TWI623378B - Grinding device - Google Patents

Abstract

The invention provides a grinding device, which is a type of "grinding body supported by the head through an elastic mechanism", which can avoid the target load during grinding when switching from position control to load control. Overshoot.

The polishing device (100) of the present invention includes a holding portion (60) for holding the material to be polished (Wa), a polishing body (10) for polishing the material to be polished (Wa), and a head portion (30) through The elastic mechanism (32) supports the grinding body (10); the driving mechanism (24) causes the head (30) to move in the direction of the Z coordinate; the control unit (50) is used to control the driving mechanism (24); the position sensor ( 34), which is used to measure the position of the abrasive body (10) relative to the head (30), and the load control is performed according to the measured value of the position sensor (34) and the spring constant of the elastic mechanism (32).

Description

Grinding device [Reference to related applications]

This application is based on Japanese Patent Application No. 2016-021315 filed on February 5, 2016, and Japanese Patent Application No. 2016-254137 filed on December 27, 2016, and claims the foregoing two The application is a priority, and the entire contents of these two priorities are incorporated into this application by reference.

The present invention relates to a polishing apparatus.

Conventionally, a polishing device for polishing a wafer surface or the like formed of a semiconductor material is known, for example, a polishing device using a polishing pad driven by rotation as described in International Publication No. 2013/038573. Generally, a polishing pad is provided at the front end of a rotating shaft, and a polishing pad including a rotating mechanism and a rotating shaft is supported by a head through an elastic mechanism. The head is supported by the device body through a drive mechanism.

As for the control method of the drive mechanism, for example, "combined position control" described in Japanese Patent Application Laid-Open No. 59-219152 can be used. And load control. " This control method is the method described below: before the polishing pad contacts the wafer and reaches the target load during polishing, the driving mechanism (position control) is controlled according to the position (coordinates) of the polishing pad, and when the aforementioned target load is reached Then, the driving mechanism is controlled (load control) according to the pressure generated at the contact surface between the polishing pad and the wafer. The position of the head (Z coordinate) when the target load during polishing is reached is determined based on the area of the polishing surface of the polishing pad and the spring constant of the elastic mechanism.

The load applied to the polishing pad is measured, for example, by a load cell provided above the rotation axis of the polishing pad. The measurement sequence is as follows. That is, the head is lowered (moved toward the wafer) along the Z coordinate axis (vertical axis), and the polishing surface of the polishing pad is brought into contact with the wafer. Along with this, the elastic mechanism (the coil spring) is deformed, and the polishing pad and the rotary shaft are relatively moved upward relative to the head. In this way, the upper end of the rotating shaft is pressure-bonded to the dynamometer, and the strain gage in the dynamometer is deformed, and the "force of pressing the strain gage on the upper end of the rotating shaft" is measured. Then, in order to make the "force measured by the dynamometer" a target load, the Z coordinate value of the head is adjusted.

In the grinding device like the above, when the load control is performed, once the grinding body passes through "the place where there are tiny protrusions and foreign objects", the polishing pad will suddenly move upward (lifted up) to make the measurement by the dynamometer The value increased sharply. It is generally difficult to perform high-accuracy load control following such rapid load changes. In addition, in high-accuracy dynamometers, due to the narrow range of load that can be measured, it may not be possible to perform appropriate Doubts about load measurement.

The inventor of this case repeatedly and thoroughly reviewed the results, and found that by performing load control based on the position sensor (for example, a linear scale) and the spring constant of the elastic mechanism, the measurable load range can be expanded, and even if a sudden It is possible to perform grinding with high accuracy even when the load changes.

The present invention has been developed based on the above findings. That is, it is an object of the present invention to provide a method for expanding the detection range of "load applied to a grinding body" and maintaining a high-precision grinding process even if the grinding body passes through "a place where there are minute protrusions and foreign objects". Grinding device.

The present invention is a polishing device, comprising: a holding portion for holding the material to be polished; a polishing body for polishing the material to be polished held by the holding portion; a head portion supporting the polishing material via an elastic mechanism; The driving mechanism causes the head to move relative to the material to be polished in a direction that "the separation distance from the material to be polished changes"; the control unit is connected to the driving mechanism and controls the driving mechanism In the elastic mechanism, elastic force is provided in a direction to offset the load of the head.

