JP6230921B2 - Polishing equipment - Google Patents

Description

  The present invention relates to a polishing apparatus for polishing a plate workpiece.

  In a polishing apparatus that polishes a plate-like workpiece such as a semiconductor wafer, the plate-like workpiece is polished while a polishing surface of a polishing pad is brought into contact with the plate-like workpiece and a slurry is supplied (see, for example, Patent Document 1). In the polishing apparatus described in Patent Document 1, the thickness of the plate workpiece is measured by bringing a contact of a measurement gauge into contact with the chuck table and the upper surface of the plate workpiece before starting polishing, and polishing is performed based on the measured thickness. By setting the time, the plate-like workpiece is finished to a desired thickness.

  Also, regarding the measurement of the thickness of the plate-like workpiece, by detecting the amount of fluctuation in the vertical direction of the carrier facing the back surface of the plate-like workpiece via the pressure fluid layer and the amount of fluctuation of the layer thickness of the pressure fluid layer. A polishing apparatus that measures the thickness of a plate-like workpiece during polishing has been proposed (for example, see Patent Document 2). Furthermore, a measuring device that irradiates the plate-like workpiece with light, determines the optical path length difference by measuring the interference between the light reflected by the upper surface of the plate-like workpiece and the light reflected by the lower surface, and measures the thickness of the plate-like workpiece. Has also been proposed (see, for example, Patent Document 3).

Japanese Patent No. 4553868 Japanese Patent No. 2897207 JP 2012-189507 A

  The method of measuring the thickness of the plate-like workpiece before starting the polishing and setting the polishing conditions such as the polishing time does not necessarily finish the plate-like workpiece to a desired thickness. For this reason, it is desirable to perform polishing while measuring the thickness of the plate-like workpiece, and finish the polishing when the desired thickness is reached.

  On the other hand, in order to measure the thickness of a plate-like workpiece by bringing a measurement gauge into contact with it or irradiating light, at least a part of the upper surface of the plate-like workpiece needs to be exposed. If the upper surface of the plate workpiece is intermittently exposed outside the polishing pad during polishing, the thickness of the plate workpiece can be measured at the timing when the upper surface of the plate workpiece is exposed outside the polishing pad. Although it is possible, if the upper surface of the plate-shaped workpiece is repeatedly exposed to the outside of the polishing pad or enters under the polishing pad, the contact resistance of the portion where the polishing pad contacts the outer periphery of the plate-shaped workpiece is reduced. It becomes large and a chip | tip may generate | occur | produce on the outer periphery of a plate-shaped workpiece. For this reason, unlike the case of grinding, normally, polishing is performed in a state where the polishing surface of the polishing pad larger than the plate-like workpiece is in full contact with the plate-like workpiece. Therefore, it is difficult to measure the thickness of the plate workpiece during polishing.

  With the measurement method described in Patent Document 2, the thickness of the plate-like workpiece can be measured during polishing, but this method cannot be applied when polishing while supplying slurry.

  The present invention has been considered in view of such problems, and an object of the present invention is to measure the thickness of a plate-like workpiece during polishing in a polishing apparatus that performs polishing while supplying slurry.

  A polishing apparatus according to the present invention includes a chuck table that holds a plate-like workpiece on a holding surface, and a polishing unit that is disposed above the chuck table and polishes the upper surface of the plate-like workpiece held on the chuck table; A polishing apparatus comprising: a slurry supply unit that supplies slurry to the upper surface of the plate-like workpiece to be polished by the polishing unit; and a thickness measuring unit that measures the thickness of the plate-like workpiece to be polished by the polishing unit. The polishing means includes a polishing pad formed in a disc shape and having a circular hole penetrating the center thereof, and the polishing pad extends in a direction perpendicular to a polishing surface in contact with the plate workpiece, A pipe-shaped rotary shaft having a cavity penetrating in the length direction, and a motor for rotating the rotary shaft. The slurry supply means includes a slurry supply pipe connected to a slurry supply source, and the rotary shaft A connecting portion connected to the rotating shaft so as to be rotatable, and supplying the slurry supplied from the slurry supply source through the slurry supply pipe along the inner wall of the rotating shaft, The thickness measuring means measures the thickness of the plate-like workpiece during polishing through the circular hole of the polishing pad and the cavity of the rotating shaft.

