TWI704613B - Surface polishing apparatus - Google Patents

Abstract

The technical problem of the present invention is to carry out the grinding according to the gap management method based on the difference between the thickness of the workpiece and the planetary wheel. It is possible to reliably measure both the thickness of the workpiece and the thickness of the planetary wheel by laser light, and obtain more The number of measurement data about the thickness of the workpiece improves the polishing accuracy.

A plane grinding device (1) is a planetary wheel (40) which is arranged between an upper plate (20) and a lower plate (10) while holding a workpiece (W), and at least a part of which is formed of a translucent material ), one side grinds both sides of the workpiece (W); it has: a first thickness measuring device (21a) installed on the upper plate (20) and measuring the thickness of the workpiece (W); and a second thickness measuring device (21b) ) Is installed at a position that is not affected by the rotation of the upper plate (20) and the lower plate (10), and the thickness of the star wheel (40) is measured.

Description

Plane grinding device

The present invention relates to a flat surface polishing device for polishing a plate-shaped workpiece such as a semiconductor wafer or a glass substrate that is held on a planetary wheel made of at least a part of a translucent material. More specifically, It is a flat grinding device for measuring and grinding the thickness of workpieces and planetary wheels.

In the flat surface grinding device, in the case of grinding both sides of the workpiece held on the planetary wheel, the thickness of the workpiece and the thickness of the planetary wheel are measured, and the difference (gap) between the thickness of the workpiece and the thickness of the planetary wheel becomes a predetermined When the value is set, the grinding ends, thereby obtaining a workpiece with high flatness.

In the case of the gap management method of grinding that manages the difference between the thickness of the workpiece and the thickness of the planetary wheel, conventionally, the thickness of the workpiece was measured by laser light during the grinding process, and the thickness of the planetary wheel was not used for grinding the workpiece. At this time, the planetary wheel was taken out of the flat grinding device and measured with a micrometer or the like. Therefore, it takes time and effort to measure the thickness of the cruiser. Not only is it inefficient, but there are also human errors such as measurement errors or input errors in measurement data. The risk of error.

Patent Document 1 discloses a thickness measuring device in which laser light is installed on the support frame of a flat surface polishing device, and the laser light from the thickness measuring device is irradiated to the workpiece through a window provided on the upper platen. The thickness of the workpiece is measured by receiving the reflected light reflected on the surface and back of the workpiece.

However, as disclosed in Patent Document 1, since the thickness measuring device is fixedly installed on the support frame, the laser light is irradiated to the workpiece through the window portion of the rotating upper platen, so only when the window portion passes the measurement position The measurement data can only be obtained, but there is a problem that the number of measurement data is small. The grinding accuracy of a workpiece is improved as the number of measurement data about the thickness of the workpiece increases. Therefore, it is desirable to obtain as many measurement data as possible.

On the other hand, Patent Document 2 discloses that an optical measuring device including a light source is attached to an upper platen, and the optical measuring device is rotated integrally with the upper platen while measuring the thickness of the workpiece. In this way, although the amount of measurement data obtained is large, the optical measurement device including the light source constituted by the laser oscillator is bulky and heavy as a whole, so the structure including not only the rotating part of the upper platen will be complicated It is very difficult to maintain the balance during the rotation of the upper plate, so the upper plate is prone to vibration. Therefore, the measurement data is easily affected by noise caused by the vibration of the upper platen. At this time, because the work piece has excellent light transmittance, it is hardly affected by the aforementioned noise and it is difficult to measure the thickness. However, in the case of a cruise wheel with a lower light transmittance than the work piece, it is irradiated with laser light. The reflection intensity is weaker than the workpiece, so it is greatly affected by the aforementioned noise and difficult The case of measuring thickness.

In Patent Document 2, although it is also proposed to separate the light source from the optical measurement device, install only the optical measurement device on the upper plate, and supply laser light to the optical measurement device through the optical rotary connector from the light source, but through The laser light or reflected light system of the optical rotary joint is easily attenuated by the optical rotary joint or contains noise accompanying rotation, which hinders the thickness measurement of the cruise wheel with lower light transmittance than the workpiece.

