Method for producing glass substrate

Abstract

The present invention provides a technology which is capable of shortening the etching time while maintaining straightness of a through hole. This method for producing a glass substrate (10) further comprises, in cases where a first etching liquid is supplied only to a first main surface (11) among the first main surface (11) and a second main surface (12), polishing the first main surface (11) after forming a modification part (13) and before forming a through hole (15). This method further comprises, in cases where the first etching liquid is supplied only to the second main surface (12) among the first main surface (11) and the second main surface (12), polishing the second main surface (12) after forming the modification part (13) and before forming the through hole (15). This method further comprises, in cases where the first etching liquid is supplied to both the first main surface (11) and the second main surface (12), polishing at least one of the first main surface (11) and the second main surface (12) after forming the modification part (13) and before forming the through hole (15).

Description

Glass substrate manufacturing method

[0001] The present disclosure relates to a method for manufacturing a glass substrate.

[0002] In recent years, progress has been made in the development of stacked semiconductor devices known as 2.5D devices and 3D devices, which mount and interconnect multiple semiconductor chips using a substrate with through-hole electrodes called an interposer. Materials under consideration for the substrate include silicon, glass, organic materials, and ceramics. Among these, glass offers excellent flatness, thermal stability, and electrical insulation.

[0003] Patent Document 1 discloses a technique for forming a through hole in a glass substrate. The method for manufacturing a glass substrate includes a step of forming a modified portion in a position of the glass substrate where the through hole is to be formed by irradiating the glass substrate with a laser beam, and a step of forming the through hole by immersing the glass substrate in an etching solution after the step. The through hole is formed by selectively etching the modified portion. In Patent Document 1, the etching rate is increased after the through hole is formed.

[0004] JP 2023-82984 A

[0005] The etching solution etches the modified portion from the surface of the glass substrate. A bottomed hole is first formed in the surface of the glass substrate. By extending the bottomed hole in the depth direction, a through hole can be formed.

[0006] To improve the straightness of through holes, it is important that sludge (residue) does not easily accumulate inside the bottomed holes. Therefore, it is important that the glass components dissolved in the etching solution can be easily discharged from the inside to the outside of the bottomed holes.

[0007] If the etching rate of the unmodified portion of the glass substrate is slow, the glass component dissolved in the etching solution is likely to be expelled from the inside of the bottomed hole to the outside. Therefore, in order to improve the straightness of the through hole, it is important that the etching rate of the unmodified portion of the glass substrate is slow.

[0008] The degree of modification of the modified portion near the surface of the glass substrate is lower than that of the interior of the glass substrate, and if an attempt is made to remove the less modified portion using an etching solution with a slow etching rate, the etching time will be long.

[0009] An embodiment of the present disclosure provides a technique that can shorten the etching time while maintaining the straightness of the through-holes.

[0010] A method for manufacturing a glass substrate according to an embodiment of the present disclosure includes: preparing a glass substrate having a first main surface and a second main surface facing opposite to the first main surface; forming a modified portion of the glass substrate by irradiating the glass substrate with a laser beam at a position where a through hole is to be formed; and supplying a first etching liquid to at least one of the first main surface and the second main surface of the glass substrate to selectively etch the modified portion relative to an unmodified portion of the glass substrate excluding the modified portion, thereby forming the through hole. When the first etching liquid is supplied only to the first main surface of the first and second main surfaces, the method for manufacturing a glass substrate further includes polishing the first main surface after forming the modified portion and before forming the through hole. When the first etching liquid is supplied only to the second main surface of the first and second main surfaces, the method for manufacturing a glass substrate further includes polishing the second main surface after forming the modified portion and before forming the through hole. When the first etching liquid is supplied to both the first main surface and the second main surface, the method for manufacturing a glass substrate further includes polishing at least one of the first main surface and the second main surface after forming the modified portion and before forming the through hole.

