Local processing method and local processing apparatus

Abstract

To provide a local working method and a local working device suitable for smoothing work for removing surface roughness of a work having an optional shape surface up to a work having a curved surface of a small radius of curvature from a planar work, and particularly suitable for correcting and finishing a reflecting surface of an X-ray mirror of highly accurately creating a shape, without impairing shape accuracy.SOLUTION: A porous elastic body sheet having a thickness of 300 μm to 1 mm and a Shore A hardness of 50 to 90 is joined to an elastic base material directly or via another elastic body, at least a part of the porous elastic body sheet is protruded to form an action part, the action part is in a self-holding state by a dome structure of the sheet itself or in an elastically supported state where a rear surface is held by another elastic body, and a catalytic pad having a film of a catalyst formed on a surface of the porous elastic body sheet is used.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a local processing method and a local processing device that use a catalyst surface-based etching method as the processing principle. [Background technology]

[0002] The Catalyst-Referred Etching (CARE) method uses pure water as a processing fluid and, by utilizing catalytic action, induces a hydrolysis reaction on the material surface, making it the ultimate surface polishing method that can atomically smooth a variety of material surfaces without introducing mechanical damage (Patent Documents 1 to 3). Because the CARE method does not use any abrasive particles or chemicals in the processing fluid and is based on pure chemical etching, it solves the problem of processing fluid disposal and is highly promising as a sustainable technology.

[0003] The CARE method has been researched and developed as a finishing technique for smoothing flat surfaces, such as semiconductor and glass substrates, at the atomic level. The CARE method uses a catalyst pad, where a catalyst film is deposited on the surface of a soft, elastic substrate, such as rubber, by sputtering or vapor deposition. The catalyst pad and the workpiece surface are brought into contact with each other at a predetermined processing pressure, causing relative displacement, which removes decomposition products resulting from hydrolysis reactions and advances the processing. Transition metals are used as catalysts, with platinum (Pt) being particularly preferred due to its excellent catalytic function and chemical stability.

[0004] Although the CARE method can achieve flattening with atomic-level precision, its processing speed is slow, making it unsuitable for creating shapes. Previous research and development into the CARE method has focused on how to improve its processing speed, which is a drawback, and therefore it has not been fully utilized as a finishing method with atomic-level precision.

[0005] Conventionally, catalyst pads have been used in which a catalyst film is formed on the surface of a porous substrate. Patent Document 4 discloses the use of catalyst pads in which a catalyst film is formed on the surface of an elastic membrane that forms a pressure chamber, catalyst pads in which a catalyst layer is provided on the outer surface of a porous sponge, and catalyst pads in which a catalyst film is formed on the surface of a polyurethane foam or a nonwoven fabric pad impregnated with polyurethane or the like. Patent Documents 5 and 6 disclose the use of catalyst pads in which a catalyst is formed to conform to the porous surface shape of a porous polyurethane foam, and the polyurethane foam has a Shore A hardness of 20 or less, preferably 10 or less, and an opening ratio in the range of 20% to 80% in terms of area ratio. Incidentally, since porous polyurethane foam is also used in traditional CMP pads, using polyurethane foam as a pad substrate is a natural idea. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5754754 [Patent Document 2] Patent No. 6188152 [Patent Document 3] Patent No. 6206847 [Patent Document 4] Patent No. 6454326 [Patent Document 5] Patent No. 6328502 [Patent Document 6] Patent No. 6577071 Summary of the Invention [Problem to be solved by the invention]

[0007] However, conventional techniques have used catalyst pads suited to planarizing flat workpieces such as semiconductor wafers and glass substrates. Therefore, the pad substrates used in polishing pads are made of foamed polyurethane, which have a flat surface and a soft hardness. When using conventional flat catalyst pads on workpieces with curved surfaces with large radii of curvature, the contact pressure between the center and periphery of the catalyst pad varies, resulting in different processing rates, making it impossible to accurately process the curved surface. Of course, conventional flat catalyst pads cannot be used at all on workpieces with curved surfaces with small radii of curvature. Furthermore, conventional catalyst pads have a catalyst film formed on the surface of the pad substrate, but the soft pad substrate means that the catalyst thin film easily peels off from the pad substrate, resulting in durability issues.

[0008] In view of the above-mentioned situation, the present invention aims to solve the problem by providing a local processing method and local processing device that are suitable for smoothing the surface of workpieces having any shape, from flat workpieces to workpieces having curved surfaces with a small radius of curvature, and that are particularly suitable for correcting and finishing the reflecting surface of an X-ray mirror whose shape has been created with high precision, without impairing the shape precision. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the present invention provides a local processing method and a local processing device configured as follows.

