JPH06227827A - Transparent silica glass and its production - Google Patents

Abstract

PURPOSE:To provide a transparent silica glass capable of being applied to a photomasking substrate useful for an excimer laser photolithography process of a super LSI production method and the production method of the transparent silica glass. CONSTITUTION:The objective silica glass contains OH group of <=10ppm, halogen of >=400ppm and hydrogen molecule and having excimer laser resistance. A porous silica glass substrate is subjected to a dehydrating treatment in a halogen atmosphere and to a vitrifying process to lead to a transparent silica glass. The objective transparent silica glass is obtained by incorporating the obtained transparent silica glass with hydrogen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent quartz glass, particularly a transparent quartz glass having excimer laser resistance, and a method for producing the same.

[0002]

2. Description of the Related Art Quartz glass is a transparent material over a wide range of wavelengths from the near infrared to the vacuum ultraviolet region, has a very small coefficient of thermal expansion and is excellent in dimensional stability, and further has chemical durability. It is widely used as a substrate material for a photomask in a lithography process at the time of manufacturing an LSI because it is excellent.

However, when conventional quartz glass is exposed to high-energy ultraviolet rays such as plasma etching and excimer laser during the photomask manufacturing process, structural defects are induced and the transmittance of ultraviolet rays decreases and fluorescent emission centers are generated. There are problems such as ArF excimer laser and K
There has been a problem as a substrate for a photomask used in the lithography of VLSI using an rF excimer laser as an exposure light source, and as an optical member when constructing an optical system using the excimer laser as a light source.

Various investigations have been made as methods for solving these problems, and it is known that hydrogen molecules may be contained in quartz glass in some form. However, the complete effect cannot always be expected unless the quartz glass to be made to contain hydrogen is specified. For example, JP-A-1-201664 discloses a method of heat-treating quartz glass in an atmosphere containing hydrogen. However, according to the method disclosed in the same publication, the absorption around 260 nm formed when the KrF laser is irradiated to the quartz glass obtained by transparently vitrifying the porous quartz glass body obtained by subjecting the glass forming raw material to flame hydrolysis. It is not possible to completely suppress the fluorescence emission in the band and around 650 nm.

On the other hand, JP-A-3-88742 discloses a method of dissolving hydrogen molecules in quartz glass in order to impart excimer laser resistance to the quartz glass body. However, in the quartz glass disclosed in the same issue, it is necessary to dissolve a large amount of hydrogen molecules, and therefore it is necessary to heat-treat the quartz glass in a hydrogen atmosphere that has a risk of explosion and under pressure, so However, there is a problem that it has to be a big one.

Further, a method for producing a quartz glass containing no OH by heat-treating a porous quartz glass body obtained by flame hydrolysis of a glass forming raw material in a halogen atmosphere is, for example, a method of producing a low loss quartz glass fiber. It is known as a transparent vitrification method of VAD method porous quartz glass which is a manufacturing method. However, the quartz glass transparentized by such a method has a strong absorption band near 250 nm, and cannot be used as a photomask substrate for excimer laser lithography using a KrF excimer laser. When further irradiated with a KrF excimer laser, strong fluorescence emission is observed in the vicinity of 285 nm, 390 nm, and 460 nm, and it looks blue in the visual sense. Especially 28
When it has fluorescence emission at 5 nm, it cannot be used as a substrate for a photomask in lithography using a KrF excimer laser as an exposure light source because it matches the photosensitive characteristics of a resist.

[0007]

DISCLOSURE OF THE INVENTION The object of the present invention is to solve the above-mentioned problems, and an excimer laser having no absorption band or fluorescence emission due to a structural defect even when irradiated by an excimer laser. A quartz glass having resistance and a method for producing the same are provided.

[0008]

The present invention has been made to solve the above-mentioned problems, and is formed by depositing and growing quartz glass fine particles obtained by flame hydrolysis of a glass forming raw material on a substrate. In the transparent quartz glass obtained by heating the porous quartz glass body thus prepared, the OH content in the transparent quartz glass is 10 ppm or less, and halogen is 4
Provided is a transparent quartz glass containing at least 00 ppm and containing hydrogen.

Further, in view of the above-mentioned conventional problems, the present inventor imparts excimer laser resistance to a transparent quartz glass obtained by converting a porous quartz glass body obtained by flame hydrolysis of a glass forming raw material into transparent vitreous. In order to do so, after performing the dehydration treatment described below in a temperature range lower than the temperature at which the porous quartz glass body becomes transparent vitrified, it is transparent vitrified, further molded into a desired shape, and then treated in a hydrogen atmosphere. Therefore, it was found that a transparent quartz glass having excimer laser resistance can be easily manufactured.

The OH content in the present invention is obtained from the absorption based on the stretching vibration of Si--OH in the silica glass found in the vicinity of 2.7 μm in the infrared spectroscopy spectrum of the silica glass (JP ．Williams
Others: J. Am. Ceram. Soc. , Vol. 55,
Pp. 524-527).

The contents of the present invention will be described below step by step. First, a porous quartz glass body formed by depositing and growing quartz glass fine particles obtained by flame hydrolysis of a glass forming raw material on a substrate is dehydrated, and then transparentized into a transparent quartz glass body. By the method, transparent quartz glass bodies having different OH concentrations were manufactured.

