Surface treatment device

Abstract

[Problem] To provide a surface treatment apparatus that can produce wafers with uniform thickness without reducing flexural strength. [Solution] The processing unit of the surface treatment apparatus for processing the surface of a workpiece includes: a laser oscillator that emits laser light; a condenser that forms the laser light emitted by the laser oscillator into multiple beams; a collimating lens disposed between the laser oscillator and the condenser to collimate the laser light into parallel light; a beam intensity adjuster disposed between the condenser and the collimating lens to adjust the intensity of the multiple beams; and a rotation mechanism that rotates the condenser.

Description

[Technical Field]

[0001] The present invention relates to a surface treatment apparatus for treating the surface of a workpiece. [Previous Technology]

[0002] A wafer system with multiple components such as ICs and LSIs formed on the front side by multiple intersecting predetermined dividing lines is ground on the back side by a grinding device. After being formed to the required thickness, it is divided into individual component chips by a dicing device and a laser processing device. The divided component chips are used in electronic devices such as mobile phones and personal computers.

[0003] The grinding apparatus comprises the following components and can process a wafer to a required thickness: a chuck stage that holds the wafer; a grinding unit that rotatably supports a grinding stone, which grinds the wafer held on the chuck stage; and a grinding feed mechanism that brings the grinding unit close to the wafer and contacts the grinding stone with the upper surface of the wafer (for example, see Patent Document 1). [Contemporary Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2000-288881 [Summary of the Invention]

[0005] [Problem to be solved by the invention] In the grinding process performed in the above-mentioned grinding apparatus, since the processing surface of the wafer is pressed by a rotating grinding stone and the process is carried out in a fine manner, there is a problem that multiple grinding marks remain on the processing surface in an arc shape, which reduces the flexural strength of the wafer after division.

[0006] Furthermore, since the finished thickness of the wafer depends on the gap between the chuck stage holding the wafer and the grinding stone, the gap is not fixed due to the wear of the grinding stone and the mechanical rigidity of the grinding unit in the grinding apparatus. This makes it difficult to uniformly form the wafer thickness over the entire area. Moreover, when the wafer thickness becomes uneven, it is also difficult to use the aforementioned grinding apparatus to locally grind the wafer and adjust it to achieve a uniform wafer thickness.

[0007] Therefore, the object of the present invention is to provide a surface treatment apparatus that does not cause a reduction in flexural strength, but can make the wafer into a uniform thickness.

[0008] [Technical Means for Solving the Problem] According to the present invention, a surface treatment apparatus is provided for treating the surface of a workpiece, and includes: a chuck stage for holding the workpiece; a processing unit for processing the surface of the workpiece held on the chuck stage; a processing feed mechanism for feeding the chuck stage and the processing unit relative to each other, and the processing unit includes: a laser oscillator for emitting laser light; a condenser for forming the laser light emitted by the laser oscillator into a plurality of beams; a collimating lens disposed between the laser oscillator and the condenser for collimating the laser light into parallel light; a beam intensity adjuster disposed between the condenser and the collimating lens for adjusting the intensity of the plurality of beams; and a rotation mechanism for rotating the condenser.

[0009] Preferably, the concentrator is composed of a microlens array or a diffractive optical element. Preferably, the beam intensity adjuster adjusts the spatial intensity distribution of the beam. Preferably, the processing unit uses the concentrator to position the focusing point on the surface of the workpiece to be processed and applies an ablation process to that surface.

[0010] Preferably, a liquid storage tank is provided between the concentrator and the workpiece, the liquid storage tank being filled with liquid to the surface of the workpiece to be treated. Preferably, the surface of the workpiece is treated by plasma, the plasma being generated by irradiating laser light onto the liquid filling the surface of the workpiece in the liquid storage tank. Alternatively, the surface of the workpiece is treated by cavitation, the cavitation being generated by irradiating laser light onto the liquid filling the surface of the workpiece in the liquid storage tank. Preferably, a measuring device is provided, the measuring device measuring the thickness or height of the workpiece held on the chuck stage.

[0011] [Effects of the Invention] According to the present invention, in the case of processing by conventional grinding apparatus, multiple grinding marks formed in an arc shape are avoided on the grinding surface, and the problem of decreased flexural strength is suppressed. Furthermore, since the finished thickness of the workpiece does not depend on the interval between the chuck table and the grinding stone as in conventional grinding apparatus, it is easy to form the workpiece with a uniform thickness.