[0010] [Configuration 1] In the presence of a processing fluid that contains water and does not contain solids, A catalyst pad having a catalyst on its surface and a workpiece having a flat or arbitrarily curved surface are moved relative to each other while being brought into contact with each other under a predetermined processing pressure; A processing method for smoothing a surface of a workpiece by using a principle of catalytic surface-based etching, which removes constituent elements from the surface of the workpiece by inducing a hydrolysis reaction using a catalyst, comprising: A porous elastic sheet having a thickness of 300 μm to 1 mm and a Shore A hardness of 50 to 90 is bonded to an elastic substrate directly or via another elastic material; At least a part of the porous elastic sheet protrudes to form an action part, In the action portion, the seat is in a self-supporting state due to the dome structure of the seat itself, or in an elastically supported state where the back surface is supported by another elastic body, a catalyst pad having a catalyst film formed on the surface of the porous elastic sheet is used; Local processing method.

[0011] [Configuration 2] The porous elastic sheet is a porous polyurethane resin sheet or a porous epoxyurethane resin sheet. The local processing method according to Configuration 1.

[0012] [Configuration 3] The catalyst is one or more alloys or mixtures of two or more transition metal elements. 3. The local processing method of configuration 1 or 2.

[0013] [Configuration 4] the catalyst is Ru; The local processing method according to configuration 3.

[0014] [Configuration 5] The area of ​​the catalyst pad is smaller than the processing range of the workpiece. 3. The local processing method according to claim 1 or 2.

[0015] [Configuration 6] In the presence of a processing fluid that contains water and does not contain solids, A catalyst pad having a catalyst on its surface and a workpiece having a flat or arbitrarily curved surface are moved relative to each other while being brought into contact with each other under a predetermined processing pressure; A processing apparatus for smoothing a surface of a workpiece by using a principle of catalytic surface-based etching, which removes constituent elements from the surface of the workpiece by inducing a hydrolysis reaction using catalytic action, comprising: a non-rotating holder that holds the workpiece; a processing head having a catalyst pad having an area smaller than the processing range of the workpiece attached directly or indirectly to a holding surface facing the surface of the workpiece; The catalyst pad is A porous elastic sheet having a thickness of 300 μm to 1 mm and a Shore A hardness of 50 to 90 is bonded to one surface of the elastic substrate directly or via another elastic support, At least a part of the porous elastic sheet protrudes from other parts to form an action part, In the action portion, the seat is in a self-supporting state due to the dome structure of the seat itself, or in an elastically supported state where the back surface is supported by another elastic body, a catalyst film formed on the surface of the porous elastic sheet; a fluid supply means for supplying the machining fluid between the surface of the workpiece and the catalyst pad; a pressing mechanism that brings the catalyst pad into contact with the surface of the workpiece at a predetermined processing pressure; a rotation mechanism that rotates the processing head; a movement mechanism that moves the machining head and the workpiece relatively; Equipped with Local processing equipment.

[0016] [Configuration 7] The catalyst pad has a plurality of working portions that bulge outward from the surface of the porous elastic sheet except for the central portion, the porous elastic sheet is directly bonded to an elastic substrate, and the sheet itself is self-supporting at the working portions due to the dome structure of the sheet itself, and a catalyst film is formed on the surface of the porous elastic sheet. 7. The local processing device according to configuration 6.

[0017] [Configuration 8] The catalyst pad has a structure in which a plurality of elastic supports are provided on the surface of an elastic substrate, excluding the central portion, and the surfaces of the elastic supports and the elastic substrate are covered with the porous elastic sheet, and an acting portion in an elastically supported state is formed at a position corresponding to the elastic supports, protruding toward the surface and having its back surface held by the elastic supports, and a catalyst is formed on the surface of the porous elastic sheet. 7. The local processing device according to configuration 6.

[0018] [Configuration 9] The catalyst pad has a structure in which an elastic substrate having a spherical surface is covered with the porous elastic sheet, the entire porous elastic sheet is made into a single working part protruding toward the surface side, and a catalyst is formed on the surface of the porous elastic sheet. 7. The local processing device according to configuration 6.

[0019] [Configuration 10] The porous elastic sheet is a porous polyurethane resin sheet or a porous epoxyurethane resin sheet. 10. The local processing device according to any one of configurations 6 to 9.

[0020] [Configuration 11] The catalyst is one or more alloys or mixtures of two or more transition metal elements. 10. The local processing device according to any one of configurations 6 to 9.

