JP6961343B2 - Polishing equipment - Google Patents

Description

The present invention relates to a polishing apparatus.

Conventionally, as a polishing device for polishing the surface of a wafer made of a semiconductor material or the like, a polishing device using a rotation-driven polishing pad as described in, for example, International Publication No. 2013/038573 (Patent Document 1) has been known. Has been done. Generally, the polishing pad is provided at the tip of the rotating shaft, and the polishing pad including the rotating mechanism and the rotating shaft is supported by the head via an elastic mechanism. The head is supported by the device body via a drive mechanism.

As a control method of the drive mechanism, for example, a method that combines position control and load control as described in Japanese Patent Application Laid-Open No. 59-219152 (Patent Document 2) can be adopted. In this control method, the drive mechanism is controlled (position control) based on the position (coordinates) of the polishing pad until the polishing pad comes into contact with the wafer and the target load at the time of polishing is achieved, and the target load is reduced. After this is achieved, the drive mechanism is controlled (load control) based on the pressure generated on the contact surface between the polishing pad and the wafer. The position (Z coordinate) of the head when the target load at the time of polishing is achieved 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 can be measured, for example, by a load cell provided above the axis of rotation of the polishing pad. The measurement procedure is as follows. That is, the head is lowered (moved in a direction closer to the wafer) along the Z coordinate axis (vertical axis), and the polishing surface of the polishing pad is pressed against the wafer. Along with this, the elastic mechanism (coil spring) is deformed, and the polishing pad and the rotating shaft are relatively moved upward with respect to the head. As a result, the upper end of the rotating shaft is pressed against the load cell, the strain gauge in the load cell is deformed, and the force with which the upper end of the rotating shaft pushes the strain gauge is measured. Then, the Z coordinate value of the head is adjusted so that the force measured by the load cell becomes the target load.

In the above-mentioned polishing apparatus, when the polishing body passes through a place where minute protrusions or foreign substances are present during load control, the polishing pad is rapidly moved upward (pushed up). , The measured value of the load cell rises sharply. It is generally difficult to perform highly accurate load control by following such a sudden change in load. Further, in a high-precision load cell, since the measurable load range is relatively narrow, there is a possibility that an appropriate load cannot be measured.

International Publication 2013/038573 JP-A-59-219152

As a result of diligent studies, the present inventor can expand the measurable load range and expand the measurable load range by performing load control based on the position sensor (for example, linear scale) and the spring constant of the elastic mechanism. It was found that polishing can be performed with high accuracy even if changes occur.

The present invention is based on the above findings. That is, an object of the present invention is to expand the detection range of the load applied to the polishing body, and to maintain high-precision polishing even if the polishing body passes through a place where minute protrusions or foreign substances exist. To provide a device.

In the present invention, a holding portion that holds the material to be polished, a polishing body that polishes the material to be polished held by the holding portion, a head that supports the polishing body via an elastic mechanism, and the head are described. The head includes a drive mechanism that moves relative to the material to be polished in a direction in which the distance from the material to be polished changes, and a control unit that is connected to the drive mechanism and controls the drive mechanism. It has a polishing body support member that supports the polishing body, and the elastic mechanism is arranged in parallel with a pressure spring that pressurizes the polishing body support member toward the polishing material, and the polishing body. A balance spring that supports the weight of the body support member is provided, and the control unit measures the load based on the position of the head and the elastic coefficient of the pressurizing spring, and controls the load to a predetermined value. a polishing apparatus characterized by.

According to the present invention, since the load applied to the abrasive body is measured without going through a load cell or the like, the detection range of the load can be expanded, and the abrasive body passes through a place where minute protrusions or foreign substances are present. Also, it is possible to provide a polishing apparatus capable of maintaining a high-precision polishing process.

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

The position sensor may be of linear scale. In this case, it is easy to accurately measure the relative position of the polished body with respect to the head.

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

According to the present invention, since the load applied to the abrasive body is not directly measured by a load cell or the like, the detection range of the load can be expanded, and even if the abrasive body passes through a place where minute protrusions or foreign substances exist. , It is possible to provide a polishing apparatus capable of maintaining a high-precision polishing process.

It is a schematic perspective view which shows the polishing apparatus by one Embodiment of this invention. It is a schematic perspective view which shows the internal structure of the head of the polishing apparatus shown in FIG. It is a schematic side view when the head of the polishing apparatus shown in FIG. 1 is seen from the upper left side of FIG. FIG. 3 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. It is a block diagram which shows schematic the control device of the polishing apparatus shown in FIG.

