JP3336761B2 - Method for producing synthetic quartz glass for light transmission - Google Patents

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 light transmission.
Relates manufacturing method, and more particularly, an excimer laser (Xe-Cl: 308nm, Kr -F: 248nm, Ar-F: 193nm), a low pressure mercury lamp (185 nm), an excimer lamp (Xe-Xe: 172n
m) vacuum ultraviolet light - ultraviolet lenses and prisms for light, such as, regarding manufacturing methods of the light-transmitting synthetic quartz glass used as an optical component of a window material or the like.

[0002]

2. Description of the Related Art Synthetic quartz glass has a thickness of about 150 nm to about 5 μm.
It has a wide range of applications because it transmits light over a wide wavelength range of m. It has a small thermal expansion coefficient, so it can be used to construct a high-precision optical system with a small deviation of the optical axis. It is a glass material that is very excellent in various points, such as being able to be used and being hardly damaged even when irradiated with high energy light because of high purity silicon dioxide. One of the applications utilizing such excellent characteristics is as an optical material of a lithography apparatus for exposing and drawing an integrated circuit pattern such as an LSI. Conventionally, g-line (435.8 nm) or i-line (365 nm) of the Hg emission line spectrum has been used as an exposure light source of this lithography apparatus.
Optical glass composed of multiple components has been used as the optical glass material. However, recently there has been a trend to shorten the wavelength of light used for exposure in order to further improve the degree of circuit integration, in which case synthetic silica glass with low light absorption in the vacuum ultraviolet to ultraviolet regions is used for illumination optical systems and It becomes necessary to use it for an exposure optical system. In addition, a low-pressure mercury lamp (185 nm)
And excimer lamps (Xe-Xe: 172 nm) use light CV
It is used for ashing, etching, and ozone generators of 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.

[0003] The quartz glass material used for these optical systems is required to have high light resistance at the used wavelength (the transmittance is hardly reduced after light irradiation) and to be used as a lens or a prism. In addition, in addition to the above properties, homogeneity of the refractive index is also required. With respect to the light resistance, it is required that light absorption is practically not detected and fluorescence is not detected in a wavelength region of light to be used, and that a light absorption band is not induced even after long-time light irradiation.
When using an excimer laser (248nm) is that lowering of the transmittance at 248nm after the irradiation of 10 ⁶ shots 400 mJ / cm ^2, 100 Hz conditions as the most severe condition is not more than 0.1% Required. Further, it is desired to develop a material that can withstand shorter-wavelength light even under a higher-density irradiation condition for a longer time.

[0004] Usually, synthetic quartz glass can be cited as a quartz glass which can meet such severe conditions. Generally, the name of synthetic quartz glass is used for all quartz glasses that do not use natural SiO ₂ as a starting material, and there are various methods for producing this synthetic quartz glass. Therefore, depending on the purity of the raw material and the manufacturing method, there are various grades of impurity element concentration (metal element concentration, non-metal element concentration), defect concentration, etc. of the manufactured synthetic quartz glass. Quartz glass cannot be the ideal glass material for transmission optics.

[0005] Synthetic quartz glass production methods are roughly classified into a gas phase method and a liquid phase method. The gas phase method is mainly used as a method for producing materials used for optical applications. There are also direct synthesis methods, plasma CVD methods, soot methods, etc., and impurities such as metals, OH groups, Cl, H ₂ , O ₂ , oxygen excess defects and oxygen deficiency defects in quartz glass due to raw materials and manufacturing methods. , Ring structure defects and the like. The concentration of these impurities and defects has a great effect on the optical properties of the synthetic quartz glass, such as light absorption, fluorescence, and refractive index. Therefore, the light resistance against the irradiation with high-energy light (lower transmittance after irradiation) Is also known to have a significant effect. Therefore, various studies have conventionally been made on the relationship between the 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, reducing the H ₂ content, possible to increase the ₂ content, eliminating the oxygen defects (excessive defects and deficient defects), etc. be dissolved inert gas molecules, such as He, various methods have been proposed.

However, as can be seen from the contents of the above proposals, there are mutually contradictory proposals, which suppress the optical damage of quartz glass to irradiation of light in the vacuum ultraviolet region to the ultraviolet region,
Alternatively, there has been a problem that the conditions to be provided for the synthetic quartz glass in order to prevent it have not yet been completely grasped.