Further, after the hydrogen molecules were contained in the quartz glass, the relationship between the OH concentration in the quartz glass and the 650 nm fluorescence emission intensity based on the structural defect induced by the excimer laser irradiation was examined. Fig. 1
As shown in, the 650 nm fluorescence intensity (measured by MPCD-1000 manufactured by Otsuka Electronics Co., Ltd.) was O
For the first time, we have found a strong dependence on the H content. That is, the 650 nm fluorescence intensity is proportional to the OH content in the quartz glass, and if the OH content is reduced to about 40 ppm, the 650 nm fluorescence emission intensity becomes extremely weak and there is substantially no problem as an optical member such as a photomask. Level, and if the OH content is 10 ppm or less, 650
It was found that it is possible to completely suppress the nm fluorescence emission, which is more preferable.

Therefore, in order to further reduce the OH content in the quartz glass, the quartz glass dehydrated by the halogen gas at a temperature below the transparent vitrification temperature was irradiated with a KrF excimer laser, and 285 nm, 390 nm, 4
It was found to have a strong fluorescence emission at 60 nm.
The present inventors evaluated excimer laser resistance after subjecting quartz glass dehydrated with a halogen gas to a heat treatment in a hydrogen atmosphere to add hydrogen. As a result, it was found that the inhibition ratio of each fluorescence emission differs depending on the concentration of halogen contained in the quartz glass. That is, the halogen concentration in the quartz glass is 400
It has been found that the fluorescence emission of 285 nm, 390 nm and 460 nm is substantially suppressed by containing hydrogen molecules at ppm or more, and more preferably each fluorescence emission is completely suppressed when the halogen concentration is 500 ppm or more. Further, when the halogen concentration is less than 400 ppm, the suppression of 390 nm fluorescence emission is incomplete, which is not preferable.

The existence state of the halogen contained in these quartz glasses is not clear, but the presence of 400 ppm or more of halogen in the quartz glass leads to a reduction in the OH content, and when hydrogen is contained, Is
The inventors have found that the fluorescence emission of 650 nm and the fluorescence emission of 285 nm, 390 nm, and 460 nm can be suppressed to the extent that there is no substantial problem with the irradiation of the KrF excimer laser, and the present invention has been completed.

Further, in order to study the influence of hydrogen molecules in the quartz glass, quartz glasses having different hydrogen contents were prepared and subjected to Raman spectroscopy (R-800 manufactured by JASCO Corporation).
The relationship between the amount of dissolved hydrogen measured in (1) and the fluorescence emission upon irradiation with a KrF excimer laser was examined. OH content is 10ppm and dissolved hydrogen amount is 4.4 × 10 ¹⁷ molecule /
With quartz glass of cm ³ , fluorescence emission of 390 nm was observed upon irradiation with KrF excimer laser. On the other hand, no Raman scattering peak was observed, the amount of dissolved hydrogen was 1 × 10 ¹⁷ molecules / cm ³ or less, which is less than the detection limit of the Raman method, and OH.
It has been found that quartz glass having a content of 10 ppm or less does not generate fluorescence emission at 390 nm, and fluorescence emission at 650 nm is substantially suppressed.

Then, when the amount of hydrogen released when the quartz glass was heated at 1000 ° C. in vacuum was evaluated, the amount of hydrogen released per surface area of the excimer laser resistant quartz glass was 0.9 × 10 ^20. The molecule / m ² . Further, in the case of quartz glass having a hydrogen release amount of 1.5 × 10 ²⁰ molecules / m ² , suppression of fluorescence emission at 390 nm was insufficient. On the other hand, quartz glass with a small hydrogen molecule content of about 5 × 10 ¹⁷ molecules / m ^{2 of} hydrogen release amount has a diameter of 285 mm, 46 mm.
Fluorescence emission of 0 nm was observed, and further an increase of 650 nm fluorescence intensity was observed with the excimer laser irradiation.

In a preferred embodiment of the present invention, a porous quartz glass is prepared by depositing and growing fine quartz glass powder obtained by flame hydrolysis of a glass forming raw material in an oxyhydrogen flame on a substrate in advance. Dehydration is performed in a halogen atmosphere in a temperature range below the temperature at which the body becomes transparent. After the dehydration treatment, the transparent quartz glass body is heated by raising the temperature to the transparent vitrification temperature. Further, after being heated to a temperature equal to or higher than the softening point to be formed into a desired shape, it is heat-treated in a hydrogen atmosphere to obtain a transparent quartz glass having excellent excimer laser resistance. A seed rod made of quartz glass (for example, JP-B-63-24973) can be used as the base material.
Further, not only quartz glass but also a plate-shaped substrate may be used.

The glass forming raw material used is not particularly limited as long as it is a gasifiable raw material.
SiCl ₄ , SiHCl ₃ , SiH ₂ Cl ₂ , SiCH
Chlorides such as ₃ Cl ₃ , SiF ₄ , SiHF ₃ , SiH ₂
Fluoride such as F ₂ ; bromide such as SiBr ₄ and SiHBr ₃ ; silicon halide compound such as iodide such as SiI ₄ are preferable from the viewpoint of workability and cost. The porous quartz glass body is formed by hydrolyzing these glass forming raw materials in an ordinary oxyhydrogen flame and depositing them on a substrate.

The thus obtained porous quartz glass body is then heated and held in a halogen atmosphere for a certain period of time and then heated to a transparent vitrification state to become a transparent vitrification into a quartz glass body. That is, for example, after the porous quartz glass body is pre-installed in an electric furnace whose atmosphere can be controlled,
It is heated at a constant heating rate. Then, after reaching a predetermined temperature, a gas containing 0.01 to 5% by volume of halogen gas is introduced to form a halogen-containing atmosphere.