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

FIG. 1 is a schematic perspective view showing a polishing apparatus 100 according to an embodiment of the present invention. As shown in FIG. 1, the polishing apparatus 100 according to the present embodiment is held on the bed 70, the table 60 as a holding portion provided on the bed 70 and holding the material to be polished (wafer Wa), and the table 60. The abrasive body 10 for polishing the polished material, the head 30 for supporting the abrasive body 10 via the elastic mechanism 32 (see FIG. 2), and the head 30 in the Z coordinate direction with respect to the apparatus main body 20 (in FIG. 1). It includes a drive mechanism 24 that moves in the vertical direction) and a control unit 50 that is connected to the drive mechanism 24 and controls the drive mechanism 24.

Of these, the table (holding portion) 60 holds a disk-shaped wafer Wa as an abrasive. The table 60 is supported by a rectangular parallelepiped support block 61 arranged on the bed 70.

Further, the polishing body 10 polishes the wafer Wa held on the table 60. As shown in FIG. 1, the polishing body 10 has a spindle 11 and a polishing pad 12 attached to one end of the spindle 11 (lower end of FIG. 1). As the polishing pad 12 of the present embodiment, a disk-shaped polishing pad 12 having a diameter of 10 mm is adopted.

The apparatus main body 20 of the present embodiment supports the head 30 via a drive mechanism 24 that moves the head 30 relative to the wafer Wa. As shown in FIG. 1, the apparatus main body 20 has a rectangular parallelepiped column 21, a columnar arm 22 whose one end is supported on one side surface 21a of the column 21 via a drive mechanism 24, and a column 21 on the upper surface 23a. It has a rectangular parallelepiped base 23 and a support in the above. A head 30 is attached to the other end of the arm 22, and the drive mechanism 24 moves the arm 22 in the vertical direction (Z coordinate direction in FIG. 1) on the one side surface 21a of the column 21. .. As a result, the head 30 is positioned in the Z coordinate direction.

Further, the column 21 of the present embodiment is moved on the base 23 in the length direction of the arm 22 (X coordinate direction in FIG. 1) by a known drive mechanism, whereby the head 30 is moved. Is positioned in the X coordinate direction.

Further, as shown in FIG. 1, the bed 70 supports the support block 61 of the table 60 and the apparatus main body 20. Specifically, the table 60 and the support block 61 are arranged at positions corresponding to the polished body 10 on the upper surface of the bed 70. In the present embodiment, on the lower surface of the support block 61, a ridge 62 that engages with two parallel grooves 71 carved along the Y coordinate direction of FIG. 1 is provided on the bed 70. The support block 61 can be moved along the two parallel grooves 71. As a result, the table 60 is positioned in the Y coordinate direction, that is, the head 30 is positioned with respect to the table 60 in the Y coordinate direction. The table 60 of the present embodiment has, for example, a mounting surface 60a having a diameter of 200 mm.

Next, the configuration of 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 case where the head 30 of the polishing apparatus 100 shown in FIG. 1 is viewed from the upper left side of FIG. FIG. 4 is a schematic side view of the head 30 of FIG. 3 in a plane parallel to the paper surface of FIG. 3 and passing through the axis of the spindle 11.

As shown in FIGS. 2 to 4, the head 30 of the present embodiment supports the polished body 10. The head 30 has a polishing body support member 31 that is supported via an elastic mechanism 32 and supports the spindle 11 of the polishing body 10. A known drive mechanism (not shown) for rotationally driving the spindle 11 is provided inside the abrasive body support member 31, so that the abrasive body 10 is rotated at a desired rotational speed. As shown in FIG. 4, the polished body support member 31 is a columnar shape having a flange portion 31a on the side surface, and above the flange portion 31a is a cover fixed to the arm 22 and surrounding the polished body support member 31. 35 is provided. As shown in FIG. 2, the outer shape of the cover 35 is an octagonal columnar shape. A through hole 35a is formed in the cover 35 in the vertical direction, and the abrasive body support member 31 can move in the vertical direction in the through hole 35a.

Further, as shown in FIG. 2, the elastic mechanism 32 of the present embodiment supports one pressure spring 32a that presses the polishing body 10 downward together with the polishing body support member 31 and the own weight of the polishing body support member 31. It is composed of two balancing springs 32b and 32c. The pressure spring 32a is installed at the upper end of the polishing body support member 31, and is adapted to generate an elastic force along the axial center of the spindle 11 of the polishing body 10. Further, the balance springs 32b and 32c are provided on the upper surface of the cover 35 in parallel with the pressure spring 32a on both sides of the pressure spring 32a in the Y-axis direction. In the present embodiment, the upper end of the pressure spring 32a is connected to the support 33, and the load applied to the polishing body 10 is measured via the pressure spring 32a.

