JP3368932B2 - Transparent quartz glass and its manufacturing method - Google Patents

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 in a wide wavelength range from near infrared to vacuum ultraviolet.
In addition, it has a very small coefficient of thermal expansion, excellent dimensional stability, and excellent chemical durability, and is therefore widely used as a substrate material for a photomask in a lithography process in manufacturing an LSI.

However, the conventional quartz glass is induced with structural defects when exposed to high-energy ultraviolet rays such as plasma etching and excimer laser during the photomask manufacturing process, resulting in a decrease in light transmittance in the ultraviolet region and fluorescence emission center. There is a problem such as the generation of light, especially, the VLSI using the ArF excimer laser or the KrF excimer laser as the exposure light source.
There is a problem as a substrate for a photomask used in the lithography process, and as an optical member when constructing an optical system using an ArF excimer laser or a KrF 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 be expected without specifying the quartz glass that should contain hydrogen.
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 publication, a quartz glass obtained by subjecting a porous quartz glass body obtained by flame hydrolysis of a glass forming raw material to transparent vitrification is irradiated with a KrF excimer laser to form a glass having a wavelength of around 260 nm. It is impossible to completely suppress the absorption band and fluorescence emission near 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. However, in the quartz glass disclosed in the publication, it is necessary to dissolve a large amount of hydrogen molecules, and therefore it is necessary to heat the quartz glass in a hydrogen atmosphere that has a risk of explosion and under pressure, and the equipment is There is a big problem.

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 in the vicinity of 250 nm and cannot be used as a photomask substrate in a lithography process using a KrF excimer laser. Further irradiation with KrF excimer laser gives 28
Strong fluorescence emission was observed in the vicinity of 5 nm, 390 nm, and 460 nm, and it appeared to be blue visually. In particular, when it has fluorescence emission at 285 nm, it cannot be used as a substrate for a photomask in a lithography process using a KrF excimer laser as an exposure light source because the resist is exposed by fluorescence emission at 285 nm.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and excimer laser resistance, which has a small absorption band or fluorescence emission due to structural defects even when irradiated with an excimer laser, is provided. A transparent quartz glass having the same and a method for producing the same are provided.

[0008]

According to the present invention, the transparent silica glass has an OH content of 10 ppm or less, a fluorine content of 400 ppm or more, a hydrogen content, and a KrF excimer laser of 200 mJ / cm ² /. pulse, 2
Wavelength 650n when irradiated for 80 minutes under the condition of 00Hz
Provided is a transparent quartz glass in which the fluorescence intensity of m is substantially unchanged. The transparent quartz glass is 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. preferable.

Further, in view of the above-mentioned conventional problems, the present inventor imparts excimer laser resistance to a transparent quartz glass obtained by transparentizing a porous quartz glass body obtained by flame hydrolysis of a glass forming raw material. 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. By doing so, it was found that a transparent quartz glass having excimer laser resistance can be easily manufactured. The present invention includes (1) a step of depositing and growing quartz glass fine 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 body Is carried out in the temperature range below the transparent vitrification temperature to dehydrate the porous quartz glass body, (3) The porous quartz glass body held in the temperature range below the transparent vitrification temperature is dehydrated Temperature rise to
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 to obtain transparent quartz glass, O in the transparent quartz glass,
If the H content is 10 ppm or less and the halogen content is 400
KrF excimer containing more than ppm and containing hydrogen
Laser 200 mJ / cm ² / pulse, 200H
When irradiated for 80 minutes under the condition of z,
Provided is a method for producing transparent quartz glass containing hydrogen so that the light intensity does not substantially change .

The OH content in the present invention is obtained from the absorption based on the stretching vibration of Si-OH in transparent quartz glass found in the vicinity of 2.7 μm in the infrared spectroscopic spectrum of transparent quartz glass (J P. Willi
ams et al .: J. Am. Am. Ceram. Soc. , Vol.
55, 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.