[0021] [Configuration 12] The catalyst is Ru. 12. The local processing device according to claim 11. [Effects of the Invention]

[0022] The local processing method and local processing device of the present invention described above are suitable for smoothing the surface roughness of workpieces with any shape, from flat workpieces to workpieces with curved surfaces with a small radius of curvature, and are particularly suitable for finishing the reflective surface of an X-ray mirror, which has been shaped with high precision, while maintaining its shape.By removing a few nanometers of the workpiece surface using this method, residual stress and surface damage can be eliminated.

[0023] In addition, the catalyst pad has fine openings on its surface, which prevents water drying at the contact surface between the catalyst pad and the workpiece, prevents suction or sticking, and has a high ability to remove processing residue.The porous elastomer sheet used for the catalyst pad is thin, at 300 μm to 1 mm, making it easy to form the working part, and its Shore A hardness of 50 to 90 prevents peeling of the catalyst thin film and improves durability. [Brief explanation of the drawings]

[0024] [Figure 1] 1A and 1B show a local machining device of the present invention, in which FIG. 1A is a conceptual diagram of the local machining device, and FIG. 1B is a simplified plan view showing the relationship between a workpiece and a machining head. [Figure 2] This shows how the workpiece surface is smoothed using the present invention, where (a) is a cross-sectional view of the workpiece before processing, (b) is a cross-sectional view showing the state in which the catalyst pad is in contact with the workpiece, and (c) is a cross-sectional view of the workpiece after the irregularities in the medium spatial wavelength range and the surface roughness with a short spatial wavelength have been removed. [Figure 3] 1 shows a catalyst pad for flat surface processing, where (a) is a plan view of the side facing the workpiece, (b) is a side view, and (c) is a cross-sectional view taken along the X1-X1 line in (a). [Figure 4] This shows a catalyst pad suitable for machining curved surfaces with a large radius of curvature. (a) is a plan view of the side facing the workpiece, (b) is a side view, and (c) is a cross-sectional view taken along line X2-X2 of (a). [Figure 5] This shows a catalyst pad suitable for processing curved surfaces with a small radius of curvature. (a) is a plan view of the side facing the workpiece, (b) is a side view, and (c) is a cross-sectional view taken along the X3-X3 line in (a). [Figure 6] This shows a modified catalyst pad suitable for processing curved surfaces with a small radius of curvature, where (a) is a plan view of the side facing the workpiece, (b) is a side view, and (c) is a cross-sectional view taken along line X4-X4 of (a). [Figure 7] 4 is a simplified side view showing an example of processing a flat work surface using the catalyst pad of FIG. 3. [Figure 8] 5 is a simplified side view showing an example of processing a work surface having a large radius of curvature using the catalyst pad of FIG. 4. [Figure 9] 6 is a simplified side view showing an example of processing a work surface having a curved surface with a small radius of curvature using the catalyst pad of FIG. 5. [Figure 10] 1 is a graph showing the surface roughness (RMS) at each point after processing of a 400 mm long flat mirror made of Si single crystal. [Figure 11]The white light interferometer images at two points on a 400 mm long plane mirror made of single-crystal silicon are shown. [Figure 12] The images shown are scanning white light interferometer images of one end, the center, and the other end of a curved mirror made of silicon single crystal, with a curvature radius of 5 m and a length of 220 mm, after LP processing and CARE processing. [Figure 13] Scanning white light interferometer images of one end, center, and other end of a toroidal mirror made of silicon single crystal, with a curvature radius of 30 mm and a length of 70 mm, after LP finishing, CARE1 (8 passes) processing, and CARE2 (16 passes) processing in the 4th order removal are shown. [Figure 14] Similarly, scanning white light microscope interferometer images of cylinder removal after LP finishing, CARE1 (8 passes) processing, and CARE2 (16 passes) processing at one end, center, and other end of the toroidal mirror in Figure 13 are shown. [Figure 15] 1 shows STM images of a Si(111) surface and a Si(100) surface after processing according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] The processing principle of the Catalyst-Referred Etching (CARE) method is essentially to remove decomposition products generated by hydrolysis reactions with elements that make up the workpiece surface. In this reaction pathway, the catalyst supports the dissociation and adsorption reaction of water, dissolving the hydrolysis decomposition products into the water. The CARE method is a spatially controlled chemical etching method in which a catalytic pad with catalytic function on the workpiece surface is brought into contact with the workpiece at a predetermined pressure and moved relative to it in a water-based machining fluid, thereby preferentially removing the contact area, i.e., the convex part of the workpiece. This results in a flat surface without introducing crystallographic damage.

