WO2021172449A1 - Manufacturing method for glass substrate and manufacturing method for euvl mask blank - Google Patents

Manufacturing method for glass substrate and manufacturing method for euvl mask blank Download PDF

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Publication number
WO2021172449A1
WO2021172449A1 PCT/JP2021/007155 JP2021007155W WO2021172449A1 WO 2021172449 A1 WO2021172449 A1 WO 2021172449A1 JP 2021007155 W JP2021007155 W JP 2021007155W WO 2021172449 A1 WO2021172449 A1 WO 2021172449A1
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Prior art keywords
glass substrate
halogen
processing container
manufacturing
water vapor
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PCT/JP2021/007155
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French (fr)
Japanese (ja)
Inventor
慎也 東
尚明 宮本
智己 古川
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Ａｇｃ株式会社
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Priority to JP2022503705A priority Critical patent/JPWO2021172449A1/ja
Publication of WO2021172449A1 publication Critical patent/WO2021172449A1/en

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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C15/00—Surface treatment of glass, not in the form of fibres or filaments, by etching
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C23/00—Other surface treatment of glass not in the form of fibres or filaments
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
    • G03F1/22—Masks or mask blanks for imaging by radiation of 100nm or shorter wavelength, e.g. X-ray masks, extreme ultraviolet [EUV] masks; Preparation thereof
    • G03F1/24—Reflection masks; Preparation thereof
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
    • G03F1/60—Substrates

