Method and apparatus for smoothing work

Abstract

To provide a method and a device for smoothing a work by which the working time of finish flattening is drastically shortened by predicting stress deformation in advance and roughly working the work into a shape corresponding to a finish shape in advance in a working method for smoothing the work in which the stress deformation is caused, especially the work having a bimetal structure in which thermal stress deformation is caused by temperature rise.SOLUTION: The method includes a first machining process for locally machining the surface of the workpiece based on machining data, and a second machining process which is performed after the first machining process and has a machining mechanism for preferentially removing a contact part between a machining pad having a planar machining reference surface and the workpiece, wherein stress deformation of the workpiece at the time of machining in the second machining process is predicted, and machining data of the first machining process is created from a difference between a predicted surface shape 4 at deformation and a predicted finished surface shape 5 or a difference between a final finished surface shape 7 and the pre-machining surface shape 6.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for smoothing a workpiece having a bimetal structure in which stress deformation occurs due to, for example, thermal changes during processing. [Background technology]

[0002] As a method for processing difficult-to-process materials such as SiC, GaN, or cemented carbide, a plasma-assisted polishing (PAP) method has been proposed (Patent Document 1). This method oxidizes the surface of the difficult-to-process material with OH radicals generated by plasma, and then polishes it with an abrasive that is harder than this oxide layer but softer than the difficult-to-process material, thereby avoiding the introduction of scratches or a process-affected layer.

[0003] Furthermore, Patent Document 2 proposes a processing method in which the surface of a movable tool is passed through a plasma generation region, radicals are adsorbed onto the tool surface to give reactive species, and the reactive species on the tool surface are transported by movement of the tool to the surface of a workpiece placed in a position different from the plasma generation region, and reaction products generated by a chemical reaction between atoms on the surface of the workpiece that comes into contact with the tool and the reactive species are removed. The polishing method described in Patent Document 2 can also be said to fall under the category of the PAP method.

[0004] When polishing a diamond substrate using the PAP method, if there is a large waviness component on the processed surface of the substrate, the polishing time to smooth the entire surface will be extremely long. Therefore, Patent Document 3 discloses that the polishing time using the PAP method can be significantly reduced by removing the waviness component in advance by laser trimming.

[0005] However, problems that are not noticeable with small-diameter diamond substrates become more pronounced when the diameter is larger. Specifically, when a diamond substrate consisting of two or more layers is polished flat using a flat surface plate, the bimetal deformation caused by temperature changes during polishing causes the substrate to become concave (convex) on the polishing surface. With the PAP method, the substrate and surface plate (polishing pad) are exposed to plasma, causing the substrate to heat up significantly compared to conventional polishing. If the substrate is polished while still warped due to the temperature rise, only the outer periphery (center) will be polished first, and it will take a long time to polish the entire surface evenly. Furthermore, once the substrate returns to room temperature after polishing, the finished surface will inevitably become convex (concave). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5614677 [Patent Document 2] Patent No. 6692010 [Patent Document 3] Japanese Patent Publication No. 2024-022232 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above situation, the present invention aims to solve the problem by providing a method for smoothing a workpiece, which undergoes stress deformation during the finishing surface machining process, particularly a workpiece having a bimetal structure in which thermal stress deformation occurs due to temperature rise, by predicting stress deformation in advance and rough machining the workpiece into a shape corresponding to the finished shape, thereby significantly shortening the processing time for finishing surface machining, and an apparatus therefor. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention provides a method and apparatus for smoothing a workpiece, which are configured as follows.

[0009] [Configuration 1] A method for smoothing a workpiece to reduce the surface roughness of the workpiece over the entire surface, comprising: a first machining step of locally machining a workpiece surface based on machining data; a finishing second machining step that is performed after the first machining step and has a machining mechanism that preferentially removes a contact portion between a machining pad having a flat machining reference surface and a workpiece; predicting stress deformation of the workpiece during processing in the second processing step, and creating processing data for the first processing step from the difference between the predicted surface shape during deformation and the predicted finished planar shape during deformation, or the difference between the surface shape before processing and the predicted finished surface shape; A method for smoothing workpieces.

[0010] [Configuration 2] A method for smoothing a workpiece according to configuration 1, wherein the workpiece has a bimetal structure in which a plurality of materials with different linear expansion coefficients are laminated together, and thermal stress deformation of the workpiece is predicted from the materials constituting the workpiece, their linear expansion coefficients, and the temperature change during processing in the second processing step, and processing data for the first processing step is created from the difference between the predicted surface shape at the time of deformation and the predicted finished planar shape at the time of deformation, or the difference between the surface shape before processing at room temperature and the predicted finished surface shape.

[0011] [Configuration 3] 3. The method for smoothing a workpiece according to claim 2, wherein the workpiece is a diamond substrate having a diamond layer laminated on a base substrate.

[0012] [Configuration 4] 4. A method for smoothing a workpiece according to claim 1, 2 or 3, wherein the second processing step is a step of flattening the contact portion between the workpiece surface and the processing reference surface of the processing pad using a plasma-assisted polishing device.

