Rotary processing tool and method for manufacturing reflective mask blank

Abstract

To provide a technology for improving processing accuracy.SOLUTION: A rotation processing tool includes a sticking part to which a polishing pad is stuck, a holding part for holding the sticking part and a rotation shaft for rotating the holding part. The sticking part has a sticking surface to which the polishing pad is stuck, and the whole body of the sticking surface has a shape obtained by notching a portion of a spherical surface. When the center of curvature of the sticking surface at the intersection of a rotation center line of the rotation shaft and the sticking surface is arranged on a normal line passing through a reference point of a flat surface and the rotation shaft is rotated by 360° with the rotation center line included to the normal line by 15°, the following D is 0 mm to 0.15 mm, and also, the following ΔRave is 0 mm to 0.15 mm. The D is swing width of a contact point of the sticking surface and the flat surface. The ΔRave is an average value of differences ΔR(ΔR=|R-R0|) between a distance R of the contact point and the center of curvature, and a distance R0 of the intersection and the center of curvature.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present disclosure relates to a rotary processing tool, a substrate processing method, and a reflective mask blank manufacturing method. [Background technology]

[0002] In recent years, with the miniaturization of semiconductor devices, EUV lithography (EUVL), an exposure technology using extreme ultraviolet (EUV) light, has been developed. EUV includes soft X-rays and vacuum ultraviolet light, and specifically refers to light with a wavelength of about 0.2 nm to 100 nm. At present, EUV with a wavelength of about 13.5 nm is mainly being considered.

[0003] In EUVL, a reflective mask is used. The reflective mask includes a substrate such as a glass substrate, a multilayer reflective film formed on the substrate, and an absorbing film formed on the multilayer reflective film. An aperture pattern is formed in the absorbing film. In EUVL, the aperture pattern of the absorbing film is transferred to a semiconductor substrate.

[0004] In manufacturing a reflective mask, it is important to flatten the surface of the substrate in order to improve the transfer accuracy of the aperture pattern. The surface of the substrate is polished and flattened by a rotary processing tool or the like.

[0005] Patent Document 1 discloses a method for processing a quartz glass substrate. In this processing method, the polishing part of a rotary processing tool is brought to a position 1 mm from the surface of the quartz glass substrate. 2 ~500mm 2 The polishing part is brought into contact with the substrate with a contact area of ​​0.01 mm and moved while rotating to polish the substrate surface. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2010-194705 A Summary of the Invention [Problem to be solved by the invention]

[0007] Conventionally, processing of a substrate using a rotary processing tool has been considered. The rotary processing tool has an attachment part to which a polishing pad is attached. The polishing pad is a consumable item and is attached to the attachment part in a replaceable manner.

[0008] The attachment portion may have an attachment surface to which the polishing pad is attached that is formed by cutting out a part of a sphere. Therefore, the polishing pad may have an abrasive surface that polishes an object that is formed by cutting out a part of a sphere.

[0009] If the sphericity of the attachment surface of the attachment part or the polishing surface of the polishing pad is poor, the polishing rate will vary during rotation of the rotating shaft, resulting in a decrease in processing accuracy.

[0010] One aspect of the present disclosure provides a technique for improving the machining accuracy of a rotary machining tool. [Means for solving the problem]

[0011] A rotary processing tool according to a first aspect of the present disclosure includes an attachment portion to which a polishing pad is attached, a holding portion that holds the attachment portion, and a rotation shaft that rotates the holding portion. Used for local processing of reflective mask blank substrates The attachment portion has an attachment surface to which the polishing pad is attached, and the attachment surface has a shape in which a part of a sphere is cut out. When the center of curvature of the attachment surface at the intersection of the rotation center line of the rotation shaft and the attachment surface is placed on a normal line passing through a reference point of a flat surface, and the rotation shaft is rotated 360° with the rotation center line tilted 15° with respect to the normal line, the following D is 0 mm to 0.15 mm, and the following ΔR ave is 0 mm to 0.15 mm. D is the amplitude of the contact point between the application surface and the flat surface. ΔR ave is the average value of the difference ΔR (ΔR=|R−R0|) between the distance R between the contact point and the center of curvature and the distance R0 between the intersection point and the center of curvature.