Definitions

  • the present disclosure relates to a method for manufacturing a glass substrate and a method for manufacturing a mask blank for EUV.
  • the photomask pattern is irradiated with light by an exposure apparatus, and the photomask pattern is transferred to a resist film.
  • EUV light includes soft X-rays and vacuum ultraviolet light, and specifically, light having a wavelength of about 0.2 nm to 100 nm. At present, EUV light having a wavelength of about 13.5 nm is mainly studied as exposure light.
  • Patent Document 1 describes a method for producing a mask blank for EUV (Extreme Ultra-Violet Lithography).
  • the EUV mask blank includes a glass substrate, a reflective film formed on the glass substrate, and an absorbing film formed on the reflective film.
  • the EUV mask blank is required to have a high flatness in order to improve the transfer accuracy of fine patterns. Since the flatness of the EUV mask blank is mainly determined by the flatness of the glass substrate which is the substrate, high flatness is required for the glass substrate.
  • Patent Document 1 by reducing the abundance of oxygen-based gas to 0.01 vol% or less, deposits on the main surface of the glass substrate are reduced.
  • the oxygen-based gas include O 2 gas, O 3 gas, CO 2 gas, and NO 2 gas.
  • the present inventor has focused on the fact that when a glass substrate is etched with halogen radicals such as fluorine radicals or chlorine radicals, deposits of titanium halide are generated.
  • halogen radicals such as fluorine radicals or chlorine radicals
  • titanium halide reacts with water vapor, a titanium compound that cannot be dissolved in a cleaning solution such as water is generated, which remains as a drawback.
  • One aspect of the present disclosure provides a technique for reducing defects caused by plasma etching of a glass substrate formed of Ti-doped quartz glass.
  • the glass substrate manufacturing method has the following (A) to (D).
  • a glass substrate made of Ti-doped quartz glass is housed inside the processing container.
  • D With the partial pressure of water vapor less than 400 Pa, the glass substrate is etched with the halogen radicals while relatively moving between the processing head and the glass substrate. When etching the glass substrate, the temperature of the entire glass substrate is 90 ° C. or higher.
  • the method for manufacturing a glass substrate according to another aspect of the present disclosure has the following (E) to (I).
  • E A glass substrate made of Ti-doped quartz glass is housed inside the processing container.
  • F Dry gas is supplied to the inside of the processing container, and the partial pressure of water vapor inside the processing container is adjusted to less than 400 Pa.
  • G A halogen-containing gas is supplied to the processing head inside the processing container, and the halogen-containing gas is turned into plasma to generate halogen radicals.
  • H In a state where the partial pressure of water vapor is less than 400 Pa, the glass substrate is etched with the halogen radical while relatively moving between the processing head and the glass substrate.
  • Titanium halide generated by the reaction between the glass substrate and the halogen radical is dissolved in a cleaning liquid and removed.
  • defects caused by plasma etching of a glass substrate formed of Ti-doped quartz glass can be reduced.
  • FIG. 1 is a flowchart showing a method for manufacturing an EUV mask blank according to an embodiment.
  • FIG. 2 is a cross-sectional view showing an example of the glass substrate used in S1 of FIG.
  • FIG. 3 is a plan view showing an example of the glass substrate of FIG.
  • FIG. 4 is a cross-sectional view showing a EUV mask blank according to an embodiment.
  • FIG. 5 is a cross-sectional view showing an example of a EUV photomask.
  • FIG. 6 is a cross-sectional view showing an example of the plasma etching apparatus used in S3 of FIG.
  • FIG. 7 is a cross-sectional view showing a modified example of the plasma etching apparatus.
  • FIG. 8 is a flowchart showing a method for manufacturing an EUV mask blank according to a modified example.
  • the method for producing a mask blank for EUV has S1 to S7.
  • a glass substrate is used to manufacture the mask blank.
  • the glass substrate is made of Ti-doped quartz glass.
  • Ti-doped quartz glass has a small coefficient of linear expansion and a small dimensional change due to temperature change.
  • Ti-doped quartz glass for example, a SiO 2 80 ⁇ 95 wt%, including TiO 2 5 ⁇ 20 wt%.
  • the coefficient of linear expansion near room temperature is substantially zero, and there is almost no dimensional change near room temperature.
  • the Ti-doped quartz glass may contain a third component other than SiO 2 and TiO 2 or impurities.
  • the glass substrate 2 has a first main surface 21, a second main surface 22, four end surfaces 23, four first chamfered surfaces 24, and four second surfaces. Includes chamfer 25.
  • the first main surface 21 has a rectangular shape. In the present specification, the rectangular shape includes a shape in which corners are chamfered. Further, the rectangle includes a square.
  • the second main surface 22 is in the opposite direction to the first main surface 21.
  • the second main surface 22 is also rectangular like the first main surface 21.
  • the end surface 23 is perpendicular to the first main surface 21 and the second main surface 22.
  • the first chamfered surface 24 is formed at the boundary between the first main surface 21 and the end surface 23.
  • the second chamfered surface 25 is formed at the boundary between the second main surface 22 and the end surface 23.
  • the first chamfered surface 24 and the second chamfered surface 25 are so-called C chamfered surfaces in the present embodiment, but may be R chamfered surfaces.
  • the first main surface 21 of the glass substrate 2 has a quality assurance region 27 shown by a dot pattern in FIG.
  • the quality assurance region 27 is an region processed to a desired flatness by S1 to S4.
  • the quality assurance region 27 is an region excluding the peripheral region 28 in which, for example, the distance L from the end surface 23 is within 5 mm when viewed from the direction orthogonal to the first main surface 21.
  • the second main surface 22 of the glass substrate 2 also has a quality assurance region and a peripheral region like the first main surface 21.
  • the quality assurance area of the second main surface 22 forming the conductive film 5 described below has a larger area than the quality assurance area 27 of the first main surface 21 forming the reflective film 3 and the like.
  • the first main surface 21 and the second main surface 22 of the glass substrate 2 are polished.
  • the first main surface 21 and the second main surface 22 may be simultaneously polished by a double-sided grinding machine, or may be sequentially polished by a single-sided grinding machine.
  • the glass substrate 2 is polished while supplying the polishing slurry between the polishing pad and the glass substrate 2.
  • the polishing slurry contains an abrasive.
  • the abrasive is, for example, cerium oxide particles.
  • the first main surface 21 and the second main surface 22 may be polished a plurality of times with abrasives of different materials or particle sizes.
  • the abrasive used in S1 is not limited to cerium oxide particles.
  • the abrasive used in S1 may be silicon oxide particles, aluminum oxide particles, zirconium oxide particles, titanium oxide particles, diamond particles, silicon carbide particles, or the like.
  • the surface shapes of the first main surface 21 and the second main surface 22 of the glass substrate 2 are measured.
  • a non-contact type measuring machine such as a laser interference type is used so that the surface is not scratched.
  • the measuring machine measures the surface shapes of the quality assurance area 27 of the first main surface 21 and the quality assurance area 22 of the second main surface 22.
  • the first main surface 21 and the second main surface 22 of the glass substrate 2 are etched with plasma in order to improve the flatness.
  • the first main surface 21 and the second main surface 22 are etched in order.
  • the order may be either first, and is not particularly limited.
  • halogen-containing gas is turned into plasma to generate halogen radicals.
  • Halogen radicals include, for example, fluorine radicals or chlorine radicals.
  • Volatile silicon halide is generated by the reaction between halogen radicals and silicon, and the etching of glass proceeds. Details of S3 will be described later.
  • finish polishing of the first main surface 21 and the second main surface 22 of the glass substrate 2 is performed.
  • the first main surface 21 and the second main surface 22 may be simultaneously polished by a double-sided grinding machine, or may be sequentially polished by a single-sided grinding machine.
  • the glass substrate 2 is polished while supplying the polishing slurry between the polishing pad and the glass substrate 2.
  • the polishing slurry contains an abrasive.
  • the abrasive is, for example, colloidal silica particles.
  • the reflective film 3 shown in FIG. 4 is formed in the quality assurance region 27 of the first main surface 21 of the glass substrate 2.
  • the reflective film 3 reflects EUV light.
  • the reflective film 3 may be, for example, a multilayer reflective film in which high refractive index layers and low refractive index layers are alternately laminated.
  • the high refractive index layer is formed of, for example, silicon (Si)
  • the low refractive index layer is formed of, for example, molybdenum (Mo).
  • a film forming method for the reflective film 3 for example, a sputtering method such as an ion beam sputtering method or a magnetron sputtering method is used.
  • the absorption film 4 shown in FIG. 4 is formed on the reflective film 3 formed in S5.
  • the absorbing film 4 absorbs EUV light.
  • the absorption film 4 is formed of, for example, a single metal containing at least one element selected from tantalum (Ta), chromium (Cr), and palladium (Pd), alloys, nitrides, oxides, oxynitrides, and the like.
  • a method for forming the absorption film 4 for example, a sputtering method is used.
  • the conductive film 5 shown in FIG. 4 is formed in the quality assurance region of the second main surface 22 of the glass substrate 2.
  • the conductive film 5 is used for electrostatically adsorbing a photomask with an electrostatic chuck of an exposure apparatus.
  • the conductive film 5 is formed of, for example, chromium nitride (CrN) or the like.
  • CrN chromium nitride
  • S7 is carried out after S5 and S6 in this embodiment, it may be carried out before S5 and S6. If S7 is carried out before S5 and S6, the glass substrate 2 can be fixed by the power contract chuck at the time of film formation of the reflective film 3 and the like.
  • the EUV mask blank 1 shown in FIG. 4 can be obtained.
  • the EUV mask blank 1 includes a glass substrate 2, a reflective film 3, an absorbing film 4, and a conductive film 5.
  • the EUV mask blank 1 does not have to include the conductive film 5. Further, the EUV mask blank 1 may include yet another film.
  • the EUV mask blank 1 may further contain a low-reflection film.
  • the low-reflection film is formed on the absorption film 4.
  • the low-reflection film is used for inspecting the opening pattern 41 of the absorption film 4 shown in FIG. 5, and has lower reflection characteristics than the absorption film 4 with respect to inspection light.
  • the low-reflection film is formed of, for example, TaON or TaO.
  • a method for forming a low-reflection film for example, a sputtering method is used.
  • the EUV mask blank 1 may further include a protective film.
  • the protective film is formed between the reflective film 3 and the absorbing film 4.
  • the protective film protects the reflective film 3 so that the reflective film 3 is not etched when the absorbent film 4 is etched to form the opening pattern 41 in the absorbent film 4.
  • the protective film is formed of, for example, Ru, Si, TiO 2 or the like.
  • a method for forming the protective film for example, a sputtering method is used.
  • the EUV photomask is obtained by forming an opening pattern 41 on the absorbing film 4.
  • a photolithography method and an etching method are used to form the opening pattern 41. Therefore, the resist film used for forming the opening pattern 41 may be included in the EUV mask blank 1.
  • the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other.
  • the X-axis direction and the Y-axis direction are the horizontal direction, and the Z-axis direction is the vertical direction.
  • the plasma etching apparatus 100 shown in FIG. 6 etches the first main surface 21 of the glass substrate 2 by a so-called PCVM (Plasma Chemical Vaporization Machining) method. If the glass substrate 2 is arranged upside down, the second main surface 22 can be etched. Since the etching of the second main surface 22 is the same as the etching of the first main surface 21, the description thereof will be omitted.
  • PCVM Chemical Vaporization Machining
  • the plasma etching apparatus 100 includes a processing container 101, a processing head 110, a stage 120, and a moving mechanism 130.
  • the processing container 101 accommodates the processing head 110 and the stage 120.
  • the processing head 110 turns the halogen-containing gas into plasma to generate halogen radicals.
  • the stage 120 holds the glass substrate 2 horizontally with the first main surface 21 of the glass substrate 2 facing upward.
  • the stage 120 includes a heater 121 that heats the glass substrate 2.
  • the moving mechanism 130 moves the machining head 110 in the X-axis direction, the Y-axis direction, and the Z-axis direction.
  • the moving mechanism 130 may move the processing head 110 and the stage 120 relatively, either of them, or both of them.
  • the processing head 110 has, for example, a ceramic tube 111 and a conductive housing 112.
  • the ceramic tube 111 is arranged vertically.
  • Carrier gas is supplied to the ceramic tube 111.
  • the carrier gas is, for example, Ar gas.
  • the housing 112 includes a tubular cavity resonator 113 that surrounds the ceramic tube 111.
  • a microwave electric field having a frequency of 2.45 GHz is applied to the inside of the cavity resonator 113. Due to this microwave, Ar plasma is generated near the lower end of the ceramic tube 111.
  • the frequency of the power source that excites the plasma is not limited to 2.45 GHz, and may be 50 Hz to 5 GHz.
  • a halogen-containing gas is supplied to the inside of the housing 112.
  • Halogen-containing gases include, for example, CF 4 , CHF 3 , C 2 F 6 , C 3 F 8 , C 4 F 10 , HF, SF 6 , C Cl 4 , NF 3 , F 2 , CF 3 Cl, or CF 2 Cl 2. including.
  • the halogen-containing gas may be supplied together with Ar gas or the like. Near the lower end of the ceramic tube 111, the generated Ar plasma collides with the halogen-containing gas, and halogen radicals are generated.
  • the halogen radical passes through the nozzle 114 provided at the lower end of the housing 112, irradiates the first main surface 21 of the glass substrate 2, and etches the first main surface 21.
  • Halogen radicals include, for example, fluorine radicals. Fluorine radicals react with SiO 2 of Ti-doped quartz glass as shown by the following reaction formula (1).
  • F * is a fluorine radical. SiO 2 + 4F * ⁇ SiF 4 ⁇ + O 2 ⁇ ⁇ ⁇ ⁇ (1) Since SiF 4 is volatile, etching of the first main surface 21 of the glass substrate 2 proceeds. When the halogen radical contains a chlorine radical, SiCl 4 is generated. Since SiCl 4 is also volatile, etching of the first main surface 21 of the glass substrate 2 proceeds.
  • the Ti-doped quartz glass contains TiO 2 in addition to SiO 2.
  • TiO 2 reacts with fluorine radicals to produce TiO 4.
  • TiF 4 volatilizes at high temperatures, but does not volatilize at room temperature.
  • the halogen radical contains a chlorine radical
  • TiCl 4 is generated.
  • TiCl 4 also volatilizes at high temperatures, but does not volatilize at room temperature.
  • the temperature of the glass substrate 2 becomes high due to the irradiation of halogen radicals, so that TiF 4 and TiCl 4 and the like volatilize. Therefore, the etching of the first main surface 21 of the glass substrate 2 proceeds.
  • the moving mechanism 130 moves the processing head 110 in the X-axis direction and the Y-axis direction in order to displace the etching position of the first main surface 21 of the glass substrate 2.
  • the moving speed is determined based on the measurement result of the surface shape in S2.
  • the moving speed is set to be slow in the convex portion so that the etching amount is increased, and the moving speed is set to be high in the concave portion.
  • TiF 4 reacts with water vapor to produce TiOF 2.
  • TiF 4 reacts with water vapor as shown by the following reaction formula (4) to generate TiO 2.
  • TiOF 2 and TiO 2 have a higher melting point than TiF 4, and are easily solidified. Further, unlike TiF 4 , TiO 2 and TiO 2 are not dissolved in a cleaning liquid such as water, and therefore, once attached to the first main surface 21 of the glass substrate 2, it is difficult to remove them.
  • TiCl 4 also reacts with water vapor to produce TiOCl 2 and TiO 2 .
  • the drying gas is supplied to the inside of the processing container 101, and the partial pressure of water vapor inside the processing container 101 is adjusted to less than 400 Pa.
  • the dry gas is not particularly limited as long as the partial pressure of water vapor is adjusted to less than 400 Pa, and includes, for example, O 2 , air, N 2 , He, Ar, CO 2 , or CO.
  • the partial pressure of water vapor is adjusted by using a dehumidifier or the like.
  • the dehumidifier may be a general one.
  • Plasma etching is performed inside the processing container 101 with a partial pressure of water vapor of less than 400 Pa.
  • the partial pressure of water vapor is preferably 250 Pa or less.
  • the partial pressure of water vapor is preferably 0.01 Pa or more.
  • the total pressure of the gas inside the processing container 101 may be atmospheric pressure. That is, the plasma etching may be atmospheric pressure plasma etching. In the present specification, the atmospheric pressure means 87,000 Pa or more and 111,430 Pa or less. If the total pressure of the gas inside the processing container 101 is atmospheric pressure, the expansion of the gas ejected from the nozzle 114 can be suppressed, the irradiation region of halogen radicals can be narrowed, and the first main surface 21 of the glass substrate 2 can be locally formed. Can be etched into.
  • the entire glass substrate 2 is heated to 90 ° C. or higher.
  • the overall temperature of the glass substrate 2 is 90 ° C. or higher, cooling of titanium halide at a position away from the processing head 110 can be suppressed.
  • the liquefaction or solidification of titanium halide can be suppressed, and the titanium halide can be discharged to the outside of the processing container 101 in the gas phase.
  • the overall temperature of the glass substrate 2 is, for example, the average temperature of the four corners and the center of the first main surface 21 when the first main surface 21 of the glass substrate 2 is rectangular.
  • the overall temperature of the glass substrate 2 is preferably 98 ° C. or higher, more preferably 130 ° C. or higher.
  • the overall temperature of the glass substrate 2 is preferably 300 ° C. or lower.
  • plasma etching is performed in a state where the partial pressure of water vapor inside the processing container 101 is less than 400 Pa and the overall temperature of the glass substrate 2 is 90 ° C. or higher. Therefore, the reaction between titanium halide and water vapor can be suppressed inside the processing container 101, and the titanium halide can be discharged to the outside of the processing container 101 in the gas phase.
  • titanium halide does not adhere to the glass substrate 2 inside the processing container 101, even if the glass substrate 2 is exposed to the atmosphere outside the processing container 101 for a long time, the occurrence of defects containing titanium oxide can be suppressed. Further, since titanium halide does not adhere to the glass substrate 2 inside the processing container 101, plasma etching of the glass substrate 2 is not hindered, and the flatness of the first main surface 21 of the glass substrate 2 is improved.
  • the plasma etching apparatus 100 of this embodiment is a remote system, and generates an halogen radical by forming an electric field having a frequency of 50 Hz to 5 GHz inside the processing head 110. Compared with the direct method described later, arc discharge can be suppressed and damage to the glass substrate 2 can be suppressed. Arc discharge is likely to occur when etching the peripheral edge of the first main surface 21 of the glass substrate 2.
  • the direct type plasma etching apparatus 100 generates an electric field having a frequency of 50 Hz to 5 GHz between the processing head 110 and the glass substrate 2.
  • the processing head 110 has a ceramic tube 116 and an electrode 117.
  • the ceramic tube 116 is arranged vertically.
  • a halogen-containing gas is supplied to the ceramic tube 116.
  • the halogen-containing gas may be supplied together with Ar gas or the like.
  • the electrode 117 is arranged inside the ceramic tube 116.
  • An electric field is applied between the electrode 117 and the glass substrate 2, and Ar plasma is generated.
  • the generated Ar plasma collides with the halogen-containing gas, and halogen radicals are generated.
  • the halogen radical irradiates the first main surface 21 of the glass substrate 2 and etches the first main surface 21.
  • the manufacturing method of this modification includes S8 (cleaning) between S3 (plasma etching) and S4 (finish polishing).
  • S8 cleaning
  • S3 plasma etching
  • S4 finish polishing
  • the glass substrate 2 is not heated by the heater 121 when performing plasma etching.
  • plasma etching is performed in a state where the partial pressure of water vapor inside the processing container 101 is less than 400 Pa.
  • the partial pressure of water vapor is preferably 250 Pa or less.
  • the partial pressure of water vapor is preferably 0.01 PaPa or more.
  • the temperature of the glass substrate 2 becomes high due to the irradiation of halogen radicals, so that titanium halide (for example, TiF 4 or TiCl 4 ) volatilizes. After volatilizing, the titanium halide is cooled and adheres to the first main surface 21 of the glass substrate 2 around the processing head 110.
  • titanium halide for example, TiF 4 or TiCl 4
  • the defects of titanium halide adhere to the first main surface 21 of the glass substrate 2. Therefore, when the glass substrate 2 is carried out of the processing container 101 and then exposed to the atmosphere for a long time, the water vapor in the atmosphere reacts with titanium halide, and a titanium compound that cannot be dissolved in a cleaning solution such as water is produced. Occurs and becomes a drawback.
  • the titanium halide is immediately dissolved in the cleaning liquid and removed after the glass substrate 2 is carried out to the outside of the processing container 101.
  • the glass substrate 2 may be stored in an atmosphere where the partial pressure of water vapor is less than 400 Pa until the start of cleaning.
  • the time of exposure to the atmosphere from carrying out to cleaning is, for example, 5 seconds or less.
  • the cleaning liquid is not particularly limited as long as it can dissolve titanium halide, but includes, for example, water, an organic solvent, an alkaline detergent, or an acid detergent.
  • the organic solvent contains alcohol.
  • As the alcohol methanol, ethanol, or isopropyl alcohol is used.
  • As the organic solvent acetone is used in addition to alcohol.
  • As the alkaline detergent sodium hydroxide, sodium carbonate, sodium metasilicate, or sodium phosphate is used.
  • As the acid detergent hydrochloric acid, nitric acid, sulfuric acid, or sulfuric acid hydrogen peroxide is used.
  • the titanium halide adhering to the glass substrate 2 is dissolved in a cleaning liquid and removed.
  • the reaction between water vapor in the atmosphere and titanium halide can be suppressed, the generation of titanium compounds that cannot be dissolved in a cleaning solution such as water can be suppressed, and the occurrence of defects can be suppressed.
  • Example 1 In Example 1, the remote type plasma etching apparatus 100 shown in FIG. 6 is used to determine the overall temperature of the glass substrate 2, the partial pressure of water vapor inside the processing container 101, and the presence or absence of TiF 4 or TiOF 2 remaining. The relationship with the presence or absence of residual TiO 2 was investigated.
  • the water vapor partial pressure was 100 Pa, 250 Pa, 400 Pa, or 600 Pa.
  • the substrate temperature was 50 ° C., 89 ° C., 98 ° C., 130 ° C., 175 ° C., or 270 ° C. Conditions other than the partial pressure of water vapor and the substrate temperature were set to be the same.
  • the glass substrate 2 was Ti-doped quartz glass containing 6.4% by mass of TiO 2.
  • the halogen-containing gas, CF 4 gas was used.
  • the total pressure of the gas inside the processing container 101 was atmospheric pressure.
  • the first main surface 21 of the glass substrate 2 is irradiated with fluorine radicals so as to draw a square grid-like locus with a side of 7 mm, and the presence or absence of an increase in Ti and F at the center of the positive grid.
  • An increase in both Ti and F means that there is a residue of TiF 4 or TiOF 2.
  • the fact that Ti increases and F does not increase means that TiO 2 remains.
  • the fact that both Ti and F do not increase means that neither TiF 4 or TiOF 2 remains nor TiO 2 remains.
  • Table 1 The experimental conditions and experimental results are shown in Table 1.
  • the substrate temperature is less than 90 ° C. and the partial pressure of water vapor is 400 Pa or more, residual TiF 4 or TiOF 2 is observed, and it is presumed that both TiF 4 and TiOF 2 are mixed.
  • Example 2 the remote type plasma etching apparatus 100 shown in FIG. 6 is used to fix the entire temperature of the glass substrate 2 to room temperature (20 ° C.), divide the water vapor inside the processing container 101, and after washing with water.
  • the relationship between the residual TiF 4 or 2 and the presence or absence of residual TiO 2 was investigated.
  • the water vapor partial pressure was 100 Pa, 250 Pa, 400 Pa, or 600 Pa.
  • the conditions other than the partial pressure of water vapor were set to be the same.
  • the glass substrate 2 was Ti-doped quartz glass containing 6.4% by mass of TiO 2.
  • the halogen-containing gas, CF 4 gas was used.
  • the total pressure of the gas inside the processing container 101 was atmospheric pressure.
  • Example 2 similarly to Example 1, the first main surface 21 of the glass substrate 2 is irradiated with fluorine radicals, and then the first main surface 21 of the glass substrate 2 carried out from the processing container 101 is spin-washed with water.
  • the presence or absence of an increase in Ti and F was measured by XPS at the center of the positive lattice, which is the irradiation locus of fluorine radicals.
  • Table 2 shows the experimental conditions and the experimental results.