[Prior Technical Literature]

[Patent Literature]

[Patent Document 1] JP 2008-227393 A

[Patent Document 2] JP 2002-59364 A

The technical problem of the present invention is that in a plane polishing device that polishes a workpiece such as a semiconductor wafer or a glass substrate held on a planetary wheel, in order to perform a gap management method according to the difference in thickness between the workpiece and the planetary wheel, it can The thickness of the workpiece and the thickness of the planetary wheel are measured by the laser beam, and more measurement data about the thickness of the workpiece can be obtained to improve the grinding accuracy.

In order to solve the aforementioned problems, the present invention is a flat surface grinding device, which has: a lower table, which is supported to be freely rotatable; an upper plate, which is supported to be liftable and rotatable; and a cruiser, which is arranged on the above Between the fixed plate and the lower fixed plate, and hold the workpiece that is ground by the upper and lower fixed plates; and the workpiece held on the planetary wheel is clamped by the upper and lower fixed plates to grind both sides of the workpiece , Characterized in that: the planetary wheel is formed at least partly with a light-transmitting material, and has: a first thickness measuring device installed on the upper platen, irradiating the workpiece with laser light and coming from the workpiece Reflected light on the surface and the inside of the light is received to measure the thickness of the workpiece; and a second thickness measuring device is installed at a position that is not affected by the rotation of the upper plate and the lower plate, and illuminates the cruise star The light is emitted and the reflected light from the surface and the inside of the star wheel is received to measure the thickness of the star wheel.

In this case, it is preferable that the surface polishing device is a light source having the laser light, and the first thickness measuring device is connected to the light source through a rotary joint.

In addition, the upper surface plate is formed with a measuring window for a workpiece and a measuring window for a planetary wheel through which laser light penetrates, and the first thickness measuring device measures the thickness of the workpiece through the measuring window for the workpiece. The second thickness measuring device preferably measures the thickness of the planetary wheel through the measuring window for the planetary wheel.

Furthermore, the position where the second thickness measuring device is mounted is preferably a body supporting the upper plate and the lower plate.

According to the present invention, the first thickness measuring device for measuring the thickness of the workpiece by irradiating laser light to the workpiece is mounted on the upper plate supported to be rotatable, and irradiates at least a part of the cruise star made of a light-transmitting material. The second thickness measuring device that emits light to measure the thickness of the planetary wheel is installed at a position that is not affected by the rotation of the upper plate and the lower plate. Therefore, both the thickness of the workpiece and the thickness of the planetary wheel can be reliably measured by laser light, and more measurement data about the thickness of the workpiece can be obtained. In addition, when measuring the thickness of the planetary wheel, there is no need to remove the planetary wheel from the grinding device every time. Therefore, it is easy to manage the gap between the thickness of the workpiece and the thickness of the planetary wheel, and the number of work steps can be reduced. In addition, since it can prevent the planetary wheel from being deformed or damaged due to the removal and reloading of the planetary wheel, it is possible to prevent the deformation or damage from causing uneven contact with the grinding surfaces of the upper and lower surface plates to make the state of the grinding surfaces unstable. This results in uneven machining accuracy of the workpiece, and stable grinding can be achieved.

1‧‧‧Plane grinding device

2‧‧‧Body

3‧‧‧Light source

6‧‧‧Rotary joint

10‧‧‧Place Fix

20‧‧‧Upper Fix

21a‧‧‧The first thickness measuring device

21b‧‧‧The second thickness tester

24a‧‧‧Measurement window for workpiece

24b‧‧‧Measurement window for cruise ship

31‧‧‧Fitting plate suspension

32‧‧‧Lift rod (lift shaft)

40‧‧‧Star Cruise

W‧‧‧Workpiece

[Figure 1] is a cross-sectional view schematically showing an embodiment of the surface polishing apparatus of the present invention.

[Figure 2] A schematic plan view of the positional relationship between the planetary wheel arranged on the lower plate and the measuring hole formed on the upper plate.

The plane polishing device 1 of this embodiment is used to polish a plate-shaped workpiece W having light transmissivity (light permeability) such as silicon wafers, sapphire wafers, ceramic wafers, crystal wafers, glass substrates, etc. The two sides of this system have: a lower plate 10, which is rotatably supported on the body 2; an upper plate 20, which is movably and rotatably supported on the body 2; and a star wheel 40, which is held by the upper fixed plate. The workpiece W to be polished by the plate 20 and the lower platen 10. Although polishing pads 18a and 18b are attached to the lower surface of the upper plate 20 and the upper surface of the lower plate 10, instead of the polishing pads 18a and 18b, a structure with a grindstone attached is adopted, or the surface itself is a polishing surface. The structure is also possible.

