Double-sided polishing apparatus, glass substrate manufacturing method, and mask blank glass substrate manufacturing method

Abstract

To provide a double-sided polishing device which can reduce recessed defects generated on a main surface of a glass substrate in polishing.SOLUTION: A double-sided polishing device includes a double-sided polishing machine which sandwiches a glass substrate between an upper platen and a lower platen, fixes the upper platen, rotates the lower platen and polishes the double sides of the glass substrate using a polishing slurry, a pumping supply part for supplying the polishing slurry to the upper platen, a slurry supply pipe which connects the pumping supply part and the upper platen and supplies the polishing slurry to the upper platen from the pumping supply part, and a filter which is provided in the middle of the slurry supply pipe and removes a foreign matter contained in the polishing slurry, wherein the upper platen has a plurality of slurry supply holes to which the slurry supply pipe is connected, and a space between at least the filter and the slurry supply hole in the slurry supply pipe is formed of a water-repellent resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a double-side polishing apparatus, a method for manufacturing a glass substrate, and a method for manufacturing a glass substrate for a mask blank. substrate This relates to a method for producing the above. [Background technology]

[0002] In the manufacture of glass plates, in order to further improve the flatness quality and surface roughness quality of the glass plate, a double-sided polishing machine is used in which the glass substrate is sandwiched between an upper platen and a lower platen, and a polishing slurry is supplied to the front and back surfaces (both main surfaces) of the glass plate to polish both main surfaces of the glass plate simultaneously.

[0003] As a double-sided polishing apparatus, for example, a double-sided polishing apparatus for workpieces has been disclosed in which polishing slurry supplied from a slurry supply source is dripped through a drip supply hose into a slurry ring, and the polishing slurry supplied into the slurry ring is supplied between the upper and lower platens by natural dripping through the supply hose from a slurry supply hole (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6197598 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the technology of Patent Document 1, the polishing slurry may adhere to the slurry ring, the drip supply hose, and the supply hose, resulting in the formation of adhered matter. If this adhered matter is supplied to the workpiece through the slurry supply hole together with newly supplied polishing slurry, there is a problem that the number of minute concave defects caused by the adhered matter on the surface of the workpiece during double-side polishing of the workpiece increases.

[0006] When the workpiece is a glass substrate used for a specific purpose, such as a glass substrate for a mask blank, the specifications required for the surface of the glass substrate are strict as ultra-LSI devices become increasingly dense and precise, and glass substrates with even fewer microscopic concave defects are therefore required.

[0007] An object of one aspect of the present invention is to provide a double-side polishing apparatus capable of reducing concave defects that occur on the main surfaces of glass substrates during polishing. [Means for solving the problem]

[0008] One aspect of the double-sided polishing apparatus of the present invention comprises a double-sided polishing machine that sandwiches a glass substrate between an upper platen and a lower platen, fixes the upper platen, and rotates the lower platen to polish both sides of the glass substrate using a polishing slurry; a pressure-feeding supply unit that supplies the polishing slurry to the upper platen; a slurry supply pipe that connects the pressure-feeding supply unit to the upper platen and supplies the polishing slurry from the pressure-feeding supply unit to the upper platen; and a filter that is provided midway in the slurry supply pipe and removes foreign matter contained in the polishing slurry, wherein the upper platen has a plurality of slurry supply holes to which the slurry supply pipes are connected, and at least the portion of the slurry supply pipe between the filter and the slurry supply holes is formed of a water-repellent resin. [Effects of the Invention]

[0009] One aspect of the double-side polishing apparatus according to the present invention can reduce concave defects that occur on the main surfaces of glass substrates during polishing. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing a configuration of a double-side polishing machine according to an embodiment of the present invention; [Figure 2] FIG. 2 is a partial perspective view of a double-sided polishing machine. [Figure 3] FIG. 4 is a diagram showing an example of the arrangement of slurry supply holes. [Figure 4] FIG. 1 is a diagram showing a configuration of a double-side polishing machine. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail. To facilitate understanding of the description, the same components in each drawing will be assigned the same reference numerals, and duplicate explanations will be omitted. The scale of each member in the drawings may differ from the actual scale. In this specification, unless otherwise specified, "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0012] A double-sided polishing apparatus according to an embodiment of the present invention will be described. FIG. 1 is a diagram showing the configuration of the double-sided polishing apparatus according to this embodiment. As shown in FIG. 1, the double-sided polishing apparatus 1 according to this embodiment includes a slurry storage unit 10, a pressure feed supply unit 20, a slurry supply pipe 30, a filter 40, and a double-sided polisher 50. In the double-sided polishing apparatus 1, a glass substrate G is sandwiched between a lower surface plate 51 and an upper surface plate 52 of the double-sided polisher 50, and polishing slurry S in the slurry storage unit 10 is directly supplied through the slurry supply pipe 30 to a slurry supply hole 522 provided in the upper surface plate 52 of the double-sided polisher 50, for use in polishing the glass substrate G.

[0013] The glass substrate G has a substantially rectangular shape and two main surfaces facing opposite directions. In this specification, a rectangular shape includes a shape with chamfered corners. A rectangular shape also includes a square. The shape of the glass substrate is not particularly limited, and may be substantially disk-shaped.

[0014] There are no particular limitations on the composition of the glass substrate G. The glass substrate G may be made of, for example, synthetic quartz glass, borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, soda-lime glass, alkali-free glass, crystallized glass, low-thermal-expansion glass, or the like.

[0015] As shown in FIG. 1, the slurry storage unit 10 is a storage tank for storing the polishing slurry S.

[0016] The polishing slurry S contains an abrasive and a dispersion medium. The abrasive is, for example, cerium oxide particles, silicon oxide particles, aluminum oxide particles, zirconium oxide particles, titanium oxide particles, diamond particles, silicon carbide particles, colloidal silica particles, etc. These may be used alone or in combination of two or more. The dispersion medium is, for example, water or an organic solvent.

[0017] The slurry storage unit 10 supplies the polishing slurry S to the pressure supply unit 20 through a slurry supply line 71 .

[0018] The pressure-feeding supply unit 20 pumps up the polishing slurry S from the slurry storage unit 10 and supplies the polishing slurry S to the upper surface plate 52 of the double-side polisher 50. As the pressure-feeding supply unit 20, a slurry supply pump or the like can be used.

[0019] The slurry supply pipe 30 connects the pressure supply unit 20 and the upper surface plate 52 and supplies the polishing slurry S from the pressure supply unit 20 to the upper surface plate 52 .