Abstract

This method for manufacturing a glass substrate includes the following (A)-(D). (A) A glass substrate, which is formed from Ti-doped quartz glass, is housed in a processing container. (B) A drying gas is supplied to the inside of the processing container and the partial water vapor pressure inside the processing container is adjusted to be less than 400 Pa. (C) A halogen-containing gas is supplied to a machining head inside the processing container, the halogen-containing gas is turned into plasma, and halogen radicals are generated. (D) In a state in which the partial water vapor pressure is less than 400 Pa, the halogen radicals are used to etch the glass substrate while the machining head and the glass substrate move relative to each other. The overall temperature of the glass substrate is 90°C or higher during the etching of the glass substrate.

Description

ガラス基板の製造方法、及びＥＵＶＬ用マスクブランクの製造方法Manufacturing method of glass substrate and mask blank for EUV
　本開示は、ガラス基板の製造方法、及びＥＵＶＬ用マスクブランクの製造方法に関する。 The present disclosure relates to a method for manufacturing a glass substrate and a method for manufacturing a mask blank for EUV.
　従来から、半導体デバイスの製造には、フォトリソグラフィ技術が用いられている。フォトリソグラフィ技術では、露光装置によって、フォトマスクのパターンに光を照射し、フォトマスクのパターンをレジスト膜に転写する。 Conventionally, photolithography technology has been used in the manufacture of semiconductor devices. In the photolithography technique, the photomask pattern is irradiated with light by an exposure apparatus, and the photomask pattern is transferred to a resist film.
　最近では、微細パターンの転写を可能とするため、短波長の露光光、例えば、ＡｒＦエキシマレーザ光、さらにはＥＵＶ（Ｅｘｔｒｅｍｅ　Ｕｌｔｒａ－Ｖｉｏｌｅｔ）光などの使用が検討されている。 Recently, in order to enable transfer of fine patterns, the use of short wavelength exposure light, for example, ArF excimer laser light, and EUV (Extreme Ultra-Violet) light has been studied.
　ここで、ＥＵＶ光とは、軟Ｘ線および真空紫外光を含み、具体的には波長が０．２ｎｍ～１００ｎｍ程度の光のことである。現時点では、露光光として１３．５ｎｍ程度の波長のＥＵＶ光が主に検討されている。 Here, EUV light includes soft X-rays and vacuum ultraviolet light, and specifically, light having a wavelength of about 0.2 nm to 100 nm. At present, EUV light having a wavelength of about 13.5 nm is mainly studied as exposure light.
　特許文献１には、ＥＵＶＬ（Ｅｘｔｒｅｍｅ　Ｕｌｔｒａ－Ｖｉｏｌｅｔ　Ｌｉｔｈｏｇｒａｐｈｙ）用マスクブランクの製造方法が記載されている。ＥＵＶＬ用マスクブランクは、ガラス基板と、ガラス基板の上に形成された反射膜と、反射膜の上に形成された吸収膜とを含む。 Patent Document 1 describes a method for producing a mask blank for EUV (Extreme Ultra-Violet Lithography). The EUV mask blank includes a glass substrate, a reflective film formed on the glass substrate, and an absorbing film formed on the reflective film.
　ＥＵＶＬ用マスクブランクには、微細パターンの転写精度を向上すべく、高い平坦度が求められる。ＥＵＶＬ用マスクブランクの平坦度は主に基板であるガラス基板の平坦度で決まるので、ガラス基板には高い平坦度が求められる。 The EUV mask blank is required to have a high flatness in order to improve the transfer accuracy of fine patterns. Since the flatness of the EUV mask blank is mainly determined by the flatness of the glass substrate which is the substrate, high flatness is required for the glass substrate.
　そこで、ガラス基板の平坦度を向上すべく、ガラス基板の主面をプラズマによってエッチングする技術が開発されている。ガラス基板がＴｉドープ石英ガラスで形成される場合、チタンと酸素の反応によって、酸化チタンの付着物がガラス基板の主面に生じることがあった。 Therefore, in order to improve the flatness of the glass substrate, a technique for etching the main surface of the glass substrate with plasma has been developed. When the glass substrate was made of Ti-doped quartz glass, the reaction between titanium and oxygen could cause titanium oxide deposits to form on the main surface of the glass substrate.
　特許文献１では、酸素系ガスの存在量を０．０１ｖｏｌ％以下にすることにより、ガラス基板の主面の付着物を低減する。酸素系ガスとして、Ｏ２ガス、Ｏ３ガス、ＣＯ２ガス、ＮＯ２ガスが例示されている。 In Patent Document 1, by reducing the abundance of oxygen-based gas to 0.01 vol% or less, deposits on the main surface of the glass substrate are reduced. Examples of the oxygen-based gas include O 2 gas, O 3 gas, CO 2 gas, and NO 2 gas.
日本国特開２００６－７６８１６号公報Japanese Patent Application Laid-Open No. 2006-76816
　本発明者は、フッ素ラジカル又は塩素ラジカル等のハロゲンラジカルでガラス基板をエッチングする際に、ハロゲン化チタンの付着物が生じることに着目した。ハロゲン化チタンと水蒸気が反応すると、水等の洗浄液で溶解できないチタン化合物が生じ、欠点として残ってしまう。 The present inventor has focused on the fact that when a glass substrate is etched with halogen radicals such as fluorine radicals or chlorine radicals, deposits of titanium halide are generated. When titanium halide reacts with water vapor, a titanium compound that cannot be dissolved in a cleaning solution such as water is generated, which remains as a drawback.
　本開示の一態様は、Ｔｉドープ石英ガラスで形成されたガラス基板のプラズマエッチングに起因する欠点を低減する、技術を提供する。 One aspect of the present disclosure provides a technique for reducing defects caused by plasma etching of a glass substrate formed of Ti-doped quartz glass.
　本開示の一態様に係るガラス基板の製造方法は、下記（Ａ）～（Ｄ）を有する。（Ａ）Ｔｉドープ石英ガラスで形成されたガラス基板を、処理容器の内部に収容する。（Ｂ）前記処理容器の内部に乾燥ガスを供給し、前記処理容器の内部の水蒸気分圧を４００Ｐａ未満に調整する。（Ｃ）前記処理容器の内部の加工ヘッドにハロゲン含有ガスを供給し、前記ハロゲン含有ガスをプラズマ化し、ハロゲンラジカルを生成する。（Ｄ）前記水蒸気分圧が４００Ｐａ未満の状態で、前記加工ヘッドと前記ガラス基板とを相対的に移動しながら、前記ハロゲンラジカルで前記ガラス基板をエッチングする。前記ガラス基板をエッチングする際に、前記ガラス基板の全体の温度が９０℃以上である。 The glass substrate manufacturing method according to one aspect of the present disclosure has the following (A) to (D). (A) A glass substrate made of Ti-doped quartz glass is housed inside the processing container. (B) Dry gas is supplied to the inside of the processing container, and the partial pressure of water vapor inside the processing container is adjusted to less than 400 Pa. (C) A halogen-containing gas is supplied to the processing head inside the processing container, and the halogen-containing gas is turned into plasma to generate halogen radicals. (D) With the partial pressure of water vapor less than 400 Pa, the glass substrate is etched with the halogen radicals while relatively moving between the processing head and the glass substrate. When etching the glass substrate, the temperature of the entire glass substrate is 90 ° C. or higher.
　本開示の別の一態様に係るガラス基板の製造方法は、下記（Ｅ）～（Ｉ）を有する。（Ｅ）Ｔｉドープ石英ガラスで形成されたガラス基板を、処理容器の内部に収容する。（Ｆ）前記処理容器の内部に乾燥ガスを供給し、前記処理容器の内部の水蒸気分圧を４００Ｐａ未満に調整する。（Ｇ）前記処理容器の内部の加工ヘッドにハロゲン含有ガスを供給し、前記ハロゲン含有ガスをプラズマ化し、ハロゲンラジカルを生成する。（Ｈ）前記水蒸気分圧が４００Ｐａ未満の状態で、前記加工ヘッドと前記ガラス基板とを相対的に移動しながら、前記ハロゲンラジカルで前記ガラス基板をエッチングする。（Ｉ）前記ガラス基板と前記ハロゲンラジカルの反応によって生じたハロゲン化チタンを、洗浄液に溶解して除去する。 The method for manufacturing a glass substrate according to another aspect of the present disclosure has the following (E) to (I). (E) A glass substrate made of Ti-doped quartz glass is housed inside the processing container. (F) Dry gas is supplied to the inside of the processing container, and the partial pressure of water vapor inside the processing container is adjusted to less than 400 Pa. (G) A halogen-containing gas is supplied to the processing head inside the processing container, and the halogen-containing gas is turned into plasma to generate halogen radicals. (H) In a state where the partial pressure of water vapor is less than 400 Pa, the glass substrate is etched with the halogen radical while relatively moving between the processing head and the glass substrate. (I) Titanium halide generated by the reaction between the glass substrate and the halogen radical is dissolved in a cleaning liquid and removed.
　本開示の一態様によれば、Ｔｉドープ石英ガラスで形成されたガラス基板のプラズマエッチングに起因する欠点を低減できる。 According to one aspect of the present disclosure, defects caused by plasma etching of a glass substrate formed of Ti-doped quartz glass can be reduced.
図１は、一実施形態に係るＥＵＶＬ用マスクブランクの製造方法を示すフローチャートである。FIG. 1 is a flowchart showing a method for manufacturing an EUV mask blank according to an embodiment. 図２は、図１のＳ１に供されるガラス基板の一例を示す断面図である。FIG. 2 is a cross-sectional view showing an example of the glass substrate used in S1 of FIG. 図３は、図２のガラス基板の一例を示す平面図である。FIG. 3 is a plan view showing an example of the glass substrate of FIG. 図４は、一実施形態に係るＥＵＶＬ用マスクブランクを示す断面図である。FIG. 4 is a cross-sectional view showing a EUV mask blank according to an embodiment. 図５は、ＥＵＶＬ用フォトマスクの一例を示す断面図である。FIG. 5 is a cross-sectional view showing an example of a EUV photomask. 図６は、図２のＳ３で使用されるプラズマエッチング装置の一例を示す断面図である。FIG. 6 is a cross-sectional view showing an example of the plasma etching apparatus used in S3 of FIG. 図７は、プラズマエッチング装置の変形例を示す断面図である。FIG. 7 is a cross-sectional view showing a modified example of the plasma etching apparatus. 図８は、変形例に係るＥＵＶＬ用マスクブランクの製造方法を示すフローチャートである。FIG. 8 is a flowchart showing a method for manufacturing an EUV mask blank according to a modified example.
以下、本開示の実施形態について図面を参照して説明する。なお、各図面において同一の又は対応する構成には同一の符号を付し、説明を省略することがある。明細書中、数値範囲を示す「～」は、その前後に記載された数値を下限値及び上限値として含むことを意味する。 Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding configurations may be designated by the same reference numerals and description thereof may be omitted. In the specification, "-" indicating a numerical range means that the numerical values described before and after the numerical range are included as the lower limit value and the upper limit value.
　図１に示すように、ＥＵＶＬ（Ｅｘｔｒｅｍｅ　Ｕｌｔｒａ－Ｖｉｏｌｅｔ　Ｌｉｔｈｏｇｒａｐｈｙ）用マスクブランクの製造方法は、Ｓ１～Ｓ７を有する。マスクブランクの製造にはガラス基板が用いられる。ガラス基板はＴｉドープ石英ガラスで形成される。Ｔｉドープ石英ガラスは、一般的なソーダライムガラスに比べて、線膨張係数が小さく、温度変化による寸法変化が小さい。Ｔｉドープ石英ガラスは、例えば、ＳｉＯ２を８０～９５質量％、ＴｉＯ２を５～２０質量％含む。ＴｉＯ２含有量が５～２０質量％であると、室温付近での線膨張係数が略ゼロであり、室温付近での寸法変化がほとんど生じない。なお、Ｔｉドープ石英ガラスは、ＳｉＯ２およびＴｉＯ２以外の第三成分、又は不純物を含んでもよい。 As shown in FIG. 1, the method for producing a mask blank for EUV (Extreme Ultra-Violet Lithography) has S1 to S7. A glass substrate is used to manufacture the mask blank. The glass substrate is made of Ti-doped quartz glass. Compared with general soda lime glass, Ti-doped quartz glass has a small coefficient of linear expansion and a small dimensional change due to temperature change. Ti-doped quartz glass, for example, a SiO 2 80 ~ 95 wt%, including TiO 2 5 ~ 20 wt%. When the TiO 2 content is 5 to 20% by mass, the coefficient of linear expansion near room temperature is substantially zero, and there is almost no dimensional change near room temperature. The Ti-doped quartz glass may contain a third component other than SiO 2 and TiO 2 or impurities.
　ガラス基板２は、図２及び図３に示すように、第１主面２１と、第２主面２２と、４つの端面２３と、４つの第１面取面２４と、４つの第２面取面２５とを含む。第１主面２１は、矩形状である。本明細書において、矩形状とは、角に面取加工を施した形状を含む。また、矩形は、正方形を含む。第２主面２２は、第１主面２１とは反対向きである。第２主面２２も、第１主面２１と同様に、矩形状である。端面２３は、第１主面２１及び第２主面２２に対して垂直である。第１面取面２４は、第１主面２１と端面２３の境界に形成される。第２面取面２５は、第２主面２２と端面２３の境界に形成される。第１面取面２４及び第２面取面２５は、本実施形態では、いわゆるＣ面取面であるが、Ｒ面取面であってもよい。 As shown in FIGS. 2 and 3, the glass substrate 2 has a first main surface 21, a second main surface 22, four end surfaces 23, four first chamfered surfaces 24, and four second surfaces. Includes chamfer 25. The first main surface 21 has a rectangular shape. In the present specification, the rectangular shape includes a shape in which corners are chamfered. Further, the rectangle includes a square. The second main surface 22 is in the opposite direction to the first main surface 21. The second main surface 22 is also rectangular like the first main surface 21. The end surface 23 is perpendicular to the first main surface 21 and the second main surface 22. The first chamfered surface 24 is formed at the boundary between the first main surface 21 and the end surface 23. The second chamfered surface 25 is formed at the boundary between the second main surface 22 and the end surface 23. The first chamfered surface 24 and the second chamfered surface 25 are so-called C chamfered surfaces in the present embodiment, but may be R chamfered surfaces.
　ガラス基板２の第１主面２１は、図３にドット模様で示す品質保証領域２７を有する。品質保証領域２７は、Ｓ１～Ｓ４によって所望の平坦度に加工される領域である。品質保証領域２７は、第１主面２１に直交する方向から見て、例えば端面２３からの距離Ｌが５ｍｍ以内の周縁領域２８を除く領域である。なお、図示しないが、ガラス基板２の第２主面２２も、第１主面２１と同様に、品質保証領域と周縁領域とを有する。以下で説明する導電膜５を形成する第２主面２２の品質保証領域は、反射膜３等を形成する第１主面２１の品質保証領域２７よりも面積が広い。 The first main surface 21 of the glass substrate 2 has a quality assurance region 27 shown by a dot pattern in FIG. The quality assurance region 27 is an region processed to a desired flatness by S1 to S4. The quality assurance region 27 is an region excluding the peripheral region 28 in which, for example, the distance L from the end surface 23 is within 5 mm when viewed from the direction orthogonal to the first main surface 21. Although not shown, the second main surface 22 of the glass substrate 2 also has a quality assurance region and a peripheral region like the first main surface 21. The quality assurance area of the second main surface 22 forming the conductive film 5 described below has a larger area than the quality assurance area 27 of the first main surface 21 forming the reflective film 3 and the like.
　先ず、図１のＳ１では、ガラス基板２の第１主面２１及び第２主面２２を研磨する。第１主面２１及び第２主面２２は、両面研磨機で同時に研磨されてもよいし、片面研磨機で順番に研磨されてもよい。Ｓ１では、研磨パッドとガラス基板２の間に研磨スラリーを供給しながら、ガラス基板２を研磨する。研磨スラリーは、研磨剤を含む。研磨剤は、例えば酸化セリウム粒子である。第１主面２１及び第２主面２２は、異なる材質又は粒度の研磨剤で、複数回研磨されてもよい。 First, in S1 of FIG. 1, the first main surface 21 and the second main surface 22 of the glass substrate 2 are polished. The first main surface 21 and the second main surface 22 may be simultaneously polished by a double-sided grinding machine, or may be sequentially polished by a single-sided grinding machine. In S1, the glass substrate 2 is polished while supplying the polishing slurry between the polishing pad and the glass substrate 2. The polishing slurry contains an abrasive. The abrasive is, for example, cerium oxide particles. The first main surface 21 and the second main surface 22 may be polished a plurality of times with abrasives of different materials or particle sizes.
　なお、Ｓ１で用いられる研磨剤は、酸化セリウム粒子には限定されない。例えば、Ｓ１で用いられる研磨剤は、酸化シリコン粒子、酸化アルミニウム粒子、酸化ジルコニウム粒子、酸化チタン粒子、ダイヤモンド粒子、又は炭化珪素粒子などであってもよい。 The abrasive used in S1 is not limited to cerium oxide particles. For example, the abrasive used in S1 may be silicon oxide particles, aluminum oxide particles, zirconium oxide particles, titanium oxide particles, diamond particles, silicon carbide particles, or the like.