A sun gear 11 is arranged in the center system of the lower surface plate 10, and an internal gear 12 is arranged on the outer periphery of the lower surface plate 10 so as to surround the lower surface plate 10. The lower surface plate 10, the upper surface plate 20, the sun gear 11, and the internal gear 12 are arranged coaxially with the axis L as the center. In addition, on the lower plate 10, a plurality of planetary gears 40 are meshed with the sun gear 11 and the internal gear 12 and are arranged. A first drive shaft 13 is connected to the lower center of the sun gear 11, a second drive shaft 14 is connected to the lower center of the bottom plate 10, and a third drive shaft 15 is connected to the lower center of the internal gear 12. In addition, a fourth drive shaft 16 is connected to the center of the bottom platen 10, and the fourth drive shaft 16 is housed in the first drive shaft 13. The first drive shaft 13 is housed in the second drive shaft 14, and the second drive shaft 14 is housed in the third drive shaft 15. The first to fourth drive shafts 13 to 16 are configured to be driven and rotated by a drive device not shown.

As shown in Figure 2, between the upper platen 20 and the lower platen 10, a plurality of planetary wheels with teeth are arranged at equal intervals on the outer circumference. 40. The tooth part meshes with the sun gear 11 and the internal gear 12, and by the rotation of the sun gear 11 and the internal gear 12, the planetary gear 40 rotates and revolves around the sun gear 11. Each planetary wheel 40 has a workpiece holding hole 41 into which the workpiece W is fitted, and the workpiece holding hole 41 is formed to be different from the center of the planetary wheel 40. The planetary wheel 40 is a part or all of it, and it is necessary to be formed of a material that can penetrate the laser light used for the measurement. As the material, glass epoxy, polyvinyl chloride resin, acrylic resin, urethane resin, amide resin, polyethylene terephthalate resin (PET), polycarbonate resin can be used Synthetic resins such as ester resins and polystyrene resins, glass, etc. are used alone or in combination of two or more.

The upper plate 20 is mounted to the lifting rod 32 of the lifting actuator 7 as a lifting shaft through a plate suspension 31. The lifting actuator 7 is supported by the body 2, and the lifting rod 32 is centered on the same axis L as the lower platen 10, the upper platen 20, the sun gear 11, and the internal gear 12.

This structure will be described in more detail; on the lower surface of the outer peripheral side of the plate suspension 31, a plurality of supporting studs 33 extending downward in the circumferential direction are provided, and the supporting studs 33 are installed on the upper surface. The upper surface of the plate 20. In addition, between the inner peripheral surface of the fixed plate suspension 31 and the outer peripheral surface of the lifting rod 32, a bearing 34 is interposed, although the fixed plate suspension 31 and the lifting rod 32 are fixed in the vertical direction. However, it is relatively free to rotate relative to the direction of rotation of the upper platen 20.

The upper platen 20 is raised to the standby position (not shown) by the contraction of the lifting rod 32 caused by the driving of the lifting actuator 7 when the workpiece W is not being polished, and when the workpiece W is being polished, With the lifting actuator The extension of the lifting rod 32 caused by the driving of 7 drops to the grinding position in FIG. 1. When the upper fixed plate 20 is lowered, because the hook 22 installed on the upper fixed plate 20 is engaged with the driver 17 at the upper end of the fourth drive shaft 16, the upper fixed plate 20 and the fixed plate suspension 31 are connected by the fourth drive shaft 16 is driven by the driver 17 to rotate integrally.

When the workpiece W is polished by the flat surface polishing device 1 constructed in this way, after each planetary wheel 40 has mounted the workpiece W, the upper platen 20 is extended from the standby position by the lift rod 32 driven by the lift actuator 7 Lower to the grinding position in FIG. 1, and the hook 22 mounted on the upper platen 20 is engaged with the driver 17. In this state, the first to fourth drive shafts 13-16 are driven and rotated by a driving device not shown, and each planetary gear 40 rotates and revolves around the sun gear 11 and is held by the planetary gear The upper and lower surfaces of the workpiece W of 40 are ground by the upper plate 20 and the lower plate 10.

The surface polishing device 1 is provided with a thickness measuring device for measuring the thickness of the workpiece W and the thickness of the planetary wheel 40, and finishing polishing when the difference in thickness (gap) becomes a predetermined value. , And used to measure the thickness of the workpiece W and the thickness of the star wheel 40 with laser light. For this person, an explanation is given below.