[0020] The slurry supply pipe 30 has a main pipe 31 , a plurality of branch pipes 32 , and a circulation pipe 33 .

[0021] The slurry supply pipe 30 has flow path adjustment valves V11 and V12 therein, and the flow path adjustment valves V11 and V12 adjust the supply amount of the polishing slurry S transported from the main pipe 31 to the branch pipe 32 and the circulation pipe 33.

[0022] One end of the main pipe 31 is connected to the pressure-feeding supply unit 20, the other end is connected to the branch pipe 32, and the main pipe 31 is connected to the circulation pipe 33 midway along the main pipe 31. The main pipe 31 transports the polishing slurry S from the pressure-feeding supply unit 20 to either or both of the plurality of branch pipes 32 and the circulation pipe 33.

[0023] As shown in FIG. 1, a plurality of branch pipes 32 branch off from a main pipe 31. One end of each of the plurality of branch pipes 32 is connected to the main pipe 31, and the other end is connected to a slurry supply hole 522 in the upper surface plate 52. The plurality of branch pipes 32 are made up of branch pipes 321...32M (M is an integer of 2 or more). For the sake of convenience, FIG. 1 shows only two branch pipes 321 and 32M connected to the main pipe 31, but it is assumed that two or more branch pipes 32 are connected. The number of branch pipes 321...32M may be appropriately determined depending on the number of slurry supply holes 522, the flow velocity and flow rate of the polishing slurry S, the degree of passage through the filter 40, etc.

[0024] As shown in Fig. 1, each of the plurality of branch pipes 32 may be further branched into two or more branches at one stage. That is, the branch pipe 321 has a first-stage branch pipe 331 and two or more second-stage branch pipes 341-1 to 341-N (N is an integer of 2 or more) branched from the first-stage branch pipe 331. The branch pipe 32M has a first-stage branch pipe 33M and two or more second-stage branch pipes 34M-1 to 34M-N branched from the first-stage branch pipe 33M. Although Fig. 1 shows only four second-stage branch pipes 341-1, 341-N, 34M-1, and 34M-N, (M × N) second-stage branch pipes 341-1 to 34M-N are connected to the slurry supply hole 522. Therefore, the (M×N) second-stage branch pipes 341-1 to 34M-N located at the final stages of the branch pipes 321 to 32M are connected to the slurry supply holes 522, respectively.

[0025] The branch pipes 32 have a total of (M×N) flow path systems through which the polishing slurry S flows. The first flow path system is a flow path system through the first branch pipe 331 and the second branch pipe 341-1, the Nth flow path system is a flow path system through the first branch pipe 331 and the second branch pipe 341-N, the Mth flow path system is a flow path system through the first branch pipe 33M and the second branch pipe 34M-1, and the (M×N)th flow path system is a flow path system through the first branch pipe 33M and the second branch pipe 34M-N.

[0026] In this embodiment, the number of branches of each of the branch pipes 321...32M is one, but may be set to two or more depending on the flow velocity and flow rate of the polishing slurry S, the degree of passage through the filter 40, etc. For example, the number of branches of each of the branch pipes 321...32M is preferably one to five in order to allow the polishing slurry S to pass through the filter 40 with as little pressure loss as possible while passing through the branch pipes 321...32M.

[0027] Each of the first-stage branch pipes 331 to 33M is branched into N branches, and the number of branches may be set appropriately depending on the number of slurry supply holes 522.

[0028] It is preferable that each of the branch pipes 32 has approximately the same inner diameter from the main pipe 31 to the slurry supply hole 522, and that the flow path length of the polishing slurry S flowing through the branch pipes 321...32M from the main pipe 31 to each slurry supply hole 522 is approximately the same. This makes it possible to make the pressure loss when the polishing slurry S flows through each branch pipe 32 approximately equal, and therefore the supply amount of the polishing slurry S flowing from each branch pipe 32 to the slurry supply hole 522 approximately uniform.

[0029] The circulation pipe 33 is connected to the middle of the main pipe 31, and connects the main pipe 31 with the slurry storage section 10. The circulation pipe 33 returns the polishing slurry S passing through the main pipe 31 to the slurry storage section 10.

[0030] The slurry supply pipe 30 is made of a water-repellent resin that lubricates the flow of the polishing slurry S between the filter 40 and the slurry supply hole 522 and has higher slipperiness than other parts of the slurry supply pipe 30. That is, the second-stage branch pipes 341-1, 341-2, . . . 34M-1, and 34M-N located between the filter 40 and the slurry supply hole 522 are made of a water-repellent resin. The water-repellent resin smooths the sliding of the polishing slurry S, thereby preventing the polishing slurry S from solidifying and adhering to the inner wall of the branch pipe 32 while passing through it.

[0031] As the water-repellent resin, a resin with high water repellency can be suitably used, for example, a fluorine-based resin and a silicone-based resin. These may be used alone or in combination of two or more. The water-repellent resin has a contact angle with water of 70 degrees or more, preferably 80 degrees or more, and more preferably 90 degrees or more. If the contact angle with water is 70 degrees or more, the polishing slurry S can be more effectively prevented from solidifying on the inner wall of the slurry supply pipe 30 made of the water-repellent resin.

[0032] Examples of fluorine-based resins include polytetrafluoroethylene (PTFE), tetraethylene-perfluoroalkoxyethylene copolymer (PFA), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (THV), polyvinyl fluoride (PVF), polyvinylidene fluoride, polytrifluoroethylene, and polyhexafluoropropylene. These may be used alone or in combination of two or more. Among these, PTFE and PFA are particularly preferred.

[0033] Examples of silicone-based resins include unmodified silicone resins such as thermosetting silicone resins and photocurable silicone resins, and modified silicone resins such as polyester-modified silicone resins, urethane-modified silicone resins, acrylic-modified silicone resins, polyimide-modified silicone resins, olefin-modified silicone resins, ether-modified silicone resins, alcohol-modified silicone resins, fluorine-modified silicone resins, amino-modified silicone resins, mercapto-modified silicone resins, and carboxy-modified silicone resins. Specific examples of silicone-based resins include dimethylpolysiloxane, diphenylpolysiloxane, methylphenylpolysiloxane, and silicone oligomers.

[0034] The slurry supply pipe 30 is preferably formed of a water-repellent resin between the pressure supply unit 20 and the filter 40. That is, the main pipe 31 and the branch pipes 32 are preferably all formed of a water-repellent resin. This prevents the polishing slurry S from solidifying and adhering while passing through the slurry supply pipe 30.

