Machining process for a workpiece and machining device

Abstract

Machining method for processing a wafer as a workpiece (11), wherein the machining method comprises: an arrangement step (ST11) comprising arranging the workpiece (11) in a gas containing a substance that generates an active species that reacts with the workpiece (11); a measurement step (ST12) comprising measuring the thickness distribution of the workpiece (11) arranged in the gas by emitting pulsed white light from a white light source (52), splitting the pulsed white light into light of each wavelength by a spectroscopy unit (54), irradiating the workpiece (11) with the light of each wavelength, acquiring information regarding the two-dimensional intensity distribution of the light of each wavelength reflected by the workpiece (11) by a two-dimensional imaging unit (64), and calculating the thickness distribution of the workpiece (11) from the information; and a laser beam irradiation step (ST13) with an irradiation of the workpiece (11) in the gas with a laser beam (A) whose power is adjusted based on the thickness distribution that was measured in the measuring step (ST12), wherein In the laser beam irradiation step (ST13), the amount of ablation by which an area irradiated with the laser beam (A) in the workpiece (11) is ablated by the active species is controlled by irradiating the workpiece (11) with the laser beam (A), the power of which is adjusted, and During processing, the gas is circulated along an annular flow path which is connected to a separation unit (12) that separates and removes from the gas any unnecessary substance that is generated as a result of the processing of the workpiece (11).

Description

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

[0001] The present invention relates to a machining method for a workpiece and a machining apparatus used when machining a workpiece such as a wafer. DESCRIPTION OF THE RELATED PRIOR ART

[0002] In electronic equipment such as mobile phones and personal computers, a component chip containing a component, such as an electronic circuit, is an essential component. For example, the component chip is obtained by dividing a wafer containing a semiconductor material such as silicon (Si) into several regions along planned dividing lines (streets), forming a component in each region, and then dividing this wafer along the planned dividing lines.

[0003] Furthermore, during the manufacturing process of the component chips described above, the wafer is sometimes processed using a chemical mechanical polishing (CMP) process or similar. While a polishing fluid (polishing slurry) containing abrasive grains is applied to a workpiece, such as a wafer, the workpiece is rubbed, for example, by a polishing pad. This can adjust the thickness of the workpiece and improve its flatness.

[0004] In recent years, a technique has been proposed in which the relationship between the polishing time and the change amount of a workpiece's thickness is obtained, and the polishing time required to achieve the target thickness of the workpiece is set based on this relationship (see, for example, Japanese Patent Laid-Open No. JP 2011-224758 A). It becomes easier to obtain the workpiece with the target thickness by setting the polishing time based on the relationship obtained from the result of actual polishing performed with this technique.

[0005] Furthermore, a technique has also been proposed that improves the flatness of a workpiece by combining a procedure used when polishing a flat workpiece, a procedure used when polishing a workpiece distorted with a protruding shape, and a procedure used when polishing a workpiece distorted with a depressed shape (see, for example, JP 2013-115381 A). In this technique, potential distortion of the workpiece after polishing is prevented to be low by properly adjusting the time period for which each procedure is applied.

[0006] US 6,033,721 A discloses an apparatus for determining the best trajectory for laser CVD using a strategy of acquiring a series of two-dimensional plane images of the substrate. These images, taken together, contain topographical information as well as information about the local reflectivity and thermal distribution. The images are combined in digital format with additional substrate imaging information to calculate the best three-dimensional trajectory for the desired laser operation.

[0007] In US Pat. No. 5,795,493 A, a laser and control unit is used to differentially heat sections of a semiconductor substrate during downstream etching. Such differential heating provides a different etch rate for each heated section, resulting in improved uniformity and less etch-induced surface damage. Furthermore, the system provides dynamic process updates through in-situ etch rate and temperature measurements.

[0008] JP 2007 - 123 638 A discloses a manufacturing method for a nitride semiconductor capable of machining a desired surface shape on the surface of the nitride semiconductor, regardless of a rough surface shape prior to machining. JP H06 - 122 985 A deals with a method for etching the surface of a metallic workpiece at high speed by focusing a laser beam onto the surface of the workpiece in the etchant and for recycling an etchant by electrolytically recovering the dissolved workpiece material from the spent etchant.

[0009] JP H06 - 327 924 A discloses a gas recovery and circulation device connected to a processing device using plasma or a radical reaction by a laser, and recovering and reusing the reaction gas and the carrier gas from the exhaust gas discharged from the processing device.

[0010] US 2016 / 0 293 447 A1 and US 2019 / 0 099 694 A1 disclose reprocessing devices for etching liquids after processing a semiconductor substrate.

[0011] US 2006 / 0 097 355 A1 relates to a method for leveling semiconductor wafers by (a) a position-dependent measurement of a wafer-characterizing parameter in order to determine the position-dependent value of this parameter over an entire surface of the semiconductor wafer, and (b) simultaneously etching the entire surface of the semiconductor wafer under the action of an etching medium while simultaneously illuminating the entire surface, wherein the material-removing etching rate depends on the light intensity at the surface of the semiconductor wafer, wherein the light intensity is determined in a position-dependent manner, so that the differences in the position-dependent values ​​of the parameter measured in step a) are reduced by the position-dependent material removal rate.

[0012] Similarly, US 2003 / 0 090 671 A1 relates to an etching apparatus and a method capable of measuring the thickness of a semiconductor wafer while performing a wet etching independently of the presence of an etchant. SUMMARY OF THE INVENTION

[0013] Incidentally, in the above-described method in which the polishing time is set based on the relationship obtained from the actual result, the workpiece cannot necessarily be machined to the target thickness when the thickness of the workpiece varies or the workpiece is warped. Similarly, in the method in which the time period during which the processes are applied is set, the workpiece cannot necessarily be machined to a flat shape when the variation in the thickness of the workpiece is large or irregular recesses and projections are present in the workpiece.

[0014] Accordingly, it is an object of the present invention to provide a novel machining method for a workpiece and a novel machining apparatus which enable a workpiece to be machined with high accuracy.

[0015] The invention is defined by the subject matter of the independent claims, with dependent claims specifying preferred embodiments.

[0016] According to one aspect of the present invention, a machining method for a workpiece is provided, which is used when machining the workpiece. The machining method includes an arranging step of arranging the workpiece in a gas containing a substance that generates an active species that reacts with the workpiece, a measuring step of measuring the thickness distribution of the workpiece arranged in the gas, and a laser beam irradiation step of irradiating the workpiece in the gas with a laser beam whose power is adjusted based on the thickness distribution measured during the measuring step. In the laser beam irradiation step, a removal amount by which an area in the workpiece irradiated with the laser beam is removed by the active species is controlled by irradiating the workpiece with the laser beam whose power is adjusted.