[0026] The catalyst used in the CARE method can be a transition metal, such as Pt, which has a high work function, as well as Pd, Ru, Ni, Co, Cr, and Mo. The catalyst can be one or more alloys or mixtures of two or more selected from these transition metal elements. Pt has excellent catalytic performance and stability but is expensive. Ni and Cr are known to be inexpensive and exhibit high catalytic performance, but are susceptible to oxidation, resulting in rapid degradation of catalytic performance. Therefore, in this embodiment, Ru is used as the catalyst, taking into consideration catalytic performance and cost. Furthermore, if the catalyst is too thick, it will easily peel off due to differences in thermal expansion coefficient with the base material or deformation, and if it is too thin, it will lose its catalytic function in a short period of time due to wear, so an appropriate thickness is set. In this embodiment, the catalyst thickness is 10 to 100 nm.

[0027] The local machining method of the present invention involves relatively moving a catalyst pad and a workpiece having a flat or arbitrarily curved surface while contacting them at a predetermined machining pressure in the presence of a machining fluid that contains water but no solids, and employing the principle of catalytic surface-based etching to remove constituent elements of the workpiece by inducing a hydrolysis reaction using catalytic action. The method uses a catalyst pad in which a porous elastic sheet having a thickness of 300 μm to 1 mm and a Shore A hardness of 50 to 80 is bonded to one side of an elastic substrate, either directly or via another elastic support, and at least a portion of the porous elastic sheet protrudes from other portions to form an active portion, and the active portion is self-supported by a dome structure or elastically supported by the elastic support at its back side. A catalyst film is formed on the surface of the porous elastic sheet. During machining of the workpiece, the catalyst formed on the active portion of the catalyst pad comes into contact with the workpiece, and only the portion in contact with the catalyst is machined.

[0028] Here, the porous elastic body sheet is preferably a porous polyurethane resin sheet or a porous epoxy urethane resin sheet having an expansion ratio of less than 5 times. The Shore A hardness of the porous elastic body sheet is preferably 50 to 90, more preferably 70 to 80. Porous polyurethane resin sheets tend to have a higher Shore A hardness and a higher processing speed than porous epoxy urethane resin sheets. If the Shore A hardness of the porous elastic body sheet is too high, it is not preferable because it will scratch the surface of the workpiece. For example, epoxy resin sheets have a high Shore A hardness and therefore a high processing speed, but they are not used in the present invention because they will scratch the surface of the workpiece.

[0029] The catalyst is deposited on the surface of the porous elastic sheet by sputtering or chemical vapor deposition. The porous elastic sheet has countless small pores, and the surface has fine openings that are continuous with the pores, so the surface also has fine openings after the catalyst is deposited. The fine openings on the surface of the catalyst pad are effective in preventing adhesion due to water drying at the contact surface between the catalyst pad and the workpiece, and are also thought to have a high ability to remove processing residues.

[0030] If the area of ​​the catalyst pad is smaller than the machining area of ​​the workpiece, localized machining of the workpiece can be achieved, thereby allowing for shape modification of the workpiece, and depending on the shape of the catalyst pad, it is possible to finish machining any curved surface. Of course, if the area of ​​the catalyst pad is larger than the machining area of ​​the workpiece, it is possible to flatten a plate-shaped workpiece such as a semiconductor wafer. The localized machining method of the present invention can remove roughness from the surface of a workpiece after high-precision machining and smooth it.

[0031] Next, the present invention will be described in more detail based on the embodiments shown in the accompanying drawings. Fig. 1 shows a conceptual diagram of the local processing device of the present invention, and Fig. 2 shows how the surface of a workpiece is smoothed. In the figure, reference numeral W denotes a workpiece, 1 denotes the local processing device, 2 denotes a holder, 3 denotes a processing head, 4 denotes a catalyst pad, 5 denotes a liquid supply means, 6 denotes a pressing mechanism, 7 denotes a rotation mechanism, 8 denotes a movement mechanism, and 9 denotes a control system. Figs. 3 to 6 show various catalyst pads 4A, 4B, 4C, and 4D, respectively, and Figs. 7 to 9 show examples of processing workpieces W1, W2, and W3 using catalyst pads 4A, 4B, and 4C, respectively.

[0032] The local processing device 1 of the present invention comprises a non-rotating holding part 2 for holding the workpiece W, a processing head 3 having a holding surface 3A facing the surface of the workpiece, and a catalyst pad 4 having an area smaller than the processing range of the workpiece, attached directly or indirectly to the holding surface 3A, and the catalyst pad 4 has a porous elastic sheet 15 having a thickness of 300 μm to 1 mm and a Shore A hardness of more than 50 bonded to one surface of an elastic base material 14, either directly or via another elastic support 18, and at least a part of the porous elastic sheet 15 protrudes from other parts to form an action part 16, and in the action part 16 The porous elastic sheet 15 is self-supporting due to its dome structure, or elastically supported with its back surface held by the elastic support 18, and has a catalyst film formed on the surface of the porous elastic sheet 15. The device includes a liquid supply means 5 that supplies the machining fluid 13 between the surface of the workpiece W and the catalyst pad 4, a pressing mechanism 6 that brings the catalyst pad 4 into contact with the surface of the workpiece W at a predetermined machining pressure, a rotation mechanism 7 that rotates the machining head 3, and a movement mechanism 8 that moves the machining head 3 and the workpiece W relatively, all of which are controlled by a control system 9. Note that the control system 9 may also have a function to control the potential of the catalyst on the catalyst pad 4. In addition, the machining surface of the workpiece W may be irradiated with ultraviolet light to activate it.

