JPH0881225A - Synthetic quartz glass for light transmission and its production - Google Patents

Abstract

PURPOSE: To obtain the subject glass having excellent light resistance, suppressing light loss even by irradiation with light in a vacuum ultraviolet range to an ultraviolet range having a high energy density by selecting synthetic quartz glass for light transmission, having a specific dissolved hydrogen molecule concentration. CONSTITUTION: Synthetic quartz glass for light transmission having >=10<15> molecules/cm<3> dissolved hydrogen molecule concentration and the total of SiH group concentration, twice oxygen deficient defect concentration and SiCl group concentration of <=5.3×10<16> molecules/cm<3> is selected. The synthetic quartz glass is obtained by synthesizing a quartz glass porous material from a high- purity silicon compound (e.g. SiCl4 ) by a vapor-phase chemical reaction, heat- treating the porous material in an O2 -containing atmosphere, transparently vitrifying under vacuum to give synthetic quartz glass containing oxygen excessive type defect and heat-treating the synthetic quartz glass in an H2 -containing atomosphere at <=800 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic quartz glass for transmitting light and a method for producing the same, more specifically, an excimer laser (Xe-Cl: 308 nm, Kr-F: 248 nm,
Ar-F: 193 nm), low pressure mercury lamp (185n
m), an excimer lamp (Xe-Xe: 172 nm), or the like, and a synthetic quartz glass for light transmission used as an optical component such as a vacuum ultraviolet light to ultraviolet light lens or prism, a window material, and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Synthetic quartz glass is about 150 nm to about 5 μm.
Since it transmits light in a wide wavelength range of m, it has a wide range of applications, and because of its small coefficient of thermal expansion, it can be used in a wide temperature range due to its high heat resistance and high precision optical system. It is a glass material that is extremely excellent in many respects, including that it can be done and that it is not easily damaged by irradiation with high-energy light because it is high-purity silicon dioxide. One of the applications that makes use of such excellent characteristics is as an optical material for a lithography apparatus that exposes and draws an integrated circuit pattern such as an LSI. Conventionally, g-line (435.8 nm) and i-line (365 nm) of Hg bright line spectrum have been used as an exposure light source of this lithographic apparatus,
As the optical glass material, multi-component optical glass has been used. However, recently there is a tendency to shorten the wavelength of light used for exposure in order to further improve the degree of integration of the circuit. In this case, synthetic quartz glass with little light absorption in the vacuum ultraviolet region to the ultraviolet region is used as an illumination optical system and It becomes necessary to use it for an exposure optical system. In addition, a low-pressure mercury lamp (185 nm)
And excimer lamp (Xe-Xe: 172nm) are light CV
It is used in ashing, etching and ozone generators for D and silicon wafers, or is being developed to be applied to the above-mentioned applications in the future. It becomes necessary to use quartz glass.

Quartz glass materials used in these optical systems are required to have high light resistance at the used wavelength (the transmittance is unlikely to decrease after light irradiation), and are also used as lenses and prisms. In addition, in addition to the above characteristics, the homogeneity of the refractive index is required. Regarding the light resistance, it is required that light absorption is practically not detected in the wavelength range of the light used and fluorescence is not detected, and that a light absorption band is not induced even after long-time light irradiation.
When an excimer laser (248 nm) is used, the most severe condition is that the decrease in transmittance at 248 nm after irradiation with 10 ⁶ shots under conditions of 400 mJ / cm ² and 100 Hz is 0.1% or less. Required. Furthermore, there is a demand for the development of a material that can withstand shorter-wavelength light for a longer period of time even under higher-density irradiation conditions.

Synthetic quartz glass is usually cited as a quartz glass which can be adapted to such severe conditions. Generally, the name synthetic quartz glass is used for all quartz glass that does not use natural SiO ₂ as a starting material, but there are various methods for producing this synthetic quartz glass. Therefore, there are various grades of impurity element concentration (metal element concentration, non-metal element concentration) and defect concentration in the synthetic quartz glass produced due to the purity of the raw materials and the production method. Quartz glass cannot be an ideal glass material for a transmission optical system.