[0017] According to another aspect of the present invention, a machining method for a workpiece is provided, which is used when machining the workpiece. The machining method includes an arranging step of arranging the workpiece in a liquid containing a substance that generates an active species that reacts with the workpiece, a measuring step of measuring the thickness distribution of the workpiece arranged in the liquid, and a laser beam irradiation step of irradiating the workpiece in the liquid with a laser beam whose power is adjusted based on the thickness distribution measured during the measuring step.In the laser beam irradiation step, an ablation amount by which an area in the workpiece irradiated with the laser beam is ablated by the active species is controlled by irradiating the workpiece with the laser beam whose power is adjusted.

[0018] Preferably, the workpiece machining method further comprises a re-measurement step of re-measuring the thickness distribution of the workpiece after the start of the laser beam irradiation step, and a re-adjustment step of re-adjusting the laser beam power based on the thickness distribution re-measured during the re-measurement step. Furthermore, the re-measurement step and the re-adjustment step are alternately repeated while the laser beam irradiation step continues.

[0019] Preferably, the laser beam irradiation step is terminated when the thickness distribution measured again in the renewed measuring step indicates that the workpiece has been machined to a target shape.

[0020] Preferably, by preventing a thin portion of the workpiece indicated by the thickness distribution from being irradiated with the laser beam and a thick portion of the workpiece from being irradiated with the laser beam, or by increasing the power of the laser beam with which a thick portion of the workpiece is irradiated compared to the laser beam with which a thin portion of the workpiece is irradiated, in the laser beam irradiation step, a removal amount by which a thick portion of the workpiece is removed by the active species is made larger than a removal amount by which a thin portion of the workpiece is removed by the active species.

[0021] In accordance with another aspect of the present invention, there is provided a machining method for a workpiece, which is used when machining the workpiece. The machining method includes an arranging step of arranging the workpiece in a liquid containing an active species that reacts with the workpiece, a measuring step of measuring the thickness distribution of the workpiece arranged in the liquid, and a laser beam irradiation step of irradiating the workpiece in the liquid with a laser beam whose power is adjusted based on the thickness distribution measured in the measuring step. In the laser beam irradiation step, a removal amount by which an area in the workpiece irradiated with the laser beam is removed by the active species is controlled by irradiating the workpiece with the laser beam whose power is adjusted.

[0022] Preferably, the workpiece machining method further comprises a re-measurement step of re-measuring the thickness distribution of the workpiece after the start of the laser beam irradiation step, and a re-adjustment step of re-adjusting the laser beam power based on the thickness distribution re-measured in the re-measurement step. Furthermore, the re-measurement step and the re-adjustment step are alternately repeated while the laser beam irradiation step continues.

[0023] Preferably, the laser beam irradiation step is terminated when the thickness distribution measured again in the renewed measuring step indicates that the workpiece has been machined to a target shape.

[0024] By preventing a thin portion of the workpiece indicated by the thickness distribution from being irradiated with the laser beam and a thick portion of the workpiece from being irradiated with the laser beam, or by increasing the power of the laser beam with which a thick portion of the workpiece is irradiated compared to the laser beam with which a thin portion of the workpiece is irradiated, in the laser beam irradiation step, preferably, a removal amount by which the thick portion of the workpiece is removed by the active species is made larger than a removal amount by which the thin portion of the workpiece is removed by the active species.

[0025] By preferably preventing irradiation of a thick portion of the workpiece indicated by the thickness distribution from being irradiated with the laser beam and a thin portion of the workpiece from being irradiated with the laser beam, or by increasing the power of the laser beam irradiated to a thin portion of the workpiece compared to the laser beam irradiated to a thick portion of the workpiece in the laser beam irradiation step, a removal amount by which the thin portion of the workpiece is removed by the active species is made smaller than a removal amount by which the thick portion of the workpiece is removed by the active species.

[0026] Preferably, the machining method for a workpiece further comprises a pre-machining step of machining the workpiece by any method such as grinding, polishing and etching before the arranging step is carried out.

[0027] In accordance with yet another aspect of the present invention, a machining apparatus is provided that is used when machining a workpiece. The machining apparatus includes a supply unit that supplies, to the workpiece, a gas containing a substance that generates an active species that reacts with the workpiece, a liquid containing a substance that generates an active species that reacts with the workpiece, or a liquid containing an active species that reacts with the workpiece, a measuring unit that is used when measuring the thickness distribution of the workpiece, a laser beam irradiation unit having an adjusting device that adjusts the power of a laser beam, and a control unit that controls the adjusting device based on the thickness distribution of the workpiece measured using the measuring unit.

[0028] Preferably, the processing device further comprises a container in which the workpiece is received. Furthermore, a window is arranged in the container, which allows the laser beam, with which irradiation is carried out from outside the container, to be transmitted through the window.

[0029] In the machining method for a workpiece and the machining apparatus according to the respective aspects of the present invention, the amount of material removed from the workpiece by the active species is controlled by adjusting the power of the laser beam irradiated onto the workpiece. Consequently, the workpiece can be machined with high precision by properly adjusting the power of the laser beam in accordance with the thickness distribution of the workpiece.

[0030] The above and other objects, features and advantages of the present invention and the mode for carrying them out will become more apparent and the invention itself will be best understood by studying the following description and appended claims with reference to the accompanying drawings which show a preferred embodiment of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing an exemplary structure of a machining apparatus; Fig. 2 is a diagram showing an exemplary structure of a laser beam irradiation unit; Fig. 3 is a diagram showing an example structure of a measuring unit; Fig. 4 is a flowchart illustrating a machining process of a workpiece; Fig. 5 is a diagram illustrating an exemplary modification of the laser beam irradiation unit; and Fig. 6 is a flowchart showing an example variation of the machining process for a workpiece. DETAILED EXPLANATION OF THE PREFERRED EMBODIMENT

[0031] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a diagram illustrating an exemplary structure of a processing apparatus 2 according to the present embodiment. In Fig. 1, some of the components of the processing device 2 are represented by functional blocks.

[0032] The processing device 2 is designed to be able to process a workpiece 11 by using a substance in a highly reactive state (hereinafter active species), such as ions and radicals, and which comprises a container 4 in which, as shown in Fig. 1, the workpiece 11 can be accommodated. For example, the container 4 is box-shaped, made of a material unlikely to react with active species, etc., and has a window 4a that allows transmission of light in the visible range through an upper portion thereof. A table 6, which can support the workpiece 11, is arranged inside the container 4.

[0033] Typically, the workpiece 11 is a circular disk-shaped wafer (semiconductor wafer) formed using a semiconductor such as Si. However, the material, shape, structure, size, etc. of the workpiece 11 are not limited. For example, it is also possible to use a substrate or the like formed using another semiconductor, a ceramic, a resin, a metal, or the like as the workpiece 11.