[0013] [Configuration 5] A workpiece smoothing processing method according to configuration 1, 2 or 3, wherein the first processing step is a step of locally processing the workpiece surface based on processing data using a laser processing device that uses laser ablation as its processing principle.

[0014] [Configuration 6] The plasma-assisted polishing device is provided with a polishing mechanism unit that brings a processing pad having an abrasive material at least on its surface into contact with the workpiece at a predetermined polishing pressure and relatively displaces the processing pad and the workpiece at a predetermined relative speed, selectively removing and smoothing the convex portions of the processing surface, and a plasma generating unit that causes neutral radicals generated in the plasma to act on at least one of the processing pad and the processing surface of the workpiece, thereby promoting the polishing action of the workpiece.

[0015] [Configuration 7] a local processing device that performs a first processing step; a finish surface processing device for performing a second processing step, A workpiece smoothing device that reduces the surface roughness of a workpiece over the entire surface, the first machining step is a step of locally machining a workpiece surface based on machining data, the second machining step is a step performed after the first machining step, and has a machining mechanism that preferentially removes a contact portion between a machining pad having a flat machining reference surface and a workpiece; The machining data for the first machining step is created by predicting the stress deformation of the workpiece during machining in the second machining step, and based on the difference between the predicted surface shape during deformation and the predicted finished planar shape during deformation, or the difference between the surface shape before machining and the predicted finished surface shape. Workpiece smoothing processing equipment.

[0016] [Configuration 8] A workpiece smoothing processing device according to configuration 7, wherein the workpiece has a bimetal structure in which a plurality of materials with different linear expansion coefficients are laminated together, and the processing data for the first processing step is generated by predicting thermal stress deformation of the workpiece from the materials constituting the workpiece, their linear expansion coefficients, and temperature changes during processing in the second processing step, and from the difference between the predicted surface shape upon deformation and the predicted finished planar shape upon deformation, or the difference between the surface shape before processing at room temperature and the predicted finished surface shape.

[0017] [Configuration 9] 9. The workpiece smoothing apparatus according to claim 8, wherein the workpiece is a diamond substrate having a diamond layer laminated on a base substrate.

[0018] [Configuration 10] 10. The workpiece smoothing processing device according to configuration 7, 8 or 9, wherein the finish flattening device is a plasma-assisted polishing device that flattens the contact portion between the workpiece surface and the processing reference surface of the processing pad.

[0019] [Configuration 11] The workpiece smoothing processing device according to configuration 7, 8 or 9, wherein the local processing device is a laser processing device that uses laser ablation as a processing principle and locally processes the workpiece surface based on processing data.

[0020] [Configuration 12] The plasma-assisted polishing device for a workpiece according to configuration 10 is provided with a polishing mechanism unit that brings a processing pad having an abrasive material at least on its surface into contact with the workpiece and the processing pad at a predetermined polishing pressure while relatively displacing the pad and the workpiece at a predetermined relative speed, thereby selectively removing and smoothing the convex portions of the processing surface, and a plasma generating unit that causes neutral radicals generated in the plasma to act on at least one of the processing pad and the processing surface of the workpiece, thereby promoting the polishing action of the workpiece. [Effects of the Invention]

[0021] The workpiece smoothing method and apparatus of the present invention described above have the following advantages.

[0022] By predicting the stress deformation of the workpiece during processing in the finish flattening process and removing the parts that will become convex due to deformation in advance in the local processing process, the processing time in the finish flattening process, which has a slow processing speed, can be significantly reduced, thereby shortening the overall processing time. In particular, when the workpiece is a diamond substrate, the finish flattening process requires a long time, but by predicting the thermal stress deformation of the diamond substrate and performing the local processing process before the finish flattening process, the overall processing time can be significantly reduced. [Brief explanation of the drawings]