Furthermore, after the hydrogen molecule is contained in the transparent quartz glass body, the OH concentration in the transparent quartz glass and the structural defect induced by the excimer laser irradiation are caused.
As a result of examining the relationship of 50 nm fluorescence emission intensity, the present inventors found that the 650 nm fluorescence intensity (measured by MPCD-1000 manufactured by Otsuka Electronics Co., Ltd.) was strong against the OH content in the transparent quartz glass as shown in FIG. It was the first time I found dependence. That is, the 650 nm fluorescence intensity is proportional to the OH content in the transparent quartz glass, and the OH content is 40 ppm.
If it is reduced to a certain level, the fluorescence emission intensity at 650 nm becomes extremely weak to a level at which there is practically no problem as an optical member such as a photomask, and the OH content is 10 ppm.
It has been found that it is possible to completely suppress 650 nm fluorescence emission and it is more preferable if it is below.

In order to further reduce the OH content in the transparent quartz glass, it was dehydrated in an atmosphere containing a halogen element-containing gas at a temperature not higher than the transparent vitrification temperature and then converted into a transparent vitrification. When the obtained transparent quartz glass body was irradiated with a KrF excimer laser, 285 nm, 390
It was found to have strong fluorescence emission at nm and 460 nm. The present inventors further heat-treated the transparent quartz glass body dehydrated with a halogen gas in a hydrogen atmosphere to make it contain hydrogen, and after obtaining the transparent quartz glass,
Excimer laser resistance was evaluated. As a result, it was found that the inhibition ratio of each fluorescence emission differs depending on the concentration of halogen contained in the transparent quartz glass. That is, when the halogen concentration in the transparent quartz glass is 400 ppm or more, the fluorescence emission of 285 nm, 390 nm and 460 nm is almost suppressed by the inclusion of hydrogen molecules,
It was further found that each fluorescence emission is completely suppressed when the halogen concentration is 500 ppm or more. If the halogen concentration is less than 400 ppm, it will be 39
Inhibition of 0 nm fluorescence emission is incomplete, which is not preferable.

The state of the halogen contained in the transparent quartz glass is not clear, but the presence of 400 ppm or more of halogen in the transparent quartz glass brings about a reduction in the OH content, and in the case of containing hydrogen. Is
It was found that the fluorescence emission at 650 nm and the fluorescence emission at 285 nm, 390 nm, and 460 nm were suppressed to the extent that there was no substantial problem with the irradiation of the KrF excimer laser.

Further, in order to study the influence of hydrogen molecules in the transparent quartz glass, transparent quartz glass having different hydrogen contents was prepared and subjected to Raman spectroscopy (R-manufactured by JASCO Corporation).
The relationship between the amount of dissolved hydrogen measured in (according to 800) and the fluorescence emission upon irradiation with KrF excimer laser was examined.
OH content is 10ppm and dissolved hydrogen amount is 4.4 × 10 ¹⁷
With the transparent quartz glass having a molecule / cm ³ , fluorescence emission of 390 nm was observed upon irradiation with KrF excimer laser. On the other hand, no transparent Raman scattering peak was observed and 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 the transparent quartz glass having an OH content of 10 ppm or less generated fluorescence emission of 390 nm. Moreover, it was found that 650 nm fluorescence emission was also substantially suppressed.

Therefore, the transparent quartz glass is vacuumed to 1000
When the amount of hydrogen released when heated at 0 ° C. was evaluated, the amount of released hydrogen molecules per surface area of the transparent quartz glass having excimer laser resistance was 0.9 × 10 ²⁰ molecules / m ² . Also, the amount of released hydrogen molecules is 1.5 × 10 ^20.
In the case of transparent quartz glass having a molecule / m ² , suppression of fluorescence emission at 390 nm was insufficient. On the other hand, the amount of released hydrogen molecules is 5 × 1
Fluorescence emission of 285 mm and 460 nm was observed in the transparent quartz glass having a low hydrogen molecule content of about 0 ¹⁷ molecule / m ² , and further 650 n was obtained according to the excimer laser irradiation.
An increase in m fluorescence intensity was observed. In the present invention, the amount of released hydrogen molecules when the temperature is raised to 1000 ° C. in vacuum is 1
It is important that it is in the range of × 10 ¹⁸ to 1 × 10 ²⁰ molecule / m ² .