[0034] Two openings (not shown) through which gas is allowed to pass are formed in the side portions of the container 4. One end portion 8a of a pipe 8 disposed outside the container 4 is connected to one opening. The other end portion 8b of the pipe 8 is connected to the other opening. That is, the two openings are connected to each other via the pipe 8, and an annular flow path in which a gas flows is formed through the container 4 and the pipe 8.

[0035] Connected to the part, on the upstream side relative to the container 4 in the pipe 8 forming the flow path, is a supply unit 10 capable of supplying the pipe 8 with a gas containing a substance that generates an active species that reacts with the workpiece 11. For example, the supply unit 10 includes a valve that controls the volume flow of the gas and adjusts the flow rate of the gas supplied to the pipe 8 from a gas cylinder or the like connected to the supply unit 10.

[0036] When machining the workpiece 11 formed using Si, for example, chlorine (Cl2) is selected as the substance that generates the active species. In this case, a chlorine gas is used as the gas containing the substance that generates the active species. That is, a gas cylinder or the like filled with chlorine gas is connected to the supply unit 10. However, the substance that generates the active species and the gas containing this substance can be optionally changed in accordance with the material, etc., of the workpiece 11.

[0037] When the workpiece 11 is irradiated by a laser beam to excite electrodes in the state in the valence band of Si to the conduction band in which the workpiece 11 is placed in the chlorine gas, the excited electrons (free electrons) are transferred to Cl2, and Cl -, which has a high reactivity, is generated. As a result, the Si, which forms the workpiece 11, reacts with the Cl - and becomes SiCl4, which is removed from the workpiece 11. This means that in this case the workpiece 11 is removed by the Cl - which is an active species.

[0038] Connected to the part on the downstream side relative to the container 4 in the pipe 8 forming the flow path is a separation unit 12 that separates and removes an unnecessary substance (e.g., SiCl4) generated due to the machining of the workpiece 11 (reaction with the workpiece 11) from the gas flowing in the pipe 8. For example, the separation unit 12 includes a device called a cold trap or the like, which removes the unnecessary substance generated due to the machining of the workpiece 11 from the gas flowing in the pipe 8 by utilizing a difference in vapor pressure between the substance that generates the active species (e.g., Cl2) and the substance generated due to the machining of the workpiece 11.

[0039] A circulation unit 14, which circulates the gas along the annular flow path formed by the container 4 and the pipe 8, is arranged between the part to which the supply unit 10 is connected in the pipe 8 and the part to which the separation unit 12 is connected in the pipe 8. The circulation unit 14 is, for example, a circulator and sends the gas discharged from the container 4, from which unnecessary substance has been removed by the separation unit 12, back to the container 4.

[0040] An evacuation unit 16 is connected to the part located between the part to which the supply unit 10 is connected in the pipe 8 and the circulation unit 14. For example, the evacuation unit 16 includes a vacuum pump, such as an ejector, and properly reduces the pressure of the annular flow path formed by the container 4 and the pipe 8 to implement an environment in which the active species is easily generated.

[0041] A laser beam irradiation unit 18, which can irradiate the workpiece 11 in the container 4 with a laser beam A from outside the container 4 through the window 4a, is arranged above the container 4. Furthermore, a measuring unit 20, which is used when measuring the thickness distribution of the workpiece 11 in the container 4 from outside the container 4, is arranged above the container 4. A control unit 22 is connected to the laser beam irradiation unit 18 and the measuring unit 20.

[0042] The control unit 22 controls the operation of the laser beam irradiation unit 18 and the measuring unit 20 in accordance with the target shape of the workpiece 11. Typically, the control unit 22 is implemented by a computer including a processing device such as a central processing unit (CPU) and a storage device such as a flash memory. Various functions of the control unit 22 are implemented by operating the processing device, etc., according to software stored in the storage device.

[0043] Fig. 2 is a diagram showing an exemplary structure of the laser beam irradiation unit 18. Also in Fig. 2, some of the components are represented by function blocks. As in Fig. 2, the laser beam irradiation unit 18 includes a laser oscillator 32 capable of generating the laser beam A having a wavelength that is absorbed by the workpiece 11.

[0044] For example, when machining the workpiece 11 formed by Si, the laser oscillator 32 capable of generating the laser beam A having a wavelength of 532 nm is used. However, the laser oscillator 32 may be configured to be capable of generating a laser beam having a different wavelength.

[0045] Furthermore, the form of laser oscillation performed in the laser oscillator 32 can be continuous wave (CW) oscillation or pulse oscillation. The efficiency of machining the workpiece 11 is higher in the case of using a laser beam in which a laser beam is generated by continuous wave oscillation than in the case of using a laser beam generated by pulse oscillation. Thus, in the present embodiment, the laser oscillator 32 capable of continuous wave oscillation is used. On the other hand, in the case of using a laser beam generated by pulse oscillation, it becomes easier to improve the accuracy of processing compared to the case of using a laser beam generated by continuous wave oscillation.

[0046] An adjusting device 34, such as an attenuator, which can adjust the power of the laser beam A emitted from the laser oscillator 32, is arranged at a position adjacent to the laser oscillator 32. A power adjusting section of the control unit 22 is connected to the adjusting device 34, and an operation of the adjusting device 34 is controlled by the power adjusting section of the control unit 22.

[0047] The laser beam A, whose power is adjusted by the adjusting device 34, is reflected, for example, by mirrors 36 and 38 or the like, and then incident on an acousto-optic deflector (laser beam scanning unit) 40. The acousto-optic deflector 40 changes the direction of movement of the laser beam A in accordance with the frequency of an applied high-frequency voltage (radio frequency (RF) voltage).

[0048] The laser beam A, whose direction of travel has been changed by the acousto-optic deflector 40, is incident on a polygon mirror (laser beam scanning unit) 42 having a plurality of reflecting surfaces. The polygon mirror 42 is connected to a rotation drive source (not shown), such as a motor. By rotating the polygon mirror 42, the direction of travel of the laser beam A, which is reflected by the reflecting surface of the polygon mirror 42, is changed. The rotation speed of the polygon mirror 42 is, for example, approximately 5,000 to 30,000 revolutions per minute.

[0049] An upper surface 11a of the workpiece 11 is irradiated with the laser beam A, which is reflected by the polygon mirror 42, through a light collector 44 and the window 4a ( Fig. 1). That is, the window 4a is configured to allow the laser beam A to pass through it, through which irradiation is performed from outside the container 4. The light collector 44 includes an fθ lens 46 and focuses the laser beam A onto the upper surface 11a of the workpiece 11, regardless of its direction of movement. The diameter of the laser beam A on the upper surface 11a of the workpiece 11 is, for example, approximately 3 µm to 1000 µm.

