WO2022185557A1

WO2022185557A1 - Method for manufacturing fine uneven surface structure on glass substrate

Info

Publication number: WO2022185557A1
Application number: PCT/JP2021/024456
Authority: WO
Inventors: 健志谷邊; 和也山本
Original assignee: ナルックス株式会社
Priority date: 2021-03-05
Filing date: 2021-06-29
Publication date: 2022-09-09
Also published as: DE112021007205T5

Abstract

Provided is a manufacturing method whereby it becomes possible to manufacture a fine uneven surface structure having a desired shape on a glass substrate having a large surface area stably by a relative simple manufacturing process. A method for manufacturing a fine uneven surface structure having an average pitch of 30 nanometers to 5 micrometers on a glass substrate having a silicon dioxide content of 50% or more without the need to form a mask prior to etching is provided. In the method, in an ion etching device, ion etching with an argon gas is performed in such a state where a high-frequency power supply is connected to a first electrode, a second electrode is earthed, and the glass substrate having a silicon dioxide content of 50% or more is arranged so as to contact with the first electrode, and subsequently reactive ion etching with a trifluoromethane (CHF₃) gas or a mixed gas comprising trifluoromethane (CHF₃) and oxygen is performed in the same state.

Description

METHOD FOR MANUFACTURING MICROPROOF SURFACE STRUCTURE ON GLASS SUBSTRATE

The present invention relates to a method for manufacturing a fine uneven surface structure on a glass substrate.

An antireflection structure consisting of a fine uneven surface structure arranged at a small pitch (period) equal to or smaller than the wavelength of light on a glass substrate is used in optical elements. As a method for manufacturing such a fine uneven surface structure, a method of manufacturing a fine uneven surface structure by creating a pattern mask by electron beam writing and performing etching (Patent Document 1), creating a pattern mask by sputtering and performing etching. (Patent Document 2), and a method of distributing nanoparticles on the surface to manufacture a fine uneven surface structure (Patent Document 3).

However, the above conventional methods have the following drawbacks. The electron beam writing method takes a long time to process, and it is difficult to manufacture a fine concave-convex surface structure over a large area. In the sputtering method, it is difficult to control a mask for obtaining a desired fine uneven surface structure, and a high antireflection function cannot be obtained. The method using nanoparticles requires a lot of man-hours to form an intermediate layer between the glass and the nanoparticles, and the cost is high because expensive nanoparticles are used.

In addition, a method has been developed for manufacturing a fine uneven surface structure on a glass substrate by reactive ion etching (Patent Document 4). This method utilizes as an etching mask a polymer that is produced by a chemical reaction between the glass and an etching gas and is randomly placed on the glass surface. However, since this method uses a chemical reaction to generate an etching mask, the type and surface condition of the glass easily affect the shape of the fine uneven surface structure, and the fine uneven surface structure of the desired shape can be stably formed. Difficult to manufacture.

Thus, a manufacturing method has not been developed that can stably manufacture a fine uneven surface structure of a desired shape on a large-area glass substrate by a relatively simple manufacturing process.

Therefore, there is a need for a manufacturing method that can stably manufacture a fine uneven surface structure of a desired shape on a large-area glass substrate by a relatively simple manufacturing process.

JP 2001-272505 JP 2019-008082 JP 2006-259711 (Patent 4520418) US8187481B1

A technical problem of the present invention is to provide a manufacturing method capable of stably manufacturing a fine uneven surface structure of a desired shape on a glass substrate having a large area by a relatively simple manufacturing process.

A method for manufacturing a fine uneven surface structure with an average pitch of 30 nanometers to 5 micrometers on a glass substrate having a silicon dioxide content of 50% or more without forming a mask prior to etching according to the present invention is an ion etching apparatus. Ion etching with argon gas in a state in which a high-frequency power supply is connected to the first electrode, the second electrode is grounded, and the glass substrate having a silicon dioxide content of 50% or more is placed in contact with the first electrode. followed by reactive ion etching with trifluoromethane (CHF ₃ ) gas or a mixed gas of trifluoromethane (CHF ₃ ) and oxygen under the same conditions.