[0023] [Figure 1] The figure shows a cross-sectional view of a workpiece in which the machined surface becomes concave due to thermal deformation caused by a temperature rise during machining. (a) shows the cross-sectional shape before machining, (b) shows the cross-sectional shape when the temperature rises, (c) shows the cross-sectional shape at room temperature when the temperature returns to room temperature from the state in (b), (b-1) shows the difference profile (machining data) between the predicted thermally deformed shape during machining and the predicted finished planar shape during machining, and (c-1) shows the difference profile (machining data) between the surface shape before machining at room temperature and the predicted final finished surface shape. [Figure 2] This shows the process of smoothing the workpiece in Figure 1, where (a) shows the state before processing, (b) shows the state after the first processing step, (c) shows the state during the second processing step, and (d) shows the finished state at room temperature. [Figure 3] The figure shows a cross-sectional view of a workpiece in which the machined surface becomes convex due to thermal deformation caused by a temperature rise during machining. (a) shows the cross-sectional shape before machining, (b) shows the cross-sectional shape when the temperature rises, (c) shows the cross-sectional shape at room temperature when the temperature returns to room temperature from the state in (b), (b-1) shows the difference profile (machining data) between the predicted thermally deformed shape during machining and the predicted finished planar shape during machining, and (c-1) shows the difference profile (machining data) between the surface shape before machining at room temperature and the predicted final finished surface shape. [Figure 4] This shows the process of smoothing the workpiece in Figure 3, where (a) shows the state before processing, (b) shows the state after the first processing step, (c) shows the state during the second processing step, and (d) shows the finished state at room temperature. [Figure 5] FIG. 1 is a conceptual diagram showing a laser processing device. [Figure 6] FIG. 1 is a conceptual diagram showing an automatic local processing device that combines a laser processing device and a shape measurement device. [Figure 7] FIG. 1 is a conceptual diagram showing a plasma-assisted polishing apparatus. [Figure 8] FIG. 2 is a cross-sectional view of a main part of a plasma-assisted polishing apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0024] Next, the present invention will be described in more detail based on the embodiments shown in the accompanying drawings. Figures 1 and 2 show the case of smoothing a workpiece whose processed surface becomes concave due to thermal deformation caused by a temperature rise during processing, and Figures 3 and 4 show the case of smoothing a workpiece whose processed surface becomes convex due to thermal deformation caused by a temperature rise during processing. In the figures, reference numerals W, 1, and 2 represent the workpiece, base substrate, and functional material layer, respectively.

[0025] The workpiece (workpiece W) in the present invention has a bimetal structure. Here, "bimetal structure" refers to a structure in which multiple materials with different linear expansion coefficients are laminated together. Typically, a bimetal refers to two metal plates with different linear expansion coefficients bonded together, but the present invention is not limited to either metal or two materials. Like bimetals, the workpiece to be processed in the present invention also has the property of bending toward the side with the smaller linear expansion coefficient as the temperature increases. In this embodiment, the back side of the workpiece W is the base substrate 1, and the front side is the functional material layer 2. The stress deformation of the workpiece W during processing is not limited to thermal deformation, but can also be applied to deformation due to external stress, such as force applied to fix the workpiece W.

[0026] Typically, the workpiece W is a substrate in which a functional material layer 2 is formed on the surface of a base substrate 1, or a substrate in which two types of substrates are bonded together. In this embodiment, a large-diameter diamond substrate of 2 inches or more is assumed. The linear expansion coefficient of diamond varies depending on the temperature and the crystal structure (single crystal, polycrystal, etc.), but is generally in the range of 1 to 4 × 10 -6 On the other hand, the linear expansion coefficient of various materials is 5 to 9 × 10 -6 / K, alumina is 7~8×10 -6 / K, cemented carbide (WC) is 5~6×10 -6 / K, and quartz glass is 0.4 to 0.6 × 10 -6 / K.

[0027] For example, in the case of a 50 mm diameter diamond substrate with a 0.6 mm thick diamond layer on a 2.4 mm thick WC substrate, the linear thermal expansion coefficient of diamond is 2 × 10 -6 / K, Young's modulus is 1000 GPa, and the linear expansion coefficient of WC is 5 × 10 -6 / K, and Young's modulus is 620 GPa. When the temperature rises from room temperature (25°C) to 120°C, the center will be recessed by approximately 34 μm relative to the outer periphery.

[0028] Several methods have been proposed for manufacturing diamond substrates, and diamond substrates are already commercially available. Large-diameter diamond substrates are manufactured by depositing a diamond film directly on a base substrate or on a buffer layer using a vapor phase growth method such as pulsed laser deposition (PLD) or chemical vapor deposition (CVD).

[0029] The present invention provides a smoothing method and apparatus for reducing the surface roughness of a workpiece over its entire surface. The method includes a first machining step for locally machining the workpiece surface based on machining data, and a second finishing machining step performed after the first machining step using a machining mechanism that preferentially removes the contact area between the workpiece and a machining pad having a flat machining reference surface. The second machining step includes predicting stress deformation of the workpiece during machining in the second machining step, and creating machining data for the first machining step from the difference between the predicted surface shape after deformation and the predicted finished planar shape after deformation, or the difference between the predicted finished surface shape and the surface shape before machining.

[0030] In addition, the workpiece smoothing processing device of the present invention comprises a local processing device that performs a first processing step and a finish flat processing device that performs a second processing step, wherein the first processing step is a step of locally processing the workpiece surface based on processing data, and the second processing step is a step that is performed after the first processing step and has a processing mechanism that preferentially removes the contact portion between the workpiece and a processing pad having a planar processing reference surface, and the processing data for the first processing step is created by predicting the stress deformation of the workpiece during processing in the second processing step, and from the difference between the predicted surface shape at the time of deformation and the predicted finished planar shape at the time of deformation, or the difference between the predicted final finished surface shape and the surface shape before processing.

[0031] Here, the workpiece has a bimetal structure in which multiple materials with different linear expansion coefficients are laminated together, and thermal stress deformation of the workpiece is predicted from the materials that make up the workpiece, their linear expansion coefficients, and the temperature change during processing in the second processing step, and processing data for the first processing step is created from the difference between the predicted surface shape at deformation and the predicted finished planar shape at deformation, or the difference between the predicted final finished surface shape at room temperature and the surface shape before processing.

