JP2004307263A - Method and apparatus for molding quartz glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for hot molding quartz glass by which the damage of the quartz glass or a graphite mold is prevented and the reaction of the quartz glass with the graphite mold is also prevented, and to provide an apparatus therefor. <P>SOLUTION: In the method of molding quartz glass 25 into a desired shape by housing the quartz glass 25 in a graphite mold 15 and heating and pressing the quartz glass 25, the inside wall surface of the graphite mold 15 is coated with a suspension containing carbon particles as a main solid component and further coated with a suspension containing SiC particles as a main solid component and dried to form a mold releasing layer 27. Then the quartz glass 25 is housed in the graphite mold 15 and heated and pressed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００６９】
【表２】

【００７０】
【発明の効果】
以上説明してきたように、各請求項に記載の発明によれば、グラファイト製モールドの内壁面に、カーボン粒子を主な固形成分とする懸濁液を塗布すると共に、ＳｉＣ粒子を主な固形成分とする懸濁液を塗布して乾燥させて離型層を形成したため、石英ガラスやグラファイト製モールドの損傷を防止すると共に、石英ガラスとグラファイト製モールドとの反応を防止することができる。これにより、四塩化ケイ素，シラン，有機ケイ素等のケイ素化合物を原料として製造される合成石英ガラス、またはＧｅ，Ｔｉ，Ｂ，Ｆ，Ａｌ等の屈折率を変化させる成分を添加した合成石英ガラスを加熱加圧成形してレチクル（フォトマスク）基板や結像光学系のレンズ材料に適する大型ガラスブロックを歩留まりよく製造することができる。
【００７１】
請求項２に記載の発明によれば、カーボン粒子を主な固形成分とする懸濁液を塗布し、乾燥後、更にＳｉＣ粒子を主な固形成分とする懸濁液を塗布するようにしたため、部分的にカーボン粒子が剥がれることなく、ＳｉＣ粒子を主な固形成分とする懸濁液を塗布し易い。
【００７２】
請求項６に記載の発明によれば、グラファイト製モールド内の離型層を真空雰囲気中もしくは塩素含有ガス雰囲気中での熱処理によって純化処理を行うことにより、石英ガラス中への不純物の拡散が微小に抑えられ、品質の良好な部分を拡大させることができる。
【図面の簡単な説明】
【図１】この発明の実施の形態の成形装置の一部を示す概略縦断面図である。
【符号の説明】
１０ 成形装置
１１ 真空チャンバ
１３ カーボンヒータ
１５ グラファイト製モールド
２３ 天板
２５ 石英ガラス
２６ シリンダロッド
２７ 離型層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a molding method and a molding apparatus for forming a homogeneous quartz glass into a predetermined shape by pressurizing while containing the quartz glass in a graphite mold and heating it. The present invention relates to a molding method and a molding apparatus with improved releasability and the like.
[0002]
[Prior art]
Conventionally, projection exposure apparatuses (or photolithography apparatuses) are mainly used for transferring integrated circuit patterns such as ICs and LSIs. The projection optical system used in this apparatus is required to have a higher exposure power over a wide exposure area and the entire exposure area as the integrated circuit is highly integrated. In order to improve the resolution of the projection optical system, the exposure wavelength is shortened or the numerical aperture (NA) of the projection optical system is increased.
[0003]
As for the exposure wavelength, the wavelength is being shortened from g-line (436 nm) to i-line (365 nm), KrF (248 nm), and ArF (193 nm) excimer laser. In order to further increase the integration, a method of using an F ₂ (157 nm) excimer laser, an X-ray, and an electron beam as a light source is currently being studied. Among them, a reduction projection exposure apparatus using an F ₂ excimer laser that can be manufactured by making use of the design concept so far has been attracting attention.
[0004]
In general, optical glass used as a lens member of an illumination optical system or a projection optical system of a reduction projection exposure apparatus using a light source having a wavelength longer than that of i-line has a light transmittance drastically decreased in a wavelength region shorter than that of i-line. In particular, most optical glasses do not transmit light in the wavelength region of 250 nm or less. Therefore, only quartz glass and calcium fluoride crystals can be used as the material of the lens constituting the optical system of the reduction projection exposure apparatus using an excimer laser as a light source. These two materials are indispensable materials for correcting chromatic aberration in the excimer laser imaging optical system.