[0011] A method for manufacturing a glass substrate according to another embodiment of the present disclosure includes: preparing a glass substrate having a first main surface and a second main surface facing opposite to the first main surface; forming a modified portion of the glass substrate by irradiating the glass substrate with a laser beam at a position where a through hole is to be formed; and supplying a first etching liquid to at least one of the first main surface and the second main surface of the glass substrate, and selectively etching the modified portion relative to a non-modified portion of the glass substrate excluding the modified portion to form the through hole. When the first etching liquid is supplied only to the first main surface of the first and second main surfaces, the method for manufacturing a glass substrate further includes supplying a second etching liquid to the first main surface after forming the modified portion and before forming the through hole. When the first etching liquid is supplied only to the second main surface of the first and second main surfaces, the method for manufacturing a glass substrate further includes supplying a second etching liquid to the second main surface after forming the modified portion and before forming the through hole. The method for manufacturing a glass substrate further includes, when the first etching liquid is supplied to both the first main surface and the second main surface, supplying a second etching liquid to at least one of the first main surface and the second main surface after forming the modified portion and before forming the through hole, wherein an etching rate of the second etching liquid in the unmodified portion of the glass substrate is faster than an etching rate of the first etching liquid.

[0012] According to an embodiment of the present disclosure, the etching time can be reduced while maintaining the straightness of the through-holes.

[0013] FIG. 1 is a flowchart showing a method for manufacturing a glass substrate according to an embodiment. FIG. 2A is a cross-sectional view showing an example of step S102. FIG. 2B is a cross-sectional view showing an example of step S103. FIG. 2C is a cross-sectional view showing an example of step S104. FIG. 3 is a flowchart showing a method for manufacturing a glass substrate according to a modified example. FIG. 4A is a cross-sectional view showing an example of step S202. FIG. 4B is a cross-sectional view showing an example of step S203. FIG. 4C is a cross-sectional view showing an example of step S204.

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or similar components are denoted by the same reference numerals, and their description may be omitted. In the specification, the symbol "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. The range of values ​​includes the range rounded up or down.

[0015] A method for manufacturing a glass substrate according to one embodiment will be described with reference to Figures 1, 2A, 2B, and 2C. The method for manufacturing a glass substrate includes, for example, steps S101 to S104 as shown in Figure 1. Note that the method for manufacturing a glass substrate may include other steps in addition to steps S101 to S104.

[0016] Step S101 includes preparing a glass substrate 10. The glass substrate 10 has a first main surface 11 and a second main surface 12 facing opposite to the first main surface 11. The material of the glass used for the glass substrate 10 is not particularly limited, but examples thereof include soda-lime glass, aluminosilicate glass, alkali-free glass, quartz, sapphire glass, and crystallized glass. The glass may or may not contain a coloring component such as Ti or Cu, but preferably does not contain a coloring component.

[0017] Before forming the modified portion (step S102), the thickness of the glass substrate 10 is not particularly limited, but is, for example, 0.2 mm to 2.0 mm. To maintain the strength or dielectric properties of the semiconductor package, the thickness of the glass substrate 10 is preferably 0.5 mm or more, more preferably 0.8 mm or more. Considering the difficulty of laser processing, the thickness of the glass substrate 10 is preferably 1.8 mm or less.

[0018] Step S102 involves forming a modified region 13 by irradiating the glass substrate 10 with a laser beam at a position where a through hole is to be formed (see FIG. 2A ). The modified region 13 is a portion where the structure of the glass has been changed by irradiating the laser beam. The modified region 13 is formed linearly from the first main surface 11 to the second main surface 12 of the glass substrate 10. Although not shown, a plurality of modified regions 13 may be provided.

[0019] The laser beam preferably has high transmittance through the glass substrate 10. The laser beam may be transmitted from the first main surface 11 to the second main surface 12, or from the second main surface 12 to the first main surface 11. The wavelength of the laser beam is preferably 300 nm to 1100 nm.