[0012] A rotary processing tool according to a second aspect of the present disclosure includes a polishing pad, an attachment part to which the polishing pad is attached, a holding part that holds the attachment part, and a rotation shaft that rotates the holding part. Used for local processing of reflective mask blank substrates The attachment portion has an attachment surface to which the polishing pad is attached, and the attachment surface has a shape in which a part of a sphere is cut out as a whole. The polishing pad has a polishing surface for polishing an object, and the polishing surface has a shape in which a part of a sphere is cut out as a whole. When the center of curvature of the polishing surface at the intersection of the rotation center line of the rotation shaft and the polishing surface is placed on a normal line passing through a reference point of a flat surface, and the rotation shaft is rotated 360° with the rotation center line tilted 15° with respect to the normal line, the following d is 0 mm to 0.15 mm, and the following Δr ave is 0 mm to 0.15 mm. d is the amplitude of the contact point between the polishing surface and the flat surface. Δr ave is the average value of the difference Δr (Δr=|r−r0|) between the distance r between the contact point and the center of curvature and the distance r0 between the intersection point and the center of curvature. Effect of the Invention

[0013] According to the first aspect of the present disclosure, by controlling the sphericity of the attachment surface with a predetermined parameter, it is possible to suppress fluctuations in the polishing rate during rotation of the rotating shaft, thereby improving the processing accuracy.

[0014] According to the second aspect of the present disclosure, by controlling the sphericity of the polishing surface with a predetermined parameter, it is possible to suppress fluctuations in the polishing rate during rotation of the rotating shaft, thereby improving the processing accuracy. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a flowchart showing a method for manufacturing a reflective mask blank according to one embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of a substrate. [Diagram 3] FIG. 3 is a plan view of the substrate of FIG. [Figure 4] FIG. 4 is a cross-sectional view showing an example of a reflective mask blank. [Diagram 5] FIG. 5 is a cross-sectional view showing an example of a reflective mask. [Figure 6] FIG. 6 is a cross-sectional view showing a rotary processing tool according to one embodiment. [Figure 7] FIG. 7 is an enlarged cross-sectional view showing a part of FIG. [Figure 8] FIG. 8 is a diagram showing an example of a method for measuring the sphericity of the application surface. [Figure 9] FIG. 9 is a diagram showing an example of the trajectory of the contact point in FIG. [Figure 10] FIG. 10 is a diagram showing an example of the vibration width D of the contact point in FIG. [Figure 11] FIG. 11 is a diagram showing an example of a method for measuring the sphericity of a polished surface. [Figure 12] FIG. 12 is a diagram showing an example of the trajectory of the contact point in FIG. [Figure 13] FIG. 13 is a diagram showing an example of the vibration width d of the contact point in FIG. [Figure 14] FIG. 14 is a cross-sectional view showing the rotary processing tool used in Example 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding components are denoted by the same reference numerals, and the description may be omitted. In the specification, the symbol "~" indicating a range of values ​​means that the values ​​before and after the symbol are included as the lower and upper limits.

[0017] As shown in Fig. 1, the method for producing a reflective mask blank has steps S1 to S7. For example, a substrate 2 shown in Figs. 2 and 3 is used for producing the reflective mask blank. The substrate 2 includes a first main surface 21 and a second main surface 22 facing opposite to the first main surface 21. The first main surface 21 is rectangular. In this specification, a rectangular shape includes a shape with chamfered corners. Moreover, a rectangle includes a square. The second main surface 22 faces opposite to the first main surface 21. The second main surface 22 is also rectangular like the first main surface 21.