[0032] The local processing device that performs the first processing step employs a processing method based on a processing principle that provides a faster processing speed than the finish surface processing device that performs the second processing step, and is generally positioned as a rough processing device. In this embodiment, a laser processing device is used as the local processing device, and a plasma-assisted polishing device is used as the finish surface processing device, but the present invention is not limited to these.

[0033] The laser processing device (local processing device) uses laser ablation as its processing principle and processes the surface of a workpiece locally based on processing data. The first processing step is carried out using this laser processing device.

[0034] The plasma-assisted polishing apparatus (finishing flatness processing apparatus) processes the contact area between the workpiece surface and the processing reference surface of the processing pad to a flat surface. More specifically, the plasma-assisted polishing apparatus includes a polishing mechanism unit that brings the processing pad, which has an abrasive material at least on its surface, into contact with the workpiece at a predetermined polishing pressure and relatively displaces the pad at a predetermined relative speed to selectively remove and smooth the convex portions of the processing surface, and a plasma generation unit that applies neutral radicals generated in the plasma to at least one of the processing pad and the processing surface of the workpiece to promote the polishing action of the workpiece. This plasma-assisted polishing apparatus is used to perform the second processing step.

[0035] <Embodiment 1: When the machined surface becomes concave due to temperature rise> The workpiece W, which has a bimetal structure, has a flat surface (machining surface 3) at room temperature (see Figure 1(a)). If the linear expansion coefficient of the functional material layer 2 of the workpiece W is smaller than that of the base substrate 1, the temperature rise during machining will cause thermal stress deformation throughout the workpiece, causing the machining surface 3 to become concave (see Figure 1(b)). Assume that the workpiece W is deformed and the machining surface 3 is machined flat using a machining mechanism that preferentially removes the contact area between the workpiece and a machining pad with a flat machining reference surface. In Figure 1(b), reference numeral 4 denotes the predicted surface shape after deformation, and reference numeral 5, shown by a dotted line, denotes the predicted finished planar shape after deformation. Figure 1(b-1) shows the difference profile 8 between the predicted surface shape 4 after deformation and the predicted finished planar shape 5 after deformation. This represents the thickness-wise machining amount distribution in the first machining step, i.e., the machining data.

[0036] On the other hand, the shape after returning to room temperature from the state shown in Figure 1(b) is shown in Figure 1(c). In Figure 1(c), reference numeral 6 denotes the pre-machining surface shape, and reference numeral 7, indicated by a dotted line, denotes the predicted final surface shape. Figure 1(c-1) shows a differential profile 9 between the pre-machining surface shape 6 and the predicted final surface shape 7, which represents the thickness-direction machining amount distribution in the first machining step, i.e., the machining data. Here, the predicted finished planar shape 5 after deformation corresponds to the predicted final surface shape 7 when the workpiece W returns to its original shape at room temperature. The differential profile 8 in Figure 1(b-1) and the differential profile 9 in Figure 1(c-1) are identical when one is flipped upside down, so either method can be used to create the machining data.

[0037] Figure 2 shows the state of the workpiece W at each step in the smoothing method of the present invention, with Figure 2(a) showing the state of the workpiece W before machining, Figure 2(b) showing the state after the first machining step is performed based on the machining data and local machining is performed (locally machined surface 10), Figure 2(c) showing the state after the second machining step is performed and finish flattening is performed using a machining mechanism that preferentially removes the contact area between the workpiece and a machining pad with a planar machining reference surface (flat-machined surface 11), and Figure 2(d) showing the final finished state (final finished surface 12) after returning to room temperature. Here, the local machined surface 10 corresponds to the predicted final finished surface shape 7, the flat-machined surface 11 corresponds to the predicted finished planar shape 5 after deformation, and the final finished surface 12 is the shape obtained by subtracting the amount of flattening performed in the second machining step from the local machined surface 10.

[0038] <Embodiment 2: When the processed surface becomes convex due to temperature rise> 1 and 2, in this second embodiment, the processed surface becomes convex due to a temperature rise. In other words, the linear expansion coefficient of the functional material layer 2 of the workpiece W is greater than the linear expansion coefficient of the base substrate 1. Although this second embodiment differs in that it is a concave or convex surface, it is basically the same as the first embodiment described above, and therefore, conceptually identical components will be described with the same reference numerals.

[0039] Figure 3(a) shows the state of the workpiece W before machining, where the machining surface 3 is flat at room temperature. As the temperature rises during machining, the entire workpiece undergoes thermal stress deformation, causing the machining surface 3 to become convex (see Figure 3(b)). Assume that, in this deformed state, the machining surface 3 is machined flat using a machining mechanism that preferentially removes the contact area between the workpiece and a machining pad with a flat machining reference surface. In Figure 3(b), reference numeral 4 denotes the predicted surface shape after deformation, and reference numeral 5, shown by a dotted line, denotes the predicted finished planar shape after deformation. Figure 3(b-1) shows the difference profile 8 between the predicted surface shape 4 after deformation and the predicted finished planar shape 5 after deformation, which is the thickness-wise machining amount distribution in the first machining process, i.e., the machining data.