The synthetic quartz glass is roughly classified into a vapor phase method and a liquid phase method, and the vapor phase method is the main method for producing a material used for optical applications. There are direct synthesis method, plasma CVD method, soot method, etc., and impurities such as metal in quartz glass, OH group, Cl, H ₂ , O ₂ , oxygen excess defect, oxygen deficiency defect due to the raw material and manufacturing method. , The concentration of ring structure defects, etc. is different. The concentrations of these impurities and defects have a great influence on the optical properties of the synthetic quartz glass such as light absorption, fluorescence, and refractive index, and therefore the light resistance to the irradiation with the above-mentioned high-energy light (the decrease in transmittance after irradiation). It is known that it also has a great influence on the degree. Therefore, various studies have hitherto been made on the relationship between the above-mentioned impurities and defects and the light resistance.

[0006]

In these studies, in order to improve the light resistance of quartz glass, for example, increasing the concentration of OH groups in quartz glass, decreasing the H ₂ content, and H ₂ Various methods have been proposed, such as increasing the content of oxygen, eliminating oxygen defects (excess defects and deficiency defects), and dissolving inert gas molecules such as He.

However, as can be seen from the contents of the above-mentioned proposals, there are proposals that contradict each other, and suppress the optical damage of quartz glass to the irradiation of light in the vacuum ultraviolet region to the ultraviolet region,
Alternatively, there is a problem that the conditions that the synthetic quartz glass must have in order to prevent it have not been completely understood.

For example, in the invention of "transmitter for laser light" described in JP-A-2-69332, the concentration of OH groups in quartz glass increases and the amount of H ₂ occluded increases. However, it is described that the light resistance to laser light is reduced.

Further, in the invention of "optical member for laser light" described in Japanese Patent Laid-Open No. 3-101282, H ₂ gas molecules contained in quartz glass improve the light resistance to laser light. That is, the proposal is completely opposite to the contents described in the above publication.

Therefore, the inventors of the present invention have proposed a synthetic quartz glass for light transmission and a method for producing the same, in which the transmittance hardly decreases even when a laser beam having a high energy density in a vacuum ultraviolet region to an ultraviolet region is irradiated for a long time. For the purpose of providing, the impurities and defects in the synthetic quartz glass and the change of the transmittance when the synthetic quartz glass is irradiated with ultraviolet rays were examined. As a result, the synthetic quartz glass has a high energy density of 172 nm, 185 nm, 193nm or 248nm
Cause of the decrease in transmittance that occurs when the laser light of
≡Si-0 ° (non-bonded oxygen) defects having an absorption centered at about 260 nm (4.7 eV) and ≡Si · having an absorption centered at about 210 nm (5.9 eV) shown in the graph of FIG. It was confirmed that this was due to the generation of (E ′ center) defects. The symbol “≡Si” does not mean a triple bond, but schematically represents a state in which a silicon atom forms a single bond with three oxygen atoms.

Then, next, it is examined which of the OH group concentration, the H ₂ concentration, the defect concentration and the like in the synthetic quartz glass influences the generation of these defects.
A synthetic quartz glass having 0 ppm of OH groups is irradiated with a laser beam, and the OH groups are irrelevant to the generation of both defects, and the synthetic quartz glass having an H ₂ concentration of 10 ¹⁵ to 10 ¹⁸ / cm ³ is laser-irradiated. And H ₂ is 4.7 eV
Although it has an effect of preventing generation of defects having absorption around (260 nm), it is 5.9 eV (210 nm).
It was found that there is no effect of suppressing or preventing the generation of defects having absorption centered on.

Furthermore, it was found that the concentration of silyl groups (SiH), the concentration of oxygen-deficient defects, and the concentration of SiCl groups are related to the generation of defects having absorption around 5.9 eV. The invention was completed.

