a pressing force is applied to the polishing pad 66, the pressing force is transmitted to the load cell 76 via the pressing rod 78, and the pressing force is detected by the load cell 76. As described above, although the load cell 76 is attached to the support table 48 via the bracket 75 and the pressure lever 78 is attached to the slide plate 54 via the bracket 77, if the load cell 76 is disposed between the support table 48 and the slide plate 54, the load cell 76 may be attached to the slide plate 54 and the pressure lever 78 may be attached to the support table 48.

Supply pipes

79a and 79b for applying slurry-like polishing liquid to the workpiece and the polishing pad 66 are attached to the side surfaces of the column 17, the supply pipe 79a applies the polishing liquid from the upper side of the semiconductor wafer W, and the supply pipe 79b applies the polishing liquid from the lower side. The coating ports of the two

supply pipes

79a and 79b face the space 26 and face each other. The

supply pipes

79a and 79b are connected to an external polishing liquid supply unit via a pipe not shown.

Fig. 11 is a block diagram showing a control circuit of the polishing apparatus 10, and the control unit 81 includes a memory for storing a control program, an arithmetic expression, mapping data, and temporary data, and a microprocessor for calculating a control signal, and transmits the control signal to the

electric motors

33, 38, 51, and 65. The operation panel 82 is connected to the control unit 81, and an operation switch or the like for instructing the start of the polishing operation of the polishing apparatus 10 is provided on the operation panel 82. A control signal is sent from the control unit 81 to the on-off valve 74, and when the on-off valve 74 is opened, compressed air is supplied to the pressure cylinder 41. The pressing force applied to the polishing pad 66 by the pressing cylinder 41 is measured by the load cell 76, and a measurement signal is sent to the control unit 81.

(grinding sequence of notches)

A semiconductor wafer W having a notch V formed in the outer peripheral portion thereof in advance is mounted on and held by the chuck 21. The workpiece mounting position at this time is rightward from the position shown in fig. 2, and the semiconductor wafer W is positioned and mounted on the chuck 21 so that the notch V is located at the center of the space 26 between the two holding bars 25. On the other hand, the support table 48 is driven by the electric motor 51, and one of the two polishing pads 66 is positioned in the space 26. In this state, the electric motor 38 is driven, the column 17 is conveyed to the grinding position shown in fig. 2 and 6, and the notch V is positioned at the position of the swing center axis O and at the position of the space 26.

When the electric motor 38 is driven, the column 17 is driven toward the grinding head 55. If the post 17 is driven to a position where the polishing pad 66 enters the notch V, the electric motor 38 is stopped. Subsequently, the on-off valve 74 is opened, and the pressing cylinder 41 applies a pressing force to the polishing pad 66 via the column 17 and the chuck 21. The time for which the opening/closing valve 74 is continuously opened is set by a timer provided in the control unit 81. The pressing force is detected by the load cell 76, and it is confirmed whether or not a predetermined pressing force is applied.

In this state, the electric motor 65 is driven to rotate the polishing pad 66, thereby polishing the notch V. During this polishing process, the electric motor 33 is driven, and the semiconductor wafer W is swung in the vertical direction within the range of the angle θ from the horizontal position shown in fig. 6 as indicated by the arrow around the notch V by the swing arm 19. Further, the electric motor 51 is driven, and the polishing pad 66 is driven to oscillate while slightly reciprocating in the Y-axis direction.

(comparison of principle of measurement of pressing force)

Fig. 12a is a schematic view showing a principle of measuring a pressing force of the polishing pad of the present invention, and fig. 12b is a schematic view showing a principle of measuring a pressing force of the polishing pad as a comparative example.

As shown in fig. 12a and 12b, the shuttle table 14 reciprocally mounted on the base member 13 receives a sliding resistance R1 from the base member 13, and the column 17 receives a wiring/piping resistance R2 from wiring/piping attached between the column 17 and an external fixed portion, piping connected to the

supply pipes

79a and 79b, and the like. A pressing force for sliding the reciprocating stage 14 including the column 17, the chuck 21, and the like is applied to the reciprocating stage 14 from the pressing cylinder 41. The sliding resistance R1 and the wiring pipe resistance R2 cannot avoid changes with time/years.