[0040] On the other hand, the shape after returning to room temperature from the state shown in Figure 3(b) is shown in Figure 3(c). In Figure 3(c), reference numeral 6 denotes the pre-machining surface shape, and reference numeral 7, indicated by a dotted line, denotes the predicted final surface shape. Figure 3(c-1) shows a differential profile 9 between the pre-machining surface shape 6 and the predicted final surface shape 7, which is the machining amount distribution in the thickness direction in the first machining step, i.e., the machining data. Here, the predicted finished planar shape 5 after deformation corresponds to the predicted final surface shape 7 when the workpiece W returns to its original shape at room temperature. The differential profile 8 in Figure 3(b-1) and the differential profile 9 in Figure 3(c-1) are identical when one is flipped upside down, so the machining data can be created using either method.

[0041] Figure 4 shows the state of the workpiece W at each step in the smoothing method of the present invention, with Figure 4(a) showing the state of the workpiece W before machining, Figure 4(b) showing the state after local machining by executing the first machining step based on machining data (locally machined surface 10), Figure 4(c) showing the state after finishing flattening by executing the second machining step using a machining mechanism that preferentially removes the contact area between the workpiece and a machining pad with a planar machining reference surface (flat-machined surface 11), and Figure 4(d) showing the final finished state (final finished surface 12) after returning to room temperature. Here, the local machined surface 10 corresponds to the predicted final finished surface shape 7, the flat-machined surface 11 corresponds to the predicted finished planar shape 5 after deformation, and the final finished surface 12 is the shape obtained by subtracting the amount of flattening in the second machining step from the local machined surface 10.

[0042] <Laser processing equipment (local processing equipment)> 5, the laser processing device 13 used in the first processing step is composed of a laser oscillator 14, a beam expander 15 that expands the laser light L, a galvanometer scanner 16 that focuses the laser light L on the surface of the workpiece W and scans along the surface, and a control device 17 such as a computer that controls them. In this embodiment, after the laser oscillator 14 generates a short-pulse laser light having a wavelength of 1064 nm, the laser light is expanded to a predetermined size by the beam expander 15 and then scanned over the surface of the workpiece W by the galvanometer scanner 16.

[0043] The laser power irradiated onto the workpiece W can be controlled by adjusting the amount of light passing through the laser beam expanded by the beam expander 15 through an aperture (not shown). If the laser oscillator 14 is equipped with a power adjustment function, the beam expander 15 can be omitted. Here, the galvano scanner 16 reflects the laser beam with two mirrors whose angles can be changed around the X and Y axes, and then focuses the beam on the surface of the workpiece W through an f-θ lens. However, in the present invention, it is not necessary to specify the laser processing device 13, and various commercially available products can be used.

[0044] Irradiating a material with laser light removes the irradiated portion through laser ablation, and scanning the laser light along the material surface allows for machining into any desired shape. When the workpiece W is a diamond substrate, irradiating the diamond substrate with laser light partially heats the surface, graphitizing it. The graphite layer then absorbs the laser light and sublimes as CO2. If defects are present during the diamond substrate manufacturing process, the laser light is preferentially absorbed by the defects, causing those areas to graphitize first, while the surface area above the defects is blown away, resulting in poor surface roughness. Depending on the depth of the defects, large recesses may form, requiring a long processing time to remove the recesses in the second processing step. To avoid this, a laser-absorbing material is uniformly deposited on the entire surface of the diamond substrate in advance.

[0045] Here, the temperature required for graphitizing diamond is usually 600 to 800°C. The aforementioned laser light absorbing material must be capable of absorbing laser light and raising the temperature of the diamond surface to the graphitization temperature. It is selected taking into consideration the laser light absorption rate and its own boiling point, and the thickness is then determined based on the required heat capacity. As the laser light absorbing material, gold, copper, aluminum, or various other metals can be used, and typically gold is evaporated to a thickness of 20 to 30 nm. Incidentally, a sputtering deposition device or the like can be used as a means for depositing the laser light absorbing material.

[0046] In this way, when the laser beam L is irradiated onto the processing surface of the diamond substrate with a layer of laser beam absorber present, the laser beam absorber absorbs the laser energy with the highest priority, raising the temperature above the graphitization temperature and forming a graphite layer in the area irradiated with the laser beam. Once graphitization has occurred, the laser beam irradiated for the second time or later is absorbed by the graphite layer, and ablation processing proceeds sequentially from the outermost surface, accompanied by graphitization.

[0047] In order to process the workpiece W using the laser processing device 13 that performs the first processing step, it is necessary to create processing data in advance and to confirm that the desired surface shape is achieved after processing. Therefore, as shown in Figure 6, a shape measuring device 18 that can measure the surface shape of the workpiece W and the laser processing device 13 are combined with an X-stage 19 that transports the workpiece W, and information is further linked to a computer 20 to form an automatic local processing device 21.