The body 2 is provided with a light source 3 that outputs laser light, and an arithmetic control unit 4, and on the upper plate 20, a first thickness measuring device 21a for measuring the thickness of the workpiece W using laser light, the light source 3, and the 1. The thickness measuring device 21a is connected through the rotary joint 6 by the optical cable 51a. At a position that is not affected by the rotation of the upper plate 20 and the lower plate 10, a A second thickness measuring device 21b for measuring the thickness of the star wheel 40. The second thickness measuring device 21b and the light source 3 are connected by an optical cable 51b. In addition, the light source 3 is connected to the arithmetic control unit 4. In this embodiment, although the laser light output from the light source 3 is an infrared laser, it can be any thickness of either the workpiece W or the cruise wheel 40. The measuring person may be other lasers.

The mechanism for measuring the thickness of the workpiece W and the star wheel 40 will be described in further detail.

A holding bracket 36 is fixed to the support stud 33. By holding the first thickness measuring device 21 a to the holding bracket 36, the first thickness measuring device (probe) 21 a is attached to the upper side of the upper platen 20. That is, the first thickness measuring device 21a is installed to rotate together with the upper platen 20. In addition, the first thickness measuring device 21a may be installed so as to rotate together with the upper platen 20, and it may be fixed to a location other than the support stud 33. Just below the first thickness measuring device 21a, a first thickness measuring hole 23a penetrating the upper platen 20 up and down is formed. The measurement window 24a for a workpiece|work is attached to the 1st thickness measurement hole 23a. The measurement window 24a for the workpiece is a cylindrical body made of synthetic resin or glass, and has an outer diameter approximately equal to the diameter of the first thickness measurement hole 23a. The upper end of the measurement window 24a for the workpiece is provided with The flange portion 25a having a larger diameter than the diameter of the first thickness measurement hole 23a is attached by engaging the flange portion 25a with the surface of the upper platen 20. In addition, a light-transmitting window plate 26a is provided at the lower end of the workpiece measurement window 24a. In this way, the first thickness measuring device 21a is constantly positioned directly above the first thickness measuring hole 23a, and more information about the workpiece W can be obtained. The number of thickness measurement data.

In addition, as shown in FIG. 2, the first thickness measurement hole 23a is formed in a range E passing through the vicinity of the center of the workpiece W during polishing. Thereby, the first thickness measurement hole 23a can measure the thickness of the workpiece W so as to pass through the center or the vicinity of the center of the workpiece W. Therefore, more measurement data about the thickness of the workpiece W can be obtained.

The second thickness measuring device (probe) 21b is installed in a position not affected by the rotation of the upper platen 20 and the lower platen 10, and is installed in the body 2 in this embodiment. Thereby, it is possible to prevent the measurement data about the thickness of the planetary wheel 40 being measured from being mixed with noise caused by vibration generated during the grinding process. At a position directly below the second thickness measuring device 21b of the upper platen 20, a second thickness measuring hole 23b penetrating the upper platen 20 up and down is formed. In the second thickness measuring hole 23b, a measuring window 24b for the cruiser having the same flange portion 25b and window plate 26b as the first thickness measuring hole 23a, the flange portion 25b is engaged with the surface of the upper plate 20 installation.

In addition, the first thickness measurement hole 23a and the second thickness measurement hole 23b are such that the distance between the center of the first thickness measurement hole 23a and the axis L and the distance between the center of the second thickness measurement hole 23b and the axis L are equal Way, formed on the upper plate 20. That is, the first thickness measurement hole 23a, the second thickness measurement hole 23b, the first thickness measurement device 21a, and the second thickness measurement device 21b are provided on the same circumference with the axis L as the center.

As for the material of the window plate 26a, the laser light irradiated from the first thickness measuring device 21a and the laser light reflected from the workpiece W are used to pass through, specifically, quartz glass, BK-7 Waiting Glass-based materials, sapphire, resin, and other materials having light transmittance (light transmittance) are preferably transparent materials. As for the material of the window plate 26b, the laser light irradiated from the second thickness measuring device 21b and the laser light reflected from the star wheel 40 can penetrate, specifically, quartz glass, BK-7 Such as glass-based materials, sapphire, resin, and other materials having light transmittance (light transmittance), preferably transparent materials.