  The thickness measuring means includes: a light emitting unit that emits measurement light; a collimator lens that converts the measurement light emitted from the light emitting unit into parallel light; and the parallel light converted by the collimator lens A diffraction grating that splits reflected light that is incident on the upper surface of the plate-like workpiece and reflected by the lower surface of the plate-like workpiece, and an image sensor that receives the light dispersed by the diffraction grating And calculating the optical path length difference between the light reflected by the upper surface of the plate-like workpiece and the light reflected by the lower surface of the plate-like workpiece based on the amount of light received by the image sensor. And control means for calculating the thickness of the plate-like workpiece.

According to the polishing apparatus of the present invention, since the thickness of the plate-like workpiece is measured via the circular hole provided in the center of the polishing pad, the polishing surface of the polishing pad larger than the plate-like workpiece is the upper surface of the plate-like workpiece. The thickness of the plate-like workpiece can be measured even when it is in contact with the entire surface and the plate-like workpiece is not exposed outside the polishing pad. The slurry supplied along the inner wall of the rotating shaft is supplied to the polishing surface from a circular hole provided in the center of the polishing pad, and spreads over the entire polishing surface by centrifugal force. For this reason, the thickness of the plate-like workpiece can be accurately measured without the slurry affecting the measurement by the thickness measuring means.
Furthermore, if the thickness of the plate workpiece is calculated by calculating the optical path length difference between the light reflected from the upper surface of the plate workpiece and the light reflected from the lower surface, the thickness of the plate workpiece can be accurately measured. .

The perspective view which shows a grinding | polishing apparatus. The perspective view which shows the grinding | polishing means, thickness measurement means, and slurry supply means of a grinding | polishing apparatus. The side view sectional drawing which shows a slurry supply means. Side surface sectional drawing which shows thickness measurement means. Side surface sectional drawing which shows the grinding | polishing means, thickness measurement means, and slurry supply means of a 2nd grinding | polishing apparatus.

  A polishing apparatus 10 shown in FIG. 1 includes a base 11, a chuck table 12 that holds a plate-like workpiece, a polishing means 13 that includes a polishing pad 70 and polishes the plate-like workpiece held on the chuck table 12, and a polishing means. Feeding means 14 for moving 13 in the ± Z direction and thickness measuring means 15 for measuring the thickness of the plate-like workpiece held on the chuck table 12 are provided.

  The chuck table 12 sucks and holds the plate-like workpiece placed on the holding surface 121 parallel to the XY plane, and rotates the held plate-like workpiece by rotating. Further, the chuck table 12 is movable in the ± Y direction.

  The feed means 14 is configured such that when the motor 41 rotates the screw shaft 42 parallel to the ± Z direction, the moving portion 43 engaged with the screw shaft 42 is guided by the guide 44 and moved in the ± Z direction. Yes. The polishing means 13 is fixed to the moving unit 43 and moves in the ± Z direction as the moving unit 43 moves.

  In the polishing apparatus 10 configured as described above, the feeding means 14 rotates while the chuck table 12 holding the plate work rotates to rotate the plate work and the polishing means 13 rotates the polishing pad 70. The plate-like workpiece is polished by moving the polishing means 13 in the −Z direction and bringing the lower surface (polishing surface) of the polishing pad 70 into contact with the upper surface of the plate-like workpiece. The polishing pad 70 has a larger diameter than the plate workpiece to be polished, and the polishing pad 70 contacts the entire upper surface of the plate workpiece during polishing.

  As shown in FIG. 2, the polishing means 13 includes a rotation shaft 31 parallel to the ± Z direction, a mount 32 fixed to the lower end of the rotation shaft 31, a housing 33 that rotatably supports the rotation shaft 31, and a rotation. And a motor 34 for rotating the shaft 31. The polishing pad 70 includes a disk-shaped base 71 and a polishing portion 72 that is fixed to the lower surface of the base 71 and polishes the plate-like workpiece. The polishing pad 70 is attached to the mount 32 with the polishing portion 72 facing downward. The The polishing surface of the polishing pad 70 attached to the mount 32 is parallel to the XY plane and perpendicular to the rotation axis 31. When the motor 34 is used as a drive source to rotate the rotating shaft 31, the mount 32 and the polishing pad 70 attached to the mount 32 rotate as the rotating shaft 31 rotates.

  The thickness measuring means 15 includes a measuring unit 51 that radiates measurement light to a plate-like workpiece and receives reflected light reflected by the plate-like workpiece, a collimator lens 52 that converts the measurement light emitted by the measuring unit 51 into parallel light, and And a control means 53 for calculating the thickness of the plate-like workpiece based on the reflected light received by the measurement unit 51.