The type of halogen can be appropriately selected from iodine, bromine, chlorine and fluorine, but chlorine or fluorine is preferable from the viewpoint of handleability. Particularly, chlorine is preferable from the viewpoint of corrosion resistance of furnace materials and the like. As a source of halogen, chlorine gas or fluorine gas may be partially or wholly used, and in the case of chlorine, CCl ₄ , CHCl ₃ , or Si.
It may be used in place of Cl ₄ or the like, and in the case of fluorine, it may be used in place of halides such as SF ₆ , CHF ₃ and SiF ₄ .

The halogen concentration during the halogen atmosphere treatment is preferably in the range of 0.01 to 5% by volume. If the halogen concentration exceeds 5%, it is not preferable because the halogen contained in the porous quartz glass is liberated and does not become transparent when the temperature is raised for the subsequent transparent vitrification, and the concentration is 0.01%. If it is less than the above range, the effect of the halogen treatment is not recognized, which is not preferable.

Next, as the temperature range for the dehydration treatment,
The temperature is preferably in the range of 800 to 1250 ° C., the dehydration effect by the dry gas or halogen is not recognized at a temperature lower than this, and the transparent vitrification proceeds on the surface of the porous quartz glass body at a temperature higher than this. It is not preferable because the porous quartz glass body is not efficiently dehydrated.

Further, the holding time in this temperature range depends on the temperature to be treated, the halogen gas concentration, the volume of the porous quartz glass body, etc., so that it is difficult to unconditionally specify, but it is 1 to 30 hours. It is preferably in the range.
The OH content in quartz glass is determined by FTIR spectroscopy as S
It can be quantified by absorption at 3680 cm ⁻¹ by i-OH, but O in quartz glass dehydrated with halogen gas
The H content is 10 ppm or less.

The porous quartz glass body dehydrated by the halogen gas in this manner is subsequently heated to a transparent vitrification temperature and heated to be vitrified. The transparent vitrification temperature is not particularly limited as long as it is in the range of 1350 to 1500 ° C. The transparent vitrified transparent quartz glass body,
Usually, it is removed from the substrate and transferred to the next step.

The transparent quartz glass thus obtained is molded into a desired shape by heating the transparent quartz glass body to a temperature range above the softening point. The temperature range at this time is preferably in the range of 1600 to 1800 ° C. At a temperature lower than 1600 ° C., it is practically difficult to mold because the viscosity of the transparent quartz glass is high, and
Devitrification occurs due to crystallization, which is not preferable.
A temperature higher than ℃ is not preferable because sublimation of the transparent quartz glass occurs.

The transparent quartz glass molded into a desired shape is placed in an electric furnace whose atmosphere can be controlled so as to subsequently contain hydrogen molecules, and heated to the processing temperature.
After reaching the processing temperature, an atmosphere gas containing hydrogen is introduced to make the atmosphere in the furnace a hydrogen atmosphere. The hydrogen concentration is preferably 30% or more. If the concentration is lower than this, it is not preferable because the required amount of hydrogen cannot be introduced. More preferably, the hydrogen concentration is 90% or more.

Further, the treatment temperature is preferably in the range of 500 to 1100 ° C. At a temperature lower than this, the time required for containing the required amount of hydrogen is extremely long because the diffusion coefficient of hydrogen molecules is small. Is not preferable, and when the temperature exceeds 1100 ° C., the reaction with hydrogen molecules forms a 390 nm fluorescent emission center, which is not preferable. Since the amount of hydrogen dissolved in the transparent quartz glass decreases as the temperature rises, it is more preferably 800 to 1
A range of 000 ° C is suitable.

The transparent quartz glass manufactured through the above steps has an OH content of 10 ppm or less and a halogen content of 400 ppm or more.

Further, the transparent quartz glass has a hydrogen molecule content below the detection limit by the Raman method and a hydrogen molecule emission amount per surface area of 1 × 10 ²⁰ molecules / m ² or less, and is suitable for irradiation with a KrF excimer laser. On the other hand, it is a quartz glass that has excimer laser resistance without the generation of absorption bands and fluorescence emission centers. Further, the transparent quartz glass produced by the present invention, since a high-purity synthetic raw material can be used as a glass forming raw material, since there is no mixing of impurities from the crucible and the like because it does not go through the melting step, iron, The total amount of impurities of heavy metal elements such as nickel and alkali metal elements such as sodium and potassium is 1 ppm or less, which is extremely high purity.

[0030]

When the transparent quartz glass is irradiated with high-energy ultraviolet rays such as an excimer laser, a 650 nm fluorescence emission center is generated and the mechanism of exhibiting a red color is not always clear, but the non-crosslinked oxygen radicals in the transparent quartz glass are not clear. Is said to be the cause. It is known that non-crosslinked oxygen radicals are formed by irradiating a dissolved oxygen molecule, oxygen excess type defects (Si-O-O-Si), etc. contained in quartz glass with an excimer laser. .
The present inventor found for the first time that an OH group becomes a non-crosslinked oxygen radical upon irradiation with an excimer laser. Therefore, reducing dissolved oxygen molecules, oxygen-excessive defects, and OH content that can be precursors of non-crosslinked oxygen radicals are important factors for excimer laser resistance.

In the present invention, the OH content is 10 ppm.
Limiting to the following is the action of reducing the OH content, which is one of the precursors of non-crosslinked oxygen radicals, to reduce the 650 nm fluorescence emission at the time of excimer laser irradiation and the absorption band near its excitation wavelength of 260 nm. Have. Further, the inclusion of hydrogen has the effect of removing oxygen excess defects and dissolved oxygen molecules, and has the effect of improving the resistance to excimer laser irradiation.