[0020] The pulse width of the laser beam is preferably 1 nsec or less, more preferably 500 psec or less, and even more preferably 100 psec or less, to easily form the modified regions 13. On the other hand, the pulse width of the laser beam is preferably 1 psec or more.

[0021] The laser beam is preferably focused by a focusing lens to have a linear focused region (focal line) extending from the first main surface 11 to the second main surface 12 of the glass substrate 10. The optical system that produces such a focal line preferably includes a lens having spherical aberration or an axicon lens.

[0022] Step S103 includes polishing the glass substrate 10 (see FIG. 2B ). The polishing target may be only the first main surface 11 or only the second main surface 12, but preferably both the first main surface 11 and the second main surface 12. The first main surface 11 and the second main surface 12 may be polished simultaneously using a double-sided polisher, or may be polished sequentially using a single-sided polisher. In the latter case, it does not matter which of the first main surface 11 and the second main surface 12 is polished first. The amount of polishing of the first main surface 11 and the amount of polishing of the second main surface 12 may be the same or different.

[0023] In step S103, the glass substrate 10 is polished while supplying a polishing slurry between the polishing pad and the glass substrate 10. The polishing is performed using, for example, loose abrasive grains. Examples of the polishing pad include a urethane-based polishing pad, a nonwoven fabric-based polishing pad, and a suede-based polishing pad. The polishing slurry 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, or silicon carbide particles. The dispersion medium is, for example, water or an organic solvent. The first main surface 11 and the second main surface 12 may be polished multiple times using abrasive grains of different materials or particle sizes. Furthermore, the polishing is not limited to polishing using loose abrasive grains, and may also be polishing using fixed abrasive grains, and is not particularly limited.

[0024] Step S104 includes supplying a first etching liquid to the glass substrate 10 and selectively etching the modified portion 13 relative to the non-modified portion 14 of the glass substrate 10 to form through-holes 15 (see FIG. 2C ). The non-modified portion 14 refers to the portion of the glass substrate 10 excluding the modified portion 13. The first etching liquid may be supplied only to the first main surface 11 or only to the second main surface 12, but is preferably supplied to both the first main surface 11 and the second main surface 12. Although not shown, a plurality of through-holes 15 may be provided.

[0025] The first etching liquid selectively etches the modified portion 13 of the glass substrate 10, forming a bottomed hole in at least one of the first main surface 11 and the second main surface 12 of the glass substrate 10 (preferably both the first main surface 11 and the second main surface 12). Thereafter, the first etching liquid further selectively etches the modified portion 13 of the glass substrate 10, extending the bottomed hole in the depth direction. As a result, a through hole 15 can be formed.

[0026] Supplying the first etching liquid to the glass substrate 10 includes immersing the glass substrate 10 in the first etching liquid or spraying the first etching liquid onto the glass substrate 10 .

[0027] The first etching solution is not particularly limited, but may be, for example, an aqueous solution containing hydrofluoric acid. The first etching solution may contain only hydrofluoric acid as an acid, or may contain at least one of hydrochloric acid and nitric acid in addition to hydrofluoric acid. The first etching solution may contain at least one of hydrochloric acid and nitric acid in addition to hydrofluoric acid, from the viewpoint of dissolving salts generated during etching and suppressing the phenomenon of sludge (residue) accumulating inside the bottomed holes.

[0028] From the viewpoint of ensuring sufficient etching, the concentration of hydrogen fluoride in the first etching solution is preferably 0.1 wt % or more relative to the entire first etching solution, while the concentration of hydrogen fluoride is preferably 5.0 wt % or less, more preferably 10 wt % or less, relative to the entire first etching solution.

[0029] When the first etching solution contains hydrochloric acid in addition to hydrofluoric acid, the concentration of hydrogen chloride is preferably 0.5 wt % or more, more preferably 1 wt % or more, relative to the entire first etching solution, from the viewpoint of significantly exhibiting the effect of dissolving salts. On the other hand, from the viewpoint of easily maintaining the speed of removing the modified portion 13 by hydrofluoric acid, the concentration of hydrogen chloride is preferably 30 wt % or less, more preferably 15 wt % or less, relative to the entire first etching solution.