In the manufacturing method according to the present invention, since ion etching with argon gas is performed before reactive ion etching is performed, the atomic arrangement on the surface of the glass substrate with a silicon dioxide content of 50% or more changes, and the silicon dioxide content changes. The surface of a glass substrate with a content of 50% or more is likely to have a fine uneven surface structure formed by reactive ion etching regardless of its initial state. Therefore, by reactive ion etching, it is possible to stably produce a fine uneven surface structure of a desired shape on a large area glass substrate having a silicon dioxide content of 50% or more. The "same state" means "a state in which a high-frequency power supply is connected to the first electrode, the second electrode is grounded, and the glass substrate having a silicon dioxide content of 50% or more is placed in contact with the first electrode." means

In the manufacturing method of the first embodiment of the present invention, the flow ratio of oxygen gas to the mixed gas is in the range of 0 to 50%.

According to the present embodiment, by supplying oxygen gas at a flow rate ratio within the above range, a polymer generated from trifluoromethane (CHF ₃ ) gas and having a silicon dioxide content of 50% or more adheres to the surface of a glass substrate. can be removed and the antireflection function can be improved.

In the manufacturing method of the second embodiment of the present invention, after performing reactive ion etching, the first electrode is grounded, the second electrode is connected to the high-frequency power supply, and the silicon dioxide content is 50%. % or more of the glass substrate is placed in contact with the first electrode, radical etching is performed with trifluoromethane (CHF ₃ ) gas or oxygen gas.

According to this embodiment, the antireflection function is further improved by radical etching. Radical etching with trifluoromethane (CHF ₃ ) gas improves water repellency, and radical etching with oxygen gas improves hydrophilicity.

In the manufacturing method of the third embodiment of the present invention, wet coating is performed on the glass substrate having a silicon dioxide content of 50% or more after performing reactive ion etching.

According to this embodiment, the wet coating further improves the antireflection function.

It is a figure which shows the structure of the etching apparatus used for the manufacturing method of the fine grooving|roughness surface structure by one Embodiment of this invention. 1 is a flowchart showing a method for manufacturing a fine uneven surface structure according to one embodiment of the present invention. It is a figure for demonstrating the manufacturing method of the fine grooving|roughness surface structure of one Embodiment of this invention. It is a figure for demonstrating the manufacturing method of the fine grooving|roughness surface structure of other embodiment of this invention. It is a figure for demonstrating the manufacturing method of the fine grooving|roughness surface structure of other embodiment of this invention. It is a figure for demonstrating the change of the shape of the fine grooving|roughness surface structure formed in the quartz glass substrate by 3rd etching. FIG. 4 is a diagram showing the transmittance of a quartz glass substrate having a fine uneven surface structure formed thereon; FIG. 4 is a diagram showing the reflectance of a quartz glass substrate having a fine uneven surface structure formed thereon; It is a photograph comparing the reflection by the quartz glass substrate on which the fine unevenness surface structure is formed and the reflection by the silica glass substrate on which the fine unevenness surface structure is not formed. 4 is a photograph showing water droplets on the surface of a quartz glass substrate on which a fine uneven surface structure is not formed. FIG. 10 is a photograph showing water droplets on the surface of a quartz glass substrate on which a fine concavo-convex surface structure is formed, which is etched with trifluoromethane (CHF ₃ ) gas as a third etching. 10 is a photograph showing water droplets on the surface of a quartz glass substrate having a fine uneven surface structure formed thereon, which is subjected to etching with oxygen gas as the third etching. It is a flowchart which shows the manufacturing method of the fine grooving|roughness surface structure of other embodiment of this invention. It is a figure for demonstrating the manufacturing method of the fine grooving|roughness surface structure of other embodiment of this invention. FIG. 10 is a diagram for explaining a change in the shape of a fine uneven surface structure formed on a quartz glass substrate due to wet coating; FIG. 3 shows the transmittance of a quartz glass substrate with a wet-coated micro-relief surface structure; FIG. 4 shows the reflectance of a quartz glass substrate with a wet-coated micro-relief surface structure; FIG. 4 shows the reflectance of a quartz glass substrate without a wet-coated micro-relief surface structure; 4 is a photograph showing water droplets on the surface of a quartz glass substrate on which a fine uneven surface structure is not formed. 1 is a photograph showing water droplets on the surface of a quartz glass substrate having a micro-relief surface structure that is not wet-coated. 1 is a photograph showing water droplets on the surface of a quartz glass substrate with a wet-coated micro-relief surface structure. FIG. 4 is a diagram showing the transmittance of a quartz glass substrate having a fine uneven surface structure formed thereon; FIG. 4 is a diagram showing the transmittance of a borosilicate glass substrate on which a fine uneven surface structure is formed, in the deep ultraviolet wavelength range. FIG. 4 is a diagram showing transmittance in the visible light region of a borosilicate glass substrate on which a fine uneven surface structure is formed. BRIEF DESCRIPTION OF THE DRAWINGS It is a flowchart which shows collectively the manufacturing method of the fine grooving|roughness surface structure of this invention.