[0050] In the present embodiment, the position of the area irradiated with the laser beam A is changed in a first direction substantially parallel to the upper surface 11a by the acousto-optic deflector 40, and is changed in a second direction substantially parallel to the upper surface 11a and substantially perpendicular to the first direction by the polygon mirror 42. That is, scanning with the laser beam A is performed based on the combination of the change in the moving direction of the laser beam A by the acousto-optic deflector 40 and the change in the moving direction of the laser beam A by the polygon mirror 42.

[0051] When scanning with the laser beam A is performed while adjusting the power of the laser beam A by the adjusting device 34, an optional area on the upper surface 11a of the workpiece 11 can be irradiated with the laser beam A at an optional power. In the machining apparatus 2 of the present embodiment, the removal amount by which a workpiece 11 is removed by an active species is controlled with respect to each area by controlling the power of the laser beam A and the area irradiated with the laser beam A.

[0052] Fig. 3 is a diagram showing an exemplary structure of the measuring unit 20. As in Fig. As shown in Figure 3, the measuring unit 20 includes a white light source 52 capable of generating white light including light in the visible range. For example, a superluminescent diode (SLD) light source, an amplified spontaneous emission (ASE) light source, a supercontinuum (SC) light source, a light-emitting diode (LED) light source, a halogen lamp, a xenon lamp, a mercury lamp, a metal halide lamp, or the like is selected as the white light source 52.

[0053] A spectroscopy unit 54, which can split the white light emitted from the white light source 52 into light of each wavelength, is arranged at a position adjacent to the white light source 52. For example, the spectroscopy unit 54 includes an optical fiber or the like with a large wavelength dispersion, and radiates light of each wavelength, which establishes the white light, to the rear at a timing different for each wavelength by using a different propagation speed of the light in accordance with the wavelength. For example, when pulsed white light is made incident on the spectroscopy unit 54, the wavelength of the light emitted from the spectroscopy unit 54 changes over time from the shorter wavelength side to the longer wavelength side.

[0054] Light B emitted by the spectroscopy unit 54 is incident, for example, through a lens 56 or the like onto a beam splitter 58. The beam splitter 58 is typically a half-mirror and reflects, through a reflecting surface 58a, a portion of the light B emitted by the spectroscopy unit 54 and passing through the lens 56 or the like to change its direction of travel. The upper surface 11a and a lower surface 11b of the workpiece 11 are irradiated with the light B reflected by the beam splitter 58 through a telecentric lens 60 and the window 4a ( Fig. 1).

[0055] The light B reflected by the upper surface 11a of the workpiece 11 and the light B reflected by the lower surface 11b of the workpiece 11 are in turn incident on the beam splitter 58 through the window 4a and the telecentric lens 60, and a portion of the light B is transmitted through the reflecting surface 58a. The light B transmitted through the reflecting surface 58a is converted into collimated light by a lens 62 or the like and is incident on a two-dimensional imaging unit 64.

[0056] The two-dimensional imaging unit 64 includes an imaging element, such as a charge-coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor. Upon receiving light having a two-dimensional intensity distribution, the two-dimensional imaging unit 64 generates an electrical signal by reproducing the intensity distribution of the light. Specifically, the two-dimensional imaging unit 64 can acquire information related to the two-dimensional intensity distribution generated by the interference between the light reflected by the upper surface 11a of the workpiece 11 and the light reflected by the lower surface 11b.

[0057] As described above, the spectroscopy unit 54 radiates the light of each wavelength, which forms the white light emitted from the white light source 52, to the rear side at a timing that differs for each wavelength. By capturing the intensity distribution of the light incident on the two-dimensional imaging unit 64 at different multiple points in time, information regarding the two-dimensional intensity distribution of light of different multiple wavelengths corresponding to the respective points in time can be acquired.

[0058] The two-dimensional imaging unit 64 is connected to a thickness distribution calculation section of the control unit 22 ( Fig. 1). The information regarding the two-dimensional intensity distribution of the light captured in the two-dimensional imaging unit 64 is sent to the thickness distribution calculation section of the control unit 22. The thickness distribution calculation section of the control unit 22 calculates the thickness distribution of the workpiece 11 from the information regarding the two-dimensional intensity distribution of the light of the different multiple wavelengths captured in the two-dimensional imaging unit 64.

[0059] Information regarding the thickness distribution of the workpiece 11 is sent to a removal amount calculation section of the control unit 22. The removal amount calculation section calculates the removal amount of the workpiece 11 to be removed by an active species with respect to each region based on the information regarding the thickness distribution of the workpiece 11 received from the thickness distribution calculation section and information regarding the target shape of the workpiece 11 (target thickness distribution).

[0060] Information regarding the calculated removal amounts is sent to the power adjustment section of the control unit 22. The power adjustment section controls the operation of the adjustment device 34 to adjust the power of the laser beam A with which each area of ​​the workpiece 11 is irradiated in such a way that an active species is generated to an extent corresponding to the calculated removal amount.

[0061] Next, a machining method for a workpiece performed by using the machining apparatus 2 described above will be described. Fig. 4 is a flowchart illustrating the workpiece machining method. In the workpiece machining method according to the present embodiment, first, the workpiece 11 is placed in a predetermined gas containing a substance that generates an active species that reacts with the workpiece 11 (placement step ST11).

[0062] Specifically, the workpiece 11 is first placed on the table 6 in the container 4, and the container 4 is sealed. In the present embodiment, a wafer formed using Si is used as the workpiece 11. Next, the interior of the container 4 and the interior of the tube 8 are evacuated by the evacuation unit 16 in such a manner that the pressure in the container 4 becomes, for example, 400 Torr or less.

[0063] While the gas containing the substance that generates the active species that reacts with the workpiece 11 is then supplied from the supply unit 10 to the pipe 8, the gas in the container 4 and the pipe 8 is circulated by the circulation unit 14. In the present embodiment, a chlorine gas is used as the gas containing the substance that generates the active species that reacts with the workpiece 11.

[0064] After the workpiece 11 is placed in the predetermined gas, the thickness distribution of the workpiece 11 is measured (measurement step ST12). In the present embodiment, the thickness distribution is measured by the measuring unit 20 throughout the workpiece 11. Specifically, pulsed white light emitted from the white light source 52 is split into light of each wavelength by the spectroscopy unit 54, and the workpiece 11 is irradiated with the light. Then, information regarding the two-dimensional intensity distribution of the light of each wavelength reflected by the workpiece 11 is acquired by the two-dimensional imaging unit 64.