[0008] For example, in the invention of are described in JP-A-2-69332 "laser-light transmissive member", the OH group concentration in the quartz glass increases, the amount of H ₂ being occluded increase However, it is described that the light resistance to laser light is reduced.

In the invention of the "optical member for laser light" described in JP-A-3-101282, H ₂ gas molecules contained in quartz glass improve the light resistance to laser light. The proposal is completely opposite to the contents described in the above publication.

Therefore, the present inventors have developed a synthetic quartz glass for light transmission and a method of manufacturing the same, wherein the transmittance is hardly reduced even when a laser beam in the vacuum ultraviolet region to the ultraviolet region having a high energy density is irradiated for a long time. For the purpose of providing, a study was made of impurities and defects in the synthetic quartz glass and a change in transmittance when the synthetic quartz glass was irradiated with ultraviolet rays, and the like. Synthetic quartz glass had a high energy density of 172 nm, 185 nm, 193 nm or 248 nm
The cause of the transmittance decrease that occurs when irradiating the laser light of
The Si—0 ° (non-bonded oxygen) defect with an absorption centered at about 260 nm (4.7 eV) and the SiSi with an absorption centered at about 210 nm (5.9 eV) shown in the graph of FIG. (E 'center) It was confirmed that the defect was caused by generation of defects. Note that 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, it is examined which of the OH group concentration, the H ₂ concentration, the defect concentration and the like in the synthetic quartz glass affects the generation of these defects.
A synthetic silica glass having 0 ppm OH group is irradiated with a laser beam, and the OH group has no relation to the formation of both defects, and the synthetic quartz glass having an H ₂ concentration of 10 ¹⁵ to 10 ¹⁸ / cm ³ is irradiated with a laser beam. And H ₂ is 4.7 eV
5.9 eV (210 nm), although it has the effect of preventing generation of defects having absorption centered at (260 nm).
It has been found that there is no effect of suppressing or preventing the generation of a defect having an absorption centered on.

Further, they found that the generation of a defect having an absorption centered at 5.9 eV is related to the concentration of a silyl group (SiH), the concentration of an oxygen-deficient defect, and the concentration of a SiCl group. The invention has been completed.

That is, the present invention is to synthesize a porous quartz glass body from a high-purity silicon compound by a gas phase chemical reaction, heat-treat the porous quartz glass body in an oxygen-containing atmosphere, and then form a transparent vitreous glass under vacuum. The obtained synthetic quartz glass containing oxygen-excess type defects is placed under a hydrogen-containing atmosphere.
00 ° C. dissolved hydrogen molecule concentration is 10 ^15, characterized in that the heat treatment at less / cm ³ or more, and the concentration of SiH groups, oxygen deficient defect concentration twice and concentration total 5.3 × 10 of SiCl groups ¹⁶
This is a method for producing a synthetic quartz glass for light transmission, which is not more than individual pieces / cm ³ .

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

Next, a method for producing a synthetic quartz glass for light transmission according to the present invention is a method for producing a synthetic quartz glass for light transmission as described above, wherein a quartz glass porous material is produced from a high-purity silicon compound by a gas phase chemical reaction. Synthesized quartz glass containing oxygen-excess type defects obtained by heat-treating the quartz glass porous body in an oxygen-containing atmosphere and then vitrifying it under vacuum at 800 ° C. or lower in a hydrogen-containing atmosphere. It is characterized by doing.

The high-purity silicon compound used as a raw material includes
For example, silicon tetrachloride or silane may be mentioned, and in order to prevent a reduction in the transmittance of vacuum ultraviolet light to ultraviolet light in the manufactured quartz glass, the alkali metal in the raw material is 10 in total.
0 ppb or less, total of 100 ppb alkaline earth metals
Hereinafter, transition metals (Ti, Cr, Fe, Ni, Cu, C
e) is preferably not more than 50 ppb in total. In the synthesis of the quartz glass porous body, no special conditions are required, and hydrolysis may be performed by a normal oxyhydrogen flame, but the hydrolysis temperature is preferably about 1000 to 2000 ° C.