[0005]
Another important element for printing a circuit on a wafer with a reduction projection exposure apparatus is a reticle. As a material used for this reticle, not only excimer laser durability but also thermal expansion due to heat generation of the substrate becomes a big problem. The quartz glass synthesized by the method for producing transparent quartz glass by the above method is used.
[0006]
In the direct method, a combustion supporting gas (oxygen-containing gas, for example, oxygen gas) and a combustible gas (hydrogen-containing gas, for example, hydrogen gas or natural gas) are mixed and burned in a quartz glass burner, and the center of the burner is mixed. A high-purity silicon compound (for example, silicon tetrachloride gas) is diluted as a raw material gas with a carrier gas (usually oxygen gas) and ejected, and the raw material gas is reacted (hydrated) by combustion of the surrounding oxygen gas and hydrogen gas. Decomposition silica) to generate quartz glass fine particles, and the quartz glass fine particles are deposited on a target made of an opaque quartz glass plate which is disposed below the burner and performs rotation, swinging and lowering movements, and at the same time, the oxygen Quartz glass ingots are obtained by melting and vitrifying with the combustion heat of gas and hydrogen gas.
[0007]
According to this method, since it is easy to obtain a quartz glass ingot having a relatively large diameter, an optical member having a desired shape and size can be manufactured by cutting out a block from the ingot.
[0008]
In recent years, in order to obtain an optical member having a large area, such as a large lens or reticle, or a large liquid crystal display, a quartz glass lump such as a pre-formed ingot is formed into a flat shape by heating and pressing. Therefore, a molding method for expanding the area is used.
[0009]
In this molding method, a quartz glass lump is accommodated in a mold and heated, and then molded by pressing with a pressure plate. Thereafter, the quartz glass lump is gradually cooled in the mold or further annealed to obtain a flat shape. A molded body having a predetermined shape with an enlarged area of the lower surface can be obtained.
[0010]
As an example of performing such heat-pressure molding, for example, in a graphite mold, heat-pressure molding is performed at a temperature of 1700 ° C. or higher in a helium gas atmosphere having an absolute pressure of 0.1 Torr or more and atmospheric pressure, Next, a method of rapidly cooling to 1100 to 1300 ° C. is known. Also, a method of pressure molding at 1600 ° C. to 1700 ° C. using a graphite mold having a structure that relieves stress caused by a difference in thermal expansion coefficient between quartz glass and a mold mold (see Patent Document 1 below). ) And a molding apparatus in which the graphite mold has a vertical structure with two or more divisions (see Patent Documents 2 and 3 below). Furthermore, a method of forming a coating layer made of quartz powder on the inner surface of a graphite mold and performing pressure molding at 1550 ° C. to 1700 ° C. (see Patent Document 4 below) is also known.
[0011]
[Patent Document 1]
Japanese Patent Publication No. 4-54626.
[0012]
[Patent Document 2]
JP-A-56-129621.
[0013]
[Patent Document 3]
JP-A-57-67031.
[0014]
[Patent Document 4]
Japanese Patent Application Laid-Open No. 2002-22020.
[0015]
[Problems to be solved by the invention]
However, in the conventional method for molding quartz glass, when the quartz glass is heat-pressed in a graphite mold, the quartz glass having the same coefficient is disposed inside the graphite mold having a large thermal expansion coefficient. After molding at a high temperature, the mold and the quartz glass after molding are substantially free of gaps. By lowering the temperature to room temperature, the graphite mold has a thermal expansion coefficient that is an order of magnitude higher than that of quartz glass. Therefore, it is necessary to release the difference in the shrinkage between the generated quartz glass and graphite. If the difference in shrinkage cannot be fully missed, unnecessary stress is applied to the quartz glass and the graphite mold, which may cause cracks in the treated quartz glass and breakage of the graphite mold. In particular, when a component that changes the refractive index is mixed, the viscosity is considerably different in addition to the coefficient of thermal expansion, so that cracks and the like are more likely to occur than in ordinary quartz glass.
[0016]
Further, in addition to the above-mentioned inconvenience due to the difference in coefficient of thermal expansion, quartz glass reacts with the graphite mold to form silicon carbide at a high temperature, and crystallization occurs at about 1400 ° C. to 1600 ° C. For this reason, the surface of the quartz glass after the treatment may have irregularities on the surface depending on the treatment temperature, and cracks may be generated therefrom.