  The rotating shaft 31 constituting the polishing means 13 is a pipe-like straight pipe, and includes a cavity 311 penetrating in the length direction (± Z direction) at the center. Further, a circular hole 73 penetrating in the ± Z direction is provided at the center of the polishing pad 70. A circular hole 73 of the polishing pad 70 attached to the mount 32 communicates with the cavity 311 of the rotating shaft 31. The measurement light emitted from the measurement unit 51 travels in the −Z direction, passes through the cavity 311 of the rotation shaft 31 and the circular hole 73 of the polishing pad 70, and reaches the plate-like work held on the chuck table 12. The reflected light reflected by the measurement light that has reached the plate-like workpiece travels in the + Z direction, returns to the measurement unit 51 through the circular hole 73 of the polishing pad 70 and the cavity 311 of the rotating shaft 31.

  Further, the polishing apparatus 10 includes a slurry supply unit 16 that supplies a slurry to the polishing surface of the polishing pad 70.

  As shown in FIG. 3, the slurry supply means 16 is supplied from the slurry supply source 80 via the bottomed cylindrical connecting portion 61, the slurry supply pipe 62 connected to the slurry supply source 80, and the slurry supply pipe 62. And a slurry supply nozzle 63 for injecting the slurry 81 to the inside of the connecting portion 61.

  The connecting portion 61 includes an opening 612 at the center of the bottom surface 611, is fixed to the rotating shaft 31, and rotates together with the rotating shaft 31. The opening 612 communicates with the cavity 311 of the rotation shaft 31. The slurry 81 injected from the slurry supply nozzle 63 flows into the cavity 311 of the rotary shaft 31 from the opening 612 while receiving a centrifugal force due to the rotation of the rotary shaft 31. The slurry 81 that has flowed into the cavity 311 also receives centrifugal force due to rotation and flows along the inner wall of the rotation shaft 31. Then, the slurry 81 that has reached the lower end of the rotating shaft 31 flows along the inner wall of the circular hole 73, is discharged from the lower end of the circular hole 73, and is a plate-like work held by the polishing surface of the polishing unit 72 and the chuck table 12. Is supplied between the upper surface and the upper surface. The slurry 81 supplied between the polishing surface and the plate-like workpiece is also subjected to centrifugal force due to rotation and spreads outside the plate-like workpiece. Thereby, the slurry 81 can be supplied to the whole polishing surface.

  Since the slurry 81 is supplied along the inner wall of the rotating shaft 31 under the centrifugal force due to the rotation, a passage through which light passes is secured at the center of the cavity 311 and the measurement light emitted by the thickness measuring means 15 is platen. Can be reached.

  As shown in FIG. 4, the measuring unit 51 of the thickness measuring unit 15 reflects the light emitting unit 511 that emits the measuring light 591 and the measuring light 591 emitted by the light emitting unit 511 toward the plate-shaped workpiece in the −Z direction. The mirror 512, the sensor head 513 that transmits the reflected measurement light 591, the diffraction grating 514 that splits the reflected light 594 reflected by the measurement light 591 on the plate-like workpiece 90, and the light 595 that is split by the diffraction grating 514 is received. And an image sensor 515. The image sensor 515 is configured by arranging a plurality of light receiving portions in a straight line.

  The light emitting unit 511 is, for example, a super luminescent diode (SLD), and the measurement light 591 emitted from the light emitting unit 511 has a relatively wide spectral width in the near infrared region, for example. The wavelength of the measuring light 591 is preferably 800 μm or more, for example. The reflected light 594 reflected by the plate-like workpiece 90 is light obtained by interference between the light 592 reflected by the upper surface 91 of the plate-like workpiece 90 and the light reflected by the lower surface 92. When the phases of the light 592 and the light 593 are aligned, the amplitude is increased. When the phases of the light 592 and the light 593 are shifted, the amplitude is decreased. In particular, the phases of the light 592 and the light 593 are reversed. In this case, the amplitude becomes zero. Since the phase difference between the light 592 and the light 593 differs depending on the wavelength, the amplitude of the reflected light 594 differs depending on the wavelength. Therefore, by analyzing the spectrum of the reflected light 594, the optical path length difference between the light 592 and the light 593 can be obtained. Since the optical path length difference between the light 592 and the light 593 is twice the thickness d of the plate-like workpiece 90, ½ of the obtained optical path length difference is the thickness d of the plate-like workpiece 90.