[0013]

That is, the synthetic quartz glass for light transmission according to the present invention has a dissolved hydrogen molecule concentration of 10 ¹⁵
/ Cm ³ or more, and the total concentration of SiH groups, twice the concentration of oxygen deficiency defects, and the concentration of SiCl groups is 5.3 ×.
The feature is that it is 10 ¹⁶ pieces / cm ³ or less.

If the synthetic quartz glass for light transmission contains metal impurities in addition to the above-mentioned impurities, the transmittance of vacuum ultraviolet light to ultraviolet light is lowered, which is not preferable.
Alkali metals total 100 ppb or less, alkaline earth metals total 100 ppb or less, transition metals (Ti, C
It is preferable that the total of r, Fe, Ni, Cu, and Ce) is 50 ppb or less.

Next, a method for producing a synthetic quartz glass for transmitting light according to the present invention is a method for producing the synthetic quartz glass for transmitting light described above, which is a porous quartz glass body produced by a vapor phase chemical reaction from a high-purity silicon compound. And the quartz glass porous body is heat-treated in an oxygen-containing atmosphere and then transparentized under vacuum to obtain a synthetic quartz glass containing oxygen-excessive defects, which is heat-treated in a hydrogen-containing atmosphere at 800 ° C. or lower. It is characterized by doing.

As the high-purity silicon compound as a raw material,
Examples thereof include silicon tetrachloride and silane. In order to prevent a decrease in the transmittance of vacuum ultraviolet light to ultraviolet light in the produced quartz glass, the total amount of alkali metal in the raw material is 10
0 ppb or less, total 100 ppb of alkaline earth metal
Hereinafter, transition metals (Ti, Cr, Fe, Ni, Cu, C
It is preferable that e) is 50 ppb or less in total. In the synthesis of the quartz glass porous body, special conditions are not required and hydrolysis with an ordinary oxyhydrogen flame may be performed, but the temperature during the hydrolysis is preferably about 1000 to 2000 ° C.

Next, the quartz glass porous body (soot) obtained in the above step is heat-treated in an oxygen-containing atmosphere.
In order to quickly diffuse oxygen molecules into soot, which is a porous body, to change ≡Si—Si≡ into ≡Si—O—Si≡ and prevent pores from being formed inside the quartz glass. The temperature is preferably in the range of 1000 to 1300 ° C., and the oxygen concentration is preferably 10 to 100 vol%.
When the oxygen content in the treatment is less than 10 vol% and the temperature is less than 1000 ° C, the above reaction does not proceed sufficiently, while when the temperature exceeds 1300 ° C, the soot sinters to some extent. However, the subsequent degassing process becomes difficult.

After the above step, the excess oxygen and other gas components contained in the above oxygen gas treatment are removed from the glass fine particles to facilitate the diffusion of H ₂ into the quartz glass in the subsequent step. Therefore, it is preferable to perform degassing treatment under the conditions of vacuum or several tens of P.
Water is not included under a reduced pressure of a or less (the dew point is -100 ° C.
Below) an inert gas atmosphere is preferred. Further, the temperature at this time is preferably 1000 to 1400 ° C. If the temperature during degassing is less than 1000 ° C, gases such as oxygen are not sufficiently removed, while the temperature is 1400 ° C.
If it exceeds, the densification will start before the gas is sufficiently removed.

Thereafter, transparent vitrification is carried out. The conditions in this case are the same as those in the degassing treatment under the same atmosphere.
It is preferably carried out in a temperature range of 00 to 1600 ° C. If the temperature is less than 1400 ° C., the densification is difficult to proceed and the productivity is deteriorated.

The subsequent heat treatment in a hydrogen-containing atmosphere
800 ° C in a reducing atmosphere with a H ₂ concentration of 20 vol% or more
It is preferably carried out below, more preferably at 700 ° C. or lower. When the hydrogen content during heat treatment is less than 20 vol%, hydrogen is not sufficiently absorbed in the quartz glass and the heat treatment temperature is 8
When the temperature exceeds 00 ° C, the stored hydrogen is ≡Si-O-Si.
It reacts with ≡ to produce ≡Si · SiH, which causes defects.