[0018] The substrate 2 also includes four end faces 23, four first chamfered faces 24, and four second chamfered faces 25. The end faces 23 are perpendicular to the first main surface 21 and the second main surface 22. The first chamfered faces 24 are formed at the boundaries between the first main surface 21 and the end faces 23. The second chamfered faces 25 are formed at the boundaries between the second main surface 22 and the end faces 23. In this embodiment, the first chamfered faces 24 and the second chamfered faces 25 are so-called C-chamfered faces, but may be R-chamfered faces.

[0019] The substrate 2 is, for example, a glass substrate. The glass of the substrate 2 is preferably quartz glass containing TiO2. Quartz glass has a smaller linear expansion coefficient and a smaller dimensional change due to temperature change than general soda-lime glass. The quartz glass may contain 80% to 95% by mass of SiO2 and 4% to 17% by mass of TiO2. When the TiO2 content is 4% to 17% by mass, the linear expansion coefficient is approximately zero near room temperature, and there is almost no dimensional change near room temperature. The quartz glass may contain a third component or impurities other than SiO2 and TiO2.

[0020] The size of the substrate 2 in plan view is, for example, 152 mm in length and 152 mm in width. The length and width may be greater than or equal to 152 mm.

[0021] The substrate 2 has a central region 27 and a peripheral region 28 on the first main surface 21. The central region 27 is a square region 142 mm long and 142 mm wide excluding the peripheral region 28 which has a rectangular frame shape surrounding the central region 27, and is a region which is processed to a desired flatness in steps S1 to S4 and is a quality assurance region. The four sides of the central region 27 are parallel to the four end faces 23. The center of the central region 27 coincides with the center of the first main surface 21.

[0022] Although not shown, the second main surface 22 of the substrate 2 also has a central region and a peripheral region, similar to the first main surface 21. The central region of the second main surface 22, like the central region of the first main surface 21, is a square region 142 mm long and 142 mm wide, which is processed to the desired flatness by steps S1 to S4 in FIG. 1 and is a quality assurance region.

[0023] First, in step S1, the first main surface 21 and the second main surface 22 of the substrate 2 are polished. In this embodiment, the first main surface 21 and the second main surface 22 are polished simultaneously by a double-sided polisher (not shown), but they may be polished sequentially by a single-sided polisher (not shown). In step S1, the substrate 2 is polished while a polishing slurry is supplied between the polishing pad and the substrate 2.

[0024] The polishing pad may be, for example, a urethane-based polishing pad, a nonwoven fabric-based polishing pad, or a suede-based polishing pad. The polishing slurry contains an abrasive and a dispersion medium. The abrasive is, for example, cerium oxide particles. The dispersion medium is, for example, water or an organic solvent. The first main surface 21 and the second main surface 22 may be polished multiple times with abrasives of different materials or particle sizes.

[0025] The abrasive used in step S1 is not limited to cerium oxide particles, and may be, for example, silicon oxide particles, aluminum oxide particles, zirconium oxide particles, titanium oxide particles, diamond particles, silicon carbide particles, or the like.

[0026] Next, in step S2, the surface shapes of the first main surface 21 and the second main surface 22 of the substrate 2 are measured. To measure the surface shape, for example, a non-contact measuring device such as a laser interference type is used so as not to scratch the surface. The measuring device measures the surface shape of the central region 27 of the first main surface 21 and the central region of the second main surface 22.

[0027] Next, in step S3, the first main surface 21 and the second main surface 22 of the substrate 2 are locally processed to improve the flatness with reference to the measurement result of step S2. The first main surface 21 and the second main surface 22 are locally processed in that order. The order in which they are processed may be either first or second, and is not particularly limited.

[0028] The local processing method is a polishing method using a rotary processing tool 100 described later. Note that, as the local processing method, a GCIB (Gas Cluster Ion Beam) method, a PCVM (Plasma Chemical Vaporization Machining) method, or a polishing method using a magnetic fluid may be used in combination.