[0035] The filter 40 is provided in the middle of the slurry supply pipe 30 and removes foreign matter contained in the polishing slurry S. The filter 40 can be a general foreign matter removal filter used for refining liquids, and examples of the filter 40 that can be used include a depth filter and a pleated filter.

[0036] The filter 40 is preferably provided in each of the second-stage branch pipes 341-1, 341-2... 34M-1 and 34M-N among the plurality of branch pipes 32. The second-stage branch pipes 341-1, 341-2... 34M-1 and 34M-N are the final-stage branch pipes connected to the slurry supply hole 522 among the slurry supply pipe 30, and are located closest to the slurry supply hole 522. Therefore, by passing the polishing slurry S flowing through the second-stage branch pipes 341-1... 34M-N through the filter 40, solid matter adhering to the inner walls of the first-stage branch pipes 331... 33N, even if it is carried along with the polishing slurry S, can be removed by the filter 40. Furthermore, the flow of the polishing slurry S is obstructed at the branched portions of the plurality of branch pipes 321... 32M, and the polishing slurry S is likely to stick to these portions. By eliminating the branching of the flow path downstream of the filter 40, the polishing slurry S that has passed through the filter 40 is less likely to contain solidified matter. Therefore, by providing the filter 40 to the second-stage branch pipes 341-1...34M-N of the branch pipe 32, the polishing slurry S with less foreign matter is supplied to the slurry supply hole 522.

[0037] The pore size of the filter 40 can be appropriately set depending on the type of polishing slurry S, etc., and the average particle size D 50The pore size of the filter 40 is preferably 5 to 50 times the median diameter, more preferably 7 to 45 times, and even more preferably 10 to 40 times. If the pore size of the filter 40 is within the above-mentioned preferred range, the polishing slurry S can pass through the filter 40 without clogging and while maintaining a constant flow rate.

[0038] The average particle size of the polishing slurry S is D 50 This is the particle diameter (volume-based cumulative 50% diameter) when the cumulative amount accumulates from the smallest particles to 50% on a volume basis in the particle size distribution curve obtained by measuring the particle size distribution of the polishing slurry S using the laser diffraction / scattering method.

[0039] 1 and 2, a double-sided polishing machine 50 includes a lower surface plate 51, an upper surface plate 52, a carrier 53, a rotating shaft 54, a sun gear 55, an internal gear 56, a lifting unit 57, and a base 58.

[0040] The double-sided polisher 50 is a three-way type in which an upper surface plate 52 is fixed, and a lower surface plate 51, a sun gear 55, and an internal gear 56 rotate about the same vertical rotation center line. The double-sided polisher 50 sandwiches a glass substrate G between the upper surface plate 52 and the lower surface plate 51, and with the upper surface plate 52 fixed, rotates the lower surface plate 51, the sun gear 55, and the internal gear 56 about the same vertical rotation center line, polishing both sides of the glass substrate G using a polishing slurry S on the polishing surfaces of the upper surface plate 52 and the lower surface plate 51.

[0041] As shown in FIG. 1, the lower surface plate 51 is arranged horizontally in the double-side polishing machine 50, and as shown in FIG. 2, is formed in a disk shape.

[0042] 1 and 2, a lower polishing pad 511 is attached to an upper surface 51a of the lower surface plate 51. As the lower polishing pad 511, for example, a urethane-based polishing pad, a nonwoven fabric-based polishing pad, or a suede-based polishing pad is used.

[0043] The lower surface plate 51 is placed on a lower surface plate receiver 61, and the lower surface plate receiver 61 is placed on a lower surface plate base 62 that rotatably supports the lower surface plate receiver 61. The lower surface plate receiver 61 rotates while being supported on the lower surface plate base 62 by a lower surface plate rotation shaft 63. The rotation of the lower surface plate receiver 61 by the lower surface plate rotation shaft 63 causes the lower surface plate 51 to rotate.

[0044] As shown in FIGS. 1 and 2, the upper surface plate 52 is disposed substantially horizontally on the surface plate hanger 575 of the lifting section 57 so as to face the lower surface plate 51, and is formed in a disk shape as shown in FIG.

[0045] 1 and 2, an upper polishing pad 521 is attached to the lower surface 52a of the upper surface plate 52. As the upper polishing pad 521, similar to the lower polishing pad 511, for example, a urethane-based polishing pad, a nonwoven fabric-based polishing pad, a suede-based polishing pad, or the like is used.

[0046] The upper surface plate 52 has a plurality of slurry supply holes 522 through which the polishing slurry S is supplied. Fig. 3 is a diagram showing an example of the arrangement of the slurry supply holes 522. As shown in Fig. 3, the plurality of slurry supply holes 522 are preferably provided approximately evenly on the upper surface plate 52. This allows the polishing slurry S to be supplied approximately evenly from the slurry supply holes 522 to the glass substrate G on the lower surface plate 51.

[0047] The plurality of slurry supply holes 522 are preferably arranged on the upper surface plate 52 so as to be symmetrical with respect to the central axis J of the upper surface plate 52 in a plan view of the upper surface plate 52. This allows the polishing slurry S to be supplied from the slurry supply holes 522 to the entire surface of the lower surface plate 51 approximately evenly.

[0048] Symmetrical with respect to the central axis J means that the supply holes are arranged so that their positions do not change when rotated 360 / n degrees (n is a natural number of 2 or more) around the central axis J. It is preferable that n be a value of 2 to 8 from the viewpoints of simplicity and maintaining quality.

[0049] As shown in FIGS. 1 and 2, the carrier 53 is disposed between the lower surface plate 51 and the upper surface plate 52. The carrier 53 has a through hole 53a, and holds the glass substrate G horizontally in the through hole 53a so that one main surface of the glass substrate G faces upward and the other main surface faces downward. Each carrier 53 holds one glass substrate G at a time, but may hold multiple glass substrates G at a time. The carrier 53 is disposed radially outward from the sun gear 55 and radially inward from the internal gear 56. A plurality of carriers 53 are disposed around the sun gear 55 at intervals.

[0050] 2, the carrier 53 has an outer peripheral gear 531 on its side. The outer peripheral gear 531 meshes with a sun gear 55 and an internal gear 56, and the carrier 53 rotates and revolves by the action of the sun gear 55 and the internal gear 56. As the lower surface plate 51 rotates, both main surfaces of the glass substrate G held by the carrier 53 are polished.