[0033] Here, the axis of the rotation shaft 10 of the machining head 3 is approximately perpendicular to the machining surface 11 of the workpiece W. In this embodiment, the workpiece W is fixed with the machining surface 11 facing upward on the bottom surface of a water tank 12 which also serves as the holder 2 and the liquid supply means 5, and machining liquid 13 is stored in the water tank 12 so that the machining surface 11 of the workpiece W is immersed. Note that, although the liquid supply means 5 is structured to immerse the workpiece W in the machining liquid in this embodiment, it may also be structured to drip the machining liquid onto the machining surface 11 of the workpiece W from a nozzle.

[0034] Furthermore, the water used in the machining fluid is preferably pure water or ultrapure water. Furthermore, a pH adjuster or complexing agent may be added to the machining fluid to promote dissolution of the hydrolysis products. The complexing agent promotes dissolution of the decomposition products and also acts to form complex ions, maintaining them stably in water. The pH of the machining fluid is preferably adjusted to a range of 2 to 12. If the pH is outside this range and is strongly acidic or alkaline, the machining speed will decrease. Since the decomposition products vary depending on the material of the workpiece W, it is desirable to adjust the pH according to the decomposition products.

[0035] Furthermore, the rotation axis 10 of the processing head 3 is driven in the vertical direction (Z direction) and controlled by the pressing mechanism 6 so that the catalyst pad 4 and the workpiece W come into contact with each other at a predetermined processing pressure. Specifically, the pressing mechanism 6 may be a mechanism in which a counterweight is used to balance the movable parts, including the processing head 3, which moves in the Z direction, and a weight is added to unbalance the processing pressure. The rotation axis 10 of the processing head 3 is then rotationally driven by the rotation mechanism 7, and the catalyst pad 4 rotates while coming into contact with the processing surface 11 of the workpiece W at a predetermined processing pressure.

[0036] The rotation axis 10 of the machining head 3 is held vertically by the movement mechanism 8, and a catalyst pad 4 attached to the lower end of the machining head 3 brings the workpiece W into contact with the machining surface 11 in the machining fluid. The movement mechanism 8 precisely drives the machining head 3 in the X and Y directions, moving the machining head 3 and the workpiece W relative to each other. The mechanism of the movement mechanism 8 is arbitrary, and is configured so that a movable body 8B can move precisely with respect to a guide shaft 8A, and a pressing mechanism 6 and a rotation mechanism 7 are linked to the movable body 8B. The scanning method of the machining head 3 is raster scan, as shown in Figure 1(b).

[0037] When the diameter of the processing head 3 (catalyst pad 4) is 15 mm, the rotation speed is 300 rpm, the weight is 300 g, the raster scan pitch is 0.1 mm, and the scanning speed is 6 mm / s, the processing speed of the Si single crystal is 1 to 3 nm per raster scan.

[0038] FIG. 2 shows a schematic diagram of the process of machining the machining surface 11 of the workpiece W using the local machining method of the present invention. In FIG. 2(a), the waviness component U and surface roughness component R present on the machining surface 11 of the workpiece W are exaggerated. The catalyst pad 3 is constructed by directly bonding a porous elastic sheet 15 to one surface of an elastic substrate 14. Of course, a catalyst film is formed on the surface of the porous elastic sheet 15. As shown in FIG. 2(b), when the catalyst pad 3 is pressed against the machining surface 11 of the workpiece W with a predetermined machining pressure, the catalyst surface of the catalyst pad 3 is pressed and slightly recessed by the high portions (indicated by H) of the waviness component U, but a gap is created between the high portions (indicated by L) of the waviness component U and the low portions (indicated by L) of the waviness component U. Since machining of the workpiece W proceeds from the point of contact with the catalyst pad 3, the high portions (H) of the workpiece W are inevitably removed, and the surface roughness component R is also removed, resulting in a smooth surface. Figure 2(c) shows the state where the catalyst pad 3 has come into contact with the lower portion L of the workpiece W, removing the surface roughness component R. As the machining continues, the waviness component U of the workpiece W is also almost completely removed.