Next, the porous quartz glass (soot) obtained in the above step is heat-treated in an oxygen-containing atmosphere.
In order to promptly diffuse oxygen molecules into the soot, which is a porous body, to convert {Si-Si} to {Si-O-Si} and prevent voids 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% or more.
When the oxygen content at the time of the treatment is less than 10 vol% and the temperature is less than 1000 ° C., the above-mentioned reaction does not sufficiently proceed. On the other hand, when the temperature exceeds 1300 ° C., the soot sintering proceeds somewhat. Then, the subsequent degassing becomes difficult.

After the above step, excess oxygen and other gas components contained by the above-described oxygen gas treatment are removed from the glass fine particles to facilitate diffusion of H ₂ into quartz glass in a later step. For this reason, it is preferable to perform a degassing treatment.
a under a reduced pressure of not more than water (with a dew point of −100 ° C.)
Hereinafter) an inert gas atmosphere is preferable. The temperature at this time is preferably 1000 to 1400 ° C. If the temperature at the time of the degassing treatment is less than 1000 ° C., gas such as oxygen is not sufficiently removed, while the temperature is 1400 ° C.
If it exceeds 300, densification starts before the gas is not sufficiently removed.

Thereafter, transparent vitrification is carried out. In this case, the conditions are as follows:
It is preferable to carry out in a temperature range of 00 to 1600 ° C. If the temperature is lower than 1400 ° C., densification hardly proceeds and productivity is deteriorated. On the other hand, if the temperature exceeds 1600 ° C., cost increases due to power consumption.

The subsequent heat treatment in a hydrogen-containing atmosphere includes
800 ° C. in a reducing atmosphere with an H ₂ concentration of 20 vol% or more
It is preferably performed at a temperature of 700 ° C. or less. If the hydrogen content at the time of heat treatment is less than 20 vol%, hydrogen is not sufficiently absorbed by the quartz glass, and the temperature of the heat treatment becomes 8%.
If the temperature exceeds 00 ° C., the absorbed hydrogen becomes ≡Si—O—Si
Reacts with ≡ to generate SiH which causes ≡Si and defects.

Since the variation in 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 is manufactured before the step of including H _2. If this is the case, a synthetic quartz glass for light transmission having homogeneity and light resistance can be produced by a subsequent heat treatment in an atmosphere containing H ₂ .

[0022]

As described above, as a result of examining the ultraviolet absorption spectrum after irradiating a synthetic quartz glass manufactured by various manufacturing processes with a KrF excimer laser, an ArF excimer laser, and a low-pressure mercury lamp, the damage caused by these light irradiations is considered. , Two types of absorption bands shown in FIG.
an oxygen-excess defect having an absorption centered at eV (260 nm) (hereinafter referred to as 260 nm band defect), and 5.9e
It was confirmed that the generation was mainly caused by oxygen deficiency defects (hereinafter, referred to as 210 nm band defects) having an absorption centered at V (210 nm). Further, in the quartz glass in which H ₂ molecules are detected, as shown in FIG.
Although the 0 nm band defect is not detected, the 210 nm band defect is detected (solid line, broken line) and not detected (dashed line), and the presence of H ₂ molecule is not a sufficient condition for improving the light resistance. found.

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

[0024]

(Equation 1)

[0025]

(Equation 2)

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

Further, the 210 nm band defect (≡Si.)
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 shown in the above equations (3) to (5) proceeds with irradiation of relatively weak light (electromagnetic waves) than in the above equation (2). Of course, there is a distortion as observed in the polarizing plate inspection, or as in the case of the ring structure defect detected in the Raman spectrum, ΔSi-OS
If the bond of 反 応 is distorted or held in a stressed state, it is considered that the reaction represented by Formula 2 proceeds easily.

When an electromagnetic wave or a particle beam having a higher energy than ultraviolet rays, such as an X-ray, a γ-ray, a neutron beam ion beam, or the like, is irradiated, the reaction represented by Formula 2 also proceeds easily.