[0048] The shape measuring device 18 is a device capable of measuring the surface shape of the workpiece W with submicron-order accuracy, and can use, for example, a non-contact shape sensor that utilizes laser light reflection. The X-stage 19 is a device for carrying the workpiece W and transporting it between the shape measuring device 18 and the laser processing device 13. Specifically, the X-stage 19 has a pair of rails 23, 23 along both sides of a base plate 22 extending in the X-direction. A table 24 that moves on the rails 23, 23 is moved with high precision by a feed screw mechanism 26 driven by a drive motor 25 provided at one end of the base plate 22. The shape measuring device 18 and the laser processing device 13 are disposed on the movement path of the table 24 of the X-stage 19. During shape measurement by the shape measuring device 18, the table 24 of the X-stage 19 moves (scans) with high precision in the X-direction, and during local processing by the laser processing device 13, the table 24 is kept stationary. Furthermore, when the workpiece W is transported between the shape measuring device 18 and the laser processing device 13, the table 24 is moved at high speed.

[0049] The workpiece W is held on the table 24 of the X-stage 19, and its surface shape is measured while it passes (scans) in the X-direction through the linear measurement area of ​​the shape measuring device 18. The computer 20 then acquires shape data obtained by measuring the pre-processing surface shape with the shape measuring device 18, predicts thermal stress deformation of the workpiece W caused by the temperature rise in the second processing step, creates the processing data, and sends it to the laser processing device 13. The laser processing device 13 performs local processing of the workpiece W based on the processing data, and then the table 24 of the X-stage 19 transports the workpiece W to the shape measuring device 18, where the post-processing surface shape is measured. If the desired surface shape is not obtained, the computer 20 creates new processing data and drives the X-stage 19 to transport the workpiece W to the processing area of ​​the laser processing device 13, issuing a command to process it. This routine is repeated until the final predicted surface shape is obtained.

[0050] <Plasma-assisted polishing (PAP) equipment (finishing flat surface processing equipment)> Next, a plasma-assisted polishing (PAP) device 27 will be described with reference to Figures 7 and 8. Figure 7 shows a conceptual diagram of the PAP device, and Figure 8 shows an enlarged cross-sectional view of the main parts. In the figures, reference numeral 28 denotes a vacuum chamber, 29 denotes a processing head equipped with a mounting surface for holding the workpiece W, 30 denotes a processing pad, 31 denotes a rotary table that also serves as an electrode plate, 32 denotes a counter electrode, 33 denotes a gas supply system, 34 denotes a gas exhaust system, and 35 denotes a high-frequency power source.

[0051] The finish surface processing apparatus of the present invention has a processing mechanism that preferentially removes the contact portion between the workpiece and a processing pad having a planar processing reference surface, and the plasma-assisted polishing apparatus 27 of this embodiment also has a similar processing mechanism. The plasma-assisted polishing apparatus 27 has a polishing mechanism unit A that brings the processing pad 30, which has an abrasive material on at least its surface, into contact with the workpiece W at a predetermined polishing pressure and relatively displaces them at a predetermined relative speed, selectively removing and smoothing the convex portions of the processing surface, and a plasma generation unit B that applies neutral radicals generated in the plasma to at least one of the processing pad 30 and the processing surface of the workpiece W, thereby promoting the polishing action of the workpiece W.

[0052] Specifically, the polishing mechanism unit A places a processing pad 30 on a rotatable turntable 31, holds a workpiece W having a processing surface smaller in area than the processing pad 30, and brings the processing surface of the workpiece W into contact with the processing pad 30 at a predetermined polishing pressure F, and is equipped with a processing head 29 that can rotate around an axis perpendicular to the processing pad 30. The plasma generation unit B supplies a process gas from a gas supply system 33 between the turntable 31, which also serves as an electrode plate, and a counter electrode 32 that is arranged at a distance from the turntable 31, and applies a high-frequency voltage from a high-frequency power source 35 between the turntable 31 and the counter electrode 32 to generate capacitively coupled high-frequency plasma.

[0053] When the workpiece W is a diamond substrate, a process gas containing an element that has the effect of bonding with the carbon atoms that make up the diamond and sublimating it, or bonding with the atoms that make up the polishing plate and the carbon atoms that make up the diamond substrate S and pulling out the surface carbon atoms through relative movement is used.

[0054] In the plasma-assisted polishing apparatus 27 of this embodiment, a structure for generating capacitively coupled plasma is shown as the plasma generation unit B, but other structures are also possible, such as a structure in which a plasma jet generated under atmospheric pressure is irradiated onto the processing pad 30, or a structure in which the processing pad 30 is exposed to corona discharge plasma generated under atmospheric pressure. Furthermore, the power input to the process gas is also not limited, and may be any power, such as direct current, commercial frequency, low frequency, high frequency, or microwave.