　次に、図１のＳ２では、ガラス基板２の第１主面２１及び第２主面２２の表面形状を測定する。表面形状の測定には、例えば、表面が傷付かないように、レーザ干渉式等の非接触式の測定機が用いられる。測定機は、第１主面２１の品質保証領域２７、及び第２主面２２の品質保証領域の表面形状を測定する。 Next, in S2 of FIG. 1, the surface shapes of the first main surface 21 and the second main surface 22 of the glass substrate 2 are measured. For the measurement of the surface shape, for example, a non-contact type measuring machine such as a laser interference type is used so that the surface is not scratched. The measuring machine measures the surface shapes of the quality assurance area 27 of the first main surface 21 and the quality assurance area 22 of the second main surface 22.
　次に、図１のＳ３では、Ｓ２の測定結果を参照し、平坦度を向上すべく、ガラス基板２の第１主面２１及び第２主面２２をプラズマでエッチングする。第１主面２１と第２主面２２は、順番にエッチングされる。その順番は、どちらが先でもよく、特に限定されない。 Next, in S3 of FIG. 1, referring to the measurement result of S2, the first main surface 21 and the second main surface 22 of the glass substrate 2 are etched with plasma in order to improve the flatness. The first main surface 21 and the second main surface 22 are etched in order. The order may be either first, and is not particularly limited.
　Ｓ３では、ハロゲン含有ガスをプラズマ化し、ハロゲンラジカルを生成する。ハロゲンラジカルは、例えば、フッ素ラジカル、又は塩素ラジカルを含む。ハロゲンラジカルとシリコンの反応によって揮発性のハロゲン化シリコンが生じ、ガラスのエッチングが進む。Ｓ３の詳細は、後述する。 In S3, the halogen-containing gas is turned into plasma to generate halogen radicals. Halogen radicals include, for example, fluorine radicals or chlorine radicals. Volatile silicon halide is generated by the reaction between halogen radicals and silicon, and the etching of glass proceeds. Details of S3 will be described later.
　次に、図１のＳ４では、ガラス基板２の第１主面２１及び第２主面２２の仕上げ研磨を行う。第１主面２１及び第２主面２２は、両面研磨機で同時に研磨されてもよいし、片面研磨機で順番に研磨されてもよい。Ｓ４では、研磨パッドとガラス基板２の間に研磨スラリーを供給しながら、ガラス基板２を研磨する。研磨スラリーは、研磨剤を含む。研磨剤は、例えばコロイダルシリカ粒子である。 Next, in S4 of FIG. 1, finish polishing of the first main surface 21 and the second main surface 22 of the glass substrate 2 is performed. The first main surface 21 and the second main surface 22 may be simultaneously polished by a double-sided grinding machine, or may be sequentially polished by a single-sided grinding machine. In S4, the glass substrate 2 is polished while supplying the polishing slurry between the polishing pad and the glass substrate 2. The polishing slurry contains an abrasive. The abrasive is, for example, colloidal silica particles.
　次に、図１のＳ５では、ガラス基板２の第１主面２１の品質保証領域２７に、図４に示す反射膜３を形成する。反射膜３は、ＥＵＶ光を反射する。反射膜３は、例えば高屈折率層と低屈折率層とを交互に積層した多層反射膜であってよい。高屈折率層は例えばシリコン（Ｓｉ）で形成され、低屈折率層は例えばモリブデン（Ｍｏ）で形成される。反射膜３の成膜方法としては、例えばイオンビームスパッタリング法、マグネトロンスパッタリング法などのスパッタリング法が用いられる。 Next, in S5 of FIG. 1, the reflective film 3 shown in FIG. 4 is formed in the quality assurance region 27 of the first main surface 21 of the glass substrate 2. The reflective film 3 reflects EUV light. The reflective film 3 may be, for example, a multilayer reflective film in which high refractive index layers and low refractive index layers are alternately laminated. The high refractive index layer is formed of, for example, silicon (Si), and the low refractive index layer is formed of, for example, molybdenum (Mo). As a film forming method for the reflective film 3, for example, a sputtering method such as an ion beam sputtering method or a magnetron sputtering method is used.
　次に、図１のＳ６では、Ｓ５で形成された反射膜３の上に、図４に示す吸収膜４を形成する。吸収膜４は、ＥＵＶ光を吸収する。吸収膜４は、例えばタンタル（Ｔａ）、クロム（Ｃｒ）、パラジウム（Ｐｄ）から選ばれる少なくとも１つの元素を含む単金属、合金、窒化物、酸化物、酸窒化物などで形成される。吸収膜４の成膜方法としては、例えばスパッタリング法が用いられる。 Next, in S6 of FIG. 1, the absorption film 4 shown in FIG. 4 is formed on the reflective film 3 formed in S5. The absorbing film 4 absorbs EUV light. The absorption film 4 is formed of, for example, a single metal containing at least one element selected from tantalum (Ta), chromium (Cr), and palladium (Pd), alloys, nitrides, oxides, oxynitrides, and the like. As a method for forming the absorption film 4, for example, a sputtering method is used.
　最後に、図１のＳ７では、ガラス基板２の第２主面２２の品質保証領域に、図４に示す導電膜５を形成する。導電膜５は、露光装置の静電チャックでフォトマスクを静電吸着するのに用いられる。導電膜５は、例えば窒化クロム（ＣｒＮ）などで形成される。導電膜５の成膜方法としては、例えばスパッタリング法が用いられる。なお、Ｓ７は、本実施形態ではＳ５及びＳ６の後に実施されるが、Ｓ５及びＳ６の前に実施されてもよい。Ｓ７をＳ５及びＳ６の前に実施すれば、反射膜３等の成膜時に請電チャックでガラス基板２を固定することができる。 Finally, in S7 of FIG. 1, the conductive film 5 shown in FIG. 4 is formed in the quality assurance region of the second main surface 22 of the glass substrate 2. The conductive film 5 is used for electrostatically adsorbing a photomask with an electrostatic chuck of an exposure apparatus. The conductive film 5 is formed of, for example, chromium nitride (CrN) or the like. As a film forming method of the conductive film 5, for example, a sputtering method is used. Although S7 is carried out after S5 and S6 in this embodiment, it may be carried out before S5 and S6. If S7 is carried out before S5 and S6, the glass substrate 2 can be fixed by the power contract chuck at the time of film formation of the reflective film 3 and the like.
　上記Ｓ１～Ｓ７により、図４に示すＥＵＶＬ用マスクブランク１が得られる。ＥＵＶＬ用マスクブランク１は、ガラス基板２と、反射膜３と、吸収膜４と、導電膜５とを含む。なお、ＥＵＶＬ用マスクブランク１は、導電膜５を含まなくてもよい。また、ＥＵＶＬ用マスクブランク１は、更に別の膜を含んでもよい。 From S1 to S7 above, the EUV mask blank 1 shown in FIG. 4 can be obtained. The EUV mask blank 1 includes a glass substrate 2, a reflective film 3, an absorbing film 4, and a conductive film 5. The EUV mask blank 1 does not have to include the conductive film 5. Further, the EUV mask blank 1 may include yet another film.
　例えば、ＥＵＶＬ用マスクブランク１は、更に、低反射膜を含んでもよい。低反射膜は、吸収膜４上に形成される。低反射膜は、図５に示す吸収膜４の開口パターン４１の検査に用いられ、検査光に対して吸収膜４よりも低反射特性を有する。低反射膜は、例えばＴａＯＮまたはＴａＯなどで形成される。低反射膜の成膜方法としては、例えばスパッタリング法が用いられる。 For example, the EUV mask blank 1 may further contain a low-reflection film. The low-reflection film is formed on the absorption film 4. The low-reflection film is used for inspecting the opening pattern 41 of the absorption film 4 shown in FIG. 5, and has lower reflection characteristics than the absorption film 4 with respect to inspection light. The low-reflection film is formed of, for example, TaON or TaO. As a method for forming a low-reflection film, for example, a sputtering method is used.
　また、ＥＵＶＬ用マスクブランク１は、更に、保護膜を含んでもよい。保護膜は、反射膜３と吸収膜４との間に形成される。保護膜は、吸収膜４に開口パターン４１を形成すべく吸収膜４をエッチングする際に、反射膜３がエッチングされないように、反射膜３を保護する。保護膜は、例えばＲｕ、Ｓｉ、またはＴｉＯ２などで形成される。保護膜の成膜方法としては、例えばスパッタリング法が用いられる。 Further, the EUV mask blank 1 may further include a protective film. The protective film is formed between the reflective film 3 and the absorbing film 4. The protective film protects the reflective film 3 so that the reflective film 3 is not etched when the absorbent film 4 is etched to form the opening pattern 41 in the absorbent film 4. The protective film is formed of, for example, Ru, Si, TiO 2 or the like. As a method for forming the protective film, for example, a sputtering method is used.
　図５に示すように、ＥＵＶＬ用フォトマスクは、吸収膜４に開口パターン４１を形成して得られる。開口パターン４１の形成には、フォトリソグラフィ法およびエッチング法が用いられる。従って、開口パターン４１の形成に用いられるレジスト膜が、ＥＵＶＬ用マスクブランク１に含まれてもよい。 As shown in FIG. 5, the EUV photomask is obtained by forming an opening pattern 41 on the absorbing film 4. A photolithography method and an etching method are used to form the opening pattern 41. Therefore, the resist film used for forming the opening pattern 41 may be included in the EUV mask blank 1.
　次に、図６を参照して、図１のＳ３の詳細について説明する。図６において、Ｘ軸方向、Ｙ軸方向、及びＺ軸方向は互いに垂直な方向である。Ｘ軸方向及びＹ軸方向が水平方向、Ｚ軸方向が鉛直方向である。 Next, the details of S3 in FIG. 1 will be described with reference to FIG. In FIG. 6, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other. The X-axis direction and the Y-axis direction are the horizontal direction, and the Z-axis direction is the vertical direction.
　図６に示すプラズマエッチング装置１００は、いわゆるＰＣＶＭ（Ｐｌａｓｍａ　Ｃｈｅｍｉｃａｌ　Ｖａｐｏｒｉｚａｔｉｏｎ　Ｍａｃｈｉｎｉｎｇ）法によって、ガラス基板２の第１主面２１をエッチングする。なお、ガラス基板２を上下逆さに配置すれば、第２主面２２のエッチングも可能である。第２主面２２のエッチングは、第１主面２１のエッチングと同様であるので、説明を省略する。 The plasma etching apparatus 100 shown in FIG. 6 etches the first main surface 21 of the glass substrate 2 by a so-called PCVM (Plasma Chemical Vaporization Machining) method. If the glass substrate 2 is arranged upside down, the second main surface 22 can be etched. Since the etching of the second main surface 22 is the same as the etching of the first main surface 21, the description thereof will be omitted.
　プラズマエッチング装置１００は、処理容器１０１と、加工ヘッド１１０と、ステージ１２０と、移動機構１３０とを有する。処理容器１０１は、加工ヘッド１１０とステージ１２０を収容する。加工ヘッド１１０は、ハロゲン含有ガスをプラズマ化し、ハロゲンラジカルを生成する。ステージ１２０は、ガラス基板２の第１主面２１を上に向けて、ガラス基板２を水平に保持する。ステージ１２０は、ガラス基板２を加熱する加熱器１２１を含む。移動機構１３０は、加工ヘッド１１０をＸ軸方向、Ｙ軸方向、及びＺ軸方向に移動させる。なお、移動機構１３０は、加工ヘッド１１０とステージ１２０とを相対的に移動させればよく、どちらを移動させてもよいし、両方を移動させてもよい。 The plasma etching apparatus 100 includes a processing container 101, a processing head 110, a stage 120, and a moving mechanism 130. The processing container 101 accommodates the processing head 110 and the stage 120. The processing head 110 turns the halogen-containing gas into plasma to generate halogen radicals. The stage 120 holds the glass substrate 2 horizontally with the first main surface 21 of the glass substrate 2 facing upward. The stage 120 includes a heater 121 that heats the glass substrate 2. The moving mechanism 130 moves the machining head 110 in the X-axis direction, the Y-axis direction, and the Z-axis direction. The moving mechanism 130 may move the processing head 110 and the stage 120 relatively, either of them, or both of them.
　加工ヘッド１１０は、例えば、セラミック管１１１と、導電性の筐体１１２とを有する。セラミック管１１１は、鉛直に配置される。セラミック管１１１には、キャリアガスが供給される。キャリアガスは、例えばＡｒガスである。筐体１１２は、セラミック管１１１を取り囲む筒状の空洞共振器１１３を含む。空洞共振器１１３の内部には、周波数２．４５ＧＨｚのマイクロ波電界が付与される。このマイクロ波によって、セラミック管１１１の下端付近にて、Ａｒプラズマが発生する。なお、プラズマを励起する電源の周波数は、２．４５ＧＨｚには限定されず、５０Ｈｚ～５ＧＨｚであればよい。 The processing head 110 has, for example, a ceramic tube 111 and a conductive housing 112. The ceramic tube 111 is arranged vertically. Carrier gas is supplied to the ceramic tube 111. The carrier gas is, for example, Ar gas. The housing 112 includes a tubular cavity resonator 113 that surrounds the ceramic tube 111. A microwave electric field having a frequency of 2.45 GHz is applied to the inside of the cavity resonator 113. Due to this microwave, Ar plasma is generated near the lower end of the ceramic tube 111. The frequency of the power source that excites the plasma is not limited to 2.45 GHz, and may be 50 Hz to 5 GHz.
　筐体１１２の内部には、ハロゲン含有ガスが供給される。ハロゲン含有ガスは、例えばＣＦ４、ＣＨＦ３、Ｃ２Ｆ６、Ｃ３Ｆ８、Ｃ４Ｆ１０、ＨＦ、ＳＦ６、ＣＣｌ４、ＮＦ３、Ｆ２、ＣＦ３Ｃｌ、又はＣＦ２Ｃｌ２を含む。ハロゲン含有ガスは、Ａｒガスなどと共に供給されてもよい。セラミック管１１１の下端付近にて、発生したＡｒプラズマがハロゲン含有ガスに衝突し、ハロゲンラジカルが生じる。ハロゲンラジカルは、筐体１１２の下端に設けられたノズル１１４を通り、ガラス基板２の第１主面２１に照射され、その第１主面２１をエッチングする。 A halogen-containing gas is supplied to the inside of the housing 112. Halogen-containing gases include, for example, CF 4 , CHF 3 , C 2 F 6 , C 3 F 8 , C 4 F 10 , HF, SF 6 , C Cl 4 , NF 3 , F 2 , CF 3 Cl, or CF 2 Cl 2. including. The halogen-containing gas may be supplied together with Ar gas or the like. Near the lower end of the ceramic tube 111, the generated Ar plasma collides with the halogen-containing gas, and halogen radicals are generated. The halogen radical passes through the nozzle 114 provided at the lower end of the housing 112, irradiates the first main surface 21 of the glass substrate 2, and etches the first main surface 21.
　ハロゲンラジカルは、例えばフッ素ラジカルを含む。フッ素ラジカルは、下記反応式（１）で示すように、Ｔｉドープ石英ガラスのＳｉＯ２と反応する。なお、「Ｆ＊」はフッ素ラジカルである。
ＳｉＯ２＋４Ｆ＊→ＳｉＦ４↑＋Ｏ２↑・・・（１）
ＳｉＦ４は揮発性であるので、ガラス基板２の第１主面２１のエッチングが進む。なお、ハロゲンラジカルが塩素ラジカルを含む場合、ＳｉＣｌ４が生成する。ＳｉＣｌ４も、揮発性であるので、ガラス基板２の第１主面２１のエッチングが進む。 Halogen radicals include, for example, fluorine radicals. Fluorine radicals react with SiO 2 of Ti-doped quartz glass as shown by the following reaction formula (1). In addition, "F *" is a fluorine radical.
SiO 2 + 4F * → SiF 4 ↑ + O 2 ↑ ・ ・ ・ (1)
Since SiF 4 is volatile, etching of the first main surface 21 of the glass substrate 2 proceeds. When the halogen radical contains a chlorine radical, SiCl 4 is generated. Since SiCl 4 is also volatile, etching of the first main surface 21 of the glass substrate 2 proceeds.
　ところで、Ｔｉドープ石英ガラスは、ＳｉＯ２に加えて、ＴｉＯ２をも含む。ＴｉＯ２は、下記反応式（２）で示すように、フッ素ラジカルと反応し、ＴｉＦ４を生成する。
ＴｉＯ２＋４Ｆ＊→ＴｉＦ４＋Ｏ２↑・・・（２）
ＴｉＦ４は、高温では揮発するが、常温では揮発しない。なお、ハロゲンラジカルが塩素ラジカルを含む場合、ＴｉＣｌ４が生成する。ＴｉＣｌ４も、高温では揮発するが、常温では揮発しない。 By the way, the Ti-doped quartz glass contains TiO 2 in addition to SiO 2. As shown in the reaction formula (2) below, TiO 2 reacts with fluorine radicals to produce TiO 4.
TiO 2 + 4F * → TiF 4 + O 2 ↑ ・ ・ ・ (2)
TiF 4 volatilizes at high temperatures, but does not volatilize at room temperature. When the halogen radical contains a chlorine radical, TiCl 4 is generated. TiCl 4 also volatilizes at high temperatures, but does not volatilize at room temperature.
　加工ヘッド１１０の真下では、ハロゲンラジカルの照射によって、ガラス基板２の温度が高温になるので、ＴｉＦ４及びＴｉＣｌ４等が揮発する。それゆえ、ガラス基板２の第１主面２１のエッチングが進む。 Immediately below the processing head 110, the temperature of the glass substrate 2 becomes high due to the irradiation of halogen radicals, so that TiF 4 and TiCl 4 and the like volatilize. Therefore, the etching of the first main surface 21 of the glass substrate 2 proceeds.
　移動機構１３０は、ガラス基板２の第１主面２１のエッチング位置を変位させるべく、加工ヘッド１１０をＸ軸方向及びＹ軸方向に移動させる。その移動速度を制御することで、エッチング量を制御でき、ガラス基板２を平坦化できる。移動速度は、Ｓ２での表面形状の測定結果に基づき決められる。凸部ではエッチング量が増えるように移動速度が遅く設定され、凹部では移動速度が速く設定される。 The moving mechanism 130 moves the processing head 110 in the X-axis direction and the Y-axis direction in order to displace the etching position of the first main surface 21 of the glass substrate 2. By controlling the moving speed, the etching amount can be controlled and the glass substrate 2 can be flattened. The moving speed is determined based on the measurement result of the surface shape in S2. The moving speed is set to be slow in the convex portion so that the etching amount is increased, and the moving speed is set to be high in the concave portion.
　ところで、ＴｉＦ４は、下記反応式（３）で示すように、水蒸気と反応し、ＴｉＯＦ２を生成する。
ＴｉＦ４＋２Ｈ２Ｏ→ＴｉＯＦ２＋２ＨＦ↑・・・（３）
また、ＴｉＦ４は、下記反応式（４）で示すように、水蒸気と反応し、ＴｉＯ２を生成する。
ＴｉＦ４＋２Ｈ２Ｏ→ＴｉＯ２＋４ＨＦ↑・・・（４）
ＴｉＯＦ２及びＴｉＯ２は、ＴｉＦ４に比べて高い融点を有し、固化し易い。また、ＴｉＯＦ２及びＴｉＯ２は、ＴｉＦ４とは異なり、水などの洗浄液に溶解しないので、一旦、ガラス基板２の第１主面２１に付着すると、除去困難である。なお、ＴｉＣｌ４も、ＴｉＦ４と同様に、水蒸気と反応し、ＴｉＯＣｌ２及びＴｉＯ２を生成する。 By the way, as shown by the following reaction formula (3) , TiF 4 reacts with water vapor to produce TiOF 2.