FIG. 1 is a diagram showing the configuration of an etching apparatus 100 used in a method for manufacturing a fine uneven surface structure according to one embodiment of the present invention. The etching apparatus 100 has a reaction chamber 101 . A gas is supplied from a gas supply port 111 to the evacuated reaction chamber 101 . The amount of gas supplied can be adjusted. Furthermore, a gas exhaust port 113 is provided in the reaction chamber 101, and a valve (not shown) is attached to the gas exhaust port 113. As shown in FIG. By operating the valve, the gas pressure in the reaction chamber 101 can be adjusted to a desired pressure value. The reaction chamber 101 is provided with an upper electrode 103 which is normally grounded and a lower electrode 105 which is normally connected to a high frequency power source 107. A high frequency voltage is applied between the electrodes by the high frequency power source 107 to excite the gas in the reaction chamber 101. Plasma can be generated from A target to be processed is placed on the lower electrode 105 . Lower electrode 105 can be cooled to a desired temperature by cooling device 109 . Cooling device 109 uses, for example, a water-cooled chiller for cooling. The reason for cooling the lower electrode 105 is to control the etching reaction by setting the temperature of the substrate 101 to a desired temperature.

FIG. 2 is a flowchart showing a method for manufacturing a fine uneven surface structure according to one embodiment of the present invention.

FIG. 3 is a diagram for explaining a method for manufacturing a fine uneven surface structure according to one embodiment of the present invention. In the following, the case of a quartz glass substrate will be described as an example of a glass substrate having a silicon dioxide content of 50% or more.

In step S1010 in FIG. 2, the quartz glass substrate 200 is placed on the lower electrode 105, the upper electrode 103 is grounded, the high frequency power supply 107 is connected to the lower electrode 105, argon gas is supplied to the etching apparatus 100, and the lower electrode is A high frequency voltage is supplied to 105 by a high frequency power supply 107 . The argon gas is turned into plasma by the high-frequency voltage, generating argon ions. The argon cations are attracted by electrons to the negatively charged lower electrode 105 and collide with the surface of the quartz glass substrate 200 to proceed with physical etching of the surface. The etching of this step is also called the first etching.

As shown in FIG. 3, the atomic arrangement on the surface of the quartz glass substrate 200 is changed by the first etching. structures are easier to form. That is, the first etching changes the state of the surface depending on the position, and the progress of the second etching, which will be described later, is made different depending on the position of the surface, so that a fine uneven surface structure is easily formed.