Implementation Method

[0013] Hereinafter, a surface treatment apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0014] FIG1 shows the workpiece of this embodiment. The workpiece is, for example, a silicon (Si) wafer 10 on the front side 10a having a plurality of elements 12 divided by intersecting multiple predetermined dividing lines 14. A protective adhesive film T is adhered to the front side 10a of the wafer 10 and, as shown in the lower part of FIG1, is integrated with the wafer 10 to protect the front side 10a when the back side 10b is processed by the surface treatment apparatus 1 described later.

[0015] FIG2 is an overall perspective view of the surface treatment apparatus 1 according to this embodiment. The surface treatment apparatus 1 includes an apparatus housing 2 and has: a body portion 21 in a generally rectangular parallelepiped shape; and an upright wall 22 disposed at the rear end of the body portion 21 and erected in the vertical direction. The surface treatment apparatus 1 includes: a holding unit 3, which includes a chuck stage 32 disposed on a cover member 31 on the body portion 21 and attracts and holds the wafer 10; and a processing unit 4, which processes the back side 10b of the wafer 10 held in the holding unit 3.

[0016] Belly-shaped members 6a and 6b are provided on both sides of the cover member 31 in the X-axis direction indicated by arrow X in the figure. Inside the body 21, a machining feed mechanism (not shown) is provided to feed the chuck table 32 of the holding unit 3 in the X-axis direction. By operating this machining feed mechanism, the cover member 31 and the chuck table 32 can be moved together in the X-axis direction, and the belly-shaped members 6a and 6b can be extended and retracted, and moved between the loading / unloading area and the processing area. The loading / unloading area is the front area in the figure where the unprocessed wafer 10 is placed on the chuck table 32, and the processing area is the inner area in the figure where processing is applied by the processing unit 4.

[0017] The processing unit 4 includes a laser irradiation unit 42. The laser irradiation unit 42 has an optical system housed in the processing unit housing 421, is disposed on the front surface of the vertical wall 22, and is mounted on the movable base 41 by means of a support member 43. The movable base 41 engages with one of the guide rails 221, 221 disposed in the vertical wall 22 of the device housing 2 on its rear surface side, and is mounted so as to be able to slide relative to the guide rails 221, 221 in the Z-axis direction (vertical direction).

[0018] The surface treatment apparatus 1 shown in Figure 2 includes a Z-axis moving mechanism 7, which moves the processing unit 4 along the pair of guide rails 221, 221 in the direction indicated by arrow Z in the figure. This Z-axis moving mechanism 7 includes an externally threaded rod 71, which is disposed on the front surface of the vertical wall 22 and extends vertically. Furthermore, the upper and lower ends of the threaded rod 71 are rotatably supported on the vertical wall 22. A pulse motor 72 is disposed at the upper end of the externally threaded rod 71, serving as a drive source for rotating the externally threaded rod 71. The output shaft of this pulse motor 72 is connected to the externally threaded rod 71. A screw connection portion (not shown) is formed on the rear surface of the movable base 41, and an internally threaded hole extending vertically is formed in this connection portion, which engages with the externally threaded rod 71. This Z-axis moving mechanism 7 can cause the pulse motor 72 to rotate forward so that the processing unit 4 and the moving base 41 can descend together, and can cause the pulse motor 72 to rotate in reverse so that the processing unit 4 and the moving base 41 can rise together.

[0019] The surface treatment apparatus 1 of this embodiment is equipped with a measuring device 5, which measures the thickness (or height) of the wafer 10 held in the chuck stage 32 of the holding unit 3. The measuring device 5 is disposed on the main body 21 of the apparatus housing 2 at a position near the Y-axis in the region where the chuck stage 32 moves in the X-axis direction, and is disposed on a sidewall portion 23 formed along the X-axis direction. Furthermore, the measuring device 5 is configured to be driven by a moving mechanism disposed inside the sidewall portion 23 (not shown in the figure), and can move along a sliding groove 23a formed along the direction shown in X1. The form of the measuring device 5 is not particularly limited, but it can be, for example, a non-contact thickness measuring device. It irradiates a measuring laser beam LB0 with a predetermined wavelength range from the front end 51 of the extension arm 52, detects the reflected light from the back side 10b and front side 10a of the wafer 10, and measures the thickness (or height) of the wafer 10 by performing a Fourier transform based on the spectral interference waveform of the reflected light. The laser irradiation unit 42, the processing feed mechanism (not shown), the measuring device 5, the Z-axis movement mechanism 7, etc., described above are connected to the controller (not shown).