[0051] The rotating shaft 54 ​​is connected to a motor (not shown) in the base 58, and is provided so as to penetrate the lower surface plate 51, the lower surface plate support 61, and the lower surface plate base 62, as shown in Fig. 1. The rotating shaft 54 ​​is rotated by the motor (not shown), causing the sun gear 55 to rotate.

[0052] 1 and 2, the sun gear 55 is provided at approximately the center of the lower surface plate 51 in a plan view of the lower surface plate 51. The sun gear 55 is formed in a substantially circular shape and has an outer peripheral gear 551 on its side. The outer peripheral gear 551 meshes with the outer peripheral gear 531 of the carrier 53.

[0053] The internal gear 56 is formed in a cylindrical shape and is supported by a casing 64 so as to be located on the outer periphery of the lower surface plate 51. The sun gear 55 and the internal gear 56 are arranged concentrically and mesh with the outer periphery gear 531 of the carrier 53.

[0054] The lifting unit 57 is provided in a state supported by a support 71, and moves the upper surface plate 52 in the up and down direction. The lifting unit 57 only needs to have a configuration that can hold the upper surface plate 52 in a state that allows it to be raised and lowered in the up and down direction, and may include, for example, a main cylinder 571, a main cylinder rod 572, a sub-cylinder 573, a sub-cylinder rod 574, a surface plate hanger 575, and a stud 576.

[0055] The main cylinder 571 is supported by a support column 71, and moves a main cylinder rod 572 up and down by a drive source (not shown). The main cylinder 571 only needs to be able to move the main cylinder rod 572 up and down, and for example, an air cylinder or a hydraulic cylinder using air or oil can be used as the drive source (not shown). In addition to air and oil, a drive mechanism such as a motor can also be used as the drive source (not shown).

[0056] The main cylinder rod 572 is a rod-shaped member provided on the bottom surface of the main cylinder 571 with a portion of it inserted into the main cylinder 571. The lower end of the main cylinder rod 572 is connected to the upper surface of the sub-cylinder 573. The main cylinder rod 572 moves up and down while inserted into the main cylinder 571, thereby moving the sub-cylinder 573 up and down.

[0057] The sub-cylinder 573 is fixed to the lower end of the main cylinder rod 572, and moves the sub-cylinder rod 574 in the up and down direction by a drive source (not shown). The drive source (not shown) is the same as that for the main cylinder 571.

[0058] Sub-cylinder rod 574 is a rod-shaped member provided on the bottom surface of sub-cylinder 573 with a portion of it inserted into sub-cylinder 573. The lower end of sub-cylinder rod 574 is connected to the upper surface of surface plate suspender 575. Sub-cylinder rod 574 moves up and down while inserted into sub-cylinder 573, thereby moving surface plate suspender 575 up and down.

[0059] The surface plate hanger 575 is a plate-shaped member, and a sub-cylinder rod 574 is connected to the upper surface of the surface plate hanger 575, and a stud 576 is fixed to the lower surface of the surface plate hanger 575. The surface plate hanger 575 supports the upper surface plate 52 via the stud 576.

[0060] A plurality of studs 576 are provided at the end of the bottom surface of the surface plate hanger 575. The studs 576 connect the surface plate hanger 575 to the upper surface plate 52. The number of studs 576 may be determined appropriately depending on the size of the bottom surface of the surface plate hanger 575.

[0061] The lifting section 57 uses the main cylinder 571 to move the main cylinder rod 572 in the vertical direction by a large amount, thereby moving the upper surface plate 52 in the vertical direction by a large amount, and uses the sub-cylinder 573 to move the sub-cylinder rod 574 in the vertical direction by a small amount, thereby fine-tuning the upper surface plate 52 in the vertical direction.

[0062] As shown in FIG. 1, the base 58 is a stand for placing the casing 64, and has inside it a motor (not shown) and a recovery section (not shown) for recovering the polishing slurry S dripped from the slurry supply hole 522.

[0063] The casing 64 has a slurry discharge pipe 641 that discharges to the outside the polishing slurry S recovered in a recovery section (not shown) in the base 58. The slurry discharge pipe 641 is connected to the slurry storage section 10, and the polishing slurry S recovered in the base 58 passes through the slurry discharge pipe 641 and is recovered in the slurry storage section 10.

[0064] Although the double-sided polisher 50 is a three-way type, it may also be a two-way type. In the two-way type, the lower surface plate 51 and the upper surface plate 52 are fixed, and the sun gear 55 and the internal gear 56 are rotated. The double-sided polisher 50 may polish the two main surfaces of the glass substrate G multiple times with polishing slurries S containing abrasives of different materials or particle sizes.

[0065] An example of a method of using the double-sided polishing apparatus 1 will be described. In the double-sided polishing apparatus 1, at the start of polishing the glass substrate G, the upper surface plate 52 is moved downward by the lifting unit 57 so that the upper surface plate 52 comes into contact with the upper surface of the glass substrate G. First, the main cylinder 571 moves the main cylinder rod 572 downward to move the upper surface plate 52 downward so that the upper polishing pad 521 is positioned near the upper surface of the glass substrate G. Thereafter, the sub-cylinder 573 moves the sub-cylinder rod 574 downward by a small amount, thereby finely adjusting the downward position of the upper surface plate 52 so that the upper polishing pad 521 comes into contact with and presses against the upper surface of the glass substrate G.

[0066] By operating the pressure supply section 20 and opening the flow path control valve V11, the polishing slurry S stored in the slurry storage section 10 passes through the main pipe 31 and branch pipe 32 of the slurry supply pipe 30, and after foreign matter contained in the polishing slurry S is removed by the filter 40 installed in the branch pipe 32, the polishing slurry S is transported to the double-sided polishing machine 50.

[0067] At this time, the second-stage branch pipes 341-1...34M-N of the branch pipe 32, which are located between the filter 40 and the slurry supply hole 522, are made of a water-repellent resin. Therefore, the polishing slurry S is less likely to adhere to the inner walls of the second-stage branch pipes 341-1...34M-N and can flow smoothly. The polishing slurry S passes through the slurry supply pipe 30 by the pressure of the pressure supply unit 20 and is transported to the slurry supply hole 522 of the upper surface plate 52, where it is used for double-side polishing of the glass substrate G.