[0017]
Furthermore, the quartz glass and the graphite mold may react and be fused, and the mold may be damaged as well as the workpiece (quartz glass).
[0018]
Accordingly, an object of the present invention is to provide a hot forming method and a forming apparatus for quartz glass that prevent damage to the quartz glass and the graphite mold and prevent the reaction between the quartz glass and the graphite mold.
[0019]
[Means for Solving the Problems]
As a result of intensive studies on the above problems, the present inventors have found that the problem can be solved as follows, and have completed the present invention.
[0020]
That is, the invention according to claim 1 is a method in which quartz glass is accommodated in a graphite mold, and the quartz glass is heated and pressed to form a desired shape. After applying a suspension containing carbon particles as a main solid component and applying a suspension containing SiC particles as a main solid component and drying to form a release layer, The method is characterized in that a method for forming quartz glass in which the quartz glass is accommodated and heated and pressed is used.
[0021]
According to a second aspect of the present invention, there is provided a method in which quartz glass is accommodated in a graphite mold, and the quartz glass is heated and pressed to form a desired shape. A suspension containing particles as a main solid component is applied, and after drying, a suspension containing SiC particles as a main solid component is applied and dried to form a release layer, and then the graphite mold The method is characterized in that the quartz glass is contained in the quartz glass and is heated and pressed.
[0022]
The invention according to claim 3 is characterized in that, in the molding method according to claim 1 or 2, the thicknesses of the carbon particle layer and the SiC particle layer of the release layer are 30 μm to 1000 μm, respectively. To do.
[0023]
Invention of Claim 4 is the shaping | molding method as described in any one of Claim 1 thru | or 3, The average particle diameter of the said carbon particle and SiC particle is 0.01 micrometer-100 micrometers, respectively, It is characterized by the above-mentioned. .
[0024]
The invention according to claim 5 is the molding method according to claim 1, wherein the carbon particle layer and the SiC particle layer have a double structure, or the carbon particles and the SiC particles are mixed. It is characterized by becoming.
[0025]
The invention according to claim 6 is the molding method according to any one of claims 1 to 5, wherein the release layer in the graphite mold is heat-treated in a vacuum atmosphere or a chlorine-containing gas atmosphere. In this case, the purification process is performed.
[0026]
The invention according to claim 7 is a molding apparatus that accommodates quartz glass in a graphite mold and heats and presses the quartz glass to form a desired shape, and on the inner wall surface of the graphite mold, A quartz glass molding apparatus in which a suspension containing carbon particles as a main solid component was applied and a suspension containing SiC particles as a main solid component was applied and dried to form a release layer. It is characterized by.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0028]
FIG. 1 shows a molding apparatus 10 of this embodiment.
[0029]
This molding apparatus 10 has an ingot of a synthetic quartz glass manufactured using a silicon compound such as silicon tetrachloride, silane, or organosilicon as a raw material or a part thereof, or a refractive index of Ge, Ti, B, F, Al, or the like. From quartz glass ingots such as synthetic quartz glass ingots and parts thereof to which the components to be changed are added, for example, large liquid crystal masks, reticles for photomasks such as semiconductor masks, and large optical imaging systems It is an apparatus for molding a plate-like body having a wide surface such as a lens material or other large glass blocks.
[0030]
The molding apparatus 10 has a heat insulating material 12 provided over the entire surface of a metal vacuum chamber 11 and a carbon heater 13 provided in a vertical wall of the heat insulating material 12. A graphite mold 15 having a hollow portion 21 (hereinafter referred to as “mold 15”) is accommodated in a substantially central portion inside.
[0031]
The mold 15 includes a bottom portion 18 including a bottom plate 16 and a receiving plate 17, and a side wall portion 20 formed in a square cylindrical shape above the bottom portion 18, and the cylindrical side wall portion 20 and the bottom portion 18 A hollow portion 21 is formed.
[0032]
In the hollow portion 21, a top plate 23 having a shape corresponding to the shape of the hollow portion 21 is disposed, and a pressing surface 23 b (upper surface) of the top plate 23 is disposed outside the vacuum chamber 11. Can be moved to the bottom 18 side of the mold 15 by being pressed by the cylinder rod 26 of the hydraulic cylinder.