Therefore, the present inventors have studied to obtain correlations with the OH group concentration, the concentration of nonmetallic impurities such as Cl, the concentration of oxygen defects, etc. in the synthetic quartz glass involved in the formation of two kinds 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 the Cl ₂ concentration was defined as the ΔSi—Cl concentration. Concentration of H _2, ≡Si-H concentration each of the laser Raman spectrum 4135 cm ^-1 and 2250 cm ^-1
Of the scattering peak at 800 cm ⁻¹ indicating the bonding of ≡Si—O— (intensity ratio). The concentration of the {Si—Si} defect was determined from the absorbance at 163 nm in the vacuum ultraviolet region. ≡Si-OO-
The Si≡ concentration was determined by the magnitude of the absorbance of the peak at 260 nm after laser irradiation.

As a result of these studies, it was found that H ₂ gas easily reacts with {Si—O—O—Si}, which is an oxygen excess defect, to form a compound represented by the following formula (6).

[0035]

(Equation 6)

That is, H ₂ is converted into a stable OH group by the reaction shown in the above equation (6), and H ₂ shown in the above equation (1) is obtained.
Since 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 thought that the difference in absorption at Therefore, it is considered that {Si—O—O—Si} type oxygen-excess defects hardly coexist in synthetic quartz glass in which H ₂ is present in a certain amount or more in quartz glass.

As described above, in order to suppress the generation of defects at the 260 nm band, it is necessary to contain H ₂ molecules in quartz glass, and at least the H ₂ molecules are present to such an extent that they can be detected by Raman spectroscopy. In this case, no 260 nm defect is generated. The lower detection limit of H ₂ in Raman spectroscopy is substantially about 10 ¹⁵ / cm ³ . If the H ₂ concentration is within 10 ¹⁸ / cm ³ , there is no adverse effect due to the presence of H ₂ .

Next, considering the oxygen deficiency defect,
The effect of H _{2 on} the oxygen deficiency defect {Si—Si} is expressed by the following equation (7).

[0039]

(Equation 7)

However, as shown in the above equation (4), once generated ＨSi—H is not very stable, and is decomposed again to generate ２１０Si · which is a 210 nm band defect. Therefore,
H ₂ molecules in quartz glass are not effective in suppressing the generation of 210 nm defects.

FIG. 3 is a graph showing a theoretical peak shape at each absorbance of a 210 nm defect. As shown in FIG. 248 nm (5.0e
V), 193 nm (6.4 eV), 185 nm (6.7
Each wavelength range of eV) becomes a part of the absorption peak, and the transmittance is reduced. FIG. 4 shows that the absorbance of a 210 nm defect is in a specific wavelength range (248 nm, 193 nm, 185 n).
7 is a graph showing the effect on transmittance in m). FIG. 4 shows that the decrease in transmittance at a wavelength of 248 nm is 0.1%.
%, The absorbance due to a 210 nm defect needs to be 0.0039 or less. To suppress the decrease in transmittance at a wavelength of 193 nm to 0.1% or less, the absorbance is 21% or less.
The absorbance due to a 0 nm band defect needs to be 0.0009 or less, and a decrease in transmittance at a wavelength of 185 nm is reduced by 0.
In order to suppress the density to 1% or less, the absorbance due to a 210 nm band defect needs to be 0.0026 or less.

Therefore, the absorption cross section of ≡Si.
Assuming that the density of the defects is 5.3 × 10 ¹⁶ / cm ³ or less (248 nm) and 1.2 × 10 ⁻²⁰ cm ² , respectively.
× 10 ¹⁶ / cm ³ or less (193 nm), 3.5 × 10
^{If the} number is ¹⁶ / cm ³ or less (185 nm), the decrease in transmittance in each wavelength region can be suppressed to 0.1% or less. From the above, theoretically, the concentration of the defect is 1.2 × 1
If the number is not more than 0 ¹⁶ / cm ³ , the decrease in transmittance at each wavelength described above can be suppressed to within 0.1%, but according to the current standard, the decrease in transmittance at 248 nm is 0.1%. %, The required standard is satisfied. Therefore, according to the above criteria, the defect concentration is 5.3.
It should be less than × 10 ¹⁶ / cm ³ . Here, the reason why the upper limit of the decrease in transmittance is set to 0.1% or less is that the limit of the accuracy of the photometer is at this level, and the decrease in transmittance is not substantially detected at a transmittance lower than this level. And ≡
The reason why the absorption cross section of Si was set to 7.37 × 10 ⁻²⁰ cm ² was reported by RAWeeks (J. Appl. Phys., 35 (1964) p19).
32 $) was obtained from a graph showing the relationship with the concentration of ≡Si—OH necessary to prevent the generation of a defect ≡Si.