In step S1020 in FIG. 2, the quartz glass substrate 200 is placed on the lower electrode 105, the upper electrode 103 is grounded, the high frequency power supply 107 is connected to the lower electrode 105, and the etching apparatus 100 is supplied with trifluoromethane (CHF ₃ ) gas or A mixed gas of trifluoromethane (CHF ₃ ) and oxygen is supplied, and a high frequency voltage is supplied to the lower electrode 105 by a high frequency power source 107 . Trifluoromethane (CHF ₃ ) gas or oxygen gas is plasmatized by the high-frequency voltage to generate trifluoromethane (CHF ₃ ) cations or oxygen cations. Trifluoromethane (CHF ₃ ) cations or oxygen cations are attracted by electrons to the negatively charged lower electrode 105 and collide with the surface of the quartz glass substrate 200 to progress physical etching of the surface. Also, trifluoromethane (CHF ₃ ) ions or radicals react with silicon dioxide (SiO ₂ ), which is a component of quartz glass, to produce various reaction products such as silicon fluoride (SiF ₄ ) and oxygen (O ₂ ). be. Etching also progresses when these reaction products leave the surface of the substrate 200 . Oxygen gas is generated from trifluoromethane (CHF ₃ ) gas and removes polymers adhering to the surface of the quartz glass substrate 200 to improve the antireflection function. The oxygen gas flow rate is preferably in the range of 0 to 50 percent. The etching of this step is also called the second etching.

As shown in FIG. 3, a fine uneven surface structure is formed on the quartz glass substrate 200 by the second etching. Thus, according to the present invention, the first and second etchings can form a fine uneven surface structure without forming a mask prior to etching.

FIG. 4 is a diagram for explaining a method for manufacturing a fine uneven surface structure according to another embodiment of the present invention.

FIG. 5 is a diagram for explaining a method for manufacturing a fine uneven surface structure according to another embodiment of the present invention.

In step S2010 of FIG. 4, the first etching is performed as in step S1010 of FIG.

In step S2020 of FIG. 4, a second etching is performed as in step S1020 of FIG.

In step S2030 in FIG. 4, the quartz glass substrate 200 is placed on the lower electrode 105, the high frequency power supply 107 is connected to the upper electrode 103, and the lower electrode 105 is grounded. Trifluoromethane (CHF ₃ ) gas or oxygen gas is supplied to the etching apparatus 100 and a high frequency voltage is applied to the upper electrode 103 . In this step, trifluoromethane (CHF ₃ ) cations or oxygen cations are attracted to the upper electrode and do not contribute to physical etching of the surface of the quartz glass substrate 200 . In this step, as shown in FIG. 5, chemical etching proceeds due to the reaction between trifluoromethane (CHF ₃ ) radicals or oxygen radicals and the surface of the quartz glass substrate 200 . As used herein, a radical refers to a molecule with an overall charge of zero and an unpaired electron pair. The etching in this step is isotropic and gentle etching compared to the second etching. The etching of this step is also called third etching.

The shape of the fine uneven surface structure formed on the quartz glass substrate 200 is changed by the third etching. This change in shape will be described below.

FIG. 6 is a diagram for explaining the change in the shape of the fine unevenness surface structure formed on the quartz glass substrate due to the third etching. Since the third etching is more isotropic than the second etching, it is considered that the side surfaces of the projections of the fine unevenness surface structure are shaved and the shape of the projections approaches a conical shape. In general, antireflection performance improves when the shape of the projections of the fine uneven surface structure approaches a conical shape. Therefore, it is expected that the third etching will improve the antireflection function.

Table 1 shows processing conditions for the first to third etchings.

The frequency of the high frequency power supply 107 is 13.56 MHz. The temperatures shown in Table 1 are the temperatures of the lower electrode 105 controlled by the cooling device 109 .

In Table 1, ion etching means mainly physical etching by bombarding the target with ions, and radical etching means chemical etching by chemical reaction between radicals and the target surface.

The average pitch of the fine uneven surface structure formed on the quartz glass substrate is 120 nanometers, and the average depth is 280 nanometers.

In general, increasing at least one of power and processing time increases the average pitch and average depth of the fine uneven surface structure. By appropriately setting processing conditions, the average pitch of the fine uneven surface structure can be changed in the range of 30 nanometers to 5 micrometers, and the average depth can be changed in the range of 50 nanometers to 10 micrometers. The fine uneven surface structure thus obtained by the manufacturing method of the present invention has antireflection performance against light with a wavelength of 180 nanometers to 10 micrometers.