Since the variation of the refractive index due to the H ₂ concentration distribution in the synthetic quartz glass is 1 × 10 ⁻⁶ or less, a material having a uniform refractive index distribution was manufactured before the step of incorporating H _2. If so, the synthetic quartz glass for light transmission having the homogeneity and the light resistance can be manufactured by the subsequent heat treatment in the atmosphere containing H ₂ .

[0022]

As described above, as a result of examining the ultraviolet absorption spectrum after irradiating the synthetic quartz glass manufactured by various manufacturing processes with the KrF excimer laser, the ArF excimer laser, and the low-pressure mercury lamp, it is found that the damage caused by the light irradiation is , The two absorption bands shown in FIG. 1, ie 4.7
Oxygen excess defects having absorption centered on eV (260 nm) (hereinafter referred to as 260 nm band defects), and 5.9 e
It was confirmed that the formation of oxygen-deficient defects (hereinafter referred to as 210 nm band defects) having absorption centered on V (210 nm) was the main cause. Further, in the quartz glass in which H ₂ molecules are detected, as shown in FIG.
0 nm band defects are not detected, but 210 nm band defects are detected (solid line, broken line) and not detected (dashed line), and the presence of H ₂ molecules is not a sufficient condition for improving light resistance. found.

It is considered that the 260 nm band defect (≡Si-O °) is generated by the dissociation reaction of the following formula 1 or formula 2.

[0024]

[Equation 1]

[0025]

[Equation 2]

In the above reaction, since the --O--O-- bond described in the above formula 1 is weaker, the reaction described in the above formula 1 proceeds by irradiation of relatively weak light (electromagnetic wave). .

Further, the 210 nm band defect (≡Si ·) is
It is considered to be generated by the dissociation reaction of the above equation 2 and the following equations 3 to 5.

[0028]

(Equation 3)

[0029]

[Equation 4]

[0030]

(Equation 5)

In these reactions, the dissociation reaction represented by the above equations (3) to (5) proceeds by irradiation of relatively weak light (electromagnetic wave) rather than the above equation (2). Of course, there are distortions that can be recognized in the inspection of the polarizing plate, and ring structure defects detected by Raman spectrum, such as ≡Si-OS
It is considered that if the bond of i≡ is distorted or held in a stressed state, the reaction represented by the equation (2) easily proceeds.

When an electromagnetic wave or a particle beam having a higher energy than ultraviolet rays such as X-rays, γ-rays, neutron rays and ion beams is irradiated, the reaction represented by the equation (2) easily proceeds.

Therefore, the present inventors conducted a study to find a correlation with the OH group concentration, the concentration of nonmetallic impurities such as Cl, and the oxygen defect concentration in the synthetic quartz glass involved in the generation of two types of defects. . The types of impurities examined are OH group, Cl, S
iCl group, H ₂ , and silyl group (≡Si—H), and the types of oxygen defects are ≡Si—Si≡ and ≡Si—O—O—.
Si≡. Here, the concentration of the OH group was determined by an infrared absorption method. The total Cl concentration was determined by neutron activation analysis, the Cl ₂ concentration was determined by thermal desorption gas analysis, and the difference between the total Cl concentration and Cl ₂ concentration was defined as ≡Si—Cl concentration. Concentration of H _2, ≡Si-H concentration each of the laser Raman spectrum 4135 cm ^-1 and 2250 cm ^-1
The intensity detected by the peak of ¹ was divided by the intensity (intensity ratio) of the scattering peak at 800 cm ⁻¹ showing the bond of ≡Si—O—. The concentration of ≡Si-Si≡ defects was determined from the absorbance at 163 nm in the vacuum ultraviolet region. ≡Si-O-O-
The Si≡ concentration was determined by the magnitude of the absorbance at the peak of 260 nm after laser irradiation.

As a result of these examinations, it was found that H ₂ gas easily reacts with oxygen excess defects ≡Si—O—O—Si≡ to form a compound represented by the following formula (6).