The reaction that easily produces a defect ΔSi when irradiated with light in the vacuum ultraviolet region to the ultraviolet region is represented by the above formulas (3) to (5).
Since the reaction is represented by the formula, in order to control the production amount of the defect ≡Si · under the above-mentioned conditions, the concentration of the 生産 Si—H and the concentration of the 2
The sum of the doubled amount and the concentration of ≡Si—Cl is 5.3 × 1
It is sufficient if the number is not more than 0 ¹⁶ pieces / cm ³ . It is more preferable that the sum of the concentrations of these bonds is 1.2 × 10 ¹⁶ / cm ³ or less, and it goes without saying that 0 is ideal. The correctness of the above estimation is also demonstrated by the following examples. Here, the concentration of {Si—Si} is set to twice because there is a possibility that two ≡Si · s are generated when the bond is broken. Of the halogenated bonds
Only Si-Cl is cited as the raw material of soot
This is because silicon chloride such as Cl ₄ is used. When fluoride is used as a raw material, the concentration of ≡Si—F becomes large, so that the concentration becomes a problem.

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

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

Next, by the degassing treatment, the excess oxygen and other gas components of the above-described oxygen gas treatment are removed from the glass fine particles, and the diffusion of H ₂ into the quartz glass in a later step becomes easy.

In the heat treatment in a hydrogen-containing atmosphere, when the temperature exceeds 700 ° C., the reaction between {Si—O—Si} and H ₂ gas starts to progress gradually as shown in the following equation (8). At a temperature exceeding 800 ° C., the formation of ≡Si—H becomes very remarkable.
It is not preferable because it causes generation.

[0048]

(Equation 8)

[0049]

Examples and Comparative Examples Hereinafter, synthetic quartz glass for light transmission according to examples of the present invention will be described. In addition, as a comparative example,
A description will also be given of synthetic quartz glass in which the transmittance is greatly reduced by irradiation with a KrF laser.

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

Next, the synthesized porous body was heat-treated under various conditions to prepare a quartz glass rod (preform). First, Examples 1 and 2, and Comparative Example 1,
In the case of No. 4, this porous body was placed in an atmosphere furnace and heat-treated at 1200 ° C. for 6 hours in a 100% oxygen atmosphere, and then transferred to a vacuum furnace and heat-treated at 1250 ° C. for 48 hours under a reduced pressure of 0.5 Pa. Thereafter, heat treatment was further performed at 1550 ° C. for 6 hours for sintering to obtain a dense and transparent quartz glass rod.
Further, in the case of the third embodiment, the first step of the heat treatment in the oxygen atmosphere is omitted, and in the case of the fourth embodiment, the heat treatment in the oxygen atmosphere is replaced with a 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 Comparative Examples 2 and 5, a treatment was performed at 1200 ° C. for 6 hours in a He gas containing 5% chlorine instead of an oxygen atmosphere, and in Comparative Examples 3 and 6, the He gas containing chlorine was used. A heat treatment was performed in the same manner as in Example 1 except that a heat treatment was performed at 1500 ° C. for 10 hours in a pure He gas atmosphere after the heat treatment in the inside.

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

Next, Examples 1, 3, and 4 and Comparative Examples 2, 3
In the case of (1), the disc-shaped body was heat-treated at 700 ° C. in an atmosphere of 1 atmosphere of H ₂ gas, so that the disc-shaped body contained H ₂ . The heat treatment time in the hydrogen-containing atmosphere was 1 hour in Example 1, 5 hours in Example 3, and Comparative Examples 2 and 3, and 100 hours in Example 4. In the case of Example 2, the heat treatment condition in a hydrogen-containing atmosphere was set to 750 ° C. for 5 hours, and in the case of Comparative Example 1, the temperature was set to 1000 ° C. for 5 hours. In the case of Comparative Examples 4 to 6, no heat treatment was performed in a hydrogen-containing atmosphere.