FIG. 7 is a diagram showing the transmittance of a quartz glass substrate on which a fine uneven surface structure is formed. The horizontal axis of FIG. 7 indicates the wavelength, and the vertical axis of FIG. 7 indicates the transmittance. The units on the horizontal axis are nanometers and the units on the vertical axis are percentages. In FIG. 7, the solid line indicated as "processed" indicates the transmittance of the quartz glass substrate on which the fine uneven surface structure is formed, and the broken line indicated as "unprocessed" indicates the quartz glass substrate without the fine uneven surface structure. The transmittance of the substrate is shown. According to FIG. 7, the transmission of the "processed" substrate is 5-7 percent higher than that of the "unprocessed" substrate over the entire wavelength range.

FIG. 8 is a diagram showing the reflectance of a quartz glass substrate on which a fine uneven surface structure is formed. The horizontal axis of FIG. 8 indicates the wavelength, and the vertical axis of FIG. 8 indicates the reflectance. The units on the horizontal axis are nanometers and the units on the vertical axis are percentages. In FIG. 8, the solid line indicated as "processing" indicates the reflectance of the quartz glass substrate on which the fine uneven surface structure is formed. The dashed line indicated as "unprocessed" indicates the reflectance of the quartz glass substrate on which the fine uneven surface structure is not formed. According to FIG. 8, the reflectance of the "processed" substrate is 2.5 to 3.5 percent lower than the reflectance of the "unprocessed" substrate over the entire wavelength range.

FIG. 9 is a photograph comparing the reflection by the quartz glass substrate on which the fine unevenness surface structure is formed and the reflection by the quartz glass substrate on which the fine unevenness surface structure is not formed. In FIG. 9, the quartz glass substrate on which the surface structure of fine unevenness is formed is described as "after processing", and the quartz glass substrate without the surface structure of fine unevenness is described as "before processing". Letters are not projected on the “after processing” board, but characters are clearly projected on the “before processing” board, confirming that the reflectance of the “after processing” board has decreased. can.

FIG. 10 is a photograph showing water droplets on the surface of a quartz glass substrate on which a fine uneven surface structure is not formed.

FIG. 11 is a photograph showing water droplets on the surface of a quartz glass substrate on which a fine uneven surface structure is formed, which is etched with trifluoromethane (CHF ₃ ) gas as the third etching.

FIG. 12 is a photograph showing water droplets on the surface of a quartz glass substrate on which a fine uneven surface structure was formed, which was etched with oxygen gas as the third etching.

The contact angles of water droplets in FIGS. 10-12 are 51.4 degrees, 141 degrees and 9.1 degrees, respectively. The contact angle is generally defined as ``the angle between the liquid surface and the solid surface where the free surface of the stationary liquid touches the solid wall (the angle inside the liquid)'' (Iwanami Rikagaku Jiten, 4th edition). be done. The larger the contact angle, the higher the water repellency and the lower the hydrophilicity.

10 to 12, etching with trifluoromethane (CHF ₃ ) gas as the third etching increases water repellency, and etching with oxygen gas as the third etching increases hydrophilicity. growing. Thus, the third etching can change the water repellency or hydrophilicity of the surface.

When etching with trifluoromethane (CHF ₃ ) gas is carried out as the third etching, only the chemical reaction by trifluoromethane (CHF ₃ ) radicals proceeds, and fluorinated hydrophobic groups grow on the surface of the fine uneven surface structure, resulting in water repellency. is expected to increase.

When etching with oxygen gas is performed as the third etching, oxygen radicals react with the products generated by the second etching on the surface of the fine uneven surface structure, and hydrophilic groups such as OH, CHO, and COOH are generated and hydrophilic. sex is likely to increase.

FIG. 13 is a flowchart showing a method for manufacturing a fine uneven surface structure according to another embodiment of the present invention.