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 treatment is performed in a temperature range below the temperature at which the body becomes vitrified, in an atmosphere containing a gas containing a halogen element. 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 as the base material (for example, Japanese Patent Publication No. 63-24973).
Can be used. Further, not only quartz glass but also a plate-shaped substrate may be used.

[0018] As the glass-forming raw material to be used is not particularly limited as long as materials capable of being gasified, S i Cl _4, S
_{iHCl 3, SiH 2 Cl 2,} CH 3 SiCl 3 chlorides such _{as, SiF 4, SiHF 3, SiH} 2 F 2 , etc. fluorides, SiBr _4, SiHBr ₃ and the like bromides, halogen iodide such as SiI ₄ A silicon compound is preferable in terms 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 preferably heated and held in an atmosphere containing a halogen element-containing gas for a certain period of time and then heated to transparent vitrification to be transparent vitrified. It becomes a transparent quartz glass body. That is, for example, the porous quartz glass body is preliminarily mounted in an electric furnace whose atmosphere can be controlled, and then heated at a constant temperature rising rate. Then, after reaching a predetermined temperature, a gas containing 0.01 to 5% by volume of the halogen element-containing gas is introduced to make an atmosphere (for example, a chlorine atmosphere or a fluorine atmosphere) containing the halogen element-containing gas.

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 halogen source, a part or all of chlorine gas and fluorine gas may be changed to CCl ₄ , CHCl ₃ , SiCl ₄ or the like in the case of chlorine, and in the case of fluorine, SF ₆ , C
Halides such as HF ₃ and SiF ₄ may be used instead.

The concentration of the halogen-containing gas is preferably in the range of 0.01 to 5% by volume. If the concentration of the halogen-containing gas exceeds 5%, it is not preferable because the halogen contained in the porous quartz glass body is liberated and does not become vitrified when the temperature is raised for subsequent vitrification. Is less than 0.01%, the effect of 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., and 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 time for holding in the temperature range during the dehydration treatment depends on the treatment temperature, the concentration of the halogen-containing gas, the volume of the porous quartz glass body, etc., and is therefore difficult to unconditionally define. Is preferably in the range of 1 to 30 hours. The OH content in the transparent quartz glass is 3680c by Si-OH by FTIR spectroscopy.
It can be quantified by the absorption of m ⁻¹ , and the OH content in the transparent quartz glass dehydrated with the halogen-containing gas is 10 p.
It becomes pm or less.

The porous quartz glass body dehydrated by the halogen-containing gas in this manner is subsequently heated to a transparent vitrification temperature and heated to be vitrified. The transparent vitrification temperature is preferably 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.

In order to mold the transparent quartz glass body thus obtained into a desired shape, the transparent quartz glass body is heated to a temperature range above the softening point. The temperature range at this time is 16
It is preferably in the range of 00 to 1800 ° C. 160
If the temperature is lower than 0 ° C, the viscosity of the transparent quartz glass body is high, so that the molding is practically difficult and devitrification occurs due to crystallization, which is not preferable. It is not preferable because it occurs.

The transparent quartz glass body molded into a desired shape is placed in an electric furnace capable of controlling the atmosphere and subsequently heated to the treatment temperature in order to contain hydrogen molecules.
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.

The processing temperature is preferably in the range of 500 to 1100 ° C. At a temperature lower than this, the diffusion coefficient of hydrogen molecules is small and the time required to contain the required amount of hydrogen is extremely long, which is not preferable. If the temperature exceeds 1100 ° C, the reaction with hydrogen molecules causes 390
nm fluorescent emission centers are formed, 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 1000.
It is in the range of ° C.

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 transparent quartz glass that has excimer laser resistance without the generation of absorption bands and fluorescence emission centers. Further, the transparent quartz glass produced according to the present invention can use a high-purity synthetic raw material as a glass-forming raw material, and since it does not undergo a melting step, it does not contain impurities such as crucibles. The total amount of impurities of the heavy metal elements 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.