[0033]
The hydraulic cylinder provided with the cylinder rod 26 is configured to move by being pressurized by adjusting the hydraulic pressure supplied from the outside, but the detailed illustration is omitted.
[0034]
The mold 15 and the top plate 23 have heat resistance and strength against temperature and pressure at the time of forming the massive quartz glass 25, and are hardly mixed with impurities even if they contact the massive quartz glass 25 at the time of molding. It is made of a material, here all made of graphite.
[0035]
A release layer 27 is provided on the inner wall surface 15 a of the mold 15 and the pressing surface 23 a (lower surface) of the top plate 23. The release layer 27 is formed by applying a suspension containing carbon particles as a main solid component, drying, and further applying and drying a suspension containing SiC particles as a main solid component. Yes.
[0036]
Here, the type of the solvent for making the suspension of carbon particles or SiC particles is preferably an alcohol type for reasons such as drying after coating and ease of handling, and in this embodiment, ethyl alcohol is used. doing. Carbon particles or SiC particles are dispersed in this ethyl alcohol and applied with a brush. In addition, it is desirable for the SiC particles to use a β-type crystal system.
[0037]
Next, a case where the massive quartz glass 25 is molded into a predetermined shape using the molding apparatus 10 will be described.
[0038]
First, a suspension containing carbon particles as a main solid component is applied to the inner wall surface of the mold 15 arranged in the vacuum chamber 11, and after drying, a suspension containing SiC particles as a main solid component is further applied. The release layer 27 is formed by applying and drying.
[0039]
In this way, a suspension containing carbon particles as a main solid component was applied, and after drying, a suspension containing SiC particles as a main solid component was further applied. Easy to apply suspension. If a suspension containing SiC particles as a main solid component is applied in an undried state with a suspension containing carbon particles as a main solid component, the carbon particles tend to partially peel off.
[0040]
The release layer 27 is formed in a double structure in which the average particle diameter of carbon particles and SiC particles is 0.01 μm to 100 μm, respectively, and the thickness of the carbon particle layer and SiC particle layer is 30 μm to 1000 μm, respectively. ing. A layer in which carbon particles and SiC particles are mixed can also be used.
[0041]
After the release layer 27 is formed in this way, a purification process in the mold 15 is performed. There are two types of purification treatment, one of which is heating in a vacuum atmosphere (1000 ° C. to 2000 ° C.) to remove impurities by evaporation, and heating in a chlorine-containing gas atmosphere is chlorine. And metal impurities are reacted and evaporated to remove.
[0042]
Thereafter, a massive quartz glass 25 is placed in the hollow portion 21 of the mold 15. In this embodiment, a synthetic quartz glass ingot is used as the massive quartz glass 25, and in order to shorten the lead time, preheating at a temperature of less than 300 ° C. in advance before accommodating in the hollow portion 21 of the mold 15 is performed. doing.
[0043]
Next, the top plate 23 is disposed on the top of the massive quartz glass 25 accommodated in the hollow portion 21, and the pressing portion 26 a of the cylinder rod 26 of the hydraulic cylinder is brought into contact with the pressing surface 23 b of the top plate 23. To do. Then, the inside of the vacuum chamber 11 is replaced with an inert gas, and the pressure inside the vacuum chamber 11 is set to a predetermined pressure.
[0044]
Next, the massive quartz glass 25 accommodated in the mold 15 and the hollow portion 21 thereof is heated by the carbon heater 13.
[0045]
In this molding, it is preferable to raise the temperature of the bulk quartz glass 25 to a temperature not lower than the crystallization temperature and not higher than the softening point. At the time of pressurization, it is sufficient that at least the top portion 25a side reaches the molding temperature.
[0046]
Then, by controlling and adjusting the hydraulic pressure to the hydraulic cylinder in a state where the massive quartz glass 25 is heated in this way, the cylinder rod 26 is moved downward, and the top portion 23 of the top plate 23 is moved by the pressing portion 26a of the cylinder rod 26. The pressing surface 23b is pressed. As a result, the top plate 23 moves in the pressing direction on the bottom 18 side of the mold 15, and the massive quartz glass 25 is pressed between the pressing surface 23 a of the top plate 23 and the bottom 18.