According to the present invention, since the load applied to the abrasive body can be measured without passing through a dynamometer or the like, it is possible to provide a method that can expand the detection range of the load even if the abrasive body passes through "a place where there are minute protrusions and foreign objects", A polishing device capable of maintaining a high-precision polishing process.

The polishing device may further include a position sensor connected to the control unit and configured to measure a position of the polishing body with respect to the head. In this case, the relative position of the abrasive body to the head can be accurately measured.

The aforementioned position sensor may also be a linear scale. In this case, the relative position of the abrasive body to the head can be easily and accurately measured.

The control unit may be configured to calculate a load to be applied to the abrasive body based on a measurement value of the position sensor and a spring constant of the elastic mechanism, and control the load. In this case, the position of the polishing body can be accurately controlled.

According to the present invention, the load applied to the grinding body is not directly measured by a dynamometer or the like, so it can provide a method that can expand the detection range of the load, even if the grinding body passes "a place where there are tiny protrusions and foreign objects", A polishing device capable of maintaining a high-precision polishing process.

Wa‧‧‧ Abrasive material (wafer)

10‧‧‧ grinding body

11‧‧‧ mandrel

12‧‧‧ Abrasive pad

20‧‧‧device body

21‧‧‧ Tower

21a‧‧‧ one side

22‧‧‧ arm

23‧‧‧ base

23a‧‧‧upper surface

24‧‧‧Drive mechanism

30‧‧‧ Head

31‧‧‧ Abrasive body support member

31a‧‧‧flange

32‧‧‧Flexible mechanism

32a‧‧‧Pressure spring

32b‧‧‧Balance spring

32c‧‧‧Balance spring

33‧‧‧ support

34‧‧‧ Linear Scale (Position Sensor)

34a‧‧‧Fixed body

34b‧‧‧movable body

35‧‧‧ cover

35a‧‧‧through hole

50‧‧‧Control Department

51‧‧‧detection department

52‧‧‧Memory Department

53‧‧‧Judgment Division

54‧‧‧Pressure Evaluation Department

60‧‧‧Workbench

60a‧‧‧mounting surface

61‧‧‧Support block

62‧‧‧ protrusion

70‧‧‧ base

71‧‧‧ Parallel trench

100‧‧‧ grinding device

Fig. 1: A polishing device showing one embodiment of the present invention Sketchy perspective view.

Fig. 2 is a schematic perspective view showing the internal structure of the head of the polishing apparatus of Fig. 1.

FIG. 3 is a schematic side view showing the head of the polishing apparatus of FIG. 1 as viewed from the upper left of FIG. 2.

Fig. 4 is a schematic cross-sectional view of the head of Fig. 3 in a plane "parallel to the paper surface of Fig. 3 and passing through the axis of the spindle".

Fig. 5 is a block diagram schematically showing a control device of the polishing device of Fig. 1.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic perspective view showing a polishing apparatus 100 according to one embodiment of the present invention. As shown in FIG. 1, the polishing apparatus 100 according to this embodiment includes a base 70, a table 60 provided on the base 70 as a holding portion for holding a material to be polished (wafer Wa), and a polishing body 10, It is used to grind the material to be ground held by the table 60; the head 30 supports the grinding body 10 via an elastic mechanism 32 (refer to FIG. 2); the driving mechanism 24 makes the head 30 toward the Z coordinate with respect to the device body 20 The control unit 50 is connected to the driving mechanism 24 and controls the driving mechanism 24.

Among them, the table (holding section) 60 is used to hold the work It is a member of a disc-shaped wafer Wa that is a material to be polished. The table 60 is supported by the "cuboid-shaped support block 61 arranged on the base 70".

The polishing body 10 is a member for polishing the wafer Wa held by the table 60. As shown in FIG. 1, the polishing body 10 includes a mandrel 11 and a polishing pad 12 attached to one end portion (the lower end portion in FIG. 1) of the mandrel 11. The polishing pad 12 of this embodiment is a disc-shaped object having a diameter of 10 mm.