[0039] <Catalyst Pad 4A> The catalyst pad 4A shown in FIG. 3 is suitable for machining a planar workpiece W. The catalyst pad 4A has multiple action portions 16,..., which bulge outward from the porous elastic sheet 15 except for the central portion. The porous elastic sheet 15 is directly bonded to the end surface of a flat, cylindrical elastic substrate 14, and the action portions 16,..., are self-supporting due to the dome structure of the sheet itself. A catalyst film is formed on the surface of the porous elastic sheet 15. In this embodiment, the elastic substrate 14 is made of rubber with a diameter of 15 mm and a thickness of 7 mm, and the porous elastic sheet 15 is a foamed polyurethane resin sheet with a thickness of 500 μm and a Shore A hardness of 80. A 5 mm diameter hole 17 is drilled in the center of the porous elastic sheet 15, and action portions 16,..., with a diameter of several mm, are formed in the remaining portions by embossing or other means, and then cut out to a diameter of 15 mm. The protruding height of the action portions 16 is greater than the thickness of the porous elastic sheet 15, but it may be less. The reason for providing holes 17 in the porous elastic sheet 15 is to avoid a decrease in the processing rate at the center of rotation. The type of rubber for the elastic substrate 14 is arbitrary, but examples include fluorine-based rubber, natural rubber, nitrile rubber, butadiene rubber, chloroprene rubber, acrylic rubber, isoprene rubber, styrene rubber, polyethylene rubber, silicone rubber, and urethane rubber.

[0040] Then, a Ru film is formed as a catalyst by sputtering on the surface of the porous elastic sheet 15 having a diameter of 15 mm on which the working portion 16 is formed. Prior to forming the Ru film, the surface of the porous elastic sheet 15 may be plasma-treated to enhance adhesion. These operations are preferably performed sequentially in a vacuum chamber without breaking the vacuum.

[0041] In the catalyst pad 4A of this embodiment, the area of ​​the porous elastic sheet 15 in a plan view is 157 mm 2 The area occupied by the total action portions 16 is approximately 50%, but it may be 30 to 70%. Here, the presence of recesses between adjacent action portions 16, 16 further enhances the ability to remove processing residues.

[0042] <Catalyst Pad 4B> The catalyst pad 4B shown in Figure 4 is suitable for machining a workpiece W having a curved surface with a large radius of curvature, for example, a radius of curvature greater than 1 m, for example, a radius of curvature greater than 5 m. The catalyst pad 4B has a structure in which a plurality of elastic supports 18, ... are protruding from the surface of the ends of a flattened cylindrical elastic substrate 14, except for the center, and the surfaces of the elastic supports 18 and elastic substrate 14 are covered with the porous elastic sheet 15. At positions corresponding to the elastic supports 18, there are formed elastically supported action portions 16 that protrude toward the surface and whose back surfaces are supported by the elastic supports 18, and a catalyst is formed on the surface of the porous elastic sheet 15. The diameter of the action portions 16 is smaller than the radius of the elastic substrate 14, and in this embodiment, three action portions 16 are provided, avoiding the center of the elastic substrate 14.

[0043] In this embodiment, the elastic substrate 14 is made of rubber with a diameter of 15 mm and a thickness of 7 mm, and the porous elastic sheet 15 is a foamed polyurethane resin sheet with a thickness of 500 μm and a Shore A hardness of 80. The elastic support 18 is a flattened cylinder with a diameter of 5 mm and a height of 1 to 3 mm, and is made of rubber with a Shore A hardness of 60. The type of rubber for the elastic substrate 14 and the elastic support 18 is arbitrary, but the above-mentioned rubber materials can be used.

[0044] <Catalyst Pad 4C> The catalyst pad 4C shown in Fig. 5 is suitable for machining a workpiece W having a curved surface with a small radius of curvature, for example, a radius of curvature of the order of m to 20 mm, for example, a curved surface of 5 m to 20 mm. The catalyst pad 4C has a structure in which an elastic substrate 14 having a spherical surface is covered with the porous elastic sheet 15, the entire porous elastic sheet 15 forms a single working portion 16 protruding toward the surface, and a catalyst is formed on the surface of the porous elastic sheet 15. The elastic substrate 14 has a shape obtained by cutting at a position radially outward from the diameter of a sphere, and the flat portion of the elastic substrate 14 is bonded to the end face of a cylindrical support member 19 made of metal or hard synthetic resin, thereby forming the catalyst pad 4C.