[0029] Next, in step S4, the first main surface 21 and the second main surface 22 of the substrate 2 are finish-polished. In this embodiment, the first main surface 21 and the second main surface 22 are polished simultaneously by a double-sided polisher (not shown), but they may be polished sequentially by a single-sided polisher (not shown). In step S4, the substrate 2 is polished while a polishing slurry is supplied between the polishing pad and the substrate 2. The polishing slurry contains an abrasive. The abrasive is, for example, colloidal silica particles.

[0030] Next, in step S5, a conductive film 5 shown in FIG. 4 is formed in the central region 27 of the first main surface 21 of the substrate 2. The conductive film 5 is used to attach the reflective mask to an electrostatic chuck of an exposure tool. The conductive film 5 is made of, for example, chromium nitride (CrN). The conductive film 5 is formed by, for example, sputtering.

[0031] Next, in step S6, a multilayer reflective film 3 shown in FIG. 4 is formed in a central region of the second main surface 22 of the substrate 2. The multilayer reflective film 3 reflects EUV. The multilayer reflective film 3 is formed by alternately laminating, for example, high refractive index layers and low refractive index layers. The high refractive index layers are formed, for example, of silicon (Si), and the low refractive index layers are formed, for example, of molybdenum (Mo). The multilayer reflective film 3 is formed, for example, by a sputtering method such as an ion beam sputtering method or a magnetron sputtering method.

[0032] Finally, in step S7, an absorbing film 4 shown in FIG. 4 is formed on the multilayer reflective film 3 formed in step S6. The absorbing film 4 absorbs EUV. The absorbing film 4 is formed of a single metal, an alloy, a nitride, an oxide, an oxynitride, or the like, including at least one element selected from tantalum (Ta), chromium (Cr), and palladium (Pd). The absorbing film 4 is formed, for example, by sputtering.

[0033] In this embodiment, steps S6 to S7 are performed after step S5, but may be performed before step S5.

[0034] The above steps S1 to S7 provide the reflective mask blank 1 shown in Fig. 4. The reflective mask blank 1 has a first main surface 11 and a second main surface 12 facing opposite to the first main surface 11, and has, from the first main surface 11 side to the second main surface 12 side, a conductive film 5, a substrate 2, a multilayer reflective film 3, and an absorbing film 4, in this order.

[0035] Although not shown, the reflective mask blank 1 has a central region and a peripheral region on the first main surface 11, similar to the substrate 2. The central region is a square region 142 mm long and 142 mm wide, excluding the rectangular frame-shaped peripheral region surrounding the central region, and is a quality assurance region. Similarly to the substrate 2, the reflective mask blank 1 also has a central region and a peripheral region on the second main surface 12. The central region is a square region 142 mm long and 142 mm wide, excluding the rectangular frame-shaped peripheral region surrounding the central region, and is a quality assurance region.

[0036] In addition to the conductive film 5, the substrate 2, the multilayer reflective film 3, and the absorbing film 4, the reflective mask blank 1 may include another film.

[0037] For example, the reflective mask blank 1 may further include a low-reflection film. The low-reflection film is formed on the absorbing film 4. Then, an opening pattern 41 is formed in both the low-reflection film and the absorbing film 4. The low-reflection film is used for inspecting the opening pattern 41, and has lower reflection characteristics with respect to inspection light than the absorbing film 4. The low-reflection film is formed of, for example, TaON or TaO. For example, a sputtering method is used as a method for forming the low-reflection film.

[0038] The reflective mask blank 1 may further include a protective film. The protective film is formed between the multilayer reflective film 3 and the absorbing film 4. The protective film protects the multilayer reflective film 3 so that the multilayer reflective film 3 is not etched when the absorbing film 4 is etched to form an opening pattern 41 in the absorbing film 4. The protective film is formed of, for example, Ru, Si, or TiO2. The protective film is formed by, for example, sputtering.

[0039] 5, the reflective mask is obtained by forming an opening pattern 41 in an absorbing film 4. Photolithography and etching are used to form the opening pattern 41. Therefore, the resist film used to form the opening pattern 41 may be included in the reflective mask blank 1.