[0068] In the double-side polisher 50, the upper surface plate 52 is fixed and does not rotate. The lower surface plate 51 rotates and presses the lower polishing pad 511 against the lower surface of the glass substrate G, and presses the upper polishing pad 521 against the upper surface of the glass substrate G. The sun gear 55 and the internal gear 56 also rotate. The lower surface plate 51, the sun gear 55, and the internal gear 56 cause the carrier 53 to rotate on its axis and revolve, and due to the rotation and revolution of the carrier 53, the glass substrate G held in the through hole 53a of the carrier 53 also rotates on its axis and revolves.

[0069] The upper surface plate 52 supplies polishing slurry S to the glass substrate G, whereby the polishing slurry S is supplied between the glass substrate G and the upper polishing pad 521. The glass substrate G, sandwiched between the lower polishing pad 511 and the upper polishing pad 521, rotates and revolves while the polishing slurry S is supplied between the glass substrate G and the upper polishing pad 521, thereby polishing the upper surface of the glass substrate G. Furthermore, the polishing slurry S flowing from the upper polishing pad 521 is supplied between the glass substrate G and the lower polishing pad 511. The glass substrate G, sandwiched between the lower polishing pad 511 and the upper polishing pad 521, rotates and revolves while the polishing slurry S is supplied between the glass substrate G and the lower polishing pad 511, thereby polishing the lower surface of the glass substrate G. In this way, the two main surfaces of the glass substrate G are polished simultaneously.

[0070] The lower surface plate 51, the sun gear 55, and the internal gear 56 may rotate in the same direction in a plan view. The carrier 53 may rotate while revolving. The revolving direction of the carrier 53 may be the same as the rotating direction of the sun gear 55 and the internal gear 56.

[0071] The rotation direction of the carrier 53 is determined by the magnitude of the product of the rotation speed and pitch circle diameter of the sun gear 55 and the product of the rotation speed and pitch circle diameter of the internal gear 56. If the product of the rotation speed and pitch circle diameter of the internal gear 56 is greater than the product of the rotation speed and pitch circle diameter of the sun gear 55, the rotation direction of the carrier 53 and the revolution direction of the carrier 53 will be the same. On the other hand, if the product of the rotation speed and pitch circle diameter of the internal gear 56 is smaller than the product of the rotation speed and pitch circle diameter of the sun gear 55, the rotation direction of the carrier 53 and the revolution direction of the carrier 53 will be opposite to each other.

[0072] The two main surfaces of the glass substrate G are finish-polished by the double-sided polisher 50 in an approximately axially symmetric manner about their respective centers. The two main surfaces may be polished in plane symmetry with respect to the central plane of the glass substrate G in the plate thickness direction. Both of the two main surfaces may be polished to a convex curved surface, or both may be polished to a concave curved surface. Note that in the finish polishing, the two main surfaces may be polished in turn using a single-sided polisher (not shown).

[0073] The amount of polishing slurry S supplied to the double-sided polisher 50 can be controlled by controlling the flow path adjustment valve V11 provided in the slurry supply pipe 30. In the double-sided polisher 1, the flow path adjustment valve V11 may be appropriately controlled while the double-sided polisher 50 is in operation, thereby controlling the amount of polishing slurry S supplied while monitoring the progress of polishing of the glass substrate G. For example, as the polishing progresses, if it is necessary to increase or decrease the amount of polishing slurry S supplied, the amount of polishing slurry S supplied can be appropriately increased or decreased.

[0074] At the end of polishing the glass substrate G, the upper surface plate 52 is moved upward by the lifting unit 57 so that the upper polishing pad 521 does not contact the upper surface of the glass substrate G. First, the sub-cylinder rod 574 is slightly moved upward by the sub-cylinder 573 so that the upper polishing pad 521 does not contact the upper surface of the glass substrate G. Then, the main cylinder 571 moves the main cylinder rod 572 upward by a large distance. When the upper surface plate 52 is moved upward by the lifting unit 57, polishing slurry S may be discharged from the slurry supply hole 522 so that the glass substrate G remains on the lower surface plate 51 side. By peeling the glass substrate G from the upper surface plate 52 by the discharge pressure of the polishing slurry S, the glass substrate G is prevented from sticking to the upper surface plate 52, improving the handleability of the double-sided polisher 50.

[0075] Furthermore, when polishing of the glass substrate G is completed, the flow path adjustment valve V11 may be closed and the flow path adjustment valve V12 may be opened. This allows the polishing slurry S to be returned to the slurry storage unit 10 while the pressure-feed supply unit 20 is kept operating.

[0076] As described above, the double-sided polishing apparatus 1 includes the pressure supply unit 20, the slurry supply pipe 30, the filter 40, and the double-sided polishing machine 50. The upper surface plate 52 has a plurality of slurry supply holes 522, and the slurry supply pipe 30 is made of a water-repellent resin at least between the filter 40 and the slurry supply holes 522. That is, the slurry supply pipe 30 is made of a water-repellent resin at least between the filter 40 and the slurry supply holes 522 of the second-stage branch pipes 341-1...34M-N. The slurry supply pipe 30 is directly connected to the slurry supply holes 522 of the upper surface plate 52, so that the polishing slurry S can be directly supplied to the slurry supply holes 522. The slurry supply pipe 30 is prevented from adhering and accumulating on the inner walls of the second-stage branch pipes 341-1 to 34M-N between the filter 40 and the slurry supply holes 522 by forming at least a water-repellent resin between the filter 40 and the slurry supply holes 522. Therefore, before the adhering matter of the polishing slurry S accumulates, the adhering matter of the polishing slurry S can be peeled off from the inner walls of the second-stage branch pipes 341-1 to 34M-N between the filter 40 and the slurry supply holes 522. The double-sided polishing apparatus 1 can reduce the amount of adhering matter of the polishing slurry S adhering to the inner walls of the slurry supply pipe 30 that is peeled off by the flow of the polishing slurry S through the slurry supply pipe 30 and discharged as foreign matter from the slurry supply pipe 30. This reduces the amount of foreign matter contained in the polishing slurry S discharged from the slurry supply pipe 30. Therefore, when the polishing slurry S discharged from the slurry supply pipe 30 is used to polish a glass substrate G, the double-sided polishing apparatus 1 can reduce the number of concave defects that occur on the two main surfaces of the glass substrate G due to foreign matter contained in the polishing slurry S, thereby reducing the number of concave defects that occur on the two main surfaces of the glass substrate G when polishing the glass substrate G.