[0035]

(Equation 6)

That is, H ₂ is changed into a stable OH group by the reaction represented by the above equation 6, and the 26 represented by the above equation 1 is obtained.
Since the 0 nm band defect ≡Si-O ° is not generated, H
260nm as indicated by the presence or absence of ₂ in Figures 1 and 2
It is considered that the difference in absorption appears in. Therefore, it is considered that oxygen excess defects of ≡Si—O—O—Si≡ type do not coexist in the synthetic quartz glass in which a certain amount of H ₂ is present in the quartz glass.

From the above, in order to suppress the generation of 260 nm band defects, it is necessary to contain H ₂ molecules in the silica glass, and at least the H ₂ molecules should be present to the extent that they can be detected by Raman spectroscopy. For example, 260 nm defects are not generated. The lower limit of detection of H ₂ in Raman spectroscopy is substantially 10 ¹⁵ pieces / cm ³ . Further, if the H ₂ concentration is within 10 ¹⁸ / cm ³ , no adverse effect due to the presence of H ₂ is observed.

Next, considering the oxygen deficiency defect,
The action of H _{2 on} the oxygen deficiency defect ≡Si—Si≡ is expressed by the following formula 7.

[0039]

(Equation 7)

However, as shown in the above equation (4), the ≡Si-H that was once generated is not so stable, and decomposes again to generate ≡Si · which is a 210 nm band defect. Therefore,
H ₂ molecules in quartz glass are not effective in suppressing the production of 210 nm defects.

FIG. 3 is a graph showing a theoretical peak shape at each absorbance of 210 nm defect, but as shown in FIG. 3, if this peak is detected with a certain size or more, it is industrially possible. 248nm (5.0e used for
V), 193 nm (6.4 eV), 185 nm (6.7)
The wavelength range of eV) is part of the absorption peak, and the transmittance is reduced. In FIG. 4, the absorbance of 210 nm defect is in a specific wavelength range (248 nm, 193 nm, 185 n
It is the graph which showed the influence which it has on the transmittance | permeability in m). From FIG. 4, the decrease in transmittance at a wavelength of 248 nm is 0.1
%, The absorbance due to 210 nm defects must be 0.0039 or less, and in order to suppress the decrease in transmittance at a wavelength of 193 nm to 0.1% or less, 21
The absorbance due to the 0 nm band defect needs to be 0.0009 or less, and the decrease in the transmittance at the wavelength of 185 nm is less than 0.009.
In order to suppress it to 1% or less, the absorbance due to 210 nm band defects needs to be 0.0026 or less.

Therefore, the absorption cross section of ≡Si · is 7.37.
When the density is × 10 ^-20 cm ² , the density of the defects is 5.3 × 10 ¹⁶ defects / cm ³ or less (248 nm) and 1.2, respectively.
× 10 ¹⁶ pieces / cm ³ or less (193 nm), 3.5 × 10
^{If the} number is ¹⁶ pieces / cm ³ or less (185 nm), the decrease in transmittance in each wavelength range can be suppressed to 0.1% or less. From the above, theoretically, the defect concentration is 1.2 × 1.
If it is 0 ¹⁶ pieces / cm ³ or less, the decrease in the transmittance at each wavelength described above can be suppressed to within 0.1%, but the current standard is that the decrease in the transmittance at 248 nm is 0.1%. If it is kept below%, the required standard will be satisfied. Therefore, according to the above criteria, the defect concentration is 5.3.
It may be × 10 ¹⁶ pieces / cm ³ or less. Here, the upper limit of the decrease in the transmittance is set to 0.1% or less because the limit of the accuracy of the photometer is at this level, and the decrease in the transmittance is not substantially detected at the transmittance below this. And ≡
It was reported by RAWeeks that the absorption cross section of Si was set to 7.37 × 10 ^-20 cm ² (J. Appl. Phys., 35 (1964) p19.
It was determined from a graph showing the relationship with the ≡Si—OH concentration necessary to prevent the generation of defects ≡Si · that are easily generated when γ-rays of (32 $) are irradiated.