[0047]
When the quartz glass 25 is formed into a predetermined shape, the pressurization by the top plate 23 is finished. Thereafter, the quartz glass 25 molded into a plate shape is cooled while being placed in the mold 15, and the quartz glass 25 is taken out from the mold 15 to complete the molding.
[0048]
As described above, if the massive quartz glass 25 is formed into a flat shape, the releasability is improved by the carbon particles. Therefore, there is a difference in shrinkage between the mold 15 and the quartz glass 25 during cooling. Even if it occurs, it is easy to cause a relative movement between the release layer 27 of the mold 15 and the quartz glass 25, so that the difference in shrinkage can be released.
[0049]
Therefore, it is possible to prevent cracks in the treated quartz glass 25 and damage to the mold 15 without applying unnecessary stress to the quartz glass 25 and the mold 15. In particular, even when a component that changes the refractive index is mixed and the viscosity is low, cracks and the like of the quartz glass 25 can be effectively prevented.
[0050]
Further, the SiC particles can prevent the mold 15 from being oxidized, prevent the mold 15 from being contaminated, prevent the mold 15 from reacting with the quartz glass 25, and prevent carburization of the quartz glass 25. As a result, the altered layer is reduced, and the portion with good quality is enlarged. Therefore, the treated quartz glass 25 can prevent the occurrence of cracks without causing irregularities on the surface.
[0051]
In addition, since the release layer 27 is provided, it is possible to prevent the quartz glass 25 and the mold 15 from reacting and fusing, so that the mold 15 and the quartz glass 25 can be prevented from being damaged.
[0052]
【Example】
Examples will be described below.
[0053]
[Example]
After the synthesized synthetic quartz glass ingot was processed into a predetermined shape, it was processed using the molding apparatus 10 under the conditions as shown in Examples 1 to 4 in Table 1. The temperature rising rate at this time is 600 ° C./hr. Table 2 shows the characteristics of the quartz glass 25 obtained by the treatment.
[0054]
That is, as shown in Table 1, in Examples 1 to 4, there are two types of coating materials for the release layer 27: carbon particles (C) and SiC particles. In Example 1, the carbon particle diameter was 0.1 μm, the SiC particle diameter was 0.1 μm, the structure was a double structure (a double structure of a carbon particle layer and an SiC particle layer), and purification was performed in vacuum. Is.
[0055]
In Example 2, the carbon particle diameter is 10 μm, the SiC particle diameter is 1 μm, the structure is a double structure, and purification is performed in Cl ₂ gas.
[0056]
In Example 3, the carbon particle diameter is 0.01 μm, the SiC particle diameter is 0.01 μm, the structure is a mixed structure (a layer in which carbon particles and SiC particles are mixed), and purification is performed in vacuum.
[0057]
In Example 4, the carbon particle diameter is 1 μm, the SiC particle diameter is 10 μm, the structure is a mixed structure, and purification is performed in Cl ₂ gas.
[0058]
[Comparative example]
The synthesized synthetic silica glass ingot was processed into a predetermined shape and processed under the conditions shown in Comparative Examples 1 to 4 in Table 1. Table 2 shows the characteristics of the quartz glass obtained by the treatment.
That is, as shown in Table 1, in Comparative Examples 1 to 4, the coating material is either carbon particles or SiC particles, but none of them is coated.
[0059]
Comparative Example 1 has a carbon particle diameter of 1 μm, no SiC particles, and no purification treatment.
[0060]
In Comparative Example 2, no carbon particles are present, the SiC particle diameter is 10 μm, and no purification treatment is performed.
[0061]
In Comparative Example 3, the carbon particle diameter was 0.1 μm, no SiC particles were present, and the product was purified in a vacuum.
[0062]
In Comparative Example 4, carbon particles are not present, the SiC particle diameter is 0.1 μm, and purification is performed in a vacuum.
[0063]
Here, when Examples 1-4 and Comparative Examples 1-4 are compared based on Table 2, in Examples 1-4, although the numerical value of the transmittance distribution (Δn) is generally small, the Comparative Example In 1-4, the numerical value of the transmittance distribution (Δn) is large overall.
[0064]
In Examples 1 to 4, the numerical value of the birefringence is generally small, whereas in Comparative Examples 1 to 4, the numerical value of the birefringence is large.