[0077] In the double-sided polishing apparatus 1, the portion between the pressure supply unit 20 of the slurry supply pipe 30 and the filter 40 can be formed of a water-repellent resin. This prevents the polishing slurry S from adhering to and accumulating on the inner wall of the slurry supply pipe 30 throughout the entire inside of the slurry supply pipe 30, thereby further reducing the amount of foreign matter contained in the polishing slurry S discharged from the slurry supply pipe 30. Therefore, the double-sided polishing apparatus 1 can further reduce concave defects that occur on the two main surfaces of the glass substrate G when the glass substrate G is polished.

[0078] The double-sided polishing apparatus 1 uses a fluorine-based resin or a silicone-based resin as the water-repellent resin. This reliably reduces adhesion of the polishing slurry S to the inner wall of the slurry supply pipe 30, thereby reliably reducing the amount of foreign matter contained in the polishing slurry S discharged from the slurry supply pipe 30. Therefore, the double-sided polishing apparatus 1 reliably reduces concave defects that occur on the two main surfaces of the glass substrate G when the glass substrate G is polished.

[0079] The double-sided polishing apparatus 1 uses at least one of PTFE and PFA as the fluorine-based resin. Among fluorine-based resins and silicone-based resins, PTFE and PFA have particularly high water repellency, which can further reduce adhesion of the polishing slurry S to the inner wall of the slurry supply pipe 30, thereby further reducing the amount of foreign matter contained in the polishing slurry S discharged from the slurry supply pipe 30. Therefore, the double-sided polishing apparatus 1 can improve the effect of reducing concave defects that occur on the two main surfaces of the glass substrate G when the glass substrate G is polished.

[0080] The double-sided polishing apparatus 1 has a slurry supply pipe 30 having a main portion 31 and a plurality of branch pipes 32 branching from the main portion 31. The plurality of branch pipes 32 include flow paths between the filter 40 and the slurry supply holes 522. Therefore, the portions between the slurry supply holes 522 and parts of the plurality of branch pipes 32 are formed of a water-repellent resin, thereby preventing the polishing slurry S from adhering to the inner walls between the portions. This reduces the amount of foreign matter contained in the polishing slurry S discharged from the slurry supply pipe 30. Therefore, even when the double-sided polishing apparatus 1 discharges the polishing slurry S from the plurality of slurry supply holes 522 and uses it to polish a glass substrate G, it is possible to reduce concave defects that occur on the two main surfaces of the glass substrate G during polishing.

[0081] The double-sided polishing apparatus 1 has a plurality of branch pipes 32 each branched at one stage. That is, each of the plurality of branch pipes 32 has second-stage branch pipes 341-1 to 34M-N. The second-stage branch pipes 341-1 to 34M-N include a flow path between the filter 40 and the slurry supply hole 522. Therefore, by forming at least the portion between the filter 40 and the slurry supply hole 522 of the second-stage branch pipes 341-1 to 34M-N with a water-repellent resin, adhesion of the polishing slurry S to the inner wall between the portion is suppressed, and the amount of foreign matter contained in the polishing slurry S discharged from the slurry supply pipe 30 is reduced. Therefore, the double-sided polishing apparatus 1 can reduce the amount of foreign matter contained in the polishing slurry S discharged from the multiple slurry supply holes 522, so even if the polishing slurry S discharged from the multiple slurry supply holes 522 is used to polish the glass substrate G, it can further reduce concave defects that occur on the two main surfaces of the glass substrate G when the glass substrate G is polished.

[0082] In the double-sided polishing apparatus 1, the filter 40 can be provided in each of the second-stage branch pipes 341-1... 34M-N, which are the final stages connected to the slurry supply holes 522. This prevents the polishing slurry S from adhering to the inner walls of each of the second-stage branch pipes 341-1... 34M-N, thereby reducing the amount of foreign matter contained in the polishing slurry S discharged from each of the second-stage branch pipes 341-1... 34M-N, even if the polishing slurry S is supplied to multiple slurry supply holes 522. Therefore, the double-sided polishing apparatus 1 uses the polishing slurry S discharged from the multiple slurry supply holes 522 to polish the glass substrate G, thereby more reliably reducing concave defects that occur on the two main surfaces of the glass substrate G during polishing.

[0083] In the double-sided polishing apparatus 1, each of the branch pipes 32 has approximately the same inner diameter from the main pipe 31 to the slurry supply hole 522, and the flow path lengths of the polishing slurry S flowing in the branch pipes from the main pipe 31 to each slurry supply hole 522 can be approximately the same. This makes it possible to make the pressure loss in the branch pipes 32 approximately equal, and therefore make the pressure loss in the flow path from the main pipe 31 to each slurry supply hole 522 approximately equal. This makes it possible to make the supply pressure of the polishing slurry S discharged from each slurry supply hole 522 approximately equal, and therefore reduces runout of the upper platen 52 caused by differences in the supply pressure of the polishing slurry S, thereby improving the uniformity of polishing of the glass substrate G.

[0084] In the double-sided polishing apparatus 1, the plurality of slurry supply holes 522 can be arranged in the upper surface plate 52 symmetrically about the central axis of the upper surface plate 52 in a plan view of the upper surface plate 52. As a result, even if the plurality of glass substrates G placed on the lower surface plate 51 rotate, the double-sided polishing apparatus 1 can supply the polishing slurry S discharged from the plurality of slurry supply holes 522 to the plurality of glass substrates G approximately uniformly, thereby polishing the glass substrates G more uniformly.

[0085] The double-side polishing apparatus 1 is configured to adjust the pore size of the filter 40 to the average particle size D of the polishing slurry S. 50The pressure loss of the polishing slurry S passing through each filter 40 can be increased by 5 to 50 times. As a result, the double-sided polishing apparatus 1 can reduce the pressure loss of the polishing slurry S passing through each filter 40, allowing the polishing slurry S to pass through the filters 40 stably and approximately uniformly, suppressing adhesion of the polishing slurry S to the filters 40. The double-sided polishing apparatus 1 can supply the polishing slurry S approximately uniformly to the multiple glass substrates G from the multiple slurry supply holes 522 while reducing the amount of foreign matter contained in the polishing slurry S discharged from the slurry supply pipe 30. Therefore, the double-sided polishing apparatus 1 can reduce unevenness in polishing of the glass substrates G and stably reduce concave defects occurring on the two main surfaces of each glass substrate G.