The apparatus body 20 of this embodiment is a member that supports the head 30 via a drive mechanism 24 that “relatively moves the head 30 relative to the wafer Wa”. As shown in FIG. 1, the device body 20 includes a rectangular parallelepiped column 21, one end of which is a cylindrical arm 22 supported on one side 21 a of the column 21 via a driving mechanism 24, and an upper surface 23 a A rectangular parallelepiped base 23 is supported by the tower column 21. A head 30 is attached to the other end of the arm 22, and the driving mechanism 24 is used to move the arm 22 on the one side surface 21a of the tower 21 in a vertical direction (Z coordinate direction in FIG. 1). In this way, the positioning of the head 30 in the Z coordinate direction can be performed.

In addition, the tower 21 of this embodiment can be moved in the length direction of the arm 22 (the X coordinate direction in FIG. 1) on the base 23 by a known driving mechanism. In this way, the head 30 can be executed. Positioning in the X coordinate direction.

In addition, as shown in FIG. 1, the base 70 is a member for supporting the support block 61 of the table 60 and the apparatus body 20. Specifically, the table 60 and the support block 61 are arranged on the upper surface of the base 70. At the position corresponding to the grinding body 10, in the present embodiment, the lower surface of the support block 61 is provided with: "two parallel grooves 71 carved on the base 70 along the Y coordinate direction of Fig. 1" The protrusion 62 forms the support block 61 to move along the two parallel grooves 71. In this way, the positioning of the table 60 in the Y coordinate direction can be performed, that is, the positioning of the head 30 relative to the table 60 in the Y coordinate direction. The table 60 of this embodiment has a mounting surface 60a having a diameter of 200 mm, for example.

Next, the head 30 will be further described. FIG. 2 is a schematic perspective view showing the internal structure of the head 30 of the polishing apparatus 100 shown in FIG. 1, and FIG. 3 is a view of the head of the polishing apparatus 100 shown in FIG. 1 as viewed from the upper left of FIG. The schematic side view at the time of the part 30, FIG. 4 is a schematic cross-sectional view of the head part 30 of FIG. 3 in a plane “parallel to the paper surface of FIG. 3 and passing through the axis of the mandrel 11”.

As shown in FIGS. 2 to 4, the head portion 30 of this embodiment is a member for supporting the polishing body 10. The head 30 is supported by an elastic mechanism 32 and includes a polishing body support member 31 "a mandrel 11 for supporting the polishing body 10". A known driving mechanism (not shown in the drawing) for driving the spindle 11 to rotate is provided inside the polishing body support member 31, and the polishing body 10 is rotated at a desired rotation speed. As shown in FIG. 4, the abrasive body supporting member 31 has a cylindrical shape “having a flange portion 31 a on the side surface”, and is provided above the flange portion 31 a: fixed to the arm 22 and surrounding the abrasive body supporting member 31的 盖 35. The cover 35. As shown in FIG. 2, the outer shape of the cover 35 is an octagonal column. A through-hole 35a is formed in the cover 35 in the up-down direction, and the polishing-body supporting member 31 can be moved upward and downward in the through-hole 35a. Move in the direction.

In addition, as shown in FIG. 2, the elastic mechanism 32 of the present embodiment is constituted by: a compression spring 32 a that presses the polishing body 10 downward together with the polishing body support member 31; and two balance springs 32b and 32c are used to support the weight of the abrasive body support member 31 itself. The compression spring 32 a is provided on the upper end of the polishing body support member 31 to form an elastic force along the axis of the spindle 11 of the polishing body 10. The balance springs 32b and 32c are provided on the upper surface of the cover 35 in parallel to the pressure spring 32a on both sides in the Y-axis direction of the pressure spring 32a. In this embodiment, the upper end of the compression spring 32 a is connected to the support body 33 so as to pass through the compression spring 32 a and measure the load applied to the polishing body 10.