TiF 4 + 2H 2 O → TiOF 2 + 2HF ↑ ・ ・ ・ (3)
Further, TiF 4 reacts with water vapor as shown by the following reaction formula (4) to generate TiO 2.
TiF 4 + 2H 2 O → TiO 2 + 4HF ↑ ・ ・ ・ (4)
TiOF 2 and TiO 2 have a higher melting point than TiF 4, and are easily solidified. Further, unlike TiF 4 , TiO 2 and TiO 2 are not dissolved in a cleaning liquid such as water, and therefore, once attached to the first main surface 21 of the glass substrate 2, it is difficult to remove them. Like TiF 4 , TiCl 4 also reacts with water vapor to produce TiOCl 2 and TiO 2 .
　そこで、本実施形態では、処理容器１０１の内部に乾燥ガスを供給し、処理容器１０１の内部の水蒸気分圧を４００Ｐａ未満に調整する。乾燥ガスは、水蒸気分圧を４００Ｐａ未満に調整したものであれば特に限定されないが、例えば、Ｏ２、空気、Ｎ２、Ｈｅ、Ａｒ、ＣＯ２、又はＣＯを含む。水蒸気分圧の調整は、除湿器などによって行う。除湿器は、一般的なものであってよい。 Therefore, in the present embodiment, the drying gas is supplied to the inside of the processing container 101, and the partial pressure of water vapor inside the processing container 101 is adjusted to less than 400 Pa. The dry gas is not particularly limited as long as the partial pressure of water vapor is adjusted to less than 400 Pa, and includes, for example, O 2 , air, N 2 , He, Ar, CO 2 , or CO. The partial pressure of water vapor is adjusted by using a dehumidifier or the like. The dehumidifier may be a general one.
　処理容器１０１の内部にて、水蒸気分圧が４００Ｐａ未満の状態で、プラズマエッチングが実施される。その結果、処理容器１０１の内部にて、水蒸気とハロゲン化チタンとの反応を抑制でき、ＴｉＯＦ２及びＴｉＯ２の生成を抑制でき、欠点の生成を抑制できる。水蒸気分圧は、好ましくは２５０Ｐａ以下である。また、水蒸気分圧は、好ましくは０．０１Ｐａ以上である。 Plasma etching is performed inside the processing container 101 with a partial pressure of water vapor of less than 400 Pa. As a result, the reaction between water vapor and titanium halide can be suppressed inside the processing container 101, the formation of TiOF 2 and TiO 2 can be suppressed, and the formation of defects can be suppressed. The partial pressure of water vapor is preferably 250 Pa or less. The partial pressure of water vapor is preferably 0.01 Pa or more.
　なお、処理容器１０１の内部のガスの全圧は、大気圧であってよい。つまり、プラズマエッチングは、大気圧プラズマエッチングであってよい。本明細書において、大気圧とは、８７０００Ｐａ以上１１１４３０Ｐａ以下を意味する。処理容器１０１の内部のガスの全圧が大気圧であれば、ノズル１１４から噴出したガスの膨張を抑制でき、ハロゲンラジカルの照射領域を狭窄でき、ガラス基板２の第１主面２１を局所的にエッチングできる。 The total pressure of the gas inside the processing container 101 may be atmospheric pressure. That is, the plasma etching may be atmospheric pressure plasma etching. In the present specification, the atmospheric pressure means 87,000 Pa or more and 111,430 Pa or less. If the total pressure of the gas inside the processing container 101 is atmospheric pressure, the expansion of the gas ejected from the nozzle 114 can be suppressed, the irradiation region of halogen radicals can be narrowed, and the first main surface 21 of the glass substrate 2 can be locally formed. Can be etched into.
　また、本実施形態では、プラズマエッチングを実施する際に、ガラス基板２の全体を９０℃以上に加熱する。ガラス基板２の全体の温度が９０℃以上であれば、加工ヘッド１１０から離れた位置での、ハロゲン化チタンの冷却を抑制できる。ハロゲン化チタンの液化又は固化を抑制でき、ハロゲン化チタンを気相のまま処理容器１０１の外部に排出できる。 Further, in the present embodiment, when performing plasma etching, the entire glass substrate 2 is heated to 90 ° C. or higher. When the overall temperature of the glass substrate 2 is 90 ° C. or higher, cooling of titanium halide at a position away from the processing head 110 can be suppressed. The liquefaction or solidification of titanium halide can be suppressed, and the titanium halide can be discharged to the outside of the processing container 101 in the gas phase.
　ガラス基板２の全体の温度は、例えばガラス基板２の第１主面２１が矩形状である場合、第１主面２１の４隅と中心の５点の平均温度である。ガラス基板２の全体の温度は、好ましくは９８℃以上、より好ましくは１３０℃以上である。また、ガラス基板２の全体の温度は、好ましくは３００℃以下である。 The overall temperature of the glass substrate 2 is, for example, the average temperature of the four corners and the center of the first main surface 21 when the first main surface 21 of the glass substrate 2 is rectangular. The overall temperature of the glass substrate 2 is preferably 98 ° C. or higher, more preferably 130 ° C. or higher. The overall temperature of the glass substrate 2 is preferably 300 ° C. or lower.
　上記の通り、本実施形態では、処理容器１０１の内部の水蒸気分圧が４００Ｐａ未満の状態であって、且つガラス基板２の全体の温度が９０℃以上の状態で、プラズマエッチングを実施する。従って、処理容器１０１の内部にて、ハロゲン化チタンと水蒸気との反応を抑制でき、ハロゲン化チタンを気相のまま処理容器１０１の外部に排出できる。 As described above, in the present embodiment, plasma etching is performed in a state where the partial pressure of water vapor inside the processing container 101 is less than 400 Pa and the overall temperature of the glass substrate 2 is 90 ° C. or higher. Therefore, the reaction between titanium halide and water vapor can be suppressed inside the processing container 101, and the titanium halide can be discharged to the outside of the processing container 101 in the gas phase.
　処理容器１０１の内部にてハロゲン化チタンがガラス基板２に付着しないので、処理容器１０１の外部でガラス基板２を大気に長時間さらしても、酸化チタンを含む欠点の発生を抑制できる。また、処理容器１０１の内部にてハロゲン化チタンがガラス基板２に付着しないので、ガラス基板２のプラズマエッチングが阻害されず、ガラス基板２の第１主面２１の平坦度が向上する。 Since titanium halide does not adhere to the glass substrate 2 inside the processing container 101, even if the glass substrate 2 is exposed to the atmosphere outside the processing container 101 for a long time, the occurrence of defects containing titanium oxide can be suppressed. Further, since titanium halide does not adhere to the glass substrate 2 inside the processing container 101, plasma etching of the glass substrate 2 is not hindered, and the flatness of the first main surface 21 of the glass substrate 2 is improved.
　本実施形態のプラズマエッチング装置１００は、リモート方式であって、加工ヘッド１１０の内部にて、周波数５０Ｈｚ～５ＧＨｚの電界を形成して、ハロゲンラジカルを生成する。後述のダイレクト方式に比べて、アーク放電を抑制でき、ガラス基板２の損傷を抑制できる。アーク放電は、ガラス基板２の第１主面２１の周縁をエッチングする際に生じやすい。 The plasma etching apparatus 100 of this embodiment is a remote system, and generates an halogen radical by forming an electric field having a frequency of 50 Hz to 5 GHz inside the processing head 110. Compared with the direct method described later, arc discharge can be suppressed and damage to the glass substrate 2 can be suppressed. Arc discharge is likely to occur when etching the peripheral edge of the first main surface 21 of the glass substrate 2.
　次に、図７を参照して、変形例に係るダイレクト方式のプラズマエッチング装置１００について説明する。以下、ダイレクト方式と、リモート方式の相違点について主に説明する。ダイレクト方式のプラズマエッチング装置１００は、加工ヘッド１１０とガラス基板２との間に周波数５０Ｈｚ～５ＧＨｚの電界を生じさせる。 Next, the direct type plasma etching apparatus 100 according to the modified example will be described with reference to FIG. 7. Hereinafter, the differences between the direct method and the remote method will be mainly described. The direct type plasma etching apparatus 100 generates an electric field having a frequency of 50 Hz to 5 GHz between the processing head 110 and the glass substrate 2.
　加工ヘッド１１０は、セラミック管１１６と、電極１１７とを有する。セラミック管１１６は、鉛直に配置される。セラミック管１１６には、ハロゲン含有ガスが供給される。ハロゲン含有ガスは、Ａｒガスなどと共に供給されてもよい。電極１１７は、セラミック管１１６の内部に配置される。 The processing head 110 has a ceramic tube 116 and an electrode 117. The ceramic tube 116 is arranged vertically. A halogen-containing gas is supplied to the ceramic tube 116. The halogen-containing gas may be supplied together with Ar gas or the like. The electrode 117 is arranged inside the ceramic tube 116.
　電極１１７とガラス基板２との間に、電界が付与され、Ａｒプラズマが発生する。発生したＡｒプラズマがハロゲン含有ガスに衝突し、ハロゲンラジカルが生じる。ハロゲンラジカルは、ガラス基板２の第１主面２１に照射され、その第１主面２１をエッチングする。 An electric field is applied between the electrode 117 and the glass substrate 2, and Ar plasma is generated. The generated Ar plasma collides with the halogen-containing gas, and halogen radicals are generated. The halogen radical irradiates the first main surface 21 of the glass substrate 2 and etches the first main surface 21.
次に、図８を参照して、変形例に係るＥＵＶＬ用マスクブランクの製造方法について説明する。本変形例の製造方法は、Ｓ３（プラズマエッチング）とＳ４（仕上げ研磨）の間に、Ｓ８（洗浄）を含む。以下、本変形例と、上記実施形態との相違点について主に説明する。 Next, a method for manufacturing the EUV mask blank according to the modified example will be described with reference to FIG. The manufacturing method of this modification includes S8 (cleaning) between S3 (plasma etching) and S4 (finish polishing). Hereinafter, the differences between the present modification and the above-described embodiment will be mainly described.
　本変形例のＳ３（プラズマエッチング）では、プラズマエッチングを実施する際に、加熱器１２１でガラス基板２を加熱しない。但し、上記実施形態と同様に、処理容器１０１の内部の水蒸気分圧が４００Ｐａ未満の状態で、プラズマエッチングを実施する。水蒸気分圧は、好ましくは２５０Ｐａ以下である。また、水蒸気分圧は、好ましくは０．０１ＰａＰａ以上である。 In S3 (plasma etching) of this modification, the glass substrate 2 is not heated by the heater 121 when performing plasma etching. However, as in the above embodiment, plasma etching is performed in a state where the partial pressure of water vapor inside the processing container 101 is less than 400 Pa. The partial pressure of water vapor is preferably 250 Pa or less. The partial pressure of water vapor is preferably 0.01 PaPa or more.
　加工ヘッド１１０の真下では、ハロゲンラジカルの照射によって、ガラス基板２の温度が高温になるので、ハロゲン化チタン（例えばＴｉＦ４又はＴｉＣｌ４）が揮発する。ハロゲン化チタンは、揮発した後、冷却され、加工ヘッド１１０の周囲にてガラス基板２の第１主面２１に付着する。 Immediately below the processing head 110, the temperature of the glass substrate 2 becomes high due to the irradiation of halogen radicals, so that titanium halide (for example, TiF 4 or TiCl 4 ) volatilizes. After volatilizing, the titanium halide is cooled and adheres to the first main surface 21 of the glass substrate 2 around the processing head 110.
　ガラス基板２の第１主面２１には、ハロゲン化チタンの欠点が付着する。それゆえ、ガラス基板２を処理容器１０１の外部に搬出した後、ガラス基板２を大気に長時間さらすと、大気中の水蒸気とハロゲン化チタンが反応し、水等の洗浄液で溶解できないチタン化合物が生じ、欠点になる。 The defects of titanium halide adhere to the first main surface 21 of the glass substrate 2. Therefore, when the glass substrate 2 is carried out of the processing container 101 and then exposed to the atmosphere for a long time, the water vapor in the atmosphere reacts with titanium halide, and a titanium compound that cannot be dissolved in a cleaning solution such as water is produced. Occurs and becomes a drawback.
　そこで、本変形例のＳ４では、処理容器１０１の外部にガラス基板２を搬出した後、直ぐに、ハロゲン化チタンを洗浄液に溶解して除去する。なお、処理容器１０１の外部にガラス基板２を搬出した後、洗浄開始までの間、水蒸気分圧が４００Ｐａ未満の雰囲気中でガラス基板２を保存してもよい。搬出から洗浄までに大気に曝される時間は、例えば５秒以下である。 Therefore, in S4 of this modification, the titanium halide is immediately dissolved in the cleaning liquid and removed after the glass substrate 2 is carried out to the outside of the processing container 101. After the glass substrate 2 is carried out of the processing container 101, the glass substrate 2 may be stored in an atmosphere where the partial pressure of water vapor is less than 400 Pa until the start of cleaning. The time of exposure to the atmosphere from carrying out to cleaning is, for example, 5 seconds or less.
　洗浄液は、ハロゲン化チタンを溶解できるものであれば特に限定されないが、例えば、水、有機溶剤、アルカリ洗剤、又は酸洗剤を含む。有機溶剤は、アルコールを含む。アルコールとしては、メタノール、エタノール、又はイソプロピルアルコールが用いられる。有機溶剤としては、アルコールの他に、アセトンが用いられる。アルカリ洗剤としては、水酸化ナトリウム、炭酸ナトリウム、メタケイ酸ナトリウム、又はリン酸ナトリウムが用いられる。酸洗剤としては、塩酸、硝酸、硫酸、又は硫酸過水が用いられる。 The cleaning liquid is not particularly limited as long as it can dissolve titanium halide, but includes, for example, water, an organic solvent, an alkaline detergent, or an acid detergent. The organic solvent contains alcohol. As the alcohol, methanol, ethanol, or isopropyl alcohol is used. As the organic solvent, acetone is used in addition to alcohol. As the alkaline detergent, sodium hydroxide, sodium carbonate, sodium metasilicate, or sodium phosphate is used. As the acid detergent, hydrochloric acid, nitric acid, sulfuric acid, or sulfuric acid hydrogen peroxide is used.
　本変形例によれば、ガラス基板２に付着したハロゲン化チタンを、洗浄液に溶解して除去する。その結果、大気中の水蒸気とハロゲン化チタンの反応を抑制でき、水等の洗浄液で溶解できないチタン化合物の発生を抑制でき、欠点の発生を抑制できる。 According to this modification, the titanium halide adhering to the glass substrate 2 is dissolved in a cleaning liquid and removed. As a result, the reaction between water vapor in the atmosphere and titanium halide can be suppressed, the generation of titanium compounds that cannot be dissolved in a cleaning solution such as water can be suppressed, and the occurrence of defects can be suppressed.
　（例１）
　例１では、図６に示すリモート方式のプラズマエッチング装置１００を用いて、ガラス基板２の全体の温度と、処理容器１０１の内部の水蒸気分圧と、ＴｉＦ４又はＴｉＯＦ２の残留の有無と、ＴｉＯ２の残留の有無との関係を調べた。水蒸気分圧は、１００Ｐａ、２５０Ｐａ、４００Ｐａ、又は６００Ｐａであった。一方、基板温度は、５０℃、８９℃、９８℃、１３０℃、１７５℃、又は２７０℃であった。水蒸気分圧と基板温度以外の条件は、同一に設定した。ガラス基板２は、ＴｉＯ２を６．４質量％含むＴｉドープ石英ガラスであった。ハロゲン含有ガスとしては、ＣＦ４ガスを用いた。処理容器１０１の内部のガスの全圧は、大気圧であった。 (Example 1)
In Example 1, the remote type plasma etching apparatus 100 shown in FIG. 6 is used to determine the overall temperature of the glass substrate 2, the partial pressure of water vapor inside the processing container 101, and the presence or absence of TiF 4 or TiOF 2 remaining. The relationship with the presence or absence of residual TiO 2 was investigated. The water vapor partial pressure was 100 Pa, 250 Pa, 400 Pa, or 600 Pa. On the other hand, the substrate temperature was 50 ° C., 89 ° C., 98 ° C., 130 ° C., 175 ° C., or 270 ° C. Conditions other than the partial pressure of water vapor and the substrate temperature were set to be the same. The glass substrate 2 was Ti-doped quartz glass containing 6.4% by mass of TiO 2. The halogen-containing gas, CF 4 gas was used. The total pressure of the gas inside the processing container 101 was atmospheric pressure.
　ガラス基板２の第１主面２１にて一辺７ｍｍの正方格子状の軌跡を描くように、第１主面２１にフッ素ラジカルを照射し、正方向格子の中心にてＴｉ及びＦの増加の有無をＸＰＳ（Ｘ－ｒａｙ　Ｐｈｏｔｏｅｌｅｃｔｒｏｎ　Ｓｐｅｃｔｒｏｓｃｏｐｙ）で測定した。Ｔｉ及びＦの両者が増加することは、ＴｉＦ４又はＴｉＯＦ２の残留が有ることを意味する。また、Ｔｉが増加しＦが増加しないことは、ＴｉＯ２の残留が有ることを意味する。更に、Ｔｉ及びＦの両者が増加しないことは、ＴｉＦ４又はＴｉＯＦ２の残留もＴｉＯ２の残留も無いことを意味する。実験条件と、実験結果を表１に示す。 The first main surface 21 of the glass substrate 2 is irradiated with fluorine radicals so as to draw a square grid-like locus with a side of 7 mm, and the presence or absence of an increase in Ti and F at the center of the positive grid. Was measured by XPS (X-ray Photoelectron Spectroscopy). An increase in both Ti and F means that there is a residue of TiF 4 or TiOF 2. Further, the fact that Ti increases and F does not increase means that TiO 2 remains. Furthermore, the fact that both Ti and F do not increase means that neither TiF 4 or TiOF 2 remains nor TiO 2 remains. The experimental conditions and experimental results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
  