[0086] As described above, the double-sided polishing apparatus 1 can reduce the amount of foreign matter contained in the polishing slurry S discharged from the slurry supply pipe 30, and is therefore suitable for use in a method for manufacturing a glass substrate when manufacturing a glass substrate G. In particular, the double-sided polishing apparatus 1 is suitable for use in the manufacture of glass for mask blanks, which are used in glass substrates for mask blanks and the like, where strict specifications are required for the surface of the glass substrate as the density and precision of VLSI devices increase. [Example]

[0087] The following examples will be used to explain the embodiments in more detail, but the embodiments are not limited to these examples. Examples 1 to 5 are working examples, and Example 5 is a comparative example.

[0088] <Example 1> (Production of double-sided polishing equipment) A double-sided polishing apparatus shown in FIG. 4 was fabricated. In the double-sided polishing apparatus shown in FIG. 4, the slurry supply pipe 30 in the double-sided polishing apparatus 1 shown in FIG. 1 was configured with a main pipe 31 and two branch pipes 321 and 322. The branch pipes 321 and 322 were formed by branching first-stage branch pipes 331 and 332 into two. The branch pipe 321 was configured with a first-stage branch pipe 331 and second-stage branch pipes 341-1 and 341-2. The branch pipe 322 was configured with a first-stage branch pipe 332 and second-stage branch pipes 342-1 and 342-2. One end of the branch pipes 321 and 322 was connected to the main pipe 31, and the other end was connected to the slurry supply hole 522 in the upper surface plate 52. The slurry supply pipe 30 was made of tetraethylene-perfluoroalkoxyethylene copolymer (PFA), and a filter 40 (DFA4201Y003, manufactured by Pall Corporation, pore size: 0.3 μm) was attached to each of the second-stage branch pipes 341-1, 341-2, 342-1, and 342-2. This resulted in the double-sided polishing apparatus shown in FIG. 1. Polishing pads (Bellatrix N7512, manufactured by Filwel Co., Ltd.) were attached to the upper and lower surface plates. The inner diameter of each of the branch pipes 321 and 322 was 8 mm. The flow path length of the first-stage branch pipe 331 of the branch pipe 321 was 3.0 m, the flow path lengths of the second-stage branch pipe 341-1 and the second-stage branch pipe 341-2 were 0.8 m, and the combined flow path length of the first-stage branch pipe 331 and the second-stage branch pipe 341-1 or the second-stage branch pipe 341-2 was 3.8 m. The flow path length of the first-stage branch pipe 332 of the branch pipe 322 was also 3.0 m, the flow path lengths of the second-stage branch pipe 342-1 and the second-stage branch pipe 342-2 were also 0.8 m, and the combined flow path length of the second-stage branch pipe 332 and the second-stage branch pipe 342-1 or the second-stage branch pipe 342-2 was also 3.8 m.

[0089] (Polishing process) A glass substrate G (synthetic quartz glass, 152 mm long x 152 mm wide) was held in a carrier 53 of a double-side polishing machine with both main surfaces of the glass substrate G exposed, and the main surfaces of the glass substrate G were polished. One glass substrate G was attached to the carrier 53 with both main surfaces exposed. Five carriers 53 were used to polish 10 glass substrates G. That is, one glass substrate G was attached to each of the five carriers 53 and polished, and then another glass substrate G was attached to each of the five carriers 53 and polished, so that a total of 10 glass substrates GC were polished.

[0090] The polishing slurry was supplied from the pressure supply unit 20 to the slurry supply pipe 30 at a supply rate of 10 liters / minute, and the glass substrate G was polished while the polishing slurry was supplied between the carrier 53 and the upper polishing pad 521. The polishing slurry contained 20 mass % colloidal silica having an average primary particle size of 20 nm, contained nitric acid as a dispersion medium, and was adjusted to a pH of 2.0.

[0091] Polishing load is 100g / cm 2 The rotation speed of the polishing platen was 10 rpm, and the polishing time was 30 minutes.

[0092] As a result, ten polished glass substrates G were obtained.

[0093] (Cleaning process) Next, ten polished glass substrates G were cleaned, with one glass substrate G attached to one carrier 53 being considered as one set. Specifically, one glass substrate G attached to the carrier 53 was immersed in the first bath and then the second bath in order to be cleaned. The first glass substrate G was removed from the second bath, and after cleaning of the first glass substrate G was completed, cleaning of the second glass substrate G was started, and cleaning of the tenth glass substrate G was then carried out.

[0094] The first and second baths each contained 50 liters of a cleaning solution with a pH of 12. The cleaning solution was an aqueous solution of potassium hydroxide (3%). In both baths, the glass substrate G was immersed for 5 minutes.

[0095] (Post-processing) Each set of glass substrates G was taken out of the second bath and then immersed for 5 minutes in a standby bath containing ultrapure water (about 40 liters) with a pH of about 7.

[0096] Thereafter, each set of glass substrates G was removed from the standby bath and washed using a single-wafer cleaning device with various solutions, in that order, including scrubbing, a mixed solution of sulfuric acid and hydrogen peroxide, alkaline detergent, and ultrapure water, while applying ultrasonic waves, and finally spin-drying.

[0097] The second glass substrate G was immersed in the standby bath after the first glass substrate G was removed from the standby bath. The same procedure was carried out for the third to tenth glass substrates G.

[0098] As a result, a total of 10 glass substrates G (hereinafter referred to as "Sample 1-1", ..., "Sample 1-10") were obtained.

[0099] (evaluation) The state of defects on one main surface of each of the ten glass substrates G was evaluated. As the state of defects, the average number of concave defects An(ave) and the size of the irregularities on the main surface of the glass substrate G were determined.

[0100] (Average number of concave defects An(ave)) Using a defect inspection machine (M7360: Lasertec Corporation), the number of concave defects 40 nm or larger in size was measured in a 142 mm × 142 mm quality assurance area in the center of the main surface of the glass substrate G. From the measurement results obtained, the average number of concave defects (average number of concave defects An (ave)) for 10 glass substrates G was calculated. When the average number of concave defects An (ave) in the quality assurance area was 3.0 or less per side, the glass substrate was evaluated as meeting the usage conditions, and when the average number of concave defects An (ave) exceeded 3.0 per side, the glass substrate was evaluated as not meeting the usage conditions.