By reducing the OH content, which is one of the precursors of non-crosslinked oxygen radicals, to 10 ppm or less,
It has the function of reducing the emission of fluorescence at 650 nm and the absorption band near its excitation wavelength of 260 nm upon irradiation with an excimer laser. The inclusion of hydrogen also removes 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 body from which the group has been removed removes oxygen-excessive defects and dissolved oxygen that could not be removed even by the halogen dehydration operation, and further generates 285 nm by the halogen dehydration operation. Three
90 nm, 460 nm fluorescence emission center is removed, excimer
It has the effect of perfecting laser resistance.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0034]

EXAMPLES Example 1 Porous quartz 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. The glass body was placed in an electric furnace having a graphite heating element at atmospheric pressure and room temperature and capable of controlling the atmosphere. Then, the temperature was raised to 1200 ° C. at a heating rate of 500 ° C./hr, nitrogen gas containing 2% by volume of chlorine gas was introduced, and the atmosphere in the furnace was changed to an atmosphere containing chlorine gas. Hold for 4 hours. After performing dehydration treatment in an atmosphere containing chlorine gas, H
After introducing a 100% gas 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 form a transparent glass. I went.

The transparent quartz glass body thus obtained was heated in an electric furnace having a carbon heating element to a temperature above the softening point of 17
It was heated to 50 ° 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 to contain hydrogen molecules in the transparent quartz glass block.

The OH content in the obtained transparent quartz glass was 1 ppm. On the other hand, the chlorine (Cl atom) concentration contained in the transparent quartz glass was 1000 ppm. Further, the amount of released hydrogen molecules when heated to 1000 ° C. in vacuum was 0.9 × 10 ²⁰ molecule / m ² . KrF excimer laser is applied to this transparent quartz glass at 200 mJ / cm ² / p.
The fluorescence emission intensity was measured while irradiating under the condition of ulse and 200 Hz. As shown in FIG. 1, this transparent quartz glass has a wavelength of 650 nm even when irradiated with a KrF excimer laser.
It became clear that no fluorescence was emitted and therefore no absorption band near 260 nm was produced. Therefore, the transparent quartz glass was most suitable for the photomask substrate or the optical member used in the step of using the KrF excimer laser as the 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 atmospheric control 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 temperature was raised to 1000 ° C. at a heating rate of 500 ° C./hr while flowing a nitrogen gas having a steam partial pressure of 0.002 mmHg. Then, at a heating rate of 50 ° C / hr, 125
The temperature was raised to 0 ° 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 body thus obtained was placed in an electric furnace having a heating element made of carbon and was heated to a softening point of 17 or higher.
16 × 16 × 30
It was molded into a cm-shaped block. Continuously, with the forming block installed in the electric furnace, the temperature of the electric furnace is 1200 ° C.
After that, the temperature was gradually reduced to 30 ° C./hr, and then gradually cooled, and when the temperature in the furnace reached 1000 ° C., the power supply was stopped and the furnace was allowed to cool.

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 the temperature reached 1, the atmosphere in the furnace was changed to a hydrogen atmosphere by introducing 100% hydrogen gas under atmospheric pressure, and the temperature was maintained for 15 hours to contain hydrogen in the transparent quartz glass body.

The OH content in the obtained transparent quartz glass was 40 ppm. Further, 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 . KrF excimer laser is applied to this transparent quartz glass at 200 mJ / cm ² /
The fluorescence emission intensity was measured while irradiating under the conditions of pulse and 200 Hz. As shown in FIG. 1, this transparent quartz glass emits a very faint 650 nm fluorescence emission to the extent that it does not substantially cause any problem as an optical member such as a photomask against the irradiation of KrF excimer laser. Admitted.

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 substituting it with the helium gas of No. 1, the glass was passed through the maximum temperature range while descending at a speed of 80 mm / hr to carry out transparent vitrification.

The transparent quartz glass body thus obtained was placed in an electric furnace having a heating element made of carbon and was heated to a softening point of 17 or higher.
18 × 18 × 24
It was molded into a cm-shaped block. Continuously, with the forming block installed in the electric furnace, the temperature of the electric furnace is 1200 ° C.
After that, the temperature was gradually reduced to 30 ° C./hr, and then gradually cooled, and when the temperature in the furnace reached 1000 ° C., the power supply was stopped and the furnace was allowed to cool.

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
Then, 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 to contain hydrogen molecules in the transparent quartz glass body.