表１にて、「〇」はＴｉＦ４又はＴｉＯＦ２の残留もＴｉＯ２の残留も無いことを示し、「×（ＴｉＦ４又はＴｉＯＦ２）」はＴｉＦ４又はＴｉＯＦ２の残留が有ることを示し、「×（ＴｉＯ２）」はＴｉＯ２の残留が有ることを示す。
Figure JPOXMLDOC01-appb-T000001
In Table 1, The symbol "" residual of TiF 4 or TiOF 2 also shows that no residual TiO 2, "× (TiF 4 or TiOF 2)" indicates that the residual TiF 4 or TiOF 2 there , "X (TiO 2 )" indicates that there is a residue of TiO 2.
　表１から明らかなように、処理容器１０１の内部の水蒸気分圧が４００Ｐａ未満の状態であって、且つガラス基板２の全体の温度が９０℃以上の状態で、プラズマエッチングを実施した場合、ＴｉＦ４又はＴｉＯＦ２の残留もＴｉＯ２の残留も無かった。 As is clear from Table 1, when plasma etching is performed when the partial pressure of water vapor inside the processing container 101 is less than 400 Pa and the overall temperature of the glass substrate 2 is 90 ° C. or higher, TiF remaining 4 or TiOF 2 also residual TiO 2 also did.
　一方、基板温度が９０℃未満であって且つ水蒸気分圧が４００Ｐａ未満である場合、ＴｉＦ４又はＴｉＯＦ２の残留が認められ、ＴｉＦ４が残留していると推定される。ＴｉＦ４は常温では揮発しにくく、気相の状態で処理容器１０１の外部に排出されないためである。 On the other hand, when the substrate temperature is less than 90 ° C. and the partial pressure of water vapor is less than 400 Pa , residual TiF 4 or TiOF 2 is observed, and it is presumed that TiF 4 remains. This is because TiF 4 is hard to volatilize at room temperature and is not discharged to the outside of the processing container 101 in the vapor phase state.
　また、基板温度が９０℃以上であって且つ水蒸気分圧が４００Ｐａ以上である場合、ＴｉＯ２の残留が有った。処理容器１０１の内部にて、ＴｉＦ４とＨ２Ｏとの反応によりＴｉＯ２が生じたと推定される。 Further, when the substrate temperature was 90 ° C. or higher and the partial pressure of water vapor was 400 Pa or higher, TiO 2 remained. It is highly probable that TiO 2 was generated by the reaction between TiF 4 and H 2 O inside the processing container 101.
　更に、基板温度が９０℃未満であって且つ水蒸気分圧が４００Ｐａ以上である場合、ＴｉＦ４又はＴｉＯＦ２の残留が認められ、ＴｉＦ４とＴｉＯＦ２の両方が混在していると推定される。 Further, when the substrate temperature is less than 90 ° C. and the partial pressure of water vapor is 400 Pa or more, residual TiF 4 or TiOF 2 is observed, and it is presumed that both TiF 4 and TiOF 2 are mixed.
　（例２）
　例２では、図６に示すリモート方式のプラズマエッチング装置１００を用いて、ガラス基板２の全体の温度を常温（２０℃）に固定し、処理容器１０１の内部の水蒸気分圧と、水洗浄後のＴｉＦ４又はＴｉＯＦ２の残留と、ＴｉＯ２の残留の有無との関係を調べた。水蒸気分圧は、１００Ｐａ、２５０Ｐａ、４００Ｐａ、又は６００Ｐａであった。水蒸気分圧以外の条件は、同一に設定した。ガラス基板２は、ＴｉＯ２を６．４質量％含むＴｉドープ石英ガラスであった。ハロゲン含有ガスとしては、ＣＦ４ガスを用いた。処理容器１０１の内部のガスの全圧は、大気圧であった。 (Example 2)
In Example 2, the remote type plasma etching apparatus 100 shown in FIG. 6 is used to fix the entire temperature of the glass substrate 2 to room temperature (20 ° C.), divide the water vapor inside the processing container 101, and after washing with water. The relationship between the residual TiF 4 or 2 and the presence or absence of residual TiO 2 was investigated. The water vapor partial pressure was 100 Pa, 250 Pa, 400 Pa, or 600 Pa. The conditions other than the partial pressure of water vapor were set to be the same. The glass substrate 2 was Ti-doped quartz glass containing 6.4% by mass of TiO 2. The halogen-containing gas, CF 4 gas was used. The total pressure of the gas inside the processing container 101 was atmospheric pressure.
　例２では、例１と同様に、ガラス基板２の第１主面２１にフッ素ラジカルを照射し、その後、処理容器１０１から搬出したガラス基板２の第１主面２１を水でスピン洗浄し、フッ素ラジカルの照射軌跡である正方向格子の中心にてＴｉ及びＦの増加の有無をＸＰＳで測定した。実験条件と、実験結果を表２に示す。 In Example 2, similarly to Example 1, the first main surface 21 of the glass substrate 2 is irradiated with fluorine radicals, and then the first main surface 21 of the glass substrate 2 carried out from the processing container 101 is spin-washed with water. The presence or absence of an increase in Ti and F was measured by XPS at the center of the positive lattice, which is the irradiation locus of fluorine radicals. Table 2 shows the experimental conditions and the experimental results.
Figure JPOXMLDOC01-appb-T000002
  