Further, by dehydration operation with halogen, OH
The inclusion of an appropriate amount of hydrogen in the transparent quartz glass from which the groups have been completely removed removes oxygen-excessive defects and dissolved oxygen that could not be removed even by the halogen dehydration operation, and further produces 285n
m, 390 nm, 460 nm to remove fluorescence emission centers and complete excimer resistance.

Hereinafter, the details of the present invention will be described with reference to Examples, but the content of the present invention is not limited to these Examples.

[0034]

【Example】

[Example 1] A porous quartz glass body having a diameter of 9 cm and a length of 10 cm formed by depositing fine particles formed by hydrolyzing SiCl ₄ in an oxyhydrogen flame on a seed rod by a known method is usually used. It was installed in an electric furnace having a heating element made of graphite under pressure and at room temperature and capable of controlling the atmosphere. Then 500 ° C / hr
After the temperature was raised to 1200 ° C. at a heating rate of 1, the nitrogen gas containing 2% of chlorine gas was introduced, and the atmosphere in the furnace was changed to an atmosphere containing chlorine, and then maintained at 1250 ° C. for 4 hours. After dehydration treatment in chlorine atmosphere, He100
% Gas was introduced to make the atmosphere He atmosphere, and then the porous quartz glass body was heated to 150 ° C. at a temperature rising rate of 500 ° C./hr.
The temperature was raised to 0 ° C., and the temperature was kept at 1500 ° C. for 3 hours to carry out transparent vitrification.

The transparent quartz glass thus obtained was placed in an electric furnace having a carbon heating element to obtain a softening point of 175 or higher.
It was heated to 0 ° C. to be deformed by its own weight and molded into a block shape of 3 × 3 × 4 cm. Subsequently, the temperature of the electric furnace was lowered to 1200 ° C while the forming block was installed in the electric furnace, and then gradually cooled at a cooling rate of 30 ° C / hr, and power supply was stopped when the temperature in the furnace reached 1000 ° C. Then, it was left to cool in the furnace.

The transparent quartz glass block thus obtained was inserted into an electric furnace capable of controlling the atmosphere and heated up to 1000 ° C. at a heating rate of 300 ° C./hr. After reaching 1000 ° C., 100% hydrogen gas was introduced under atmospheric pressure to make the atmosphere in the furnace a hydrogen atmosphere, and the temperature was maintained for 7 hours so that hydrogen molecules were contained in the transparent quartz glass.

The OH content in the obtained transparent quartz glass was 1 ppm. On the other hand, the chlorine concentration contained in the transparent quartz glass was 1000 ppm. The amount of released hydrogen molecules when heated to 1000 ° C in vacuum is 0.9 x 1
It was 0 ²⁰ molecule / m ² . KrF excimer laser is applied to this quartz glass at 200 mJ / cm ² · pulse, 20
The fluorescence emission intensity was measured while irradiating under the condition of 0 Hz. As shown in FIG. 1, this transparent quartz glass is made of KrF.
650nm as irradiated by excimer laser
It became clear that no fluorescence was emitted, and therefore no absorption band near 260 nm was produced. Therefore, Kr
Quartz glass was most suitable for a photomask substrate or an optical member using an F excimer laser as a light source.

Comparative Example 1 A porous quartz glass body having a diameter of 35 cm and a length of 100 cm formed by the same method as in Example 1 was placed in an electric furnace capable of controlling the atmosphere at normal pressure and room temperature. Then, after replacing the atmosphere in the electric furnace with nitrogen gas having a steam partial pressure of 0.002 mmHg, the steam partial pressure is 0.0
The temperature was raised to 1000 ° C. at a temperature rising rate of 500 ° C./hr while flowing a nitrogen gas of 02 mmHg. Subsequently, the temperature rising rate was set to 50 ° C./hr, the temperature was raised to 1250 ° C., and the temperature was maintained for 5 hours for dehydration treatment.

The heat-treated porous quartz glass body thus obtained has a maximum temperature of 145 in the furnace for transparent vitrification.
It is installed in the upper part of the electric furnace controlled at 0 ° C, the inside of the furnace is replaced with helium gas with a steam partial pressure of 0.002 mmHg, and then it is passed through the maximum temperature range while descending at a speed of 80 mm / hr to clear glass Was made.

The transparent quartz glass thus obtained was heated in an electric furnace having a heating element made of carbon to 175 above the softening point.
Heat to 0 ° C to cause self-weight deformation, 16 × 16 × 30c
It was molded into a block shape of m. Subsequently, the temperature of the electric furnace was lowered to 1200 ° C while the forming block was installed in the electric furnace, and then gradually cooled at a cooling rate of 30 ° C / hr, and power supply was stopped when the temperature in the furnace reached 1000 ° C. Then, it was left to cool in the furnace.

A transparent quartz glass block of 16 × 16 × 2 cm was cut out from the transparent quartz glass block thus obtained, and then the transparent quartz glass block was inserted into an electric furnace capable of controlling the atmosphere to 1000 ° C.
Up to 300 ° C./hr. 1000 ° C
After reaching 1, the hydrogen atmosphere was introduced into the transparent quartz glass by introducing 100% hydrogen gas under atmospheric pressure to make the atmosphere in the furnace a hydrogen atmosphere and maintaining the temperature for 15 hours.