[0055] More specifically, as shown in FIG. 7, the plasma-assisted polishing apparatus 27 has the polishing mechanism section A and the plasma generation section B provided inside a vacuum chamber 28, and further has a gas supply system 33 for supplying a process gas and a gas exhaust system 34 for exhausting the gas connected to the vacuum chamber 28. The vacuum chamber 28 is filled with a process gas at a predetermined pressure, and a high-frequency voltage is applied from the high-frequency power supply 35 between the turntable 31 and the counter electrode 32, generating plasma between the turntable 31 and the counter electrode 32.

[0056] A rotary table 31 is disposed at the bottom of the vacuum chamber 28 with its rotation axis 36 oriented vertically, and a processing pad 30 is fixed to its upper surface. When the workpiece W is a diamond substrate, it is preferable to use quartz glass for the processing pad 30. The rotary table 31 is formed of a conductor, is grounded together with the vacuum chamber 28, and also serves as a lower electrode. The counter electrode 32 is held by an insulator on a fixed portion within the vacuum chamber 28 and is fixed in a position parallel to the rotary table 31 (processing pad 30). A high-frequency power supply 35 is connected to the counter electrode 32. The center of rotation of the rotation axis 37 of the processing head 29 is set at a position radially eccentric from the center of rotation of the rotary table 31. The processing head 29 contacts the processing pad 30 via the workpiece W through an opening 38 provided in the counter electrode 32, and the rotation axis 37 extends upward and is connected to an appropriate rotational power means and an axial polishing pressure applying means 39.

[0057] The gas supply system 33 supplies process gas into the vacuum chamber 28. When the workpiece W is a diamond substrate, the process gas is a mixture of argon gas and oxygen gas. Water vapor can be used instead of oxygen gas. Furthermore, oxygen gas and water vapor can be used together. Oxygen gas and water vapor (H2O molecules) become O radicals and OH radicals in the plasma, bond with the carbon atoms that make up the diamond, and sublimate as carbon dioxide. Alternatively, O radicals and OH radicals bond with both the atoms that make up the processing pad and the carbon atoms on the diamond surface, and pull out the surface carbon atoms through relative motion. Alternatively, an inert gas such as helium gas can be used instead of argon gas.

[0058] The gas exhaust system 34 is composed of a vacuum pump and an abatement tube, and evacuates the inside of the vacuum chamber 28. The gas exhaust system 34 evacuates the inside of the vacuum chamber 28 to a vacuum, and then injects a process gas to maintain the inside of the vacuum chamber 28 at a predetermined pressure.

[0059] The effects of plasma irradiation include supplying neutral radicals that promote polishing to the contact point between the workpiece W and the processing pad 30, as well as oxidizing carbon deposits (derived from workpieces such as diamonds) on the processing pad by irradiation with oxygen radicals or OH radicals, thereby vaporizing and removing them as CO2, thereby maintaining a clean surface.

[0060] In addition to quartz glass, other materials that can be used for the processing pad 30 include sapphire, alumina, borosilicate glass, and B4C (boron carbide). It is known that the polishing rate increases in the following order: borosilicate glass > quartz glass > alumina > sapphire. On the other hand, it is known that the surface roughness decreases in the following order: quartz glass < borosilicate glass < sapphire ≒ alumina.

[0061] In the plasma-assisted polishing apparatus 27, polishing can be performed not only by rotating the rotary table 31 and the processing head 20 but also by adding an oscillating motion that changes the distance between their rotation axes 36, 37. Since this apparatus is equipped with a special plasma generation unit B, the rotary table 31 may be oscillated by adding a mechanism that drives it linearly back and forth in a direction perpendicular to the rotation axis 36. The size relationship between the processing pad 30 and the workpiece W may also be reversed. In that case, the workpiece W may be fixed to the rotary table 31, and the processing pad 30 may be fixed to the processing head 29.

[0062] Generally, there is an inverse correlation between processing (polishing) accuracy and processing (polishing) speed, and the two are in a trade-off relationship. Plasma-assisted polishing (PAP) equipment is a finishing (polishing) method that can achieve high-precision smoothing without introducing scratches or mechanically altered layers. Compared to conventional polishing equipment, PAP equipment has superior surface roughness and a fast processing (polishing) speed, but if all processes are performed using the PAP equipment alone, it takes a long time to achieve the desired final smoothness. However, by performing rough processing using a laser processing equipment with a high processing speed as a pre-processing step to achieve a shape close to the final finished shape (final finished surface), the subsequent finishing time can be significantly reduced, thereby shortening the overall processing time. [Explanation of symbols]

[0063] Double work, L laser light, A polishing mechanism section, B plasma generating unit, 1. Underlying substrate, 2 functional material layer, 3 Machining surface, 4. Predicted surface shape during deformation 5. Predicted finished plane shape after deformation, 6 Surface shape before processing, 7. Final finish predicted surface shape, 8 Differential Profile, 9 Differential Profile, 10 Locally machined surface, 11 Plane machined surface, 12 Final finish surface, 13 Laser processing equipment, 14 laser oscillator, 15 beam expander, 16 galvanometer scanner, 17 control device, 18 Shape measurement device, 19 X stage, 20 computers, 21 Automatic local processing equipment, 22 base plate, 23 rails, 24 tables, 25 drive motor, 26 Lead screw mechanism, 27 Plasma-assisted polishing equipment, 28 vacuum chambers, 29 machining head, 30 processing pads, 31 Rotating table, 32 counter electrode, 33 Gas supply system, 34 Gas exhaust system, 35 High frequency power supply, 36 rotation axis, 37 rotation axis, 38 aperture, 39 Polishing pressure applying means.