[0040] Next, the rotary processing tool 100 will be described with reference to Fig. 6 and Fig. 7. The rotary processing tool 100 is used in step S3 of Fig. 1 to planarize the substrate 2. The rotary processing tool 100 rotates a polishing pad 101 and brings it into contact with the processing surface of the substrate 2 to polish the processing surface.

[0041] A slurry containing an abrasive may be supplied to the processing surface of the substrate 2. As the abrasive, ceria oxide particles, silicon oxide particles, aluminum oxide particles, zirconium oxide particles, titanium oxide particles, diamond particles, silicon carbide particles, or the like may be used. The average particle size of the abrasive is, for example, 10 nm to 10 μm. The dispersion medium of the abrasive may be water or an organic solvent.

[0042] The processing surface of the substrate 2 is the second main surface 22 in Fig. 6, but may be the first main surface 21. The substrate 2 is held so that the processing surface stands substantially vertically. A control device (not shown) moves the rotary processing tool 100 and the substrate 2 relatively to each other, and brings the polishing pad 101 into contact with the entire processing surface. The control device is a computer or the like.

[0043] The processing surface of the substrate 2 has projections and recesses. The control device controls the relative movement speed of the rotary processing tool 100 and the substrate 2 so that the amount of polishing of the projections is greater than the amount of polishing of the recesses. Specifically, the control device controls the movement speed at the projections to be slower than the movement speed at the recesses. The movement speed is set, for example, in the range of 1 mm / s to 3000 mm / s.

[0044] The control device controls the relative moving speed of the rotary processing tool 100 and the substrate 2, as well as the rotation speed of the rotary processing tool 100 and the polishing pressure with which the polishing pad 101 is pressed against the substrate 2, and the like.

[0045] The rotation speed of the rotary processing tool 100 is, for example, 100 rpm to 10,000 rpm. If the rotation speed is 100 rpm or more, the polishing rate is high. On the other hand, if the rotation speed is 10,000 rpm or less, scratches are less likely to occur. The rotation speed is preferably 500 rpm to 7,000 rpm, and more preferably 1,000 rpm to 5,000 rpm.

[0046] The polishing pressure with which polishing pad 101 is pressed against substrate 2 is, for example, 10 kPa to 5 MPa. If the polishing pressure is 10 kPa or more, the polishing rate is high. On the other hand, if the polishing pressure is 5 MPa or less, scratches are less likely to occur. The polishing pressure is preferably 100 kPa to 4 MPa.

[0047] The rotary processing tool 100 brings the polishing pad 101 into contact with the processing surface of the substrate 2 in a state in which a rotation center line 130R of the rotary processing tool 100 is inclined with respect to a normal line N1 to the processing surface of the substrate 2.

[0048] The inclination angle θ of the rotation center line 130R with respect to the normal line N1 is, for example, 5° to 85°, preferably 10° to 80°, and more preferably 15° to 60°. In this embodiment, the inclination angle θ is 15°.

[0049] 6, the rotary processing tool 100 includes, for example, an attachment part 110 to which the polishing pad 101 is attached, a holding part 120 that holds the attachment part 110, and a rotation shaft 130 that rotates the holding part 120. The polishing pad 101 is a consumable item, and is therefore replaceably attached to the attachment part 110. The rotary processing tool 100 may be distributed separately from the polishing pad 101, or may be distributed together with the polishing pad 101 as a set.

[0050] 7, the attachment portion 110 includes, for example, a spherical notch portion 112 that forms an attachment surface 111 to which the polishing pad 101 is attached, and a cylindrical portion 114 provided on a flat surface 113 of the spherical notch portion 112. The cylindrical portion 114 is provided in the center of the flat surface 113 of the spherical notch portion 112, and protrudes perpendicularly from the flat surface 113. The material of the attachment portion 110 is, for example, rubber.