The OH content in the obtained transparent quartz glass was 40 ppm. The amount of dissolved hydrogen determined by Raman spectroscopy was 1 × 10 ¹⁷ molecule / cm ³ or less. Further, the amount of released hydrogen molecules at 1000 ° C. in vacuum was 0.3 × 10 ²⁰ molecule / m ² . A KrF excimer laser is applied to this transparent quartz glass at 200 mJ / cm.
^The fluorescence emission intensity was measured while irradiating under the conditions of ² pulse and 200 Hz. As shown in FIG. 1, this transparent quartz glass was irradiated with a KrF excimer laser.
Although it is not a problem as an optical member such as a photomask, a very weak fluorescence emission of 650 nm was observed.

[Comparative Example 2] A porous quartz glass body having a diameter of 35 cm and a length of 100 cm formed by the same method as in Example 1 was placed in an electric furnace capable of controlling the atmosphere at normal pressure and room temperature. Here, without dehydration treatment, the porous quartz glass body was installed in the upper part of the electric furnace where the maximum temperature in the furnace for transparent vitrification was controlled to 1450 ° C, and the steam partial pressure in the furnace was 0.002 mmHg. After replacing with helium gas of
While descending at a speed of mm / hr, it passed through the maximum temperature range to be transparent vitrified.

The transparent quartz glass thus obtained was placed in an electric furnace having a heating element made of carbon and the temperature of the softening point was 175 or higher.
18 × 18 × 24c
It was molded into a block shape of m. Subsequently, the temperature of the electric furnace was lowered to 1200 ° C while the forming block was installed in the electric furnace, and then gradually cooled at a cooling rate of 30 ° C / hr, and power supply was stopped when the temperature in the furnace reached 1000 ° C. Then, it was left to cool in the furnace.

After cutting out a transparent quartz glass body of 18 × 18 × 1 cm from the transparent quartz glass block thus obtained, it was inserted into an electric furnace capable of controlling the atmosphere and 1000 ° C.
Up to 300 ° C./hr. 1000 ° C
After reaching 1, the hydrogen atmosphere was introduced into the furnace by introducing 100% hydrogen gas under atmospheric pressure, and the temperature was maintained for 7 hours so that hydrogen molecules were contained in the transparent quartz glass.

The OH content in the obtained transparent quartz glass was 200 ppm. The molecular weight of dissolved hydrogen determined by Raman spectroscopy was 1 × 10 ¹⁷ molecule / cm ³ or less. Further, the amount of released hydrogen molecules at 1000 ° C. in vacuum was 0.5 × 10 ²⁰ molecule / m ² . A KrF excimer laser is added to this transparent quartz glass at 200 mJ /
The fluorescence emission intensity was measured while irradiating under conditions of cm ² · pulse and 200 Hz. As shown in FIG. 1, it was revealed that this transparent quartz glass emits fluorescence at 650 nm, and hence an absorption band near 260 nm, as it is irradiated with a KrF excimer laser. Therefore, it was not suitable for a photomask substrate or an optical member using a KrF excimer laser as a light source.

[Comparative Example 3] A porous quartz glass body having a diameter of 8 cm and a length of 10 cm formed by the same method as in Example 1 was placed in an electric furnace capable of controlling the atmosphere at atmospheric pressure and room temperature. Then, He gas, which was passed through a bubbler in which pure water was heated to 80 ° C., was introduced at a rate of 3 liter / min to create an atmosphere containing water vapor. In the atmosphere, the porous quartz glass body was heated to 1500 ° C. under the condition of 500 ° C./hr and kept at 1500 ° C. for 3 hours to carry out transparent vitrification.

The transparent quartz glass thus obtained was placed in an electric furnace having a heating element made of carbon, and was heated to 175 or above the softening point.
It was heated to 0 ° C. to be deformed by its own weight and molded into a block shape of 3 × 3 × 4 cm. Subsequently, the temperature of the electric furnace was lowered to 1200 ° C while the forming block was installed in the electric furnace, and then gradually cooled at a cooling rate of 30 ° C / hr, and power supply was stopped when the temperature in the furnace reached 1000 ° C. Then, it was left to cool in the furnace.

The transparent quartz glass block thus obtained was inserted into an electric furnace capable of controlling the atmosphere and heated up to 1000 ° C. at a heating rate of 300 ° C./hr. After reaching 1000 ° C., 100% hydrogen gas was introduced under atmospheric pressure to make the atmosphere in the furnace a hydrogen atmosphere, and the temperature was maintained for 7 hours so that hydrogen molecules were contained in the transparent quartz glass.

The OH content in the obtained transparent quartz glass was 1100 ppm. The molecular weight of dissolved hydrogen determined by Raman spectroscopy was 1 × 10 ¹⁷ molecule / cm ³ or less. Further, the amount of released hydrogen molecules at 1000 ° C. in vacuum was 0.9 × 0 ²⁰ molecule / m ² . A KrF excimer laser is added to this transparent quartz glass at 200 mJ /
The fluorescence emission intensity was measured while irradiating under conditions of cm ² · pulse and 200 Hz.

As shown in FIG. 1, this transparent quartz glass was irradiated with a KrF excimer laser,
650 nm fluorescence emission is most likely to occur, thus 26
It became clear that an absorption band near 0 nm is also likely to occur. Therefore, the transparent quartz glass is the most unsuitable for a photomask substrate or an optical member using a KrF excimer laser as a light source.

[Embodiment 2] An electric furnace in which a porous quartz glass body having a diameter of 9 cm and a length of 10 cm formed by the same method as that of Embodiment 1 was heated at normal pressure and at room temperature and had a graphite heating element, and the atmosphere was controllable Installed in. Then, the temperature was raised to 1200 ° C. at a heating rate of 500 ° C./hr, nitrogen gas containing 1% chlorine gas was introduced, and the atmosphere in the furnace was changed to an atmosphere containing chlorine. Held for hours. After performing dehydration treatment in a chlorine atmosphere, it was further held in a nitrogen atmosphere for 4 hours. Then, introducing a gas of 100% He and setting the atmosphere as a He atmosphere, the porous quartz glass body is heated to 1500 ° C. at a heating rate of 500 ° C./hr,
Transparent vitrification was carried out by holding at 1500 ° C. for 3 hours.