Further, the polishing apparatus 100 includes a linear scale 34 as a position sensor for measuring the vertical coordinates (W coordinates in FIG. 2) of the polishing body 10 with respect to the head 30. As shown in FIG. 2, the linear scale 34 has a stator 34a fixed to the upper end of the abrasive body support member 31 and a mover 34b fixed above the cover 35 via the support member 36. .. The linear scale 34 measures the relative position of the polished body support member 31 with respect to the cover 35. Then, based on this measured value, the control device 50 evaluates the position (W coordinate) of the polished body 10 with respect to the head 10.

FIG. 5 is a schematic block diagram of the control device 50 connected to the polishing device 100 shown in FIG. As shown in FIG. 5, the control device 50 of the present embodiment includes a detection unit 51 that detects the relative positional relationship between the axial center of the spindle 11 of the polishing body 10 and the center of rotation of the table 60, and a load from the position control. A storage unit 52 that stores the Z coordinate of the abrasive body support member 31 when switching to control, a determination unit 53 that determines whether or not the abrasive body support member 31 has reached the Z coordinate, and a detection unit 51 The contact area between the polishing pad 12 and the wafer Wa is evaluated based on the relative positional relationship between the detected axial center of the spindle 11 of the polishing body 10 and the center of rotation of the table 60, and the contact area and the linear scale 34 are measured. It has a pressure evaluation unit 54 that evaluates whether or not the pressure applied to the wafer Wa is appropriate based on the value.

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

First, prior to the polishing process, the table 60 has two parallel grooves carved on the bed 70 so that the center of rotation of the table 60 and the axis of the spindle 11 of the polishing body 10 coincide with each other in the Y-axis direction. Positioned along. A wafer Wa as a material to be polished is placed on the table 60 with the surface to be polished facing upward. Then, when the polishing device 100 is activated by the user, the column 21 is moved on the base 23 until the center of rotation of the table 60 and the axis of the spindle 11 coincide with each other in the X-axis direction of FIG. At this time, the head 30 is retracted to a sufficient height in the initial state so that the polishing pad 12 of the polishing body 10 does not interfere with the edge of the table 60.

Then, based on the user's instruction, the driving mechanisms of the spindle 11 and the table 60 of the polishing body 10 are activated, respectively, and the polishing 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 is moved downward together with the arm 22 by the drive mechanism provided on the column 21, and the polishing pad 12 is pressed against the wafer Wa. In the present embodiment, in order to perform a smooth polishing process, the polishing liquid is supplied to the surface to be polished on the wafer Wa before the polishing pad 12 is pressed against the wafer Wa.

In the polishing apparatus 100 according to the present embodiment, the movement of the head 30 until the polishing pad 12 is pressed against the wafer Wa is position control, that is, control based on the position (Z coordinate) of the head 30. Then, when the polishing pad 12 is pressed against the wafer Wa and the target load at the time of polishing is achieved, the load control is switched based on the position (W coordinate) of the polishing body 10 with respect to the head 30 detected by the linear scale 34. In the load control of the present embodiment, the polishing body support member 31 takes into consideration the spring constant of the elastic mechanism 32 so that the pressure (surface pressure) applied to the contact surface between the wafer Wa and the polishing pad 12 becomes constant. The position (W coordinate) is controlled.

As is clear from the above, the load control in the present embodiment is not performed by directly measuring the load applied to the polishing body 10, but is measured by the linear scale 34 of the polishing body 10 with respect to the head 30. It is performed based on the position (W coordinate). Specifically, the load applied to the abrasive body 10 is evaluated by 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 this load becomes a predetermined value. ..

When the load control starts, the pressure evaluation unit 54 monitors the W coordinate of the abrasive body support member 31 in real time. The polishing pad 12 gradually approaches the wafer Wa from above the wafer Wa, and at the same time, is moved from the radial outer side to the radial inner side of the wafer Wa. Then, a part of the polishing pad 12 is pressed against the wafer Wa, and polishing of the wafer Wa is started. The polishing pad 12 is gradually moved inward in the radial direction 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 all of the polishing surface comes into contact with the wafer Wa, and the contact area becomes constant. In the present embodiment, the position (Z coordinate) of the head 30 is controlled so that the pressure (surface pressure) applied to the contact surface between the polishing pad 12 and the wafer Wa is constant, so that the load applied to the polishing body 10 is applied. Gradually increases and then becomes constant.