FIG. 14 is a diagram for explaining a method for manufacturing a fine uneven surface structure according to another embodiment of the present invention.

In step S3010 of FIG. 13, the first etching is performed similarly to step S1010 of FIG.

In step S3020 of FIG. 13, a second etching is performed as in step S1020 of FIG.

In step S3030 of FIG. 13, the quartz glass substrate 200 is removed from the etching apparatus 100, and as shown in FIG. As such, wet coating is performed by immersing in SPRA-101) manufactured by Tokyo Ohka Kogyo Co., Ltd. Wet coating is a technique of applying a coating film by immersion in a liquid.

FIG. 15 is a diagram for explaining the change in the shape of the fine uneven surface structure formed on the surface of the quartz glass substrate due to wet coating. A coat film is formed on the surface of the fine unevenness surface structure by wet coating. As shown in FIG. 15, this film changes the shape of the projections of the fine uneven surface structure. As an example, the average pitch of the micro-relief surface structure is 120 nanometers as described above, and the thickness of the film is 10-20 nanometers. In addition, since the refractive index of the coating liquid, which is the material of the coating film, is a value between the refractive index of quartz and the refractive index of air, it is preferable as an intermediate layer between quartz and air from the viewpoint of antireflection performance.

FIG. 16 is a diagram showing the transmittance of a quartz glass substrate provided with a wet-coated fine uneven surface structure. The wet coating liquid is a water-repellent coating liquid (FG-5080F130-0.1 manufactured by Fluoro Technology). The horizontal axis of FIG. 16 indicates the wavelength, and the vertical axis of FIG. 16 indicates the transmittance. The units on the horizontal axis are nanometers and the units on the vertical axis are percentages. In FIG. 16 , the solid line labeled “after coating” indicates the transmittance of the quartz glass substrate with the wet-coated microrelief surface structure, and the dashed line labeled “before coating” indicates the transmittance of the microscopic surface structure not wet-coated. The transmittance of the quartz glass substrate provided with the uneven surface structure is shown, and the dotted line indicated as "unprocessed" shows the transmittance of the quartz glass substrate without the fine uneven surface structure. According to FIG. 16, the transmission of the "as coated" substrate is 5-6.5 percent higher than that of the "raw" substrate over the entire wavelength range. Also, in the 450-800 nanometer wavelength region, the transmittance of the "as-coated" substrate is higher than the transmittance of the "before-coated" substrate.

FIG. 17 is a diagram showing the reflectance of a quartz glass substrate provided with a wet-coated fine uneven surface structure. The horizontal axis of FIG. 17 indicates the wavelength, and the vertical axis of FIG. 17 indicates the reflectance. The units on the horizontal axis are nanometers and the units on the vertical axis are percentages. In FIG. 17 , the solid line labeled “after coating” indicates the reflectance of the wet-coated quartz glass substrate with the micro-relief surface structure, and the broken line labeled “before coating” indicates the micro-surface structure without wet coating. The reflectance of a quartz glass substrate with a textured surface structure is shown, and the dotted line labeled "unprocessed" shows the reflectance of a quartz glass substrate without a micro-textured surface structure. According to FIG. 17, the "as coated" reflectance is 2.5 to 3.5 percent lower than the "raw" reflectance over the entire wavelength range. Also, in the wavelength region of 450-800 nanometers, the reflectance of the "after-coated" substrate is lower than the reflectance of the "before-coated" substrate.

FIG. 18 is a diagram showing the reflectance of a wet-coated quartz glass substrate without a micro-roughened surface structure. The horizontal axis of FIG. 18 indicates the wavelength, and the vertical axis of FIG. 18 indicates the reflectance. The units on the horizontal axis are nanometers and the units on the vertical axis are percentages. In FIG. 18 , the dashed line labeled “with coating” indicates the reflectance of the wet-coated quartz glass substrate without the fine uneven surface structure, and the solid line labeled “without coating” indicates no wet coating. 10 shows the reflectance of a quartz glass substrate without a micro-roughened surface structure.