In addition, the polishing apparatus 100 is provided with a linear scale 34 which is used to measure the positional sense of the coordinate (the W coordinate in the second figure) of the abrasive body 10 with respect to the vertical direction of the head 30. Tester. As shown in FIG. 2, the linear scale 34 includes a fixed body 34 a that is fixed to the upper end of the polishing body support member 31 and a movable body 34 b that is fixed to the cover 35 above the transparent support member 36. This linear scale 34 measures the relative position of the abrasive body support member 31 to the cover 35. Then, based on the measured value, the control device 50 evaluates the "position (W coordinate) of the abrasive body 10 with respect to the head portion 30".

Fig. 5 is a schematic block diagram of a control device 50 connected to the polishing device 100 shown in Fig. 1. As shown in FIG. 5, the control device 50 according to this embodiment includes a detecting unit 51 for detecting the distance between the “axis of the spindle 11 of the grinding body 10” and the “center of rotation of the table 60”. phase For the positional relationship; the memory unit 52 is used to memorize the Z coordinate of the grinding body support member 31 when switching from the position control to the load control; the determination unit 53 is used to determine whether the grinding body support member 31 has reached the aforementioned Z coordinate; pressure evaluation The unit 54 evaluates the polishing pad 12 and the wafer based on the relative positional relationship between the “axial center of the mandrel 11 of the polishing body 10” and the “center of rotation of the table 60” detected by the detecting unit 51. The contact area between Wa, and based on the measurement of the contact area and the linear scale 34, evaluate whether the pressure applied to the wafer Wa is appropriate.

Next, an operation of the polishing apparatus 100 according to this embodiment will be described.

First, before the grinding process, the table 60 is positioned along the "two parallel grooves scribed on the base 70", and then the center of rotation of the table 60 and the axis of the spindle 11 of the grinding body 10 It is aligned in the Y-axis direction. The wafer Wa as a material to be polished is placed on the table 60 with the surface to be polished facing upward. Then, once the grinding device 100 is activated by the user, the tower 21 will move on the base 23 until "the center of rotation of the table 60" and "the axis of the mandrel 11" are in the X-axis direction of Fig. 1 Be consistent. At this time, in order to prevent the polishing pad 12 of the polishing body 10 from interfering with the edge portion of the table 60, the head portion 30 is retracted to a sufficient height in the initial state.

Then, according to a user's instruction, the driving mechanism of the spindle 11 and the table 60 of the grinding body 10 are activated respectively, and the grinding body 10 and the table 60 are rotated at a desired speed. That is, the polishing pad 12 and the wafer Wa are each rotated at a desired speed. In this state, the head 30 borrows The driving mechanism provided on the column 21 moves downward together with the arm 22 so that the polishing pad 12 abuts on the wafer Wa. In this embodiment, in order to perform a smooth polishing process, a polishing liquid is supplied to the polishing target surface of the wafer Wa before the polishing pad 12 abuts on the wafer Wa.

In the polishing apparatus 100 according to this embodiment, the movement of the head 30 before the "polishing pad 12 abuts on the wafer Wa" is controlled based on position control, that is, based on the position (Z coordinate) of the head 30 control. Next, when the polishing pad 12 abuts on the wafer Wa and reaches the target load during polishing, it is switched according to the "position (W coordinate) of the polishing body 10 relative to the head 30" detected by the linear scale 34. Load control. In the load control of this embodiment, in order to make the pressure (surface pressure) applied to the contact surface between the wafer Wa and the polishing pad 12 constant, the spring constant of the elastic mechanism 32 is considered to control the polishing body support member 31. Location (W coordinate).

It is clear from the above description that the load control in this embodiment is not performed by "directly measuring the load applied to the grinding body 10", but based on the "grinding body" measured by the linear scale 34 10 position (W coordinate) with respect to the head 30 ". Specifically, the load applied to the polishing body 10 is evaluated based on the W-coordinate and the spring constant of the elastic mechanism 32, and the position (Z-coordinate) of the head 30 is controlled so that the load becomes a predetermined value.