When the thickness of the wafer Wa decreases with the polishing process of the wafer Wa and the load applied to the polishing body 10 decreases, the head 30 moves downward together with the arm 22 by the drive mechanism 24 provided on the column 21. Will be done. Due to this movement, the polishing body 10 is pressed more strongly against the wafer Wa, so that the load applied to the polishing body 10 increases and the pressure spring 32a is compressed. Then, when the linear scale 34 detects that the W coordinate of the polishing body support member 31 registered in advance in the polishing apparatus 100 has been restored, the movement is stopped.

When polishing the wafer Wa, the column 21 is moved on the base 23, so that the polishing body 10 is linearly moved from one peripheral edge portion of the wafer Wa to the other peripheral edge portion along the X coordinate direction. In this polishing process, when the polishing body 10 passes through a place where minute protrusions or foreign substances exist on the surface of the wafer Wa, the polishing body 10 is rapidly moved upward (pushed up).
However, in the present embodiment, since the load is indirectly measured by using the linear scale 34, the measurable load range is wider than that of the case where the load is directly measured by, for example, a load cell.

Then, when the desired polishing process is achieved, the supply of the polishing liquid is stopped, and the head 30 is moved upward together with the arm 22 by the drive mechanism 24. Then, based on the user's instruction, the rotation of the polishing body 10 and the table 60 is stopped, and the wafer Wa is removed from the table 60. At this time, if necessary, the column 21 is moved on the base 23 in the negative direction of the X coordinate of FIG. 1, and the head 30 is retracted.

According to the present embodiment as described above, since the load applied to the polishing body 10 is measured without going through a load cell or the like, the detection range of the load can be expanded and a place where minute protrusions or foreign matters are present. It is possible to provide a polishing apparatus 100 capable of maintaining high-precision polishing processing even when the polishing body 10 passes through.

In the present embodiment, since the linear scale 34 is adopted as the position sensor, the relative position of the polishing body 10 with respect to the head 30 can be easily and accurately measured.

In the present embodiment, the polishing body 10 is rotatably supported by the polishing body support member 31 via the spindle 11, but the polishing body 10 does not necessarily have to be rotatably supported.

Further, in the present embodiment, when the target load at the time of polishing is achieved, the position control is switched to the load control, but the load control may be switched before the target load is achieved. In this case, it is possible to avoid overshoot of the load with respect to the target load caused by the repulsive force of the elastic mechanism 32.

10 Polished body 11 Spindle 12 Polished pad 20 Device body 21 Column 21a One side of column 22 Arm 23 Base 23a Top surface of base 30 Head 31 Polished body support member 31a Flange 32 Elastic mechanism 32a Pressurized spring 32b, 32c Balance spring 33 Support 34 Linear scale 34a Stator 34b Movable 35 Cover 50 Control device 51 Detection unit 52 Storage unit 53 Judgment unit 54 Pressure evaluation unit 60 Table 60a Mounting surface 61 Support block 62 Protrusion 70 Bed 71 Parallel groove 100 Polishing device Wa Wafer

Claims (4)

A holding part that holds the material to be polished and
An abrasive body that polishes the material to be polished held in the holding portion, and
A head that supports the polished body via an elastic mechanism,
A drive mechanism that moves the head relative to the material to be polished in a direction in which the distance from the material to be polished changes.
A control unit connected to the drive mechanism and controlling the drive mechanism,
With
The head has a polishing body support member that supports the polishing body, and has a polishing body support member.
The elastic mechanism includes a pressure spring that pressurizes the abrasive body support member toward the material to be polished, and a balance spring that is arranged in parallel with the pressure spring and supports the weight of the abrasive body support member. Prepare,
The control unit is a polishing device that measures a load based on the position of the head and the elastic modulus of the pressure spring, and controls the load so as to have a predetermined value. The polishing apparatus according to claim 1, wherein the polishing apparatus is connected to the control unit and includes a position sensor for measuring the position of the polishing body with respect to the head. The polishing apparatus according to claim 2, wherein the position sensor is a linear scale. The control unit calculates the load applied to the polished body based on the measured value of the position sensor and the spring constant of the elastic mechanism, and controls the load. The polishing apparatus according to 3.

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