[0065]
In Examples 1 to 4, the transmittance is in the range of 99.5% / cm to 99.7% / cm, whereas in Comparative Examples 1 to 4, the transmittance is 99.0% / cm to 99.4%. It can be seen that the transmittance is better in Examples 1 to 4 than in Comparative Examples 1 to 4.
[0066]
In Examples 1 to 4, all the durability was good, but in Comparative Examples 1 to 4, all the durability was bad.
[0067]
In Examples 1-4, the thickness of the deteriorated layer from the outer periphery is in the range of 5 mm to 10 mm, whereas in Comparative Examples 1-4, the thickness of the deteriorated layer from the outer periphery is in the range of 15 mm to 25 mm. Yes, it can be seen that in Examples 1 to 4, the altered layer from the outer periphery is thinner than Comparative Examples 1 to 4.
[0068]
[Table 1]

[0069]
[Table 2]

[0070]
【The invention's effect】
As described above, according to the invention described in each claim, a suspension containing carbon particles as a main solid component is applied to the inner wall surface of a graphite mold, and SiC particles are used as a main solid component. Since the release layer was formed by applying and drying the suspension, it is possible to prevent the quartz glass and the graphite mold from being damaged, and to prevent the reaction between the quartz glass and the graphite mold. As a result, synthetic quartz glass manufactured using silicon compounds such as silicon tetrachloride, silane, and organic silicon as raw materials, or synthetic quartz glass added with components that change the refractive index, such as Ge, Ti, B, F, and Al. A large glass block suitable for a reticle (photomask) substrate or a lens material for an imaging optical system can be manufactured with high yield by heating and pressing.
[0071]
According to the invention described in claim 2, since the suspension having carbon particles as the main solid component is applied, and after drying, the suspension having SiC particles as the main solid component is further applied. It is easy to apply a suspension containing SiC particles as a main solid component without carbon particles partially peeling off.
[0072]
According to the sixth aspect of the present invention, the diffusion of impurities into the quartz glass is minimized by performing a purification treatment on the release layer in the graphite mold by heat treatment in a vacuum atmosphere or a chlorine-containing gas atmosphere. Therefore, it is possible to enlarge a portion with good quality.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view showing a part of a molding apparatus according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Molding apparatus 11 Vacuum chamber 13 Carbon heater 15 Graphite mold 23 Top plate 25 Quartz glass 26 Cylinder rod 27 Release layer

Claims (7)

In a method of forming quartz glass in a desired shape by housing quartz glass in a graphite mold and heating and pressing the quartz glass,
On the inner wall of the graphite mold, a suspension containing carbon particles as a main solid component is applied, and a suspension containing SiC particles as a main solid component is applied and dried to form a release layer. Then, the quartz glass is accommodated in the graphite mold and heated and pressed, and the method for molding the quartz glass is characterized in that: In a method of forming quartz glass in a desired shape by housing quartz glass in a graphite mold and heating and pressing the quartz glass,
On the inner wall surface of the graphite mold, a suspension containing carbon particles as a main solid component is applied, and after drying, a suspension containing SiC particles as a main solid component is applied and dried to release the release layer. Then, the quartz glass is accommodated in the graphite mold and heated and pressed. 3. The method for molding quartz glass according to claim 1, wherein thicknesses of the carbon particle layer and the SiC particle layer of the release layer are 30 μm to 1000 μm, respectively. 4. 4. The method for molding quartz glass according to claim 1, wherein the average particle diameters of the carbon particles and the SiC particles are 0.01 μm to 100 μm, respectively. 5. 2. The molding method according to claim 1, wherein the carbon particle layer and the SiC particle layer have a double structure, or a layer in which the carbon particles and the SiC particles are mixed. Method for forming quartz glass. 6. The molding method according to claim 1, wherein the release layer in the graphite mold is purified by heat treatment in a vacuum atmosphere or a chlorine-containing gas atmosphere. A method for forming quartz glass. In a molding apparatus that houses quartz glass in a graphite mold and heats and presses the quartz glass to form a desired shape,
On the inner wall of the graphite mold, a suspension containing carbon particles as a main solid component is applied, and a suspension containing SiC particles as a main solid component is applied and dried to form a release layer. A quartz glass molding apparatus characterized by the above.

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