[0051] The rubber material of the attachment part 110 has a hardness of, for example, A50 to A75, measured with an Asker rubber hardness tester type A. If the hardness is A50 or more, excessive deformation of the attachment part 110 can be suppressed. On the other hand, if the hardness is A75 or less, the variation in sphericity described below can be absorbed, and processing precision can be improved. The hardness is preferably A65 to A70.

[0052] 7, the holding portion 120 includes, for example, a cylindrical portion 121 that surrounds the columnar portion 114 of the attachment portion 110 and contacts the flat surface 113 of the spherical notch portion 112. The holding portion 120 may further include a flange portion 122 at one end of the cylindrical portion 121. The flange portion 122 is attached to a disk portion 131 (see FIG. 6) provided at the tip of the rotating shaft 130 by a bolt (not shown) or the like. The material of the holding portion 120 is, for example, a metal such as aluminum.

[0053] The attachment part 110 may be integrated with the holding part 120 by insert molding or the like, or may be molded separately from the holding part 120 and then press-fitted into the holding part 120 to be fixed thereto.

[0054] 7, the attachment part 110 has an attachment surface 111 to which the polishing pad 101 is attached. The attachment surface 111 has a shape in which the entire surface is a sphere with a part cut out. The polishing pad 101 has a polishing surface 102 that polishes an object. The polishing surface 102 has a shape in which the entire surface is a sphere with a part cut out.

[0055] The inventor has discovered that by controlling the sphericity of the attachment surface 111 of the attachment portion 110 or the polishing surface 102 of the polishing pad 101 using predetermined parameters, it is possible to suppress fluctuations in the polishing rate during rotation of the rotating shaft 130, thereby improving the processing accuracy.

[0056] 8 to 10, the sphericity of the attachment surface 111 of the attachment part 110 will be described. In Fig. 8, P1 is the intersection of the rotation center line 130R of the rotation shaft 130 and the attachment surface 111, CR1 is the center of curvature of the attachment surface 111 at the intersection P1, P0 is the reference point of the flat surface 150, and N2 is the normal line passing through the reference point P0 of the flat surface 150.

[0057] The center of curvature CR1 is measured at each of 10 cross sections arranged radially around the rotation centerline 130R, and the average of the measured values ​​is used. The 10 cross sections are arranged at equal pitches (18° pitch) around the rotation centerline 130R. The flat surface 150 is, for example, a polished glass plate. The PV (Peak to Valley) value of the flat surface 150 is 50 nm or less.

[0058] According to this embodiment, when the center of curvature CR1 is disposed on the normal line N2 and the rotation axis 130 is rotated 360° in a state where the rotation center line 130R is inclined by 15° with respect to the normal line N2, the following D is 0 mm to 0.15 mm and the following ΔR ave is 0mm~0.15mm. D and ΔR ave are both physical property values ​​that represent the sphericity of the attachment surface 111. ave In each case, the measurement is performed while the load pressing the attachment surface 111 against the flat surface 150 is controlled to a constant value (about 1 N).

[0059] D is the amplitude of the contact point P2 between the attachment surface 111 and the flat surface 150, as shown in FIG. 10. If the attachment surface 111 is not a perfect sphere, when the rotation shaft 130 is rotated, the contact point P2 will move to the left and right of the reference point P0 on the X-axis shown in FIG. 8. FIG. 8 shows a state in which the contact point P2 and the reference point P0 are coincident. The position of the contact point P2 is measured every time the rotation shaft 130 is rotated 18° around the rotation center line 130R, for a total of 20 measurements (see FIG. 9). The amplitude of the 20 measurement data is used as D. The smaller D is, the higher the sphericity of the attachment surface 111.

[0060] ΔR ave is the average value of the difference ΔR (ΔR=|R-R0|) between the distance R between the contact point P2 and the center of curvature CR1 and the distance R0 between the intersection point P1 and the center of curvature CR1. ΔR is measured every time the rotation shaft 130 is rotated 18° around the rotation center line 130R, and is measured at 20 contact points P2. ΔR ave The smaller the value, the higher the sphericity of the attachment surface 111.