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

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

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

[0057]

[Table 1]

As is clear from the results shown in Table 1 above, the quartz glasses according to Examples 1 to 4 containing H ₂ at a concentration of 10 ¹⁵ / cm ³ or more showed light absorption spectra after laser irradiation. No absorption due to defects at 260 nm band is recognized, 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, The absorption in the 210 nm band was almost no trace or detected, and the decrease in transmittance at each wavelength was 0.2% or less, and excellent light resistance to high energy light in the vacuum ultraviolet region to the ultraviolet region was confirmed.

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 quartz glass network structure were changed.
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 increases, and the transmittance at each wavelength decreases significantly. In Comparative Examples 2 and 3, even though H ₂ was sufficiently present in the quartz glass, the silyl group concentration, twice the oxygen deficiency defect concentration, and ΔSi
The sum of the -Cl concentration exceeds 5.3 × 10 ¹⁶ / cm ³ , the absorption in the 210 nm band increases, and the transmittance at each wavelength decreases. Furthermore, in Comparative Examples 4 to 6, H
_Two molecules were not detected, and the sum of the silyl group concentration, twice the oxygen deficiency defect concentration, and the ΔSi—Cl concentration was 5.3 × 10 ¹⁶
/ Cm ³ , the absorption in the 260 nm and 210 nm bands becomes remarkable, and the transmittance in each wavelength region is greatly reduced. In particular, 248 nm due to the presence of a 260 nm band defect.
, The decrease in transmittance is remarkable.

[0060]

As described in detail above, 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 of the SiH group concentration, twice the oxygen deficiency defect concentration and the SiCl group concentration is 5.3.
× 10 ¹⁶ / cm ³ or less, so that even when irradiated with light of high energy density in the vacuum ultraviolet
A 0-nm band defect and a 260-nm band defect are not generated, the absorption in the wavelength region can be prevented, and a synthetic quartz glass for light transmission excellent in light resistance can be provided. Therefore, the synthetic quartz glass for light transmission according to the present invention,
Window materials and lenses for various devices that use vacuum ultraviolet to ultraviolet lasers and lamps, such as excimer laser oscillation devices, lithography laser exposure devices, laser CVD devices, ashers, etchers, ozonizers, laser processing devices, and laser medical devices. , Mirrors, prisms, gas-filled containers for lamps, etc.

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. A synthetic quartz glass containing oxygen-excess type defects obtained by performing vitrification under vacuum after heat treatment in vacuum at 800 ° C. in a hydrogen-containing atmosphere.
Since the heat treatment is performed below, the synthetic quartz glass for light transmission having excellent light resistance can be reliably manufactured.

[Brief description of the drawings]

FIG. 1 is a graph showing absorption in a vacuum ultraviolet region to an ultraviolet region due to a defect 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 a 210 nm (5.9 eV) band defect.

FIG. 4 shows the absorbance of a 210 nm defect in a specific wavelength range (248
9 is a graph showing the effect on the transmittance at 193 nm and 185 nm).

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-21540 (JP, A) JP-A-4-195101 (JP, A) JP-A-6-234545 (JP, A) Kuzuu, Physical Review B, (US), The American Physical Society, 1991, USA, Vol. 17, p. 9265-9270 Silica Glass Data Book, 1988, New Glass Forum, Japan, March 1, 1990, p. 59-61 (58) Field surveyed (Int. Cl. ⁷ , DB name) C03B 8/04 C03B 20/00 C03C 3/06

Claims (1)

(57) [Claims] 1. An oxygen obtained by synthesizing a porous quartz glass body from a high-purity silicon compound by a gas phase chemical reaction, heat-treating the porous quartz glass body in an oxygen-containing atmosphere, and then vitrifying it under vacuum. The synthetic quartz glass containing excess defects is heat-treated at 800 ° C or less in a hydrogen-containing atmosphere. The dissolved hydrogen molecule concentration is 10 ¹⁵ / cm ³ or more.
And twice the concentration of SiH groups and oxygen deficiency defects
A method for producing a synthetic quartz glass for light transmission, wherein the total concentration of SiCl and SiCl groups is 5.3 × 10 ¹⁶ / cm ³ or less .