  The diffraction grating 514 disperses the reflected light 594 by reflecting the reflected light 594 in different directions depending on the wavelength, and the image sensor 515 receives the light 595 dispersed by the diffraction grating 514. Since the angle of the reflected light 594 with respect to the reflection point of the diffraction grating 514 differs depending on the position of the light receiving unit of the image sensor 515, each light receiving unit receives a component of a specific wavelength in the reflected light 594.

  The image sensor 515 outputs a signal indicating the intensity of light received by each light receiving unit. The control means 53 shown in FIG. 2 calculates the optical path length difference between the light 592 and the light 593 by, for example, Fourier transforming the signal output from the image sensor 515, and obtains the thickness d of the plate workpiece 90.

  Thus, the thickness d of the plate-like workpiece 90 is obtained by calculating the optical path length difference between the light 592 reflected by the upper surface 91 of the plate-like workpiece 90 and the light 593 reflected by the lower surface 92. The thickness d can be accurately measured.

  As shown in FIG. 2, the thickness measuring means 15 measures the thickness of the plate-like workpiece held on the chuck table 12 through the circular hole 73 of the polishing pad 70 and the cavity 311 inside the rotating shaft 31. . Thereby, even if the upper surface of the plate-like workpiece is not exposed to the outside of the polishing pad 70, the thickness of the plate-like workpiece can be measured. That is, even during the polishing process in which the upper surface of the plate-like workpiece is not exposed to the outside of the polishing pad 70, the thickness of the plate-like workpiece can be measured. Since it is not necessary to expose the upper surface of the plate-shaped workpiece to the outside of the polishing pad 70, it is possible to prevent the outer periphery of the plate-shaped workpiece from being chipped.

  The control means 53 of the thickness measuring means 15 repeatedly calculates the thickness of the plate workpiece at a predetermined interval. Thereby, the thickness of the plate workpiece to be polished can be managed without reducing the polishing efficiency. When the thickness of the plate-like workpiece calculated by the control means 53 reaches a preset finish thickness, the polishing apparatus 10 ends the polishing. Thereby, a plate-shaped workpiece can be finished to a desired thickness with certainty.

  A second polishing apparatus 10A shown in FIG. 5 includes a thickness measuring means 15A and a slurry supplying means 16A in place of the thickness measuring means 15 and the slurry supplying means 16 of the polishing apparatus 10 described above. The rest is the same as the polishing apparatus 10.

  The slurry supply means 16A includes a hollow columnar connection portion 61A and a slurry supply pipe 62 connected to the slurry supply source 80 to communicate the slurry supply source 80 and the connection portion 61A. 61 A of connection parts are rotary joints, have circular opening in an upper surface and a lower surface, and the rotating shaft 31 has penetrated the inside. The upper and lower openings and the rotary shaft 31 are sealed so that the rotary shaft 31 can rotate and the slurry does not leak.

  On the side surface of the rotating shaft 31, a slurry intake port 312 that connects the cavity 311 and the outer peripheral side of the rotating shaft 31 is provided. The slurry inlet 312 is disposed at a height corresponding to the inside of the connecting portion 61A, and is always located in the connecting portion 61A even if the rotating shaft 31 rotates. The slurry supplied from the slurry supply source 80 via the slurry supply pipe 62 is accumulated in the connecting portion 61A and flows into the cavity 311 via the slurry intake port 312. The slurry that has flowed into the cavity 311 descends along the inner wall of the rotating shaft 31, passes between the rotating shaft 31 and the rod-shaped portion 54, and is discharged from the lower end of the circular hole 73.

  The thickness measuring unit 15A includes a rod-like portion 54 extending in the ± Z direction, a tip portion 55 provided at the tip of the rod-like portion 54, and the rod-like portion 54 inserted into the cavity 311 of the rotating shaft 31 of the polishing means 13. And a support portion 56 that is supported by. The tip portion 55 is located inside the circular hole 73 of the polishing pad 70 attached to the mount 32 of the polishing means 13.

  The thickness measuring means 15A, like the thickness measuring means 15 of the polishing apparatus 10 shown in FIG. 2, measures the thickness of the plate workpiece by radiating measurement light to the plate workpiece and performing spectral analysis of the reflected light. The rod-like portion 54 is, for example, an optical fiber, and transmits the measurement light emitted from the measurement portion provided at the upper end to be emitted from the distal end portion 55 to the plate-like workpiece, and the reflected light reflected by the plate-like workpiece is reflected by the measurement light. Communicate and return to measurement section. Note that the rod-like portion 54 may be a cylindrical simple straight pipe having a through hole penetrating in the ± Z direction.