[0020] Referring to Figures 2 and 3, the optical system of the laser irradiation unit 42 constituting the processing unit 4 of this embodiment will be described in more detail. The laser irradiation unit 42 is composed of the following components: a laser oscillator 44 that emits laser light LB1; a condenser 45 that forms the laser light LB1 emitted by the laser oscillator 44 into multiple beams LB2; a collimating lens 46 disposed between the laser oscillator 44 and the condenser 45 to collimate the laser light LB1 into parallel light; a beam intensity adjuster 47 disposed between the condenser 45 and the collimating lens 46 to adjust the intensity of the multiple beams LB2; and a rotation mechanism 48 that rotates the condenser 45 and rotates the multiple beams LB2 in the direction indicated by arrow R1. The optical system of the laser irradiation unit 42 described above is housed in a processing unit housing 421, which is supported by a support member 43.

[0021] The condenser 45 can be, for example, a microlens array or a diffractive optical element (DOE). The microlens array is an optical lens composed of multiple micron-sized microlenses arranged sequentially, and the diffractive optical element uses the diffraction phenomenon of light to branch the laser light in space. According to the laser irradiation unit 42, the laser light LB1 emitted from the laser oscillator 44 can be formed into multiple beams LB2 by the condenser 45, and dispersed and focused in a predetermined irradiation area (see P1~P5 in the figure) for irradiation. In addition, in FIG3, for ease of explanation, the focusing points of the multiple beams LB2 formed by the condenser 45 are simplified and represented by P1~P5, but in reality, they are dispersed into any number of multiple beams within the predetermined irradiation area, for example, several hundred or so beams. Furthermore, the condenser 45 is not limited to being composed only of the aforementioned microlens array or diffractive optical element, but can also be combined with other condensing lenses or aspherical lenses.

[0022] The rotating mechanism 48 is, for example, a hollow motor. The hollow motor is formed into a ring by equipping an encoder on the outer periphery of the hollow shaft, and holds the aforementioned condenser 45 in the space at the center of the shaft, so that the condenser 45 can rotate at a high speed (for example, less than 50,000 rpm), and cause the multiple beams LB2 irradiated from the condenser 45 to rotate in the direction indicated by arrow R1.

[0023] The beam intensity adjuster 47 can be, for example, a spatial light modulator (LCOS) or a digital micromirror device (DMD). The laser beam LB1, which has passed through the collimating lens 47, is adjusted by the beam intensity adjuster 47, and the spatial intensity distribution of the multiple beams LB2 irradiated from the condenser 45 can be adjusted to the required spatial intensity distribution. Furthermore, although this embodiment shows an example of using a transmissive spatial light modulator (LCOS), a reflective spatial light modulator can also be used.

[0024] As shown in FIG. 3, the laser irradiation unit 42 of this embodiment positions the focusing points (e.g., P1~P5) of the plurality of beams LB2 irradiated from the concentrator 45 onto the back surface 10b of the wafer 10 and irradiates it, thereby applying an ablation process to the back surface 10b of the wafer 10. The processing conditions for performing surface treatment by means of the laser irradiation unit 42 of this embodiment are as follows: Wavelength: 355nm; Pulse width: 10ps; Repetition rate: 1MHz; Average output: 10W; Numerical aperture (NA): 0.2

[0025] The procedure for processing the back side 10b of the wafer 10 by means of the surface treatment apparatus 1 described above will be explained in more detail.

[0026] As shown in Figure 2, if the holding unit 3 is positioned in the loading / unloading area, the back side 10b of the wafer 10, which is integrated with the protective film T, is placed on the chuck stage 32 with the protective film T side facing upwards and held in an attractive manner. Next, the processing feed mechanism (not shown) is operated to move the chuck stage 32 to the processing area side in the X-axis direction, and the outer periphery of the wafer 10 is positioned at the position where multiple beams LB2 are irradiated from the aforementioned condenser 45 of the processing unit 4.