[0061] D is 0mm to 0.15mm, and ΔR aveIf D is 0 mm to 0.15 mm, the sphericity of the attachment surface 111 is sufficiently high. Therefore, it is possible to suppress fluctuations in the polishing rate during rotation of the rotating shaft 130, and it is possible to improve the processing accuracy. D is preferably 0.10 mm or less, and more preferably 0.05 mm or less. ave is preferably 0.10 mm or less, and more preferably 0.05 mm or less.

[0062] 11 to 13, the sphericity of polishing surface 102 of polishing pad 101 will be described. In Fig. 11, P3 is the intersection of rotation center line 130R of rotation shaft 130 and polishing surface 102, CR2 is the center of curvature of polishing surface 102 at intersection P3, P0 is a reference point of flat surface 150, and N2 is a normal line passing through reference point P0 of flat surface 150.

[0063] The center of curvature CR2 is measured at each of 10 cross sections radially arranged around the rotation centerline 130R, and the average value of the measured values ​​is used. The 10 cross sections are arranged at equal intervals (18° intervals) around the rotation centerline 130R.

[0064] According to this embodiment, when the center of curvature CR2 is disposed on the normal line N2 and the rotation axis 130 is rotated 360° in a state where the rotation center line 130R is inclined by 15° with respect to the normal line N2, the following d is 0 mm to 0.15 mm and the following Δr ave is 0mm to 0.15mm. d and Δr ave are both physical properties that represent the sphericity of the polishing surface 102. ave In each case, the measurement is performed while the load pressing the polishing surface 102 against the flat surface 150 is controlled to a constant value (about 1 N).

[0065] d is the amplitude of the contact point P4 between the polishing surface 102 and the flat surface 150, as shown in FIG. 13. If the polishing surface 102 is not a perfect sphere, when the rotation shaft 130 is rotated, the contact point P4 will move to the left and right of the reference point P0 on the X-axis shown in FIG. 11. FIG. 11 shows a state in which the contact point P4 and the reference point P0 are coincident. The position of the contact point P4 is measured every time the rotation shaft 130 is rotated 18° around the rotation center line 130R, for a total of 20 measurements (see FIG. 12). The amplitude of the 20 measurement data is used as d. The smaller d is, the higher the sphericity of the polishing surface 102.

[0066] Δr ave is the average value of the difference Δr (Δr=|r-r0|) between the distance r between the contact point P4 and the center of curvature CR2 and the distance r0 between the intersection point P3 and the center of curvature CR2. Δr is measured every time the rotation shaft 130 is rotated 18° around the rotation center line 130R, and is measured at 20 contact points P4. Δr ave The smaller the value, the higher the sphericity of the polishing surface 102.

[0067] d is 0 mm to 0.15 mm, and Δr ave If d is 0 mm to 0.15 mm, the sphericity of the polishing surface 102 is sufficiently high. Therefore, it is possible to suppress fluctuations in the polishing rate during rotation of the rotating shaft 130, and it is possible to improve the processing accuracy. d is preferably 0.10 mm or less, and more preferably 0.05 mm or less. ave is preferably 0.10 mm or less, and more preferably 0.05 mm or less. EXAMPLES

[0068] Next, experimental data will be described. In Examples 1 to 7, local processing of glass plates was carried out using the rotary processing tools shown in Table 1. The local processing conditions were set to be the same except for the conditions shown in Table 1. Table 1 shows the conditions and results. Examples 1 to 5 are working examples, and Examples 6 and 7 are comparative examples.

[0069] [Table 1] In Table 1, the PV value before local processing and the shape error after local processing were measured using a flatness measuring device (product name: Ultra Flat 200Mask) manufactured by Corning Tropel. The PV value before local processing and the shape error after local processing were measured in the central region 27 shown in Fig. 3. The shape error after local processing is the maximum error between the target surface shape in local processing and the actual surface shape obtained by local processing.