[0065] After the information regarding the two-dimensional intensity distribution of the light of each wavelength is acquired, the thickness distribution of the workpiece 11 is calculated by the thickness distribution calculation section of the control unit 22. Specifically, the thickness distribution of the workpiece 11 is calculated from information regarding the two-dimensional intensity distribution of light of different multiple wavelengths by using the interference conditions, which are different for each wavelength, between the light reflected by the upper surface 11a of the workpiece 11 and the light reflected by the lower surface 11b. This thickness distribution information is sent to the removal amount calculation section of the control unit 22.

[0066] After the thickness distribution of the workpiece 11 has been measured, irradiation of the workpiece 11 with the laser beam A is started (laser beam irradiation step ST13). In the present embodiment, the workpiece 11 in the gas is irradiated by the laser beam irradiation unit 18 with the laser beam A, the power of which is adjusted based on the thickness distribution information.

[0067] Specifically, the removal amount calculation section of the control unit 22 first calculates the removal amount of the workpiece 11 to be removed with respect to each region from the information regarding the thickness distribution of the workpiece 11 and the information regarding the target shape of the workpiece 11 (target thickness distribution). That is, a difference between the thickness of the workpiece 11 in each region and the target thickness is calculated as the removal amount.

[0068] Information regarding this removal amount is sent to the power adjustment section of the control unit 22. Upon receiving the information regarding the removal amount, the power adjustment section controls the operation of the adjustment unit 34 to adjust the power of the laser beam A irradiated onto each area of ​​the workpiece 11 in such a way that the active species is generated in an amount corresponding to the removal amount.

[0069] This can irradiate each area of ​​the workpiece 11 in the gas with the laser beam A, the power of which is adjusted based on the information regarding the thickness distribution. When each area of ​​the workpiece 11 is irradiated with the laser beam A, electrons are excited in each area of ​​the workpiece 11 to an extent corresponding to the power of the laser beam with which the irradiation is carried out, and Cl -(active species) is generated in the vicinity of each region to an extent corresponding to the amount of excited electrons.

[0070] As a result, each area of ​​the workpiece 11 is illuminated by Cl generated in the environment - removed. The amount of removal in each area corresponds to the amount of Cl produced - . That is, the removal amount of each region depends on the power of the laser beam A. By irradiating each region of the workpiece 11 with the laser beam A while adjusting the power as described in the present embodiment, the removal amount by which each region in the workpiece 11 irradiated with the laser beam A is removed by the active species can be controlled.

[0071] For example, by preventing irradiation of a thin portion of the workpiece 11 indicated by the thickness distribution with the laser beam A and irradiation of a thick portion of the workpiece 11 with a laser beam A, the removal amount by which the thick portion of the workpiece 11 is removed by the active species can be set larger than the removal amount by which the thin portion of the workpiece 11 is removed by the active species.

[0072] Furthermore, the removal amount by which the thick portion of the workpiece 11 is removed by the active species can be set larger than the removal amount by which the thin portion of the workpiece 11 is removed by the active species, for example, by increasing the power of the laser beam A with which a thick portion of the workpiece 11 is irradiated compared to the laser beam A with which a thin portion of the workpiece 11 is irradiated.

[0073] After the irradiation of the workpiece 11 with the laser beam A has begun, the thickness distribution of the workpiece 11 is measured again (remeasurement step ST14). This remeasurement is performed using a method similar to the first measurement round described above. Information regarding the remeasured thickness distribution is sent to the removal amount calculation section of the control unit 22.

[0074] After the thickness distribution of the workpiece 11 has been re-measured, it is determined whether the workpiece 11 has been machined to the target shape (determination step ST15). Specifically, the removal amount calculation section of the control unit 22 calculates the removal amount of the workpiece 11 to be removed with respect to each area from the information regarding the re-measured thickness distribution and the information regarding the target shape of the workpiece 11 (target thickness distribution).

[0075] For example, if none of the removal amounts of the respective regions calculated by the removal amount calculation section exceeds a base amount (the range within which the shape of the workpiece 11 after machining is acceptable as the target shape), the control unit 22 determines that the workpiece 11 has been machined to the target shape. In this case (determination step ST15: Yes), the control unit 22 stops irradiating the workpiece 11 with the laser beam A (irradiation termination step ST16). That is, the control unit 22 stops machining the workpiece 11.

[0076] On the other hand, for example, if any of the removal amounts of the respective regions calculated by the removal amount calculation section exceeds the base amount (region in which the shape of the workpiece 11 after machining is acceptable as the target shape), the control unit 22 determines that the workpiece 11 has not been machined to the target shape. In this case (determination step ST15: No), the control unit 22 readjusts the power of the laser beam A irradiated onto the workpiece 11 (re-adjustment step ST17).

[0077] Specifically, the power adjustment section of the control unit 22 receives information regarding the removal amount calculated based on the re-measured thickness distribution, and readjusts the power of the laser beam A irradiated to each area of ​​the workpiece 11 in such a way that the active species is generated in an amount corresponding to this removal amount. After the power of the laser beam A is readjusted, the thickness distribution of the workpiece 11 is re-measured at a predetermined timing (re-measurement step ST14).

[0078] By alternately repeating the remeasurement of the thickness distribution of the workpiece 11 and the readjustment of the power of the laser beam A based on the remeasured thickness distribution as described above, machining of the workpiece 11 with high accuracy is enabled. There is no particular limitation on the frequency (or cycle) of repeating the remeasurement of the thickness distribution and the readjustment of the power of the laser beam A. However, machining of the workpiece 11 with high accuracy is facilitated by increasing this frequency to a certain extent (shortening the cycle to a certain extent). For example, it is preferable to set the repetition frequency to 0.5 Hz to 1 kHz inclusive.

[0079] As above, in the workpiece machining method and machining apparatus according to the present embodiment, the amount of active species removed from the workpiece 11 is controlled by adjusting the power of the laser beam A irradiated onto the workpiece 11. Consequently, the workpiece 11 can be machined with high accuracy by properly adjusting the power of the laser beam A in accordance with the thickness distribution of the workpiece 11.

[0080] The present invention is not limited to the description of the above-described embodiment and can be implemented with various modifications. For example, the workpiece 11 can be processed by any of the grinding, polishing, and etching (chemical etching) methods before the workpiece 11 is placed in the gas containing the substance that generates the active species that reacts with the workpiece 11 (pre-processing step).

[0081] Furthermore, in the above-described embodiment, the laser beam irradiation unit 18 that irradiates each area with the laser beam A by using the acousto-optic deflector 40 and the polygon mirror 42 is exemplary. However, there is no particular limitation on the structure of the laser beam irradiation unit 18 included in the machining apparatus 2. For example, as the laser beam irradiation unit 18 that irradiates each area with the laser beam A, a galvanometer scanner, a diffractive optical element (DOE), a liquid crystal on silicon (LCOS), a digital micromirror device (DMD), or the like can be employed.