The transparent quartz glass thus obtained was placed in an electric furnace having a heating element made of carbon, and the transparent quartz glass was heated to a temperature above the softening point of 175.
It was heated to 0 ° C. to be deformed by its own weight and molded into a block shape of 3 × 3 × 4 cm. Subsequently, the temperature of the electric furnace was lowered to 1200 ° C while the forming block was installed in the electric furnace, and then gradually cooled at a cooling rate of 30 ° C / hr, and power supply was stopped when the temperature in the furnace reached 1000 ° C. Then, it was left to cool in the furnace.

The transparent quartz glass block thus obtained was inserted into an electric furnace capable of controlling the atmosphere, and kept at 900 ° C. for 3 hours.
The temperature was raised at a heating rate of 00 ° C./hr. After reaching 900 ° C., 100% hydrogen gas was introduced under atmospheric pressure to make the furnace atmosphere a hydrogen atmosphere, and the temperature was maintained for 7 hours to allow hydrogen molecules to be contained in the transparent quartz glass.

The OH content in the obtained transparent quartz glass was 3 ppm. On the other hand, the chlorine concentration contained in the transparent quartz glass was 440 ppm. Also in vacuum 1
The amount of released hydrogen molecules when heated to 000 ° C is 0.3 x 10
^{It was 20} molecules / m ² . KrF excimer laser is applied to this transparent quartz glass at 200 mJ / cm ² · pulse, 2
The fluorescence emission intensity was measured while irradiating under the condition of 00 Hz. It was found that this quartz glass did not emit 650 nm fluorescence at all as it was irradiated with the KrF excimer laser, but a weak 390 nm fluorescence was observed. The 390 nm fluorescence intensity was weaker than the 650 nm fluorescence intensity of Comparative Example 1, and it was revealed that there is no problem even if this transparent quartz glass is used as a photomask substrate or an optical member using a KrF excimer laser as a light source.

[Comparative Example 4] A porous quartz glass body having a diameter of 9 cm and a length of 10 cm formed by the same method as in Example 1 was used in an electric furnace capable of controlling the atmosphere and having a graphite heating element at normal pressure and room temperature. Installed in. Then, the temperature was raised to 1200 ° C. at a heating rate of 500 ° C./hr, nitrogen gas containing 1% chlorine gas was introduced, and the atmosphere in the furnace was changed to an atmosphere containing chlorine. Held for hours. After performing dehydration treatment in a chlorine atmosphere, it was further held in a nitrogen atmosphere for 8 hours. Then, introducing a gas of 100% He and setting the atmosphere as a He atmosphere, the porous quartz glass body is heated to 1500 ° C. at a heating rate of 500 ° C./hr,
Transparent vitrification was carried out by holding at 1500 ° C. for 3 hours.

The transparent quartz glass thus obtained was placed in an electric furnace having a heating element made of carbon and the temperature was 175 or above the softening point.
It was heated to 0 ° C. to be deformed by its own weight and molded into a block shape of 3 × 3 × 4 cm. Subsequently, the temperature of the electric furnace was lowered to 1200 ° C while the forming block was installed in the electric furnace, and then gradually cooled at a cooling rate of 30 ° C / hr, and power supply was stopped when the temperature in the furnace reached 1000 ° C. Then, it was left to cool in the furnace.

The transparent quartz glass block thus obtained was inserted into an electric furnace capable of controlling the atmosphere and heated up to 1000 ° C. at a heating rate of 300 ° C./hr. After reaching 1000 ° C., 100% hydrogen gas was introduced under atmospheric pressure to make the atmosphere in the furnace a hydrogen atmosphere, and the temperature was maintained for 7 hours so that hydrogen molecules were contained in the transparent quartz glass.

The OH content in the obtained transparent quartz glass was 3 ppm. On the other hand, the chlorine concentration contained in the transparent quartz glass was 360 ppm. Also in vacuum 1
The amount of released hydrogen molecules when heated to 000 ° C is 0.4 × 10
^{It was 20} molecules / m ² . KrF excimer laser is applied to this transparent quartz glass at 200 mJ / cm ² · pulse, 2
The fluorescence emission intensity was measured while irradiating under the condition of 00 Hz. It was found that this transparent quartz glass did not emit 650 nm fluorescence at all when irradiated with a KrF excimer laser, but a strong 390 nm fluorescence was observed. The 390 nm fluorescence intensity was about two orders of magnitude higher than the 390 nm fluorescence intensity of Example 2, and it was revealed that this transparent quartz glass cannot be used as a photomask substrate or an optical member using a KrF excimer laser as a light source.

[Embodiment 3] An electric furnace in which a porous quartz glass body having a diameter of 9 cm and a length of 10 cm formed by the same method as that of Embodiment 1 was heated under normal pressure and at room temperature and which had a heating element made of graphite and whose atmosphere could be controlled Installed in. Then, after heating up to 1200 ° C. at a heating rate of 500 ° C./hr, CHF of 1.5% concentration
Nitrogen gas containing ₃ was introduced, the atmosphere in the furnace was changed to an atmosphere containing fluorine, and then the furnace was held at 1250 ° C. for 4 hours. After performing dehydration treatment in a fluorine atmosphere, He1
After introducing a gas of 00% and making the atmosphere He atmosphere, the temperature of the porous quartz glass body was raised to 1500 ° C. at a temperature rising rate of 500 ° C./hr, and the temperature was kept at 1500 ° C. for 3 hours to obtain transparent vitrification. I went.