表２にて、「〇」はＴｉＦ４又はＴｉＯＦ２の残留もＴｉＯ２の残留も無いことを示し、「×（ＴｉＦ４又はＴｉＯＦ２）」はＴｉＦ４又はＴｉＯＦ２の残留が有ることを示す。
Figure JPOXMLDOC01-appb-T000002
In Table 2, The symbol "" residual of TiF 4 or TiOF 2 also shows that no residual TiO 2, "× (TiF 4 or TiOF 2)" indicates that the residual TiF 4 or TiOF 2 there ..
　表２から明らかなように、処理容器１０１の内部の水蒸気分圧が４００Ｐａ未満の状態でプラズマエッチングを実施した後、ガラス基板２の第１主面２１を水でスピン洗浄した場合、ＴｉＦ４又はＴｉＯＦ２の残留もＴｉＯ２の残留も無かった。 As is clear from Table 2, when the first main surface 21 of the glass substrate 2 is spin-cleaned with water after plasma etching is performed in a state where the partial pressure of water vapor inside the processing container 101 is less than 400 Pa, TiF 4 or residual TiOF 2 also residual TiO 2 also did.
　一方、水蒸気分圧が４００Ｐａ以上である場合、ＴｉＦ４又はＴｉＯＦ２の残留が認められ、ＴｉＦ４は水に溶けるため、ＴｉＯＦ２が残留していると推定される。処理容器１０１の内部にて、ＴｉＦ４とＨ２Ｏとの反応によりＴｉＯＦ２が生じたと推定される。 On the other hand, when the partial pressure of water vapor is 400 Pa or more, residual TiF 4 or TiOF 2 is observed, and since TiF 4 is soluble in water, it is presumed that TiOF 2 remains. It is presumed that TiOF 2 was generated by the reaction between TiF 4 and H 2 O inside the processing container 101.
　以上、本開示に係るガラス基板の製造方法、及びＥＵＶＬ用マスクブランクの製造方法について説明したが、本開示は上記実施形態等に限定されない。特許請求の範囲に記載された範疇内において、各種の変更、修正、置換、付加、削除、及び組み合わせが可能である。それらについても当然に本開示の技術的範囲に属する。 The method for manufacturing a glass substrate and the method for manufacturing a mask blank for EUV according to the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiment and the like. Within the scope of the claims, various changes, modifications, replacements, additions, deletions, and combinations are possible. Of course, they also belong to the technical scope of the present disclosure.
　本出願は、２０２０年２月２７日に日本国特許庁に出願した特願２０２０－０３１４２２号に基づく優先権を主張するものであり、特願２０２０－０３１４２２号の全内容を本出願に援用する。 This application claims priority based on Japanese Patent Application No. 2020-031422 filed with the Japan Patent Office on February 27, 2020, and the entire contents of Japanese Patent Application No. 2020-031422 are incorporated into this application. ..
２　　　ガラス基板
１０１　処理容器
１１０　加工ヘッド 2 Glass substrate 101 Processing container 110 Processing head