Reactions that easily generate defects ≡Si · when irradiated with light in the vacuum ultraviolet region to the ultraviolet region are expressed by the above formulas 3 to 5
Since the reaction is represented by the equation, in order to control the production amount of this defect ≡Si · to be equal to or less than the above-mentioned conditions, the concentration of ≡Si-H and the concentration of ≡Si-Si≡ which are the production sources of the defect. 2
The sum of the doubled amount and the concentration of ≡Si—Cl is 5.3 × 1.
It may be 0 ¹⁶ pieces / cm ³ or less. It is needless to say that the sum of the concentrations of these bonds is more preferably 1.2 × 10 ¹⁶ pieces / cm ³ or less, and 0 is ideal. The correctness of the above estimation is also demonstrated by the following examples. Here, the reason that the ≡Si-Si≡ concentration is twice is that there is a possibility that two ≡Si. Among halogenated bonds ≡
Only Si-Cl is mentioned as the soot raw material.
This is because silicon chloride such as Cl ₄ is used, and when fluoride is used as a raw material, the concentration of ≡Si—F also becomes large, and the concentration becomes a problem.

Next, the operation of the method for producing the synthetic quartz glass for transmitting light will be described. First, the use of a high-purity silicon compound as a raw material is to prevent a decrease in transmittance of vacuum ultraviolet light to ultraviolet light due to impurities in the raw material remaining in the quartz glass, and the porous body is first synthesized. The reason is that, when performing the treatment in the oxygen-containing atmosphere, the treatment in the following oxygen atmosphere is efficiently performed.

That is, by heat-treating the porous body in an oxygen-containing atmosphere, the ˜Si—H bond or ≡Si—Cl bond of several ppm to several tens of ppm due to the high-purity silicon compound raw material is reduced to 1 ppm or less. Therefore, the formation of ≡Si—Si≡ bond due to a simple decomposition reaction of silane or the like is prevented, and the ≡Si—Si≡ once formed is changed into a normal ≡Si—O—Si≡ bond by oxygen in the atmosphere.

Next, degassing treatment removes excess oxygen and other gas components from the above-mentioned oxygen gas treatment from the glass fine particles, and facilitates the diffusion of H ₂ into the quartz glass in a subsequent step.

When the temperature of the heat treatment in a hydrogen-containing atmosphere exceeds 700 ° C., the reaction between ≡Si—O—Si≡ and H ₂ gas begins to proceed gradually as shown in the following equation (8). At temperatures above 800 ° C., the formation of ≡Si—H becomes very remarkable, and this ≡Si—H is an oxygen-deficient defect ≡Si.
It is not preferable because it causes the generation.

[0048]

[Equation 8]

[0049]

EXAMPLES AND COMPARATIVE EXAMPLES Hereinafter, synthetic quartz glass for transmitting light according to examples of the present invention will be described. As a comparative example,
Synthetic silica glass, which has a large decrease in transmittance due to irradiation with a KrF laser, will also be described.

Using silicon tetrachloride (SiCl ₄ ) which is a high-purity silicon compound as a raw material, in an oxygen-hydrogen flame, 180
Quartz glass fine particles were synthesized by vapor-phase chemical reaction at 0 ° C. and deposited, and a porous body (soot) having a diameter of 35 cm and a length of 100 cm was synthesized.