In the lifting rod 32, a rotary joint 6 is arranged on the same axis as the axis L of the lifting rod 32. In this embodiment, a rotary joint 6 is arranged between the lower end of the lifting rod 32 and the table suspension 31, and through the rotary joint 6, the light source 3 and the first thickness measuring device 21a are operated by the optical cable 51a. connection.

Using the above thickness measuring device, when performing the grinding of the gap management method that manages the difference between the thickness of the workpiece and the thickness of the planetary wheel, the thickness of the planetary wheel 40 is measured when the workpiece W is not polished, and the thickness of the workpiece is measured It is carried out during grinding.

That is, the thickness measurement of the planetary wheel 40 is performed before the first workpiece is polished, or after the polishing of the workpiece is completed, after removing water from the polishing slurry or washing water, and before the next workpiece W is polished.

Specifically, the thickness measurement of the star wheel 40 is performed by stopping the rotation of the upper surface plate 20 with the star wheel measuring window 24b installed in the second thickness measuring hole 23b positioned directly below the second thickness measuring device 21b. In the ascending state, in this state, the star wheel 40 is slowly rotated and revolved. At this time, the laser light irradiated from the second thickness measuring device 21b passes through the window plate 26b of the measuring window 24b for the planetary wheel and reaches the swimming pool. The surface and the back surface of the star wheel 40, and the reflected light from the surface and the back surface passes through the window plate 26b and is received by the second thickness measuring device 21b. In addition, the received reflected light is transmitted to the calculation control unit 4 through the optical cable 51b, and the thickness of the star wheel 40 is calculated by the calculation control unit 4 based on the reflected light.

At this time, since the second thickness measuring device 21b is connected by the optical cable 51b without passing through the rotary joint 6 from the light source 3, it will not receive the laser light irradiated on the cruise wheel 40 or the like when the rotary joint 6 is connected. The thickness can be reliably measured due to the attenuation of reflected light or the influence of noise.

On the other hand, the thickness measurement of the workpiece W is performed while grinding the workpiece W while supplying the polishing slurry between the upper table 20 and the lower table 10.

Specifically, the laser light irradiated from the first thickness measuring device 21 a is the laser light output from the light source 3 and is transmitted by the optical cable 51 a that passes through the rotary joint 6. The laser light irradiated from the first thickness measuring device 21a is located directly below the window plate 26a of the workpiece measuring window 24a installed in the first thickness measuring hole 23a formed directly under the first thickness measuring device 21a. When the workpiece W passes directly under the window plate 26a, it passes through the window plate 26a and reaches the surface and the back surface of the workpiece W, and the reflected light from the surface and the back surface of the workpiece W passes through the window plate 26a to be measured by the first thickness measuring device 21a By the light. The reflected light of the received light is transmitted to the calculation control unit 4 through the optical cable 51 a and the rotary joint 6, and the thickness of the workpiece W is calculated by the calculation control unit 4 based on the reflected light.

The measured thickness of the workpiece W and the thickness of the star wheel 40, The arithmetic control unit 4 compares, and finishes polishing when the difference reaches a predetermined value. Thereby, the desired workpiece W with high flatness can be obtained.

In addition, in this embodiment, the first thickness measuring device 21a and the second thickness measuring device 21b are formed on the upper side so that the first thickness measuring hole 23a and the second thickness measuring hole 23b are equidistant from the axis L. Disk 20. However, considering the structure of the device, the first thickness measuring device 21a and the first thickness measuring hole 23a, or the second thickness measuring device 21b and the second thickness measuring hole 23b are formed at positions at different distances from the axis L It can be.

In addition, the thickness measurement of the planetary wheel 40 may be performed when the workpiece W is being polished. The thickness measurement of the planetary wheel 40 during the grinding of the workpiece W is based on the rotation of the upper plate 20 and the rotation and revolution of the planetary wheel 40, and the planetary wheel 40 is located in the second thickness measuring device 21b and the second thickness measuring hole Measure when it is directly below 23b. At this time, since the polishing slurry is supplied between the upper platen 20 and the lower platen 10, the reflected light received by the second thickness measuring device 21b includes noise caused by the polishing slurry, washing water, etc. However, by appropriately selecting the material of the cruise star 40 whose reflection intensity from the cruise star 40 is greater than the value of the noise, it is possible to perform the measurement with less influence of the noise.