According to FIG. 18, the reflectance of the quartz glass substrate without the micro-roughness surface structure is not affected by the wet coating. Therefore, it was confirmed that the decrease in reflectance due to wet coating is a phenomenon peculiar to the fine uneven surface structure.

FIG. 19 is a photograph showing water droplets on the surface of a quartz glass substrate on which a fine uneven surface structure is not formed.

FIG. 20 is a photograph showing water droplets on the surface of a quartz glass substrate having a fine uneven surface structure that is not wet-coated.

FIG. 21 is a photograph showing water droplets on the surface of a quartz glass substrate having a wet-coated micro-relief surface structure.

According to FIGS. 19 to 21, the water repellency of the surface of the quartz glass substrate provided with the fine uneven surface structure is lower than the water repellency of the surface of the quartz glass substrate without the fine uneven surface structure. The water repellency of the surface of the quartz glass substrate provided with the wet-coated fine uneven surface structure is significantly improved compared to the water repellency of the surface of the quartz glass substrate without the fine uneven surface structure formed thereon.

The above manufacturing method forms a fine uneven surface structure that improves the antireflection function of visible light. A manufacturing method for forming a fine concave-convex surface structure that improves the anti-reflection function of deep ultraviolet light will be described below.

The manufacturing method of the fine uneven surface structure that improves the antireflection function of deep ultraviolet light is the same as the manufacturing method shown in the flow chart of FIG. However, it is necessary to determine processing conditions so as to reduce the average pitch and average depth of the fine uneven surface structure corresponding to the wavelength of the deep ultraviolet.

Table 2 is a table showing processing conditions for the first and second etchings for forming a fine uneven surface structure that improves the antireflection function of deep ultraviolet light.

The processing time for the second etching is shorter than the processing time for visible light shown in Table 1 so as to reduce the average pitch and average depth of the fine uneven surface structure. The average pitch of the fine uneven surface structure in the case of deep ultraviolet light is 65 nanometers, and the average depth is 200 nanometers.

FIG. 22 is a diagram showing the transmittance of a quartz glass substrate on which a fine uneven surface structure is formed. The horizontal axis of FIG. 22 indicates the wavelength, and the vertical axis of FIG. 22 indicates the transmittance. The units on the horizontal axis are nanometers and the units on the vertical axis are percentages. In FIG. 22, the solid line indicated as "processed" indicates the transmittance of the quartz glass substrate on which the fine uneven surface structure is formed, and the broken line indicated as "unprocessed" indicates the quartz glass substrate on which the fine uneven surface structure is not formed. The transmittance of the substrate is shown. According to FIG. 22, the transmittance of the "processed" substrate is 5 to 6.5 percent higher than that of the "unprocessed" substrate over the entire wavelength range.

The case where the glass substrate is a quartz glass substrate has been described above. It is particularly effective in the case of a quartz glass substrate made of silicon dioxide to change the state of the surface by the position by the first etching. The reason for this is that, in the case of a quartz glass substrate made of silicon dioxide, if the second etching is performed without performing the first etching, the state of the surface of the substrate is uniform, so that the etching progresses uniformly, resulting in fine etching. This is because it is difficult to form an uneven surface structure. In general, in the case of a glass substrate having a silicon dioxide content of 50% or more, the first etching is performed before the second etching so that the state of the surface of the substrate changes depending on the position. is effective for forming a fine uneven surface structure.

A case where the present invention is applied to a borosilicate glass substrate will be described below. The content of silicon dioxide in the borosilicate glass of this example is about 65%, and also includes oxides of boron and aluminum.

Table 3 is a table showing processing conditions for the first and second etchings for forming a fine uneven surface structure that improves the antireflection function on a borosilicate glass substrate.

The average pitch of the micro-relief surface structure is 50 nanometers, and the average depth is 110 nanometers.