The transparent quartz glass thus obtained was placed in an electric furnace having a heating element made of carbon and was heated to 175 or above the softening point.
It was heated to 0 ° C. to be deformed by its own weight and molded into a block shape of 3 × 3 × 4 cm. Subsequently, the temperature of the electric furnace was lowered to 1200 ° C while the forming block was installed in the electric furnace, and then gradually cooled at a cooling rate of 30 ° C / hr, and power supply was stopped when the temperature in the furnace reached 1000 ° C. Then, it was left to cool in the furnace.

The transparent quartz glass block thus obtained was inserted into an electric furnace capable of controlling the atmosphere and heated up to 1000 ° C. at a heating rate of 300 ° C./hr. After reaching 1000 ° C., 100% hydrogen gas was introduced under atmospheric pressure to make the atmosphere in the furnace a hydrogen atmosphere, and the temperature was maintained for 7 hours so that hydrogen molecules were contained in the transparent quartz glass.

The OH content in the obtained transparent quartz glass was 5 ppm. On the other hand, the concentration of fluorine contained in the transparent quartz glass was 2500 ppm. The molecular weight of dissolved hydrogen determined by Raman spectroscopy is 1 × 10 ¹⁷
The molecule / cm ³ or less. Furthermore, 100 in vacuum
The amount of released hydrogen molecules at 0 ° C is 0.4 × 10 ²⁰ molecule / m
^{Was 2} . The fluorescence emission intensity was measured while irradiating this transparent quartz glass with a KrF excimer laser under the conditions of 200 mJ / cm ² · pulse and 200 Hz. It was clarified that this transparent quartz glass did not generate fluorescence emission at 650 nm at all as it was irradiated with the KrF excimer laser, and therefore did not generate an absorption band near 260 nm. Therefore, it was the most suitable quartz glass for a photomask substrate or an optical member using a KrF excimer laser as a light source.

[Embodiment 4] An electric furnace in which a porous quartz glass body having a diameter of 9 cm and a length of 10 cm formed by the same method as that of Embodiment 1 is under atmospheric pressure and at room temperature and a graphite heating element is capable of controlling the atmosphere Installed in. Then, the temperature was raised to 1200 ° C. at a heating rate of 500 ° C./hr, nitrogen gas containing 2% chlorine gas was introduced, and the furnace atmosphere was changed to an atmosphere containing chlorine. Held for hours. After performing a dehydration treatment in a chlorine atmosphere, introducing a 100% He gas to make the atmosphere a He atmosphere, the porous quartz glass body was heated to 1500 ° C. at a heating rate of 500 ° C./hr. It was kept at 1500 ° C. for 3 hours for transparent vitrification.

The transparent quartz glass thus obtained was placed in an electric furnace having a heating element made of carbon and the temperature of the softening point was 175 or higher.
It was heated to 0 ° C. to be deformed by its own weight and molded into a block shape of 3 × 3 × 4 cm. Subsequently, the temperature of the electric furnace was lowered to 1200 ° C while the forming block was installed in the electric furnace, and then gradually cooled at a cooling rate of 30 ° C / hr, and power supply was stopped when the temperature in the furnace reached 1000 ° C. Then, it was left to cool in the furnace.

The transparent quartz glass block thus obtained was inserted into an electric furnace capable of controlling the atmosphere, and heated up to 1000 ° C. at a heating rate of 300 ° C./hr. After reaching 1000 ° C., 30% hydrogen gas was introduced under atmospheric pressure to make the atmosphere in the furnace a hydrogen atmosphere, and the temperature was maintained for 7 hours to contain hydrogen molecules in the transparent quartz glass.

The OH content in the obtained transparent quartz glass was 1 ppm. On the other hand, the chlorine concentration contained in the transparent quartz glass was 1500 ppm. The amount of released hydrogen molecules when heated to 1000 ° C in vacuum is 2 × 10 ^18.
The molecule / m ² . KrF excimer laser is applied to this quartz glass at 200 mJ / cm ² · pulse, 200H
The fluorescence emission intensity was measured while irradiating under the condition of z. This transparent quartz glass does not produce 650 nm fluorescence emission at all when irradiated with a KrF excimer laser, and therefore 26
It became clear that an absorption band near 0 nm did not occur.
Therefore, it was the most suitable quartz glass for a photomask substrate or an optical member using a KrF excimer laser as a light source.

[Comparative Example 5] A porous quartz glass body having a diameter of 9 cm and a length of 10 cm formed by the same method as in Example 1 was used in an electric furnace capable of controlling the atmosphere and having a graphite heating element at normal pressure and room temperature. Installed in. Then, the temperature was raised to 1200 ° C. at a heating rate of 500 ° C./hr, nitrogen gas containing 1.5% chlorine gas was introduced, and the atmosphere in the furnace was changed to an atmosphere containing chlorine. Hold for 5 hours. After performing a dehydration treatment in a chlorine atmosphere, introducing a 100% He gas to make the atmosphere a He atmosphere, the porous quartz glass body was heated to 1500 ° C. at a heating rate of 500 ° C./hr. It was kept at 1500 ° C. for 3 hours for transparent vitrification.