[0027] Next, the laser oscillator 44, beam intensity adjuster 47, rotation mechanism 48 and Z-axis movement mechanism 7 are operated as shown in Figures 3 and 4. The focusing points (P1~P5) of the multiple beams LB2 irradiated by the laser irradiation unit 42 are positioned on the back surface 10b of the wafer 10 and irradiated. The multiple beams LB2 are rotated in the direction indicated by arrow R1, and the chuck stage 32 is rotated in the direction indicated by arrow R2 while moving in the X-axis direction. The multiple beams LB2 perform the surface treatment until they reach the center O of the wafer 10.

[0028] By applying the ablation process performed by the surface treatment described above to the back surface 10b of the wafer 10, the area S irradiated by the plurality of light beams LB2 in the back surface 10b gradually expands, and the thickness of the wafer 10 decreases. As described above, the surface treatment apparatus 1 of this embodiment is equipped with a measuring device 5, and the extension arm 52 of the measuring device 5 is moved in the direction shown by X1 along the sliding portion 23a of the sidewall portion 23, and the front end portion 51 is positioned at a predetermined position from the center O of the wafer 10, and a measuring laser beam LB0 is irradiated. The measuring laser beam LB0 detects the reflected light from the back surface 10b and the front surface 10a of the wafer 10, and performs a Fourier transform based on the spectral interference waveform of the reflected light to measure the thickness of the wafer 10 at the predetermined position. While moving the extension arm 52 and rotating the chuck stage 32, this measurement is performed at multiple positions on the wafer 10 defined by the X and Y coordinates, thus measuring the thickness of the entire area of ​​the wafer 10 in detail. Furthermore, when measuring the thickness of the wafer 10 using the measuring device 5, it is preferable to stop the surface treatment performed by the laser irradiation unit 42. The controller (not shown) is used to confirm whether the thickness of the wafer 10 detected by this measurement is the required thickness. If it is not the required thickness, the surface treatment of the wafer surface 10 performed by the laser irradiation unit 42 is performed until the required thickness is achieved. Alternatively, a high-pressure cleaning water jetting means can be provided in the area where the measuring device 5 irradiates the measuring laser beam LB0, and the thickness measurement can be performed while cleaning the area of ​​the wafer 10 to be measured.

[0029] According to this embodiment, the multiple beams LB2 irradiated by the condenser 45 are rotated in the direction shown by R1 by the action of the rotating mechanism 48, and the wafer 10 and the chuck stage 32 are rotated together in the direction shown by R2. In this way, the back surface 10b of the wafer 10 is uniformly removed in the area irradiated by the multiple beams LB2, thus avoiding the presence of multiple arc-shaped grinding marks on the grinding surface in the case of conventional grinding equipment, and suppressing the problem of decreased flexural strength. Furthermore, as described above, the finished thickness of the wafer 10 does not depend on the distance between the chuck stage and the grinding stone as in conventional grinding equipment, and it is easier to form the wafer 10 with a uniform thickness. Furthermore, by having the above-described configuration, it is possible to move the chuck stage 32, position the multiple beams LB2 at the required position on the wafer 10, stop the movement of the chuck stage 32, stop the rotation of the condenser 45, etc., while locally processing the surface (back side 10b) of the wafer 10, and processing the surface of the wafer 10 into the required shape.

[0030] The present invention is not limited to the processing apparatus 1 of the above-described embodiments. Other embodiments will be described with reference to FIGS. 5 to 7.

[0031] FIG5 illustrates another embodiment of the present invention, namely, the surface treatment apparatus 1'. The surface treatment apparatus 1' has a configuration substantially the same as the surface treatment apparatus 1 described above, and the same numbers are used for the same configurations and detailed descriptions are omitted.