[0101] (Size of unevenness) The shapes of the glass substrates G before and after polishing were measured using a flatness measuring device (UltraFlat (registered trademark) 200 Mask, manufactured by Tropel), and the differential shape of a 142 mm × 142 mm quality assurance region in the center of the main surface of the glass substrate G was determined. From the obtained measurement results, the average value of the irregularity magnitude of 10 glass substrates G was calculated. Although the differential shape was a convex shape, secondary components that did not affect exposure were removed. The pure flatness (PV value) (unit: nm) of the differential shape in the quality assurance region of the main surface was approximately 60 nm after 20 minutes of polishing. If the average irregularity magnitude was 20 nm or less, it was evaluated as meeting the usage conditions, and if the average irregularity magnitude was more than 20 nm, it was evaluated as not meeting the usage conditions.

[0102] <Example 2> The same procedure as in Example 1 was carried out, except that the material of the slurry supply pipe was changed from PFA to silicone resin.

[0103] <Example 3> The same procedure as in Example 1 was repeated except that the pore size of the filter was changed to 0.5 μm.

[0104] <Example 4> In Example 1, the flow path length of second-stage branch pipe 341-1 and second-stage branch pipe 341-2 of branch pipe 321 was 1.0 m, and the flow path length of second-stage branch pipe 342-1 and second-stage branch pipe 342-2 of branch pipe 322 was 0.6 m. The combined flow path length of first-stage branch pipe 331 and second-stage branch pipe 341-1 or second-stage branch pipe 341-2 was 4.0 m, and the combined flow path length of first-stage branch pipe 332 and second-stage branch pipe 342-1 or second-stage branch pipe 342-2 was 3.6 m, but the flow path lengths of branch pipe 321 and branch pipe 322 were changed to different lengths. Otherwise, the same procedure as in Example 1 was performed.

[0105] <Example 5> The procedure was the same as in Example 1, except that a slurry ring for storing polishing slurry was provided on the double-sided polisher, a slurry branch pipe was connected to the slurry ring, and the material of the slurry supply pipe was changed to a silicone-based resin.

[0106] Table 1 shows the measurement results of the configuration conditions of the double-sided polisher and the polishing results of the glass substrate G for each example. The configuration conditions of the double-sided polisher include the particle size of the polishing slurry, the material of the slurry supply pipe, the connection destination of the branch pipe, the branching form of the branch pipe, the flow path length of the branch pipe 321 or 322 from the main pipe 31 to the slurry supply hole 522, and the pore size of the filter 40. The polishing results of the glass substrate G include the average number of concave defects and the size of the unevenness on the main surface of the glass substrate G.

[0107] [Table 1]

[0108] As can be seen from Table 1, in Examples 1 to 3, the average number of concave defects An(ave) was 0.5 per surface or less, and the size of the irregularities on the main surfaces was 18 nm or less, all of which met the criteria. In Example 4, the size of the irregularities on the main surfaces was 30 nm, but the average number of concave defects An(ave) was 0.1 per surface, which met the criteria. On the other hand, in Example 5, the average number of concave defects was 4.5 per surface, which did not meet the criteria.

[0109] Therefore, it was confirmed that the double-sided polishing apparatus having the configurations of Examples 1 to 4, unlike the double-sided polishing apparatus of Example 5, has multiple slurry supply holes in the upper platen and the slurry supply pipe is formed of PFA or silicone resin as a water-repellent resin, so that the polishing slurry can be directly supplied from the branched slurry supply pipe to the glass plate through the slurry supply holes in the upper platen, thereby significantly reducing the number of concave defects on the glass plate.

[0110] Although the embodiments have been described above, they are presented as examples and the present invention is not limited to the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as set forth in the claims. [Explanation of symbols]

[0111] 1 Double-sided polishing machine 20 Pressure feed supply section 30 Slurry supply pipe 31 Master 32, 321, 32M branch pipe 331, 33M First stage branch pipe 341-1, 341-N, 34M-1, 34M-N Second stage branch pipe 40 filters 50 Double-sided polishing machine 51 Lower surface plate 52 Upper surface plate 522 Slurry supply hole 53 Career S Polishing Slurry

Claims

1. a double-side polishing machine that sandwiches a glass substrate between an upper surface plate and a lower surface plate, fixes the upper surface plate, and rotates the lower surface plate to polish both sides of the glass substrate using a polishing slurry; a pressure supply unit that supplies the polishing slurry to the upper platen; a slurry supply pipe connecting the pressure supply unit and the upper surface plate and supplying the polishing slurry from the pressure supply unit to the upper surface plate; a filter provided in the slurry supply pipe for removing foreign matter contained in the polishing slurry; Equipped with the upper surface plate has a plurality of slurry supply holes to which the slurry supply pipes are connected, the slurry supply pipe is formed of a water-repellent resin at least between the filter and the slurry supply hole, the slurry supply pipe has a main pipe connected to the pressure-feed supply unit and a plurality of branch pipes branched from the main pipe, In the double-side polishing apparatus, each of the branch pipes is further branched into two or more stages.

2. 2. The double-side polishing apparatus according to claim 1, wherein the water-repellent resin is formed between the pressure-feed supply portion of the slurry supply pipe and the filter.

3. 3. The double-side polishing apparatus according to claim 1, wherein the water-repellent resin is a fluorine-based resin or a silicone-based resin.

4. 4. The double-side polishing apparatus according to claim 3, wherein the fluorine-based resin contains at least one of polytetrafluoroethylene (PTFE) and tetraethylene-perfluoroalkoxyethylene copolymer (PFA).

5. 5. The double-side polishing machine according to claim 1, wherein the filter is provided in each of the branch pipes at the final stage connected to the slurry supply holes.

6. each of the plurality of branch pipes has the same inner diameter from the main pipe to the slurry supply hole; 6. The double-side polishing machine according to claim 1, wherein the lengths of the flow paths for the polishing slurry flowing through the branch pipes from the main pipe to each of the slurry supply holes are the same.

7. 7. A double-side polishing apparatus according to claim 1, wherein the plurality of slurry supply holes are arranged on the upper surface plate symmetrically with respect to a central axis of the upper surface plate when viewed from above.

8. The pore size of the filter is set to be equal to or smaller than the average particle size D of the polishing slurry. ５０ 8. The double-side polishing machine according to claim 1, wherein the polishing force is 5 to 50 times greater than the polishing force.

9. A method for manufacturing a glass substrate, comprising polishing a glass substrate using the double-side polishing apparatus according to any one of claims 1 to 8.

10. A method for manufacturing a glass substrate for a mask blank, which comprises polishing a glass substrate using a double-sided polishing apparatus described in any one of claims 1 to 8.

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