[0070] As is clear from Table 1, in Examples 1 to 5, D is 0 mm to 0.15 mm and ΔR ave In Examples 1 to 5, d was 0 mm to 0.15 mm, so the sphericity of the attachment surface 111 was sufficiently high, and higher processing accuracy was obtained than in Examples 6 and 7. In Examples 1 to 5, d was 0 mm to 0.15 mm, and Δr ave Since the diameter was 0 mm to 0.15 mm, the sphericity of the polished surface 102 was sufficiently high, and higher machining accuracy was obtained compared to Examples 6 and 7.

[0071] In Example 7, as shown in Fig. 14, the attachment part 110 was curved and easily deformed when pressed against the glass plate. Therefore, D was greater than 0.15 mm and Δr ave was larger than 0.15 mm, and the processing accuracy was low.

[0072] The rotary processing tool, the substrate processing method, and the reflective mask blank manufacturing method according to the present disclosure have been described above, but the present disclosure is not limited to the above-mentioned embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These naturally fall within the technical scope of the present disclosure. [Explanation of symbols]

[0073] 100 Rotational Machining Tools 101 Polishing Pad 102 Polished surface 110 Attachment part 111 Attachment surface 120 Holding part 130 Rotational Axis 130R rotation centerline N2 normal P0 reference point P1 Intersection Point P2 contact point CR1 Center of curvature

Claims

1. A rotary processing tool used for local processing of a reflective mask blank substrate, comprising: an attachment part to which a polishing pad is attached; a holding part that holds the attachment part; and a rotation shaft that rotates the holding part, the attachment portion has an attachment surface to which the polishing pad is attached, the attachment surface having a shape in which a part of a sphere is cut out, When the center of curvature of the attachment surface at the intersection of the rotation center line of the rotation axis and the attachment surface is disposed on a normal line passing through a reference point of a flat surface, and the rotation axis is rotated 360° with the rotation center line tilted 15° with respect to the normal line, the swing width D of the contact point between the attachment surface and the flat surface is 0 mm to 0.15 mm, and the average value ΔR of the difference ΔR between the distance R between the contact point and the center of curvature and the distance R0 between the intersection point and the center of curvature (ΔR=|R−R0|) is ａｖｅ is 0 mm to 0.15 mm.

2. A rotary processing tool used for local processing of a reflective mask blank substrate, comprising: a polishing pad; an attachment part to which the polishing pad is attached; a holding part that holds the attachment part; and a rotation shaft that rotates the holding part, the attachment portion has an attachment surface to which the polishing pad is attached, the attachment surface having a shape obtained by cutting out a part of a sphere as a whole, the polishing pad has a polishing surface for polishing an object, the polishing surface being in a shape of a sphere with a part cut out; When the center of curvature of the polishing surface at the intersection of the rotation center line of the rotation shaft and the polishing surface is placed on a normal line passing through a reference point of the flat surface, and the rotation center line is inclined by 15° with respect to the normal line, the swing width d of the contact point between the polishing surface and the flat surface is 0 mm to 0.15 mm, and the average value Δr of the difference Δr (Δr = |r - r0|) between the distance r of the contact point and the center of curvature and the distance r0 of the intersection point and the center of curvature ａｖｅ is 0 mm to 0.15 mm.

3. The attachment portion includes a spherical recess portion that forms the attachment surface, and a cylindrical portion provided on a plane of the spherical recess portion, The rotary machining tool according to claim 1 , wherein the holding portion includes a cylindrical portion surrounding the columnar portion and in contact with the flat surface of the spherical notch portion.

4. The rotary processing tool according to any one of claims 1 to 3, wherein the attachment portion is made of rubber.

5. The rotary processing tool according to claim 4, wherein the rubber has a hardness of A50 to A75 as measured by an Asker rubber hardness tester type A.

6. planarizing the reflective mask blank substrate using the rotary processing tool according to any one of claims 1 to 5; forming a multilayer reflective film on the planarized main surface of the reflective mask blank substrate; forming an absorbing film on the multilayer reflective film; A method for producing a reflective mask blank, comprising the steps of:

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