[0082] Fig. Fig. 5 is a diagram illustrating an exemplary modification of the laser beam irradiation unit 18. In Fig. 5, some of the components are represented by functional blocks. The laser beam irradiation unit 18 according to the exemplary modification includes a laser oscillator 72 capable of generating the laser beam A. An adjusting device 74, such as an attenuator, capable of adjusting the power of the laser beam A is arranged at a position adjacent to the laser oscillator 72. The laser oscillator 72 and the adjusting device 74 may be components equivalent to the laser oscillator 32 and the adjusting device 34 of the above-described embodiment.

[0083] The laser beam A, whose power is adjusted by the adjustment device 74, is incident on a galvanometer scanner 76. The galvanometer scanner 76 includes a first mirror 78 and a second mirror 80. The first mirror 78 is connected to a rotational drive source (not shown), such as a motor, and rotates about a first axis. Similarly, the second mirror 80 is connected to a rotational drive source (not shown), such as a motor, and rotates about a second axis perpendicular to the first axis.

[0084] The direction of movement of the laser beam A is controlled by adjusting the angle of the first mirror 78 about the first axis and the angle of the second mirror 80 about the second axis. The upper surface 11a of the workpiece 11 is irradiated with the laser beam A, which is reflected by the galvanometer scanner 76, through a light collector 82 and the window 4a ( Fig. 1). The light collector 82 includes an fθ lens 84 and focuses the laser beam A onto the upper surface 11a of the workpiece 11, regardless of its direction of movement. The diameter of the laser beam A on the upper surface 11a of the workpiece is, for example, approximately 3 µm to 1000 µm.

[0085] In the present embodiment, the position of the area irradiated with the laser beam A is changed in a first direction substantially parallel to the upper surface 11a by the first mirror 78, and is changed in a second direction substantially parallel to the upper surface 11a and substantially perpendicular to the first direction by the second mirror 80. That is, scanning with the laser beam A is performed by the first mirror 78 and the second mirror 80, which constitute the galvanometer scanner 76.

[0086] Furthermore, in the machining method for a workpiece according to the above-described embodiment, the workpiece 11 is machined by using the gas containing the substance that generates the active species that reacts with the workpiece 11. However, it is also possible to machine the workpiece 11 by using a liquid containing the active species that reacts with the workpiece 11. The structure of the machining apparatus used this time may be similar to the structure of the machining apparatus 2. However, the supply unit 10 is configured to be capable of supplying the liquid containing the active species that reacts with the workpiece 11 to the pipe 8. That is, an annular flow path in which liquid flows is implemented through the container 4 and the pipe.

[0087] Furthermore, the separation unit 12 is configured to be capable of removing an unnecessary substance generated due to the machining of the workpiece 11 from the liquid flowing in the pipe 8, and the circulation unit 14 is configured to be capable of circulating the liquid along the annular flow path formed by the container 4 and the pipe 8. The separation unit 12, the circulation unit 14, the evacuation unit 16, etc., may be omitted.

[0088] Fig.6 is a flowchart illustrating an exemplary modification of the workpiece machining method. The main part of the workpiece machining method according to the exemplary modification is the same as the workpiece machining method according to the above-described embodiment. Therefore, the following mainly describes the different points. In the workpiece machining method according to the exemplary modification, the workpiece 11 is first placed in a liquid containing an active species that reacts with the workpiece 11 (placement step ST21).

[0089] Specifically, first, the workpiece 11 is placed on the table 6 in the container 4, and the container 4 is sealed. In the present exemplary modification, a wafer formed by using Si is used as the workpiece 11. Thereafter, the liquid containing the active species that reacts with the workpiece 11 is supplied from the supply unit 10 to the pipe 8 and circulated by the circulation unit 14.

[0090] In the present exemplary modification, an aqueous solution of potassium hydroxide (KOH) is used as the liquid containing the active species that reacts with the workpiece 11. However, there is no particular limitation on the liquid containing the active species that reacts with the workpiece 11. For example, it is also possible to use an aqueous solution of tetramethylammonium hydroxide (TMAH), hydrazine, ethylenediamine pyrocatechol (EDP), or the like.

[0091] After the workpiece 11 is placed in the predetermined liquid, the thickness distribution of the workpiece 11 is measured (measurement step ST22). Details of the method for measuring the thickness distribution are similar to those of the above-described embodiment. After the thickness distribution of the workpiece 11 is measured, irradiation of the workpiece 11 with the laser beam A is started (laser beam irradiation step ST23). In the present exemplary modification, the workpiece 11 in the liquid is irradiated by the laser beam irradiation unit 18 with the laser beam A, the power of which has been adjusted based on information regarding the thickness distribution.

[0092] For example, when the workpiece 11 is irradiated with the laser beam A in the state where the workpiece 11 is placed in an aqueous solution of KOH, the temperature of the area in the workpiece 11 irradiated with the laser beam A increases, and the rate of reaction between Si and OH - increases. In the present exemplary modification, the removal amount of the workpiece 11 is adjusted by utilizing this phenomenon. That is, in the present exemplary modification, the workpiece 11 is cut by OH - which is the active species.

[0093] Specifically, the removal amount calculation section of the control unit 22 first calculates the removal amount of the workpiece 11 to be removed with respect to each region from the information regarding the thickness distribution of the workpiece 11 and the information regarding the target shape of the workpiece 11 (target thickness distribution). That is, the difference between the thickness of the workpiece 11 in each region and the target thickness is calculated as the removal amount.

[0094] Information regarding this removal amount is sent to the power adjustment section of the control unit 22. Upon receiving the information regarding the removal amount, the power adjustment section controls the operation of the adjustment device 34 to adjust the power of the laser beam A with which each area of ​​the workpiece 11 is irradiated in such a way as to realize a response speed corresponding to the removal amount.

[0095] This can irradiate each area of ​​the workpiece 11 in the liquid with the laser beam A whose power has been adjusted based on the information related to the thickness distribution. When irradiation with the laser beam A is performed, each area of ​​the workpiece 11 is removed at the reaction speed in accordance with the power of the laser beam A with which the irradiation is performed. By irradiating each area of ​​the workpiece 11 with the laser beam A whose power is adjusted as above, the removal amount by which each area in the workpiece 11 irradiated with the laser beam is removed by the active species can be controlled.

[0096] For example, by preventing irradiation of a thin portion of the workpiece 11 indicated by the thickness distribution with the laser beam A and by irradiating a thick portion of the workpiece 11 with the laser beam A, the removal amount by which the thick portion of the workpiece 11 is removed by the active species can be set larger than the removal amount by which the thin portion of the workpiece 11 is removed by the active species.