  Thus, even if the amount of the slurry 81 supplied by the slurry supply means 16 is large due to the measurement light and the reflected light passing through the rod-shaped portion 54, the measurement light and the reflected light are not blocked by the slurry 81. The thickness of the plate-like workpiece can be measured.

  Note that the thickness measuring unit 15A is not a spectral interference thickness measuring device that measures the thickness of the plate-like workpiece based on the optical path difference length of the reflected light, but may measure the thickness of the plate-like workpiece with a different configuration. . For example, the thickness measuring unit 15A radiates ultrasonic waves from the tip portion 55, and receives the ultrasonic waves reflected from the upper surface and the lower surface of the plate-like workpiece, thereby measuring the thickness of the plate-like workpiece. It may be a sonic sensor. Further, the thickness measuring means 15A calculates the distance from the tip 55 to the upper surface of the plate workpiece by blowing a fluid such as air from the tip 55 to the upper surface of the plate workpiece and measuring the pressure of the fluid. It may be a back pressure sensor that measures the thickness of the plate-like workpiece by calculating the difference from the distance from the tip 55 calculated in advance to the holding surface 121 of the chuck table 12.

  The polishing apparatus may be a combination of the thickness measurement means 15 shown in FIG. 2 and the slurry supply means 16A shown in FIG. 5, or the thickness measurement means 15A shown in FIG. 5 and the thickness measurement means 15A shown in FIG. A combination with the slurry supply means 16 may also be used.

  The thickness measuring means only needs to access the plate-like workpiece through the circular hole 73 of the polishing pad 70 and the cavity 311 inside the rotary shaft 31 and measure the thickness of the plate-like workpiece. May be arranged on the top, a part may be arranged in the cavity 311 of the rotating shaft 31, or the whole may be arranged in the cavity 311 of the rotating shaft 31.

10, 10A polishing device,
11 base, 12 chuck table, 121 holding surface,
13 polishing means, 31 rotation axis, 311 cavity, 312 slurry inlet,
32 mount, 33 housing, 34 motor,
14 feeding means, 41 motor, 42 screw shaft, 43 moving part, 44 guide,
15, 15A thickness measuring means,
51 measuring unit, 511 light emitting unit, 512 mirror, 513 sensor head,
514 diffraction grating, 515 image sensor, 52 collimator lens,
53 control means, 54 rod-shaped part, 55 tip part, 56 support part,
591 measurement light, 592,593,595 light, 594 reflected light,
16, 16A slurry supply means, 61, 61A connection portion, 611 bottom surface,
612 opening, 62 slurry supply pipe, 63 slurry supply nozzle,
70 polishing pad, 71 base, 72 polishing part, 73 circular hole,
80 slurry source, 81 slurry,
90 plate work, 91 upper surface, 92 lower surface

Claims (2)

A chuck table for holding a plate-like workpiece on the holding surface;
A polishing means disposed above the chuck table and polishing an upper surface of the plate-like workpiece held by the chuck table;
Slurry supply means for supplying slurry to the upper surface of the plate-like workpiece to be polished by the polishing means;
Thickness measuring means for measuring the thickness of the plate-like workpiece polished by the polishing means;
A polishing apparatus comprising:
The polishing means includes
A polishing pad formed in a disk shape and having a circular hole penetrating the center;
A pipe-shaped rotating shaft having a cavity extending in a direction perpendicular to the polishing surface where the polishing pad is in contact with the plate-like workpiece and penetrating in the length direction;
A motor for rotating the rotating shaft;
With
The slurry supply means
A slurry supply pipe connected to the slurry supply source;
A connecting portion connected to the rotating shaft so as to be rotatable, and supplying the slurry supplied from the slurry supply source via the slurry supply pipe along the inner wall of the rotating shaft; ,
With
The thickness measuring means measures the thickness of the plate-like workpiece during polishing through the circular hole of the polishing pad and the cavity of the rotating shaft. The thickness measuring means includes
A light emitting part for emitting measurement light;
A collimator lens that converts the measurement light emitted from the light emitting unit into parallel light;
A diffraction grating that splits the reflected light in which the parallel light converted by the collimator lens is incident on the plate-like workpiece and reflected by the upper surface of the plate-like workpiece and the light reflected by the lower surface of the plate-like workpiece. When,
An image sensor that receives light separated by the diffraction grating;
By calculating the optical path length difference between the light reflected by the upper surface of the plate-like workpiece and the light reflected by the lower surface of the plate-like workpiece based on the amount of light received by the image sensor. Control means for calculating the thickness of the plate workpiece;
The polishing apparatus according to claim 1, comprising:

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