Once the load control is started, the pressure evaluation unit 54 monitors the W coordinate of the polishing body support member 31 in real time. The polishing pad 12 gradually approaches the wafer Wa from above the wafer Wa, and The radially outer side of the wafer Wa moves toward the radially inner side. Then, a part of the polishing pad 12 abuts on the wafer Wa, and polishing of the wafer Wa is started. The polishing pad 12 is gradually moved radially inward of the wafer Wa. Along with this, the contact area between the polishing surface of the polishing pad 12 and the wafer Wa gradually increases, and finally the entire polishing surface contacts the wafer Wa, and the contact area is formed constant. In this embodiment, in order to make the pressure (surface pressure) applied to the contact surface between the polishing pad 12 and the wafer Wa constant, and the position (Z coordinate) of the head 30 is controlled, the load applied to the polishing body 10 , Will gradually increase after a certain amount.

In the case where the thickness of the wafer Wa is reduced and the load applied to the polishing body 10 is reduced with the polishing process of the wafer Wa, the head 30 is coupled with the arm 22 by the drive mechanism 24 provided on the tower 21 Move down. By this movement, the polishing body 10 abuts more strongly on the wafer Wa, so the load applied to the polishing body 10 increases, and the compression spring 32a is compressed. Then, if it is detected by the linear scale 34 that "the W-coordinate of the grinding body support member 31 registered in the grinding apparatus 100 in advance" has been restored, the movement is stopped.

When the wafer Wa is polished, the column 21 is moved on the pedestal 23 to move the polishing body 10 linearly from the peripheral edge portion on one side of the wafer Wa to the peripheral edge portion on the other side in the X coordinate direction. . In the process of polishing, once the polishing body 10 passes through the “location where there are minute protrusions and foreign objects on the surface of the wafer Wa”, the polishing body 10 will move upward (lifted up) sharply.

However, in this embodiment, the linear scale 34 is used. The load is measured indirectly, so the range of load that can be measured, for example, is wider than when it is directly measured by a dynamometer.

Then, once the desired polishing process is achieved, the supply of the polishing liquid is stopped, and the head 30 and the arm 22 are moved upward together by the driving mechanism 24. Then, in accordance with an instruction from the user, the rotation of the polishing body 10 and the table 60 is stopped, and the wafer Wa is unloaded from the table 60. At this time, if necessary, the tower column 21 is moved on the base 23 in the negative direction of the X coordinate in FIG. 1 to make the head 30 retreat.

According to this embodiment as described above, since the load applied to the abrasive body 10 can be measured without passing through a dynamometer or the like, it is possible to provide a method that can expand the detection range of the load, even if the abrasive body 10 passes "there is a small amount of "Positions of protrusions and foreign objects" can also maintain the polishing device 100 with a high precision polishing process.

In this embodiment, since the linear scale 34 is used as the position sensor, the relative position of the polishing body 10 to the head 30 can be accurately measured.

Although the polishing body 10 is rotatably supported by the polishing body support member 31 through the mandrel 11 in this embodiment, the polishing body 10 does not necessarily need to be rotatably supported.

Next, in this embodiment, when the target load during polishing is achieved, the position control is switched to the load control, but it may be switched to the load control before the target load during polishing is achieved. In this case, it is possible to avoid "overshoot of the target load" caused by the restoring force of the elastic mechanism 32.

Claims (4)

A polishing device comprising: a holding portion for holding a material to be polished; and a polishing body for polishing the material to be polished held by the holding portion; and a head portion for supporting the polishing body via an elastic mechanism. And a driving mechanism for urging the head to move in a direction in which a separation distance from the material to be polished is changed relative to the material to be ground; and a control unit connected to the driving mechanism for controlling the driving A mechanism in which the head includes a polishing body support member for supporting the polishing body, and the elastic mechanism includes a pressure spring that presses the polishing body support member toward the material to be polished, and is arranged in parallel with the pressure spring A balance spring for supporting the weight of the abrasive body supporting member itself. The polishing device according to claim 1, wherein the polishing device includes a position sensor connected to the control unit and configured to measure a position of the polishing body with respect to the head. The polishing device according to claim 2, wherein the position sensor is a linear scale. The polishing device according to claim 2, wherein the control unit calculates a load to be applied to the polishing body based on a measurement value of the position sensor and a spring constant of the elastic mechanism, and controls the load.