The OH content in the obtained transparent quartz glass was 200 ppm. Further, 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 0.5 × 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 condition of ² / pulse, 200 Hz. As shown in FIG. 1, this transparent quartz glass emits 650 nm fluorescence as it is irradiated with a KrF excimer laser, and therefore 260
It became clear that an absorption band near nm was also generated. Therefore, it was not suitable for a photomask substrate or an optical member used in the step of using a KrF excimer laser as a light source.

Comparative Example 3 A diameter of 8 cm and a length of 1 formed by the same method as in Example 1
A 0 cm porous quartz glass body was placed in an electric furnace capable of atmospheric control at normal pressure and room temperature. Then, 3 liters of He gas was passed through a bubbler in which pure water was heated to 80 ° C.
It was introduced under the condition of min and made an atmosphere containing water vapor. The porous quartz glass body is heated to 500 ° C./h in the above atmosphere.
The temperature is raised to 1500 ° C. at a heating rate of r, and at 1500 ° C., 3
It was kept for a period of time to carry out transparent vitrification.

The transparent quartz glass body thus obtained was placed in an electric furnace having a heating element made of carbon and had a softening point of 17 or higher.
It was heated to 50 ° 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 to contain hydrogen molecules in the transparent quartz glass body.

The OH content in the obtained transparent quartz glass was 1100 ppm. Further, 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 0.9 × 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 condition of ² / pulse, 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 unsuitable for the photomask substrate or the optical member used in the step of using the KrF excimer laser as the light source.

[Example 2] A diameter of 9 cm and a length of 1 formed by the same method as in Example 1
A 0 cm porous quartz glass body was placed in an electric furnace having a graphite heating element at atmospheric pressure and a controllable atmosphere. Then, after heating up to 1200 ° C. at a heating rate of 500 ° C./hr, nitrogen gas containing 1% by volume of chlorine gas was introduced, and the atmosphere in the furnace was changed to an atmosphere containing chlorine gas,
Hold at 1250 ° C for 4 hours. After performing dehydration treatment in an atmosphere containing chlorine gas, 4
Held for hours. Then introduce He100% gas,
After setting the atmosphere to He atmosphere, the porous quartz glass body is set to 5
The temperature is raised to 1500 ° C. at a heating rate of 00 ° C./hr for 15
It was kept at 00 ° C. for 3 hours for transparent vitrification.

The transparent quartz glass body thus obtained was placed in an electric furnace having a heating element made of carbon, and was heated to a softening point of 17 or higher.
It was heated to 50 ° 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 contain hydrogen molecules in the transparent quartz glass block.

The OH content in the obtained transparent quartz glass was 3 ppm. On the other hand, the concentration of chlorine contained in the transparent quartz glass was 440 ppm. Also in vacuum 10
The amount of released hydrogen molecules when heated to 00 ° C is 0.3 × 10 ^20.
The molecule / m ² . KrF excimer laser is applied to this transparent quartz glass at 200 mJ / cm ² / pulse, 20
The fluorescence emission intensity was measured while irradiating under the condition of 0 Hz. This transparent quartz glass was found not to emit 650 nm fluorescence even when irradiated with a KrF excimer laser, but a weak 390 nm fluorescence was observed. 390
The nm fluorescence intensity is weaker than the 650 nm fluorescence intensity of Comparative Example 1, and it is clear that there is no problem even if this transparent quartz glass is used as a photomask substrate or an optical member used in the step of using a KrF excimer laser as a light source. became.

Comparative Example 4 Diameter 9 cm and length 1 formed by the same method as in Example 1
A 0 cm porous quartz glass body was placed in an electric furnace having a graphite heating element at atmospheric pressure and a controllable atmosphere. Then, after heating up to 1200 ° C. at a heating rate of 500 ° C./hr, nitrogen gas containing 1% by volume of chlorine gas was introduced, and the atmosphere in the furnace was changed to an atmosphere containing chlorine gas,
Hold at 1250 ° C for 4 hours. After performing dehydration treatment in an atmosphere containing chlorine gas, further 8 in a nitrogen atmosphere.
Held for hours. Then introduce He100% gas,
After setting the atmosphere to He atmosphere, the porous quartz glass body is set to 5
The temperature is raised to 1500 ° C. at a heating rate of 00 ° C./hr for 15
It was kept at 00 ° C. for 3 hours for transparent vitrification.