Next, a quartz glass rod (preform) was produced by heat-treating the synthesized porous body under various conditions. First, Examples 1, 2 and Comparative Example 1,
In the case of 4, the porous body was placed in an atmosphere furnace, heat-treated at 1200 ° C. for 6 hours in a 100% oxygen atmosphere, then transferred to a vacuum furnace and heat-treated at 1250 ° C. for 48 hours under a reduced pressure of 0.5 Pa. After that, heat treatment was further performed at 1550 ° C. for 6 hours to sinter, and a dense and transparent quartz glass rod was obtained.
In the case of Example 3, the first step, that is, the heat treatment in an oxygen atmosphere is omitted, and in the case of Example 4, instead of the heat treatment in the oxygen atmosphere, a vacuum atmosphere is set to 1200 ° C.
Other heat treatments were performed in the same manner as in Example 1 except that the heat treatment was performed for 6 hours. Further, in the case of Comparative Examples 2 and 5, in He gas containing 5% of chlorine instead of the oxygen atmosphere, the treatment was performed at 1200 ° C. for 6 hours, and in the case of Comparative Examples 3 and 6, the He gas containing chlorine described above. The subsequent heat treatment was performed in the same manner as in Example 1 except that the heat treatment was performed in the pure He gas atmosphere at 1500 ° C. for 10 hours after the heat treatment in the atmosphere.

The quartz glass rod (preform) obtained by the heat treatment had a diameter of 120 mm and a length of about 650 mm in all cases. next,
Each of these preforms was sliced to produce a disc-shaped body having a thickness of 10 mm.

Next, Examples 1, 3, 4 and Comparative Examples 2, 3
In this case, the disc-shaped body was heat-treated at 700 ° C. in an atmosphere of H ₂ gas at 1 atm, so that the disc-shaped body contained H ₂ . The heat treatment time in the hydrogen-containing atmosphere was 1 hour in the case of Example 1, 5 hours in the case of Example 3 and Comparative Examples 2 and 3, and 100 hours in the case of Example 4. Further, in the case of Example 2, the heat treatment condition under a hydrogen-containing atmosphere was 750 ° C. for 5 hours, and in the case of Comparative Example 1, it was 1000 ° C. for 5 hours. In Comparative Examples 4 to 6, heat treatment was not performed in a hydrogen-containing atmosphere.

H ₂ concentration, SiH group concentration, and ≡Si--Si in the disk-shaped quartz glass produced under the above conditions.
The concentration of ≡ and the concentration of the SiCl group were measured by the method described in the “Action” column. The results are shown in Table 1 below.

Quartz glass according to Examples and Comparative Examples having such characteristics (diameter: 120 mm, thickness: 10 m)
m), a 248 nm KrF excimer laser 400
Irradiation was performed for 10 ⁶ shots under the condition of mJ / cm ² and 100 Hz, and the transmittance at each wavelength of 248 nm, 193 nm, and 185 nm was measured before and after the irradiation, and the evaluation of the decrease in transmittance was performed. Moreover, after irradiation with the KrF excimer laser, 2
The transmittance at 60 nm was measured. The results are also shown in Table 1 below.

In Table 1, only the evaluation of the light resistance by the KrF excimer laser is shown. However, even when the ArF excimer laser, the low pressure mercury lamp and the excimer lamp are used, the transmittance due to the light damage when irradiated with ultraviolet rays is shown. Similar results were obtained because the degradation behavior was exactly the same.

[0057]

[Table 1]

As is clear from the results shown in Table 1 above, the silica glasses according to Examples 1 to 4 containing H ₂ at a concentration of 10 ¹⁵ pieces / cm ³ or more had a light absorption spectrum after laser irradiation. To 260 nm band defect is not observed, and the sum of the silyl group (SiH) concentration, twice the oxygen deficiency defect concentration and the SiCl group concentration is 5.3 × 10 ¹⁶ / cm ³ or less, Absorption in the 210 nm band was not traced or detected, and the decrease in transmittance at each wavelength was 0.2% or less, confirming excellent light resistance to high-energy light in the vacuum ultraviolet region to the ultraviolet region.