[0032] In addition to the surface treatment apparatus 1 described above, the surface treatment apparatus 1' of this embodiment, as shown in FIG5, further includes a liquid storage tank 8. The liquid storage tank 8 is, for example, a concave container with an opening on the lower side, and includes: a cylindrical frame member 81; and a transparent plate member 82, which closes the upper surface of the frame member 81 and allows multiple beams LB2 irradiated from the concentrator 45 of the laser irradiation unit 42 to pass through. The plate member 82 may be, for example, a glass plate, an acrylic plate, etc. The liquid storage tank 8 is detachably disposed on the cover member 31' of the holding unit 3', and is disposed between the concentrator 45 and the wafer 10 held on the chuck stage 32' by being placed on the chuck stage 32' in the state of attracting and holding the wafer 10. As shown in Figures 6 and 7, in this embodiment, the cover member 31' includes: a liquid supply port 31a' for supplying liquid W (e.g., pure water) stored inside the liquid storage tank 8; and a liquid discharge port 31b' for discharging the liquid W. Liquid W, pressurized from a liquid supply unit (not shown), is supplied from the liquid supply port 31a' into the liquid storage tank 8, filling it with liquid W, and then appropriately discharged from the liquid discharge port 31b'. Furthermore, the liquid supply port 31a' and liquid discharge port 31b' are not limited to being located on the cover member 31'; for example, they can also be located on the side surface of the frame member 81 of the liquid storage tank 8. Moreover, the liquid storage tank 8 and the cover member 31' are not limited to being in a tight seal. An appropriate gap can also be provided between the liquid storage tank 8 and the cover member 31', through which liquid W can be discharged.

[0033] The surface treatment performed by the surface treatment apparatus 1' is performed by a process that is substantially the same as that of the surface treatment apparatus 1 described above. More specifically, with the holding unit 3' positioned in the loading / unloading area, before placing the liquid storage tank 8 on the cover member 31', the wafer 10, which is integrally formed by attaching a protective film T to the front side 10a, is placed on the chuck stage 32' with the protective film T side facing upwards and held in place. Next, the liquid storage tank 8 is placed on the cover member 31', and liquid W is supplied from the liquid supply port 31a', filling the interior of the liquid storage tank 8 with liquid W. Next, the processing feed mechanism (not shown) is operated to move the chuck stage 32' to the processing area side in the X-axis direction, and the outer periphery of the wafer 10 is positioned so that multiple beams LB2 are irradiated from the concentrator 45 of the laser irradiation unit 42, thus placing the liquid storage tank 8 between the concentrator 45 and the wafer 10.

[0034] Next, the laser oscillator 44, beam intensity adjuster 47, rotation mechanism 48, and Z-axis movement mechanism 7 are operated as shown in Figures 6 and 7. The focusing points (P1~P5) of the multiple beams LB2 irradiated by the laser irradiation unit 42 are positioned on the back surface 10b of the wafer 10 and irradiated. The multiple beams LB2 are rotated in the direction indicated by arrow R1, and the chuck stage 32' is rotated in the direction indicated by arrow R2 while moving in the X-axis direction. The multiple beams LB2 perform the surface treatment until they reach the center O of the wafer 10. During this period, liquid W is supplied from the liquid supply port 31a' inside the liquid storage tank 8 and discharged from the liquid outlet 31b'. In this way, the processing chips and the like generated by the surface treatment are removed by the liquid W.

[0035] By applying the above-described surface treatment to the back surface 10b of the wafer 10 through ablation, the area S irradiated by the multiple beams LB2 on the back surface 10b gradually expands, and the thickness of the wafer 10 decreases. Since a liquid storage tank 8 is provided in the surface treatment apparatus 1', it is preferable to remove the liquid storage tank 8 when measuring the thickness of the wafer 10 by the measuring device 5. The measuring device 5 measures the thickness of the wafer 10 at multiple positions defined by the X and Y coordinates on the wafer 10, and measures the thickness of the entire area of ​​the wafer 10 in detail. The controller (not shown) confirms whether the thickness of the wafer 10 detected by the measurement is the required thickness. If the thickness is not the required thickness, the liquid storage tank 8 is placed back on, and the processing of the crystal surface 10 by the laser irradiation unit 42 continues until the required thickness is achieved.

[0036] By using the liquid storage tank 8 described above and filling the back side 10b of the wafer 10 to be processed with liquid, as described above, not only can the processing chips generated during processing be quickly removed, but the following processing can also be achieved.