[0030] When the first etching solution contains nitric acid in addition to hydrofluoric acid, the concentration of nitric acid is preferably 0.5 wt % or more, more preferably 1 wt % or more, based on the entire first etching solution, from the viewpoint of significantly exhibiting the effect of dissolving salts. On the other hand, the concentration of nitric acid is preferably 35 wt % or less, more preferably 15 wt % or less, based on the entire first etching solution, from the viewpoint of easily maintaining the speed of removing the modified portion by hydrofluoric acid.

[0031] The first etching solution may be an aqueous solution containing an alkali. The alkali in the first etching solution may include, for example, NaOH, KOH, LiOH, or TMAH (tetramethylammonium hydroxide). The first etching solution may also include, as a chelating agent, EDTA (ethylenediaminetetraacetic acid), HEDP (1-hydroxyethane-1,1-diphosphonic acid), NTA (nitrilotriacetic acid), or DTPA (diethylenetriaminepentaacetic acid). However, the present invention is not limited to these.

[0032] To improve the straightness of the through-holes 15, it is important to slow down the etching rate of the unmodified portions 14 by the first etching liquid. This is because the glass components dissolved in the first etching liquid are easily discharged from the inside of the bottomed holes to the outside, and sludge (residue) is less likely to accumulate inside the bottomed holes.

[0033] The straightness of the through holes 15 can be evaluated by the ratio (Dmin / D1) of Dmin to D1. D1 is the opening diameter of the through holes 15 in the first main surface 11. Dmin is the minimum diameter of the through holes 15. The ratio (Dmin / D1) is preferably 0.40 or more. The larger the ratio (Dmin / D1), the more preferable it is. In FIG. 2C , D2 is the opening diameter of the through holes 15 in the second main surface 12. When the first etching liquid is supplied simultaneously to both the first main surface 11 and the second main surface 12, D1 and D2 are approximately the same.

[0034] The opening diameters D1 and D2 are preferably 10 μm to 300 μm, more preferably 20 μm to 250 μm, and even more preferably 50 μm to 200 μm. The length of the through-hole 15, in other words, the thickness of the glass substrate 10 after step S104, is, for example, 0.2 mm to 2.0 mm. To maintain the strength or dielectric properties of the semiconductor package, the thickness of the glass substrate 10 is preferably 0.5 mm or more, more preferably 0.8 mm or more. Considering the difficulty of laser processing, the thickness of the glass substrate 10 is preferably 1.8 mm or less.

[0035] As described above, in order to improve the straightness of the through-holes 15, it is important to slow down the etching rate of the unmodified portions 14 of the glass substrate 10. The etching rate of the unmodified portions 14 is preferably 0.01 μm / min or more and less than 1.00 μm / min. If the etching rate of the unmodified portions 14 is 0.01 μm / min or more, etching of the modified portions 13 progresses easily. If the etching rate of the unmodified portions 14 is less than 1.00 μm / min, the straightness of the through-holes 15 is good.

[0036] The etching rate of the unmodified portion 14 is preferably less than 1.00 μm / min, more preferably 0.50 μm / min or less, and even more preferably 0.20 μm / min or less, from the viewpoint of improving the straightness of the through-hole 15. Moreover, the etching rate of the unmodified portion 14 is preferably 0.01 μm / min or more, more preferably 0.02 μm / min or more, and even more preferably 0.03 μm / min or more, from the viewpoint of shortening the etching time.

[0037] Incidentally, the first etching liquid etches the modified portion 13 from at least one of the first main surface 11 and the second main surface 12 of the glass substrate 10 (preferably both the first main surface 11 and the second main surface 12) in order to form the through-hole 15. The degree of modification of the modified portion 13 is lower near the surface of the glass substrate 10 (both the first main surface 11 and the second main surface 12) than in the interior of the glass substrate 10. If an attempt is made to remove the portion with a lower degree of modification using the first etching liquid, which has a slow etching rate, the etching time for the first etching liquid will be longer.