Claims

1. A method for smoothing a workpiece to reduce the surface roughness of the workpiece over the entire surface, comprising: a first machining step of locally machining a workpiece surface based on machining data; a finishing second machining step which is carried out after the first machining step and has a machining mechanism which preferentially removes a contact portion between a machining pad having a flat machining reference surface and a workpiece, predicting stress deformation of the workpiece during processing in the second processing step, and creating processing data for the first processing step from a difference between a predicted surface shape during deformation and a predicted finished planar shape during deformation, or a difference between a pre-processing surface shape and a predicted final finished surface shape; A method for smoothing workpieces.

2. 2. A method for smoothing a workpiece according to claim 1, wherein the workpiece has a bimetal structure in which a plurality of materials with different linear expansion coefficients are laminated together, and the thermal stress deformation of the workpiece is predicted from the materials constituting the workpiece, their linear expansion coefficients, and the temperature change during processing in the second processing step, and processing data for the first processing step is created from the difference between the predicted surface shape at the time of deformation and the predicted finished planar shape at the time of deformation, or the difference between the surface shape before processing at room temperature and the predicted finished surface shape.

3. 3. The method for smoothing a workpiece according to claim 2, wherein the workpiece is a diamond substrate having a diamond layer laminated on a base substrate.

4. 4. A method for smoothing a workpiece according to claim 1, wherein the second processing step is a step of processing a contact portion between the workpiece surface and the processing reference surface of a processing pad into a flat surface using a plasma-assisted polishing device.

5. 4. A method for smoothing a workpiece according to claim 1, 2 or 3, wherein the first processing step is a step of locally processing the workpiece surface based on processing data using a laser processing device that uses laser ablation as its processing principle.

6. The plasma-assisted polishing device is provided with a polishing mechanism unit that brings a processing pad having an abrasive material on at least the surface thereof into contact with the workpiece at a predetermined polishing pressure while relatively displacing the pad and the workpiece at a predetermined relative speed, selectively removing and smoothing the convex portions of the processing surface, and a plasma generating unit that acts on at least one of the processing pad and the processing surface of the workpiece with neutral radicals generated in the plasma to promote the polishing action of the workpiece.

7. a local processing device that performs a first processing step; a finish surface processing device that performs the second processing step, A workpiece smoothing device that reduces the surface roughness of a workpiece over the entire surface, the first machining step is a step of locally machining a workpiece surface based on machining data, the second machining step is a step performed after the first machining step, and has a machining mechanism that preferentially removes a contact portion between a machining pad having a flat machining reference surface and a workpiece; The machining data for the first machining step is created by predicting stress deformation of the workpiece during machining in the second machining step, and based on a difference between a predicted surface shape upon deformation and a predicted finished planar shape upon deformation, or a difference between a pre-machining surface shape and a predicted final finished surface shape. Workpiece smoothing processing equipment.

8. 8. A workpiece smoothing processing device as described in claim 7, wherein the workpiece has a bimetal structure in which a plurality of materials with different linear expansion coefficients are laminated together, and the processing data for the first processing step is generated by predicting thermal stress deformation of the workpiece from the materials constituting the workpiece and their linear expansion coefficients and the temperature change during processing in the second processing step, and from the difference between the predicted surface shape upon deformation and the predicted finished planar shape upon deformation, or the difference between the surface shape before processing at room temperature and the predicted finished surface shape.

9. 9. The workpiece smoothing apparatus according to claim 8, wherein the workpiece is a diamond substrate having a diamond layer laminated on a base substrate.

10. 10. The workpiece smoothing apparatus according to claim 7, 8 or 9, wherein the finish flattening device is a plasma-assisted polishing device that flattens the contact portion between the workpiece surface and the processing reference surface of the processing pad.

11. 10. The workpiece smoothing processing device according to claim 7, 8 or 9, wherein the local processing device is a laser processing device that uses laser ablation as a processing principle and locally processes the workpiece surface based on processing data.

12. The plasma-assisted polishing device for a workpiece according to claim 10, further comprising: a polishing mechanism unit that brings a processing pad having an abrasive material on at least the surface thereof into contact with the workpiece at a predetermined polishing pressure while relatively displacing the pad and the workpiece at a predetermined relative speed, thereby selectively removing and smoothing the convex portions of the processing surface; and a plasma generating unit that acts on at least one of the processing pad and the processing surface of the workpiece with neutral radicals generated in the plasma to promote the polishing action of the workpiece.

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