[0037] In the above-described surface treatment, although the focusing points (P1~P5) of the plurality of beams LB2 are positioned on the back surface 10b of the wafer 10 and an ablation process is applied, for example, the focusing points (P1~P5) are slightly removed from the back surface 10b of the wafer 10 (for example, less than 1 mm, preferably 0.5 mm) when the plurality of beams LB2 are irradiated. Thereby, the liquid W is plasma-plated near the back surface 10b of the wafer 10, and in addition to the above-described ablation process, a plasma process is also applied to the back surface 10b. Therefore, by applying a composite process to the back surface 10b, a more uniform process can be applied. Furthermore, the focusing points (P1~P5) of the plurality of beams LB2 can be removed from the back surface 10b of the wafer 10 (for example, more than 1 mm, preferably 1 mm) to generate cavitation near the focusing points, and the back surface 10b is processed by the impact pressure of the collapsing cavitation bubbles.

[0038] By means of the surface treatment apparatus 1' described above, the same effect as that obtained by means of the surface treatment apparatus 1 described above can also be obtained. Furthermore, liquid W can be plasma-plated near the back side 10b of the wafer 10 and surface treatment can be performed by means of the plasma, or cavitation can be generated near the back side 10b and surface treatment can be performed by means of the impact pressure when the bubbles are eliminated, so that the back side 10b can be processed more uniformly.

[0039] The above-described ablation process, plasma process, and cavitation process are preferably applied to the back surface 10b of the wafer 10 in combination rather than individually. However, since the respective processing conditions (focusing point position of multiple beams LB2, average output, etc.) for the most appropriate ablation process, plasma process, and cavitation process are different, it is preferable to determine the most appropriate processing conditions for processing the wafer 10 with a more uniform thickness through prior simulation, experimentation, etc. [Simplified Explanation of the Diagram]

[0012] FIG1 is a perspective view of the wafer of the workpiece. FIG2 is an overall perspective view of the surface treatment apparatus of this embodiment. FIG3 is a partial cross-sectional side view of the optical system of the processing unit provided in the surface treatment apparatus shown in FIG2, showing a portion thereof, and the state of the surface treatment performed by the processing unit. FIG4 is a perspective view of the implementation state of the surface treatment shown in FIG3. FIG5 is an overall perspective view of the surface treatment apparatus of another embodiment. FIG6 is a perspective view of the state of the surface treatment performed by the processing unit and the liquid storage tank provided in the surface treatment apparatus shown in FIG5, showing a portion thereof, in cross-section. FIG7 is a partial cross-sectional side view of the implementation state of the surface treatment shown in FIG6.

Claims

1. A surface treatment apparatus for treating the surface of a workpiece, comprising: a chuck stage for holding the workpiece; a processing unit for processing the surface of the workpiece held on the chuck stage; a processing feed mechanism for feeding the chuck stage relative to the processing unit, the processing unit comprising: a laser oscillator for emitting laser light; a condenser for forming the laser light emitted by the laser oscillator into a plurality of beams; a collimating lens disposed between the laser oscillator and the condenser for collimating the laser light into parallel light; a beam intensity adjuster disposed between the condenser and the collimating lens for adjusting the intensity of the plurality of beams; and a rotation mechanism for rotating the condenser, thereby positioning the focusing point of the plurality of beams on the upper surface of the workpiece and irradiating an entire area from the outer periphery to the center of the workpiece to perform a surface treatment that reduces the thickness of the workpiece.

2. The surface treatment apparatus as claimed in claim 1, wherein, The condenser is a microlens array or a diffractive optical element.

3. The surface treatment apparatus as claimed in claim 1, wherein, This beam intensity adjuster adjusts the spatial intensity distribution of the beam.

4. The surface treatment apparatus as claimed in claim 1, wherein, The processing unit uses the condenser to position the light-gathering point on the surface of the workpiece to be processed and applies an ablation process to the surface.

5. The surface treatment apparatus as claimed in claim 1, wherein, The processing unit further includes a liquid storage tank disposed between the condenser and the workpiece to fill the surface of the workpiece with liquid.

6. The surface treatment apparatus as claimed in claim 5, wherein, The surface of the workpiece is treated by plasma, which is generated by irradiating a liquid that is filled in the liquid storage tank of the workpiece with laser light.

7. The surface treatment apparatus as claimed in claim 5, wherein, The surface of the workpiece is treated by cavitation, which is generated by irradiating the surface of the workpiece with a liquid that is filled in the liquid storage tank by laser light.

8. The surface treatment apparatus as claimed in claim 1, wherein, The aforementioned processing unit further includes a measuring device that measures the thickness or height of the workpiece held on the chuck stage.

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