[0038] Therefore, in this embodiment, polishing of the glass substrate 10 (step S103) is performed after the formation of the modified portion 13 (step S102) and before the formation of the through-hole 15 (step S104). By polishing, the portions with a low degree of modification can be removed in advance. Therefore, the etching time of the first etching solution can be shortened while maintaining the straightness of the through-hole 15.

[0039] If the first etching liquid is supplied only to the first main surface 11 of the first main surface 11 and the second main surface 12 in step S104, the first main surface 11 is polished in step S103. If the first etching liquid is supplied only to the second main surface 12 of the first main surface 11 and the second main surface 12 in step S104, the second main surface 12 is polished in step S103. If the first etching liquid is supplied to both the first main surface 11 and the second main surface 12 in step S104, at least one of the first main surface 11 and the second main surface 12 is polished in step S103.

[0040] From the viewpoint of shortening the etching time, the amount A1 of polishing of the first main surface 11 is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, and particularly preferably 3.0 μm or more. From the viewpoint of shortening the polishing time, the amount A1 of polishing of the first main surface 11 is preferably 300 μm or less, more preferably 100 μm or less, and particularly preferably 20 μm or less.

[0041] Similarly, from the viewpoint of shortening the etching time, the amount A2 of polishing of the second main surface 12 is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, and particularly preferably 3.0 μm or more. Also, from the viewpoint of shortening the polishing time, the amount A2 of polishing of the second main surface 12 is preferably 300 μm or less, more preferably 100 μm or less, and particularly preferably 20 μm or less.

[0042] Next, a method for manufacturing a glass substrate according to a modified example will be described with reference to Figures 3, 4A, 4B, and 4C. The method for manufacturing a glass substrate includes, for example, steps S201 to S204 as shown in Figure 3. Steps S201, S202, and S204 are performed in the same manner as steps S101, S102, and S104 described above, and therefore detailed description thereof will be omitted. Note that the method for manufacturing a glass substrate may include other steps in addition to steps S201 to S204.

[0043] Step S203 includes supplying a second etching liquid to the glass substrate 10 after the formation of the modified portion 13 (step S202) and before the formation of the through-hole 15 (step S204) (see FIG. 4B ). The second etching liquid may be supplied only to the first main surface 11 or only to the second main surface 12, but is preferably supplied to both the first main surface 11 and the second main surface 12.

[0044] If the first etching liquid is supplied only to the first main surface 11 of the first main surface 11 and the second main surface 12 in step S204, the second etching liquid is supplied to the first main surface 11 in step S203. Also, if the first etching liquid is supplied only to the second main surface 12 of the first main surface 11 and the second main surface 12 in step S204, the second etching liquid is supplied to the second main surface 12 in step S203. Furthermore, if the first etching liquid is supplied to both the first main surface 11 and the second main surface 12 in step S204, the second etching liquid is supplied to at least one of the first main surface 11 and the second main surface 12 in step S203.

[0045] Supplying the second etching liquid to the glass substrate 10 includes immersing the glass substrate 10 in the second etching liquid or spraying the second etching liquid onto the glass substrate 10 .

[0046] In the unmodified portion 14 of the glass substrate 10, the etching rate V2 of the second etching liquid is faster than the etching rate V1 of the first etching liquid. By supplying the second etching liquid, the less modified portion can be removed in advance. Therefore, the etching time with the first etching liquid can be shortened while maintaining the straightness of the through hole 15.

[0047] The second etching liquid is not particularly limited as long as it has a faster etching rate for the unmodified portion 14 than the first etching liquid. The etching rate can be controlled by the type and concentration of the chemical (e.g., acid or alkali), the temperature, etc. When the type of chemical is the same, the higher the concentration of the chemical and the higher the temperature, the faster the etching rate.