On the other hand, in the case of Comparative Example 1, the H ₂ treatment temperature was too high, and Si and H ₂ in the network structure of quartz glass were
Molecules are silyl groups by reaction generates a large amount, regardless Thus, also in H ₂ is present sufficiently in the quartz glass 2
The absorption due to the 10 nm band defect is large, and the transmittance of each wavelength is greatly reduced. In addition, in the cases of Comparative Examples 2 and 3, even though H ₂ was sufficiently present in the silica glass, the silyl group concentration, the oxygen deficiency defect concentration doubled, and ≡Si.
The sum of the —Cl concentrations exceeds 5.3 × 10 ¹⁶ pieces / cm ³ , the absorption in the 210 nm band becomes large, and the transmittance at each wavelength decreases. Further, in Comparative Examples 4 to 6, H
_Two molecules were not detected, and the sum of silyl group concentration, double oxygen deficiency defect concentration and ≡Si—Cl concentration was 5.3 × 10 ¹⁶
The number of particles per cm ³ is exceeded, the absorption in the 260 nm and 210 nm bands becomes remarkable, and the transmittance in each wavelength region is greatly reduced. Especially 248 nm due to the presence of 260 nm band defect
The decrease in transmittance is remarkable.

[0060]

As described in detail above, in the synthetic quartz glass for light transmission according to the present invention, the concentration of dissolved hydrogen molecules is 10 or less.
¹⁵ pieces / cm ³ or more, and the total concentration of SiH groups, twice the oxygen deficiency defect concentration, and the concentration of SiCl groups is 5.3.
Since it is less than × 10 ¹⁶ pieces / cm ^3, it is 21 even when irradiated with light having a high energy density in the vacuum ultraviolet region to the ultraviolet region.
A 0 nm band defect and a 260 nm band defect are not generated, absorption in the above wavelength region can be prevented, and a synthetic quartz glass for light transmission having excellent light resistance can be provided. Therefore, the synthetic quartz glass for light transmission according to the present invention,
Excimer laser oscillator, laser exposure device for lithography, laser CVD device, asher, etcher, ozonizer, laser processing device, laser medical device, etc., window materials and lenses for various devices using lasers and lamps in the vacuum ultraviolet region to ultraviolet region , A mirror, a prism, a gas-filled container for a lamp, etc. can be used for various purposes.

Further, in the method for producing a synthetic quartz glass for light transmission according to the present invention, a quartz glass porous body is synthesized from a high-purity silicon compound by a gas phase chemical reaction, and the quartz glass porous body is subjected to an oxygen-containing atmosphere. Synthetic silica glass containing oxygen-excessive defects obtained by transparentizing vitrified in vacuum after heat treatment in a hydrogen-containing atmosphere at 800 ° C.
Since the heat treatment is performed below, it is possible to reliably manufacture the above-described light-transmitting synthetic quartz glass having excellent light resistance.

[Brief description of drawings]

FIG. 1 is a graph showing absorption in a vacuum ultraviolet region to an ultraviolet region due to defects generated when a conventional synthetic quartz glass is irradiated with a KrF excimer laser.

FIG. 2 is a graph showing absorption in a vacuum ultraviolet region to an ultraviolet region when a synthetic quartz glass containing hydrogen is irradiated with a KrF excimer laser.

FIG. 3 is a graph showing the shape of an absorption peak at each absorbance of 210 nm (5.9 eV) band defect.

[Fig. 4] Absorbance of 210 nm defect is in a specific wavelength range (248
(nm, 193 nm, 185 nm) is a graph showing the influence on the transmittance.

Claims (2)

[Claims] 1. The dissolved hydrogen molecule concentration is 10 ¹⁵ / cm ³ or more, and the concentration of SiH groups and the concentration of oxygen-deficient defects are 2 or more.
And the total concentration of SiCl groups is 5.3 × 10 ¹⁶ pieces / c
Synthetic quartz glass for light transmission, characterized by having a size of m ³ or less. 2. Oxygen obtained by synthesizing a quartz glass porous body from a high-purity silicon compound by a gas-phase chemical reaction, heat-treating the quartz glass porous body in an oxygen-containing atmosphere, and then vitrifying it under vacuum. The synthetic quartz glass for light transmission according to claim 1, wherein the synthetic quartz glass containing excess type defects is heat-treated in a hydrogen-containing atmosphere at 800 ° C. or lower.