Claims (9)

  1. 　Ｔｉドープ石英ガラスで形成されたガラス基板を、処理容器の内部に収容することと、
    　前記処理容器の内部に乾燥ガスを供給し、前記処理容器の内部の水蒸気分圧を４００Ｐａ未満に調整することと、
    　前記処理容器の内部の加工ヘッドにハロゲン含有ガスを供給し、前記ハロゲン含有ガスをプラズマ化し、ハロゲンラジカルを生成することと、
    　前記水蒸気分圧が４００Ｐａ未満の状態で、前記加工ヘッドと前記ガラス基板とを相対的に移動しながら、前記ハロゲンラジカルで前記ガラス基板をエッチングすることと、を有し、
    　前記ガラス基板をエッチングする際に、前記ガラス基板の全体の温度が９０℃以上である、ガラス基板の製造方法。     A glass substrate made of Ti-doped quartz glass is housed inside the processing container, and
    To supply dry gas to the inside of the processing container and adjust the partial pressure of water vapor inside the processing container to less than 400 Pa.
    Halogen-containing gas is supplied to the processing head inside the processing container, and the halogen-containing gas is turned into plasma to generate halogen radicals.
    Etching the glass substrate with the halogen radical while relatively moving the processing head and the glass substrate in a state where the partial pressure of water vapor is less than 400 Pa.
    A method for manufacturing a glass substrate, wherein the temperature of the entire glass substrate is 90 ° C. or higher when the glass substrate is etched.
  2. 　Ｔｉドープ石英ガラスで形成されたガラス基板を、処理容器の内部に収容することと、
    　前記処理容器の内部に乾燥ガスを供給し、前記処理容器の内部の水蒸気分圧を４００Ｐａ未満に調整することと、
    　前記処理容器の内部の加工ヘッドにハロゲン含有ガスを供給し、前記ハロゲン含有ガスをプラズマ化し、ハロゲンラジカルを生成することと、
    　前記水蒸気分圧が４００Ｐａ未満の状態で、前記加工ヘッドと前記ガラス基板とを相対的に移動しながら、前記ハロゲンラジカルで前記ガラス基板をエッチングすることと、
    　前記ガラス基板と前記ハロゲンラジカルの反応によって生じたハロゲン化チタンを、洗浄液に溶解して除去することと、を有する、ガラス基板の製造方法。     A glass substrate made of Ti-doped quartz glass is housed inside the processing container, and
    To supply dry gas to the inside of the processing container and adjust the partial pressure of water vapor inside the processing container to less than 400 Pa.
    Halogen-containing gas is supplied to the processing head inside the processing container, and the halogen-containing gas is turned into plasma to generate halogen radicals.
    Etching the glass substrate with the halogen radical while relatively moving the processing head and the glass substrate in a state where the partial pressure of water vapor is less than 400 Pa.
    A method for producing a glass substrate, which comprises dissolving titanium halide generated by the reaction of the glass substrate and the halogen radicals in a cleaning liquid and removing the titanium halide.
  3. 　前記洗浄液は、水、有機溶剤、アルカリ洗剤、又は酸洗剤を含む、請求項２に記載のガラス基板の製造方法。 The method for manufacturing a glass substrate according to claim 2, wherein the cleaning liquid contains water, an organic solvent, an alkaline detergent, or an acid detergent.
  4. 　前記ハロゲン含有ガスは、ＣＦ４、ＣＨＦ３、Ｃ２Ｆ６、Ｃ３Ｆ８、Ｃ４Ｆ１０、ＨＦ、ＳＦ６、ＣＣｌ４、ＮＦ３、Ｆ２、ＣＦ３Ｃｌ、又はＣＦ２Ｃｌ２を含む、請求項１～３のいずれか１項に記載のガラス基板の製造方法。 The halogen-containing gas is CF 4 , CHF 3 , C 2 F 6 , C 3 F 8 , C 4 F 10 , HF, SF 6 , C Cl 4 , NF 3 , F 2 , CF 3 Cl, or CF 2 Cl 2. The method for manufacturing a glass substrate according to any one of claims 1 to 3, which comprises.
  5. 　前記乾燥ガスは、Ｏ２、空気、Ｎ２、Ｈｅ、Ａｒ、ＣＯ２、又はＣＯを含む、請求項１～４のいずれか１項に記載のガラス基板の製造方法。 The method for producing a glass substrate according to any one of claims 1 to 4, wherein the drying gas contains O 2 , air, N 2 , He, Ar, CO 2, or CO.
  6. 　前記処理容器の内部のガスの全圧が大気圧である、請求項１～５のいずれか１項に記載のガラス基板の製造方法。 The method for manufacturing a glass substrate according to any one of claims 1 to 5, wherein the total pressure of the gas inside the processing container is atmospheric pressure.
  7. 　前記加工ヘッドの内部にて、周波数５０Ｈｚ～５ＧＨｚの電界を形成して、前記ハロゲンラジカルを生成する、請求項１～６のいずれか１項に記載のガラス基板の製造方法。 The method for manufacturing a glass substrate according to any one of claims 1 to 6, wherein an electric field having a frequency of 50 Hz to 5 GHz is formed inside the processing head to generate the halogen radical.
  8. 　前記ガラス基板は、ＥＵＶＬ用マスクブランクの製造に用いられる、請求項１～７のいずれか１項に記載のガラス基板の製造方法。 The method for manufacturing a glass substrate according to any one of claims 1 to 7, wherein the glass substrate is used for manufacturing a mask blank for EUV.
  9. 　請求項１～８のいずれか１項に記載の製造方法で得られた前記ガラス基板上に、ＥＵＶ光を反射する反射膜を形成することと、
    　前記反射膜上に、前記ＥＵＶ光を吸収する吸収膜を形成することと、を有する、ＥＵＶＬ用マスクブランクの製造方法。     To form a reflective film that reflects EUV light on the glass substrate obtained by the production method according to any one of claims 1 to 8.
    A method for producing a mask blank for EUV, which comprises forming an absorbing film that absorbs EUV light on the reflective film.
PCT/JP2021/007155 2020-02-27 2021-02-25 Manufacturing method for glass substrate and manufacturing method for euvl mask blank WO2021172449A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
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JP2006076816A (en) * 2004-09-08 2006-03-23 Tosoh Corp Machining method for surface of glass substrate
JP2013184872A (en) * 2012-03-09 2013-09-19 Nippon Electric Glass Co Ltd Edge treatment method of glass substrate, edge treatment device for glass substrate, and glass substrate
JP2018061007A (en) * 2016-07-29 2018-04-12 ラム リサーチ コーポレーションＬａｍ Ｒｅｓｅａｒｃｈ Ｃｏｒｐｏｒａｔｉｏｎ Doped ALD film for semiconductor patterning application
JP2019071407A (en) * 2017-10-10 2019-05-09 積水化学工業株式会社 Surface treatment method and apparatus

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006076816A (en) * 2004-09-08 2006-03-23 Tosoh Corp Machining method for surface of glass substrate
JP2013184872A (en) * 2012-03-09 2013-09-19 Nippon Electric Glass Co Ltd Edge treatment method of glass substrate, edge treatment device for glass substrate, and glass substrate
JP2018061007A (en) * 2016-07-29 2018-04-12 ラム リサーチ コーポレーションＬａｍ Ｒｅｓｅａｒｃｈ Ｃｏｒｐｏｒａｔｉｏｎ Doped ALD film for semiconductor patterning application
JP2019071407A (en) * 2017-10-10 2019-05-09 積水化学工業株式会社 Surface treatment method and apparatus

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