[0048] From the viewpoint of shortening the etching time with the first etching liquid, the etching amount B1 of the first main surface 11 by the second etching liquid is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, and particularly preferably 3.0 μm or more. Also, from the viewpoint of shortening the etching time with the second etching liquid, the etching amount B1 is preferably 300 μm or less, more preferably 100 μm or less, and particularly preferably 20 μm or less.

[0049] Similarly, from the viewpoint of shortening the etching time with the first etching liquid, the etching amount B2 of the second main surface 12 by the second etching liquid is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, and particularly preferably 3.0 μm or more. Also, from the viewpoint of shortening the etching time with the second etching liquid, the etching amount B2 is preferably 300 μm or less, more preferably 100 μm or less, and particularly preferably 20 μm or less.

[0050] The experimental data will be explained below. Example 1 below is a comparative example, and Examples 2 to 10 are working examples.

[0051] In Example 1, steps S101, S102, and S104 shown in FIG. 1 were performed, excluding step S103. In step S101, a glass substrate made of alkali-free glass was prepared. In step S102, a laser beam having a laser wavelength of 532 nm, a pulse width of 10 ps, ​​and an output of 30 W was irradiated to form a modified portion. In step S104, an aqueous solution containing 10 mass% NaOH and 7 mass% EDTA (V1: 0.07 μm / min, temperature: 90° C.) was used as the first etching solution. In step S104, the entire glass substrate was immersed in the aqueous solution.

[0052] In Examples 2 to 7, all of steps S101 to S104 shown in FIG. 1 were performed. In step S103, both the first and second principal surfaces were polished sequentially to the same degree using an Engis single-sided polisher. The polishing pad was a suede pad, the abrasive was cerium oxide, and the polishing rate was 0.14 μm / min. In Examples 2 to 7, steps S101, S102, and S104 were performed in the same manner as in Example 1.

[0053] The experimental results of Examples 1 to 7 are shown in Table 1. In Table 1, A1 indicates the amount of polishing of the first main surface, D1 indicates the opening diameter of the through hole in the first main surface, Dmin indicates the minimum diameter of the through hole, T indicates the etching time of the first etching solution, and ΔT indicates the time by which T in Examples 2 to 7 is reduced relative to T in Example 1. In Table 1, the plate thickness is a value measured after step S104.

[0054]

[0055] As shown in Table 1, in Examples 2 to 7, unlike Example 1, step S103 was performed, so that the etching time T of the first etching liquid could be shortened while maintaining the straightness of the through-holes.

[0056] In Examples 8 to 10, all of steps S201 to S204 shown in Fig. 3 were performed. In step S203, the second etching solution contained 2 mass % of HF and NO ３ An aqueous solution (V2: 1.00 μm / min, temperature: 30° C.) containing 10 mass % of the compound was used. In step S203, the entire glass substrate was immersed in the aqueous solution, and the first and second main surfaces were etched to the same extent. Note that steps S201, S202, and S204 in Examples 8 to 10 were performed in the same manner as steps S101, S102, and S104 in Example 1.

[0057] The experimental results of Example 1 and Examples 8 to 10 are shown in Table 2. In Table 2, B1 indicates the amount of etching of the first main surface by the second etching liquid, D1 indicates the opening diameter of the through hole in the first main surface, Dmin indicates the minimum diameter of the through hole, T indicates the etching time of the first etching liquid, and ΔT indicates the time by which T in Examples 8 to 10 is reduced relative to T in Example 1. In Table 2, the plate thickness is a value measured after step S204.

[0058]

[0059] As shown in Table 2, in Examples 8 to 10, unlike Example 1, step S203 was performed, so that the etching time T of the first etching liquid could be shortened while maintaining the straightness of the through-holes.

[0060] The glass substrate manufacturing method according to the present disclosure has been described above, but the present disclosure is not limited to the above-described embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These changes also naturally fall within the technical scope of the present disclosure.