The transparent quartz glass body thus obtained was placed in an electric furnace having a heating element made of carbon and had a softening point of 17 or higher.
It was heated to 50 ° 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 to contain hydrogen molecules in the transparent quartz glass block.

The OH content in the obtained transparent quartz glass was 3 ppm. On the other hand, the concentration of chlorine contained in the transparent quartz glass was 360 ppm. Also in vacuum 10
The amount of released hydrogen molecules when heated to 00 ° C is 0.4 × 10 ^20.
The molecule / m ² . KrF excimer laser is applied to this transparent quartz glass at 200 mJ / cm ² / pulse, 20
The fluorescence emission intensity was measured while irradiating under the condition of 0 Hz. This transparent quartz glass did not generate 650 nm fluorescence emission even when irradiated with KrF excimer laser, but a strong 390 nm fluorescence emission 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 became clear that this transparent quartz glass cannot be used as a photomask substrate or an optical member used in the step of using a KrF excimer laser as a light source. .

[Embodiment 3] Diameter of 9 cm and length of 1 formed by the same method as in Embodiment 1.
A 0 cm porous quartz glass body was placed in an electric furnace having a graphite heating element at atmospheric pressure and a controllable atmosphere. Then, after the temperature was raised to 1200 ° C. at a heating rate of 500 ° C./hr, nitrogen gas containing 1.5% by volume of CHF ₃ gas was introduced, and the furnace atmosphere was changed to an atmosphere containing CHF ₃ gas. Then, the temperature was maintained at 1250 ° C. for 4 hours. After performing dehydration treatment in an atmosphere containing CHF ₃ gas, 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 body thus obtained was placed in an electric furnace having a heating element made of carbon and had a softening point of 17 or higher.
It was heated to 50 ° 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 to contain hydrogen molecules in the transparent quartz glass block.

The OH content in the obtained transparent quartz glass was 5 ppm. On the other hand, the concentration of fluorine (F atom) contained in the transparent quartz glass was 2500 ppm. The amount of dissolved hydrogen obtained from Raman spectroscopy is 1 × 1.
It was 0 ¹⁷ molecule / cm ³ or less. Furthermore, 1 in vacuum
The amount of released hydrogen molecules at 000 ° C. was 0.4 × 10 ²⁰ molecule / m ² . KrF excimer laser is applied to this transparent 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 emit fluorescence at 650 nm even when irradiated with a KrF excimer laser, and therefore 260n
It became clear that there was no absorption band near m. Therefore, the transparent quartz glass was most suitable for the photomask substrate or the optical member used in the step of using the KrF excimer laser as the light source.

Example 4 A diameter of 9 cm and a length of 1 formed by the same method as in Example 1
A 0 cm porous quartz glass body was placed in an electric furnace having a graphite heating element at atmospheric pressure and a controllable atmosphere. Then, the temperature was raised to 1200 ° C. at a heating rate of 500 ° C./hr, nitrogen gas containing 2% by volume of chlorine gas was introduced, and the furnace atmosphere was changed to an atmosphere containing chlorine gas.
Hold at 1250 ° C for 5 hours. After dehydration treatment in an atmosphere containing chlorine gas, 100% He gas was introduced to make the atmosphere He atmosphere, and then the porous quartz glass body was heated to 1500 ° C. at a heating rate of 500 ° C./hr. The temperature was raised to 1,500 ° C., and the temperature was maintained at 1500 ° C. for 3 hours to carry out transparent vitrification.

The transparent quartz glass body thus obtained was heated in an electric furnace having a heating element made of carbon to a temperature above the softening point of 17
It was heated to 50 ° 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 so that hydrogen molecules were contained in the transparent quartz glass block.