In addition, when measuring the thickness of the planetary wheel 40 during the grinding of the workpiece W, it is preferable to form a plurality of second thickness measurement holes 23b on the upper surface plate 20. At this time, the second thickness measurement holes 23b are formed to be equidistant from each other on the same circumference centered on the axis L, and are formed as the distance between the second thickness measurement holes 23b and the axis L and the second thickness Tester The distance between 21b and the axis L is equal.

Furthermore, although the measurement data about the thickness of the workpiece W and the planetary wheel 40 measured by the first thickness measuring device 21a and the second thickness measuring device 21b are maintained in the state of the reflected light, the calculation control unit 4 calculates the data from The reflected light of the workpiece W and the star wheel 40 is converted into electrical signals by the first thickness measuring device 21a and the second thickness measuring device 21b, and the first thickness measuring device 21a and the calculation control unit 4 are connected through the rotary joint 6 A cable (not shown) is sent to the calculation control unit 4, and is sent to the calculation control unit 4 via a cable (not shown) connecting the second thickness measuring device 21b and the calculation control unit 4 without passing through the rotary joint 6 Alternatively, or by wirelessly transmitting from the first thickness measuring device 21a and the second thickness measuring device 21b to the arithmetic control unit 4, the same effects as the present invention can be obtained.

Furthermore, the installation positions of the light source 3, the arithmetic control unit 4, and the second thickness measuring device 21b are required to be installed at locations other than the configuration accompanying the rotation or elevation of the upper plate 20 or the lower plate 10, etc., by connecting with the body 2 It is also possible to obtain the effects of the present invention if it is provided at a location other than the body 2 for additional holding means or the like.

1‧‧‧Plane grinding device

2‧‧‧Body

3‧‧‧Light source

4‧‧‧Computer control unit

6‧‧‧Rotary joint

7‧‧‧Elevating actuator

10‧‧‧Place Fix

11‧‧‧Sun Gear

12‧‧‧Internal gear

13‧‧‧1st drive shaft

14‧‧‧2nd drive shaft

15‧‧‧3rd drive shaft

16‧‧‧4th drive shaft

17‧‧‧Drive

18a‧‧‧Lapping Pad

18b‧‧‧Lapping Pad

20‧‧‧Upper Fix

21a‧‧‧The first thickness measuring device

21b‧‧‧The second thickness tester

22‧‧‧hook

23a‧‧‧The first thickness measuring hole

23b‧‧‧The second thickness measuring hole

24a‧‧‧Measurement window for workpiece

24b‧‧‧Measurement window for cruise ship

25a‧‧‧Flange

25b‧‧‧Flange

26a‧‧‧Window panel

26b‧‧‧Window panel

31‧‧‧Fitting plate suspension

32‧‧‧Lift rod (lift shaft)

33‧‧‧Support stud

34‧‧‧Bearing

36‧‧‧Keep the bracket

40‧‧‧Star Cruise

51a‧‧‧Optical Cable

51b‧‧‧Optical Cable

W‧‧‧Workpiece

L‧‧‧Axis

Claims (3)

A plane grinding device is provided with: a lower plate, which is supported to be freely rotatable; an upper plate, which is supported to be lifted and rotatably freely; and a star wheel, which is arranged between the aforementioned upper plate and lower plate, and Holds the workpieces ground by the upper and lower plates; and clamps the workpiece held on the planetary wheel with the upper and lower plates to grind both sides of the workpiece, characterized by: the planetary wheel, At least a part is formed of a light-transmitting material, and has: a first thickness measuring device, which is installed on the upper platen, irradiates the workpiece with laser light, and receives the reflected light from the surface and back of the workpiece The thickness of the workpiece is measured by this; and a second thickness measuring device is installed at a position that is not affected by the rotation of the upper and lower platens, and irradiates the laser light from the surface of the cruise wheel The reflected light from and inside is received to measure the thickness of the planetary wheel, and the position where the second thickness measuring device is installed is a body supporting the upper plate and the lower plate. The surface polishing device described in the first item of the patent application, wherein the light source having the laser light, and the first thickness measuring device is connected to the light source through a rotary joint. The flat surface polishing device described in claim 1 or 2, wherein the upper surface plate is formed with a measuring window for a workpiece and a measuring window for a star wheel through which laser light penetrates, and the first thickness measuring device The thickness of the workpiece is measured through the measuring window for the workpiece, and the second thickness measuring device measures the thickness of the planetary wheel through the measuring window for the planetary wheel.

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