[0097] Furthermore, by increasing the power of the laser beam A irradiated to a thick portion of the workpiece 11 compared to the laser beam A irradiated to a thin portion of the workpiece 11, for example, the removal amount by which the thick portion of the workpiece 11 is removed by the active species can be set larger than the removal amount by which the thin portion of the workpiece 11 is removed by the active species.

[0098] After irradiation of the workpiece 11 with the laser beam A has begun, the thickness distribution of the workpiece 11 is measured again (remeasurement step ST24). After the thickness distribution of the workpiece 11 has been measured again, it is determined whether the workpiece 11 has been machined to the target shape (determination step ST25). Then, in accordance with the result of this determination, irradiation of the workpiece 11 with the laser beam A is terminated (irradiation termination step ST26) or the power of the laser beam A with which the workpiece 11 is irradiated is re-adjusted (re-adjustment step ST27).

[0099] Also, in the machining method for a workpiece according to the above-described exemplary modification, the workpiece 11 may be machined by any method such as grinding, polishing, and etching (chemical etching) before the workpiece 11 is placed in the liquid containing the active species that reacts with the workpiece 11 (pre-machining step).

[0100] Furthermore, in the machining method for a workpiece in accordance with the above-described exemplary modification, the reaction rate between Si and OH -in the workpiece 11 by irradiating the workpiece 11 with the laser beam A and forming an oxide film (SiO2) with a thickness in accordance with the power of the laser beam A on the upper surface 11a of the workpiece 11. In this case, it is preferable to add an additive such as ozone (O3) or hydrogen peroxide (H2O2) to the liquid so that the formation of the oxide film can be facilitated.

[0101] By preventing irradiation of a thick portion of the workpiece 11 indicated by the thickness distribution with the laser beam A and irradiation of a thin portion of the workpiece 11 with the laser beam A, the removal amount by which the thin portion of the workpiece 11 is removed by the active species can be set smaller than the removal amount by which the thick portion of the workpiece 11 is removed by the active species.

[0102] Furthermore, by increasing the power of the laser beam A with which a thin region of the workpiece 11 is irradiated, compared to the laser beam A with which a thick region of the workpiece 11 is irradiated, for example, the removal amount by which the thin region of the workpiece 11 is removed by the active species can be set smaller than the removal amount by which the thick region of the workpiece 11 is removed by active species.

[0103] Furthermore, in the above-described exemplary modification, the workpiece 11 is machined by using the liquid containing the active species that reacts with the workpiece 11. However, the workpiece 11 may be machined by a liquid containing a substance that generates an active species that reacts with the workpiece 11. That is, in this case, the active species is generated by irradiation with the laser beam A. The structure of a machining apparatus may be the same as that of the machining apparatus used in the above-described exemplary modification.