The OH content in the obtained transparent quartz glass was 1 ppm. On the other hand, the concentration of chlorine contained in the transparent quartz glass was 1500 ppm. Also in vacuum 1
The amount of released hydrogen molecules when heated to 000 ° C. was 2 × 10 ¹⁸ 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. This transparent quartz glass does not emit fluorescence at 650 nm even when irradiated with a KrF excimer laser, and therefore 260 nm.
It became clear that there was no absorption band in the vicinity. Therefore, the transparent quartz glass was most suitable for the photomask substrate or the optical member used in the step of using the KrF excimer laser as the light source.

[Comparative Example 5] A diameter of 9 cm and a length of 1 formed by the same method as in Example 1
A 0 cm porous quartz glass body was placed in an electric furnace having a graphite heating element at atmospheric pressure and a controllable atmosphere. Then, after heating up to 1200 ° C. at a heating rate of 500 ° C./hr, nitrogen gas containing 1.5 volume% of chlorine gas was introduced, and the atmosphere in the furnace was changed to an atmosphere containing chlorine gas, Hold at 1250 ° C for 5 hours. After dehydration treatment in an atmosphere containing chlorine gas, 100% He gas was introduced to make the atmosphere He atmosphere, and then the porous quartz glass body was heated to 1500 ° C. at a heating rate of 500 ° C./hr. The temperature was raised to 1,500 ° C., and the temperature was maintained at 1500 ° C. for 3 hours to carry out transparent vitrification.

The transparent quartz glass body thus obtained was placed in an electric furnace having a heating element made of carbon and was heated to a softening point of 17 or higher.
It was heated to 50 ° 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 contain hydrogen molecules in the transparent quartz glass block.

The OH content in the obtained transparent quartz glass was 2 ppm. On the other hand, the concentration of chlorine contained in the transparent quartz glass was 900 ppm. Also in vacuum 10
The amount of released hydrogen molecules when the temperature was raised to 00 ° C. was 5 × 10 ¹⁷ molecules / m ² . The fluorescence emission intensity was measured while irradiating this quartz glass with a KrF excimer laser under the conditions of 200 mJ / cm ² / pulse and 200 Hz. 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 transparent quartz glass cannot be used as a photomask substrate or an optical member using a KrF excimer laser as a light source.

[0072]

EFFECTS OF THE INVENTION The transparent quartz glass of the present invention has a small absorption band or fluorescence emission due to structural defects even when irradiated with an excimer laser, and has excellent excimer laser resistance.

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 65.
Transparent quartz glass capable of reducing the absolute amounts of OH groups, oxygen-excessive defects, and dissolved oxygen molecules, which are precursors of 0 nm fluorescence emission center and 260 nm absorption band, and are substantially resistant to excimer laser irradiation. Is obtained.

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 the effect of removing the nm fluorescence emission center. Furthermore, 250 nm and 163 nm generated by halogen dehydration
The absorption band in the vicinity also has an excellent effect of being removed by containing 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.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI C03C 3/06 C03C 3/06

Claims (4)

(57) [Claims] 1. The transparent silica glass has an OH content of 10 pp.
m or less, 400 ppm or more of fluorine and hydrogen, and 200 mJ of a KrF excimer laser.
/ Cm ² / pulse, a transparent quartz glass whose fluorescence intensity at a wavelength of 650 nm does not substantially change when irradiated for 80 minutes under the conditions of 200 Hz. 2. The transparent quartz glass obtained by heating a porous quartz glass body formed by depositing and growing fine quartz glass particles obtained by flame hydrolysis of a glass forming raw material on a substrate. The transparent quartz glass according to claim 1, which is glass. 3. 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 molded quartz glass body to a heat treatment in an atmosphere containing hydrogen to obtain a transparent quartz glass, wherein the OH content in the transparent quartz glass is 10 ppm. The following content, containing 400 ppm or more of halogen, and containing hydrogen,
KrF excimer laser at 200 mJ / cm ² / pul
A method for producing transparent quartz glass containing hydrogen such that the fluorescence intensity at a wavelength of 650 nm does not substantially change when irradiated for 80 minutes under the conditions of se and 200 Hz. 4. The atmosphere in the step (2) is an atmosphere containing a halogen element-containing gas, and the halogen element-containing gas contained in the atmosphere is 0.01 to 5% by volume. A method for producing the transparent quartz glass described above.