[0045] In this embodiment, the elastic substrate 14 is made of rubber having a diameter of 15 mm, a maximum thickness of approximately 5 mm, and a Shore A hardness of 60, and the porous elastic sheet 15 is a foamed polyurethane resin sheet having a thickness of 500 μm and a Shore A hardness of 80. The support member 19 is made of metal in the shape of a flat cylinder having a diameter of 15 mm. The type of rubber for the elastic substrate 14 is arbitrary, but the rubber materials described above can be used.

[0046] <4D catalytic pad> The catalyst pad 4D shown in Figure 6 is a modified example of the catalyst pad 4C, and has a structure in which a large number of small protrusions 20 are provided on the surface side of the porous elastic sheet 15, and these small protrusions 20 serve as the action portion 16. The small protrusions 20 of the porous elastic sheet 15 can be formed by embossing. The other configuration is the same as that of the catalyst pad 4C, so the same components are denoted by the same reference numerals and their description will be omitted.

[0047] FIG. 7 shows the catalytic pad 4A being used to machine the flat workpiece W surface 11. FIG. 8 shows the catalytic pad 4B being used to machine the workpiece W surface 11, which has a large curvature radius. FIG. 9 shows the catalytic pad 4C being used to machine the workpiece W surface 11, which has a small curvature radius. By selecting the optimal catalytic pad 4 for the surface condition (flatness, large or small radius of curvature) of the workpiece W surface 11, it is possible to modify the shape of the workpiece W surface 11 and improve its surface roughness. The amount of machining performed locally on the workpiece W surface 11 can be controlled by controlling the scanning speed of the moving mechanism 8 to control the dwell time of the machining head 3, or by controlling the contact pressure applied by the pressing mechanism 6, or by controlling the catalytic potential of the catalytic pad 4. [Example]

[0048] A 400 mm long flat mirror made of single-crystal Si was finish-machined using the catalyst pad 4A. Figure 10 is a graph showing the surface roughness (RMS) at various points along the length of the mirror after machining. Figure 11 shows images (SWLI images) taken with a scanning white light interferometer (SWLI; Zygo NewView 200) at two representative points (50 mm and 350 mm from the left end) on the 400 mm long flat mirror made of single-crystal Si. The results show that the surface roughness is in the range of 0.045 to 0.065 nm RMS along the length of the mirror. [Example]

[0049] A curved mirror made of single-crystal silicon, measuring 5 m in radius of curvature and 220 mm in length, was finish-machined using the catalyst pad 4B. Figure 12 shows SWLI images of the mirror after local polishing (LP) and CARE at one end (10 mm from the reference end), the center (110 mm from the reference end), and the other end (210 mm from the reference end), respectively. After LP, the surface roughness was 0.218 nm RMS, 0.170 nm RMS, and 0.159 nm RMS at the one end, center, and other end, respectively. After CARE, the surface roughness improved to 0.089 nm RMS, 0.065 nm RMS, and 0.048 nm RMS, respectively. [Example]

[0050] A toroidal mirror made of single-crystal silicon with a curvature radius of 30 mm and a length of 70 mm was processed using the catalyst pad 4C. Figure 13 shows SWLI images of the 4th-order removal at the longitudinal direction of the toroidal mirror (10 mm from the reference end), the center (35 mm from the reference end), and the other end (60 mm from the reference end), from left to right. The upper row shows SWLI images after local polishing (LP) finishing, the middle row after CARE1 (8 passes), and the bottom row after CARE2 (16 passes). As a result, it can be seen that the surface roughness at one end improved to 0.143nmRMS, 0.103nmRMS, and 0.098nmRMS for LP, CARE1, and CARE2, respectively, the surface roughness at the center improved to 0.131nmRMS, 0.122nmRMS, and 0.081nmRMS, and the surface roughness at the other end improved to 0.164nmRMS, 0.154nmRMS, and 0.090nmRMS.

[0051] Figure 14 shows SWLI images of cylinder removal at one end, center, and other end of the toroidal mirror in the longitudinal direction, from left to right. The top row shows SWLI images after LP finishing, the middle row after CARE1 (8 passes), and the bottom row after CARE2 (16 passes). As a result, it can be seen that the surface roughness of the one end improved to 0.174nmRMS, 0.136nmRMS, and 0.135nmRMS, respectively, for LP, CARE1, and CARE2, the surface roughness of the center improved to 0.177nmRMS, 0.150nmRMS, and 0.103nmRMS, and the surface roughness of the other end improved to 0.259nmRMS, 0.283nmRMS, and 0.134nmRMS, respectively. [Example]

[0052] Figure 15 shows STM images (5 μm × 5 μm) of Si(111) and Si(100) surfaces processed using the catalyst pad 4A. Step-terrace structures appeared on both surfaces. This confirmed that the processing mechanism was a step-flow mechanism without catalytic oxidation. [Explanation of symbols]

[0053] W, W1, W2, W3 work, 1 local processing device, 2 holding part, 3 processing heads, 4,4A,4B,4C,4D Catalyst pads, 5 liquid supply means; 6 pressing mechanism, 7 Rotation mechanism, 8 moving mechanism; 9 control system, 10 rotation axis, 11 Machining surface, 12 aquariums, 13 Processing fluid, 14 Elastic substrate, 15 porous elastic sheet, 16 Working part, 17 holes, 18 elastic support, 19 support member, 20 Small projections.