As in the comparative example shown in fig. 12b, when the load cell 76 is mounted between the pressing cylinder 41 and the reciprocating stage 14 and the pressing force applied to the semiconductor wafer W is measured by the pressing load applied to the reciprocating stage 14 by the pressing cylinder 41, the pressing force including the sliding resistance R1 and the wiring pipe resistance R2 is measured as the measured value. Therefore, the load cell 76 can only monitor whether or not the pressing load of the pressing cylinder 41 is output as a command value, and the measurement value of the load cell 76 is affected by aging, and therefore is not an actual pressing load applied to the semiconductor wafer W.

In contrast, in the case where the load cell 76 is disposed between the polishing head 55 and the support table 48 as in the present invention shown in fig. 12a, even if the sliding resistance R1 and the wiring line resistance R2 change, the load cell 76 can detect the load actually applied to the semiconductor wafer W from the polishing pad 66. This improves the detection accuracy of the pressing load, and improves the polishing quality of the outer peripheral surface of the semiconductor wafer W over a long period of time. When the slide table 54 is moved a long distance on the support table 48, the slide table 54 receives sliding resistance against the support table 48 and piping resistance of the power supply cable connected to the electric motor 65, but when the load cell 76 detects a load, the slide plate 54 moves only a distance that transmits a pressing load to the load cell 76, that is, only a distance of a micrometer unit of 1mm or less, for example, and the load measurement value of the load cell 76 does not receive sliding resistance of the slide table 54 and piping resistance of the power supply cable.

Further, the pressure of the compressed air supplied to the pressing cylinder 41 can be feedback-controlled based on the pressing load detected by the load cell 76 so that the pressing load of the pressing cylinder 41 on the semiconductor wafer W can be changed. Since the pressure can be freely controlled by controlling the pressure regulating valve 73 shown in fig. 10, the pressing force of the polishing pad 66 can be always maintained at the set value by controlling the pressure of the compressed air supplied to the pressing cylinder 41 to detect the pressing force set by the load cell 76.

(grinding of orientation flat)

As shown in fig. 4b, the polishing apparatus 10 can also perform polishing processing on the flat surface F of the semiconductor wafer W. At this time, a cylindrical polishing pad is attached to the polishing head 55 instead of the polishing pad 66 on the disk. Further, the holding rod 25 shown in fig. 5 is replaced with a flat polishing rod. The space 26 of the holding rod 25 for flat polishing is different in size from that for notch polishing.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

Claims

1. A polishing apparatus for a semiconductor wafer comprises:

a column to which a chuck holding a semiconductor wafer is provided;

a reciprocating stage mounted on the base member to be capable of reciprocating, and on which the column is mounted;

a polishing head that rotatably supports a polishing pad having a rotation center axis perpendicular to a reciprocating direction of the reciprocating stage, and that polishes an outer peripheral portion of the semiconductor wafer;

a support table that supports the slide plate to which the polishing head is attached so as to be movable in the same direction as the direction in which the reciprocating stage moves;

a pressing force applying member attached to the base member and applying a pressing force to the semiconductor wafer toward the polishing head via the reciprocating stage; and

and an actual load measuring device which is attached between the support table and the slide plate and measures an actual load applied to the polishing pad and the semiconductor wafer by the pressing force applying member.

2. The apparatus for polishing a semiconductor wafer according to claim 1, wherein,

the column includes a swing arm having a swing center at an outer peripheral portion of the semiconductor wafer, the chuck is provided to the swing arm,

the semiconductor wafer is swung by a swing arm around an outer peripheral portion to be ground.

3. The apparatus for polishing a semiconductor wafer according to claim 1, wherein,

the polishing device for a semiconductor wafer comprises:

a support table that supports the support table to be movable in a direction parallel to the rotation center axis; and

a feed motor provided on the support table and driving a feed screw screwed to the support table,

the grinding head has a plurality of grinding pads with the same rotation central axis,

positioning any one of a plurality of polishing pads at a polishing position of the semiconductor wafer by the feed motor.

4. The apparatus for polishing a semiconductor wafer according to claim 1, wherein,

the pressing force applying member is attached to a bracket driven by an electric motor for positioning, and the electric motor for positioning reciprocates the chuck between a machining position and a workpiece mounting position via the pressing force applying member.