Claims

[1] A machining method for machining a wafer as a workpiece (11), the machining method comprising: an arranging step (ST11) comprising arranging the workpiece (11) in a gas containing a substance that generates an active species reacting with the workpiece (11); a measuring step (ST12) comprising measuring a thickness distribution of the workpiece (11) arranged in the gas by radiating pulsed white light from a white light source (52), splitting the pulsed white light into light of each wavelength by a spectroscopy unit (54), irradiating the workpiece (11) with the light of each wavelength, detecting information regarding the two-dimensional intensity distribution of the light of each wavelength reflected by the workpiece (11) by a two-dimensional imaging unit (64), and calculating the thickness distribution of the workpiece (11) from the information; and a laser beam irradiation step (ST13) comprising irradiating the workpiece (11) in the gas with a laser beam (A) whose power is adjusted based on the thickness distribution measured in the measuring step (ST12), wherein in the laser beam irradiation step (ST13), an ablation amount by which an area irradiated with the laser beam (A) in the workpiece (11) is ablated by the active species is controlled by irradiating the workpiece (11) with the laser beam (A) whose power is adjusted, and during machining, the gas is circulated along an annular flow path connected to a separation unit (12) which separates and removes from the gas an unnecessary substance generated due to the machining of the workpiece (11). [2] A machining method for a workpiece (11) according to claim 1, further comprising a new measuring step (ST14) with a new measurement of the thickness distribution of the workpiece (11) after the start of the laser beam irradiation step (ST13); and a new adjustment step (ST17) with a new adjustment of the power of the laser beam (A) based on the thickness distribution measured again during the new measurement step (ST14), wherein the re-measurement step (ST14) and the re-adjustment step (ST17) are repeated alternately while the laser beam irradiation step (ST13) continues. [3] A machining method for a workpiece (11) according to claim 2, wherein the laser beam irradiation step (ST13) is terminated when the thickness distribution measured again during the re-measuring step (ST14) indicates that the workpiece (11) has been machined to a target shape. [4] A machining method for a workpiece (11) according to any one of the preceding claims, wherein, during the laser beam irradiation step (ST13), by preventing irradiation of the laser beam (A) to a thin portion of the workpiece (11) indicated by the distribution thickness and irradiating a thick portion of the workpiece (11) with the laser beam (A), or by increasing the power of the laser beam (A) irradiated to a thick portion of the workpiece (11) compared to the laser beam (A) irradiated to a thin portion of the workpiece (11), a removal amount by which the thick portion of the workpiece (11) is removed by the active species is made larger than a removal amount by which the thin portion of the workpiece (11) is removed by the active species. [5] Machining method for a workpiece (11) according to any one of the preceding claims, further comprising: a pre-processing step comprising processing the workpiece (11) by grinding, polishing and / or etching before the arrangement step (ST11) is carried out. [6] A machining method for machining a wafer as a workpiece (11), the machining method comprising: an arranging step (ST11) comprising arranging the workpiece (11) in a liquid containing a substance that generates an active species reacting with the workpiece (11); a measuring step (ST12) comprising measuring a thickness distribution of the workpiece (11) arranged in the liquid by radiating pulsed white light from a white light source (52), splitting the pulsed white light into light of each wavelength by a spectroscopy unit (54), irradiating the workpiece (11) with the light of each wavelength, detecting information regarding the two-dimensional intensity distribution of the light of each wavelength reflected by the workpiece (11) by a two-dimensional imaging unit (64), and calculating the thickness distribution of the workpiece (11) from the information; and a laser beam irradiation step (ST13) comprising irradiating the workpiece (11) in the liquid with a laser beam (A) whose power is adjusted based on the thickness distribution measured during the measuring step (ST12), wherein in the laser beam irradiation step (ST13), an ablation amount by which an area irradiated with the laser beam (A) in the workpiece (11) is ablated by the active species is controlled by irradiating the workpiece with the laser beam (A) whose power is adjusted, and during machining, the liquid is circulated along an annular flow path connected to a separation unit (12) which separates and removes from the liquid an unnecessary substance generated due to the machining of the workpiece (11). [7] Machining method for a workpiece (11) according to claim 6, further comprising a new measuring step (ST14) with a new measurement of the thickness distribution of the workpiece (11) after the start of the laser beam irradiation step (ST13); and a new adjustment step (ST17) with a new adjustment of the power of the laser beam based on the thickness distribution measured again during the new measurement step (ST14), wherein the re-measurement step (ST14) and the re-adjustment step (ST17) are repeated alternately while the laser beam irradiation step (ST13) continues. [8] A machining method for a workpiece (11) according to claim 7, wherein the laser beam irradiation step (ST13) is terminated when the thickness distribution measured again during the re-measuring step (ST14) indicates that the workpiece (11) has been machined to a target shape. [9] The machining method for a workpiece (11) according to any one of claims 6 to 8, wherein, during the laser beam irradiation step (ST13), by preventing irradiation of the laser beam (A) to a thin portion of the workpiece (11) indicated by the distribution thickness and irradiating the laser beam (A) to a thick portion of the workpiece (11), or by increasing the power of the laser beam (A) irradiated to a thick portion of the workpiece (11) compared to the laser beam (A) irradiated to a thin portion of the workpiece (11), a removal amount by which the thick portion of the workpiece (11) is removed by the active species is made larger than a removal amount by which the thin portion of the workpiece (11) is removed by the active species. [10] Machining method for a workpiece (11) according to one of claims 6 to 9, further comprising: a pre-processing step comprising processing the workpiece (11) by grinding, polishing and / or etching before the arrangement step (ST11) is carried out. [11] A machining method for machining a wafer as a workpiece (11), the machining method comprising: an arranging step (ST11) comprising arranging the workpiece (11) in a liquid containing an active species reacting with the workpiece (11); a measuring step (ST12) comprising measuring a thickness distribution of the workpiece (11) arranged in the liquid by radiating pulsed white light from a white light source (52), splitting the pulsed white light into light of each wavelength by a spectroscopy unit (54), irradiating the workpiece (11) with the light of each wavelength, detecting information regarding the two-dimensional intensity distribution of the light of each wavelength reflected by the workpiece (11) by a two-dimensional imaging unit (64), and calculating the thickness distribution of the workpiece (11) from the information; and a laser beam irradiation step (ST13) comprising irradiating the workpiece (11) in the liquid with a laser beam (A) whose power is adjusted based on the thickness distribution measured during the measuring step (ST12), wherein in the laser beam irradiation step (ST13), a removal amount by which an area in the workpiece (11) irradiated with the laser beam (A) is removed by the active species is controlled by irradiating the workpiece (11) with the laser beam (A) whose power is adjusted, and during machining, the liquid is circulated along an annular flow path connected to a separation unit (12) which separates and removes from the liquid an unnecessary substance generated due to the machining of the workpiece (11). [12] A machining method for a workpiece (11) according to claim 11, further comprising a new measuring step (ST14) with a new measurement of the thickness distribution of the workpiece (11) after the start of the laser beam irradiation step (ST13); and a new adjustment step (ST17) with a new adjustment of the power of the laser beam (A) based on the thickness distribution measured again during the new measurement step (ST14), wherein the re-measurement step (ST14) and the re-adjustment step (ST17) are repeated alternately while the laser beam irradiation step (ST13) continues. [13] A machining method for a workpiece (11) according to claim 12, wherein the laser beam irradiation step (ST13) is terminated when the thickness distribution re-measured during the re-measuring step (ST14) indicates that the workpiece (11) has been machined to a target shape. [14] The machining method for a workpiece (11) according to any one of claims 11 to 13, wherein, during the laser beam irradiation step (ST13), by preventing irradiation of the laser beam (A) to a thin portion of the workpiece (11) indicated by the distribution thickness and irradiating a thick portion of the workpiece (11) with the laser beam (A), or by increasing the power of the laser beam (A) irradiated to a thick portion of the workpiece (11) compared to the laser beam (A) irradiated to a thin portion of the workpiece (11), a removal amount by which the thick portion of the workpiece (11) is removed by the active species is made larger than a removal amount by which the thin portion of the workpiece (11) is removed by the active species. [15] The machining method for a workpiece (11) according to any one of claims 11 to 13, wherein, during the laser beam irradiation step (ST13), by preventing irradiation of the laser beam (A) to a thick portion of the workpiece (11) indicated by the distribution thickness and irradiating a thin portion of the workpiece (11) with the laser beam (A), or by increasing the power of the laser beam (A) irradiated to a thin portion of the workpiece (11) compared to the laser beam (A) irradiated to a thick portion of the workpiece (11), a removal amount by which the thin portion of the workpiece (11) is removed by the active species is made larger than a removal amount by which the thick portion of the workpiece (11) is removed by the active species. [16] Machining method for a workpiece (11) according to one of claims 11 to 15, further comprising: a pre-processing step comprising processing the workpiece (11) by grinding, polishing and / or etching before the arrangement step (ST11) is carried out. [17] Processing device (2) for processing a wafer as a workpiece (11), the processing device comprising: a supply unit (10) that supplies the workpiece (11) with a gas containing a substance that produces an active species that reacts with the workpiece (11), a liquid containing a substance that produces an active species that reacts with the workpiece (11), or a liquid containing an active species that reacts with the workpiece (11); a measuring unit (20) used when measuring a thickness distribution of the workpiece (11), the measuring unit (20) being configured to emit pulsed white light from a white light source (52), split the pulsed white light into light of each wavelength by a spectroscopy unit (54), irradiate the workpiece (11) with the light of each wavelength, acquire information regarding the two-dimensional intensity distribution of the light of each wavelength reflected by the workpiece (11) by a two-dimensional imaging unit (64), and calculate the thickness distribution of the workpiece (11) from the information by a thickness distribution calculation section; a laser beam irradiation unit (18) having an adjusting device (34) which adjusts a power of a laser beam (A); a control unit (22) which controls the adjusting device (34) based on the thickness distribution of the workpiece (11) measured by the measuring unit (20); a circulation unit (14) for circulating the gas or liquid along an annular flow path; and a separator (12) for separating and removing an unnecessary substance generated due to the machining of the workpiece (11) from the gas or liquid in the annular flow path. [18] A processing apparatus according to claim 17, further comprising: a container (4) in which the workpiece (11) is received, wherein a window (4a) is arranged in the container (4) which allows the laser beam (A) with which irradiation is carried out from outside the container (4) to be transmitted through the window (4a).

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