[0061] This application claims priority based on Japanese Patent Application No. 2024-011698, filed January 30, 2024, the disclosure of which is incorporated herein in its entirety by reference.

[0062] REFERENCE SIGNS LIST 10 Glass substrate 11 First main surface 12 Second main surface 13 Modified portion 14 Non-modified portion 15 Through-hole

Claims

1. A method for manufacturing a glass substrate, comprising: preparing a glass substrate having a first main surface and a second main surface facing opposite to the first main surface; forming a modified portion of the glass substrate by irradiating it with a laser beam at a position where a through hole is to be formed; supplying a first etching liquid to at least one of the first main surface and the second main surface of the glass substrate, and selectively etching the modified portion relative to an unmodified portion of the glass substrate excluding the modified portion, thereby forming the through hole; when the first etching liquid is supplied only to the first main surface of the first and second main surfaces, the method further comprises polishing the first main surface after forming the modified portion and before forming the through hole; when the first etching liquid is supplied only to the second main surface of the first and second main surfaces, the method further comprises polishing the second main surface after forming the modified portion and before forming the through hole; When the first etching liquid is supplied to both the first main surface and the second main surface, the method for manufacturing a glass substrate further comprises polishing at least one of the first main surface and the second main surface after forming the modified portion and before forming the through hole.

2. The method for manufacturing a glass substrate according to claim 1, wherein the polishing amount of at least one of the first main surface and the second main surface is 0.1 μm to 300 μm.

3. A method for manufacturing a glass substrate according to claim 1 or 2, further comprising polishing both the first main surface and the second main surface of the glass substrate after forming the modified portion and before forming the through hole.

4. The method for manufacturing a glass substrate according to claim 3, wherein forming the through-holes includes supplying the first etching liquid to both the first main surface and the second main surface.

5. A method for manufacturing a glass substrate, the method comprising: preparing a glass substrate having a first main surface and a second main surface facing opposite to the first main surface; forming a modified portion of the glass substrate by irradiating it with a laser beam at a position where a through hole is to be formed; supplying a first etching liquid to at least one of the first main surface and the second main surface of the glass substrate, and selectively etching the modified portion relative to a non-modified portion of the glass substrate excluding the modified portion, thereby forming the through hole; when the first etching liquid is supplied only to the first main surface of the first and second main surfaces, the method further comprises supplying a second etching liquid to the first main surface after forming the modified portion and before forming the through hole; when the first etching liquid is supplied only to the second main surface of the first and second main surfaces, the method further comprises supplying a second etching liquid to the second main surface after forming the modified portion and before forming the through hole; When the first etching liquid is supplied to both the first main surface and the second main surface, the method further comprises supplying a second etching liquid to at least one of the first main surface and the second main surface after forming the modified portion and before forming the through hole, wherein an etching rate of the second etching liquid is faster than an etching rate of the first etching liquid in the unmodified portion of the glass substrate.

6. The method for manufacturing a glass substrate according to claim 5, wherein the etching amount of at least one of the first main surface and the second main surface by the second etching solution is 0.1 μm to 300 μm.

7. A method for manufacturing a glass substrate according to claim 5 or 6, further comprising supplying the second etching liquid to both the first main surface and the second main surface of the glass substrate after forming the modified portion and before forming the through hole.

8. The method for manufacturing a glass substrate according to claim 7, wherein forming the through-holes includes supplying the first etching liquid to both the first main surface and the second main surface.

9. The method for manufacturing a glass substrate according to claim 1, 2, 5 or 6, wherein the etching rate of the first etching solution in the unmodified portion of the glass substrate is 0.01 μm / min or more and less than 1.00 μm / min.

10. The method for manufacturing a glass substrate according to claim 1, 2, 5 or 6, wherein the thickness of the glass substrate after the through holes are formed is 0.2 mm to 2.0 mm.

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