The transparent quartz glass thus obtained was placed in an electric furnace having a heating element made of carbon and was heated to 175 or above the softening point.
It was heated to 0 ° C. to be deformed by its own weight and molded into a block shape of 3 × 3 × 4 cm. Subsequently, the temperature of the electric furnace was lowered to 1200 ° C while the forming block was installed in the electric furnace, and then gradually cooled at a cooling rate of 30 ° C / hr, and power supply was stopped when the temperature in the furnace reached 1000 ° C. Then, it was left to cool in the furnace.

The transparent quartz glass block thus obtained was inserted into an electric furnace capable of controlling the atmosphere and heated up to 1000 ° C. at a heating rate of 300 ° C./hr. After reaching 1000 ° C., 10% hydrogen gas was introduced under atmospheric pressure to make the atmosphere in the furnace a hydrogen atmosphere, and the temperature was maintained for 7 hours to allow hydrogen molecules to be contained in the transparent quartz glass.

The OH content in the obtained transparent quartz glass was 2 ppm. On the other hand, the chlorine concentration contained in the transparent quartz glass was 900 ppm. Also in vacuum 1
The amount of released hydrogen molecules when the temperature was raised to 000 ° C. was 5 × 10 ¹⁷ molecules / m ² . KrF excimer laser is applied to this quartz glass at 200 mJ / cm ² pulse, 200 Hz.
The fluorescence emission intensity was measured while irradiating under the conditions. When this transparent quartz glass was irradiated with a KrF excimer laser, fluorescence emission was observed at 285 nm and 460 nm. When irradiation was further continued, it became clear that fluorescence emission of 650 nm was observed, the intensity increased with irradiation, and therefore an absorption band near 260 nm was also generated. Therefore, the quartz glass cannot be used as a photomask substrate or an optical member using a KrF excimer laser as a light source.

[0072]

The transparent quartz glass of the present invention has excellent excimer laser resistance against irradiation of excimer laser without absorption bands or fluorescence emission due to structural defects.

Further, according to the present invention, since the amount of OH contained in the transparent quartz glass is reduced and hydrogen is contained, it is generated by the irradiation of the excimer laser.
A transparent quartz glass that can reduce the absolute amount of OH groups, oxygen-excessive defects, and dissolved oxygen molecules that are the precursor bands of the 50 nm fluorescence emission center and the 260 nm absorption band, and that is substantially resistant to excimer laser irradiation. And has the effect.

When hydrogen molecules are contained in transparent quartz glass which has been dehydrated by halogen, it is produced by halogen dehydration at 285 nm, 390 nm and 460.
It also has an effect of removing the luminescence center having a nm tendency. In addition, 250n produced by halogen dehydration
The absorption band in the vicinity of m and 163 nm also has an excellent effect of removing by including hydrogen molecules.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between irradiation time and 650 nm fluorescence intensity when a transparent quartz glass is irradiated with a KrF excimer laser.

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Claims (9)

[Claims] 1. A transparent quartz glass obtained by heating a porous quartz glass body formed by depositing and growing quartz glass fine particles obtained by flame hydrolysis of a glass forming raw material on a substrate, wherein the transparent quartz glass is obtained. OH content in glass is 10
A transparent quartz glass containing less than ppm, containing 400 ppm or more of halogen, and containing hydrogen. 2. The transparent quartz glass according to claim 1, wherein the halogen contained in the transparent quartz glass is chlorine. 3. The transparent quartz glass according to claim 1, wherein the halogen contained in the transparent quartz glass is fluorine. 4. The transparent quartz glass is heated to 1000 ° C. in vacuum.
The amount of released hydrogen molecules when the temperature is raised to 1 × 10 ¹⁸ to 1 ×
The transparent quartz glass according to claim 1, which has a range of 10 ²⁰ molecules / m ² . 5. A step of (1) depositing and growing fine quartz glass particles formed by flame hydrolysis of a glass forming raw material on a substrate to form a porous quartz glass body, (2) the porous quartz glass. A step of dehydrating the porous quartz glass body by holding the body in a temperature range below the transparent vitrification temperature, (3) holding the body in the temperature range below the transparent vitrification temperature and dehydrating the transparent quartz glass body, Raise to vitrification temperature
A step of obtaining a transparent quartz glass body by subjecting it to a transparent vitrification, (4) a step of heating the transparent quartz glass body to a temperature equal to or higher than a softening point and shaping it into a desired shape to obtain a shaped quartz glass body,
And (5) a step of subjecting the formed quartz glass body to a heat treatment in an atmosphere containing hydrogen, and an OH content in the transparent quartz glass of 10 ppm.
The following is a method for producing transparent quartz glass containing 400 ppm or more of halogen and hydrogen. 6. The atmosphere in the step (2) of dehydrating in the temperature range below the transparent vitrification temperature is a chlorine atmosphere, and the chlorine concentration contained in the atmosphere is 0.01-by volume.
It is 5%, The manufacturing method of the transparent quartz glass of Claim 5 characterized by the above-mentioned. 7. The atmosphere in the step (2) of dehydrating in the temperature range below the transparent vitrification temperature is a fluorine atmosphere, and the fluorine concentration contained in the atmosphere is 0.0 by volume.
It is 1-5%, The manufacturing method of the transparent quartz glass of Claim 5 characterized by the above-mentioned. 8. The temperature range in the step of dehydrating in the temperature range below the transparent vitrification temperature of (2) above is 800 to 1250.
The method for producing transparent quartz glass according to claim 5, wherein the temperature is in the range of ° C. 9. A temperature range in which the molded quartz glass body in the step (5) is heat treated in an atmosphere containing hydrogen is 500.
The temperature is ˜1100 ° C. 6. The method for producing transparent quartz glass according to claim 5, wherein