FIG. 23 is a diagram showing the transmittance in the deep ultraviolet wavelength range of a borosilicate glass substrate on which a fine uneven surface structure is formed. The horizontal axis of FIG. 23 indicates the wavelength, and the vertical axis of FIG. 23 indicates the transmittance. The units on the horizontal axis are nanometers and the units on the vertical axis are percentages. In FIG. 23 , the solid line labeled “processed” indicates the transmittance of the borosilicate glass substrate on which the fine uneven surface structure is formed, and the broken line labeled “unprocessed” indicates the borosilicate glass substrate on which the fine uneven surface structure is not formed. 1 shows the transmittance of an acid glass substrate. According to FIG. 23, the transmittance of the borosilicate glass substrate on which the fine uneven surface structure is formed over the entire wavelength range is 5% or more higher than the transmittance of the borosilicate glass substrate on which the fine uneven surface structure is not formed.

FIG. 24 is a diagram showing the transmittance in the visible light range of a borosilicate glass substrate on which a fine uneven surface structure is formed. The horizontal axis of FIG. 25 indicates wavelength, and the vertical axis of FIG. 24 indicates transmittance. The units on the horizontal axis are nanometers and the units on the vertical axis are percentages. In FIG. 24 , the solid line labeled “processed” indicates the transmittance of the borosilicate glass substrate on which the fine uneven surface structure is formed, and the broken line labeled “unprocessed” indicates the borosilicate glass substrate on which the fine uneven surface structure is not formed. 1 shows the transmittance of an acid glass substrate. According to FIG. 24, for example, the transmittance of the borosilicate glass substrate on which the fine uneven surface structure is formed at a wavelength of 550 nanometers is higher than the transmittance of the borosilicate glass substrate on which the fine uneven surface structure is not formed by more than 3 percent. .

FIG. 25 is a flow chart generally showing the method for manufacturing the fine uneven surface structure of the present invention.

At step S4010 in FIG. 25, the initial values of the processing conditions are determined.

In step S4020 of FIG. 25, the first etching is performed.

In step S4030 of FIG. 25, a second etching is performed.

In step S4040 of FIG. 25, a third etching or wet coating is performed. The first to third etchings are performed in an etching apparatus, and wet coating is performed by immersing the substrate in a wet coating liquid in a container.

In step S4050 of FIG. 25, the water repellency or hydrophilicity of the substrate provided with the fine uneven surface structure is evaluated. If the evaluation result is affirmative, the process proceeds to step S4060. If the evaluation result is negative, the process proceeds to step S4070. Note that steps S4040 and S4050 may be omitted.

In step S4060 of FIG. 25, the antireflection performance of the substrate provided with the fine uneven surface structure is evaluated. If the evaluation result is positive, the process is terminated. If the evaluation result is negative, the process proceeds to step S4070.

In step S4070 of FIG. 25, the processing conditions are corrected, and the process returns to step S4020.

Claims

1. A method for manufacturing a fine uneven surface structure with an average pitch of 30 nanometers to 5 micrometers on a glass substrate having a silicon dioxide content of 50% or more without forming a mask prior to etching, the method comprising the steps of:
In an ion etching apparatus, a high-frequency power supply is connected to the first electrode, the second electrode is grounded, and the glass substrate having a silicon dioxide content of 50% or more is placed in contact with the first electrode, and argon gas is applied. Perform ion etching with
A manufacturing method of subsequently performing reactive ion etching with trifluoromethane (CHF 3 ) gas or a mixed gas of trifluoromethane (CHF 3 ) and oxygen in the same state.
The manufacturing method according to claim 1, wherein the flow ratio of oxygen gas to the mixed gas is in the range of 0 to 50%.
After performing reactive ion etching, the first electrode is grounded, the high-frequency power supply is connected to the second electrode, and the glass substrate having a silicon dioxide content of 50% or more is brought into contact with the first electrode. 3. The manufacturing method according to claim 1 or 2, wherein radical etching is performed with trifluoromethane (CHF3) gas or oxygen gas in a state of being arranged in a state where the substrates are arranged in the same direction.
The manufacturing method according to claim 1 or 2, wherein the glass substrate having a silicon dioxide content of 50% or more is subjected to wet coating after reactive ion etching.