Claims

1. In the presence of a processing fluid that contains water and does not contain solids, A catalyst pad having a catalyst on its surface and a workpiece having a flat or arbitrarily curved surface are moved relative to each other while being brought into contact with each other under a predetermined processing pressure; A processing method for smoothing a surface of a workpiece by using a principle of catalytic surface-based etching, which removes constituent elements from the surface of the workpiece by inducing a hydrolysis reaction using a catalyst, comprising: A porous elastic sheet having a thickness of 300 μm to 1 mm and a Shore A hardness of 50 to 90 is bonded to an elastic substrate directly or via another elastic material; At least a part of the porous elastic sheet protrudes to form an action part, In the action portion, the seat is in a self-supporting state due to the dome structure of the seat itself, or in an elastically supported state where the back surface is supported by another elastic body, a catalyst pad having a catalyst film formed on the surface of the porous elastic sheet is used; Local processing method.

2. The porous elastic sheet is a porous polyurethane resin sheet or a porous epoxyurethane resin sheet. The local processing method according to claim 1.

3. The catalyst is one or more alloys or mixtures of two or more transition metal elements. The local processing method according to claim 1 or 2.

4. The catalyst is Ru. The local processing method according to claim 3.

5. The area of ​​the catalyst pad is smaller than the processing range of the workpiece. The local processing method according to claim 1 or 2.

6. In the presence of a processing fluid that contains water and does not contain solids, A catalyst pad having a catalyst on its surface and a workpiece having a flat or arbitrarily curved surface are moved relative to each other while being brought into contact with each other under a predetermined processing pressure; A processing apparatus for smoothing a surface of a workpiece by using a principle of catalytic surface-based etching, which removes constituent elements from the surface of the workpiece by inducing a hydrolysis reaction using catalytic action, comprising: a non-rotating holder that holds the workpiece; a processing head having a catalyst pad having an area smaller than the processing range of the workpiece attached directly or indirectly to a holding surface facing the surface of the workpiece; The catalyst pad is A porous elastic sheet having a thickness of 300 μm to 1 mm and a Shore A hardness of 50 to 90 is bonded to one surface of the elastic substrate directly or via another elastic support; At least a part of the porous elastic sheet protrudes from other parts to form an action part, In the action portion, the seat is in a self-supporting state due to the dome structure of the seat itself, or in an elastically supported state where the back surface is supported by another elastic body, a catalyst film formed on the surface of the porous elastic sheet; a fluid supply means for supplying the machining fluid between the surface of the workpiece and the catalyst pad; a pressing mechanism that brings the catalyst pad into contact with the surface of the workpiece at a predetermined processing pressure; a rotation mechanism that rotates the processing head; a movement mechanism that moves the machining head and the workpiece relatively; Equipped with Local processing equipment.

7. The catalyst pad has a plurality of working portions that bulge outward from the surface of the porous elastic sheet except for the central portion, the porous elastic sheet is directly bonded to an elastic substrate, and the sheet itself is self-supporting at the working portions due to the dome structure of the sheet itself, and a catalyst film is formed on the surface of the porous elastic sheet. The local processing device according to claim 6.

8. The catalyst pad has a structure in which a plurality of elastic supports are provided on the surface of an elastic substrate, excluding the central portion, and the surfaces of the elastic supports and the elastic substrate are covered with the porous elastic sheet, and an acting portion in an elastically supported state is formed at a position corresponding to the elastic supports, protruding toward the surface and having its back surface held by the elastic supports, and a catalyst is formed on the surface of the porous elastic sheet. The local processing device according to claim 6.

9. The catalyst pad has a structure in which an elastic substrate having a spherical surface is covered with the porous elastic sheet, the entire porous elastic sheet is made into a single working part protruding toward the surface side, and a catalyst is formed on the surface of the porous elastic sheet. The local processing device according to claim 6.

10. The porous elastic sheet is a porous polyurethane resin sheet or a porous epoxyurethane resin sheet. The local processing device according to any one of claims 6 to 9.

11. The catalyst is one or more alloys or mixtures of two or more transition metal elements. The local processing device according to any one of claims 6 to 9.

12. The catalyst is Ru. The local processing device according to claim 11.

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