JP2002316825A - Method for manufacturing synthetic quartz glass member for excimer laser and synthetic quartz glass member for excimer laser optical use obtained by this manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a synthetic quartz glass member for an excimer laser by introducing hydrogen molecules sufficient for obtaining high laser resistance into quartz glass body under suppression of the formation of reducing defects to degrade the laser resistance in view of the defects of the prior art and uniformly introducing the hydrogen molecule in such a manner that the refractive index distribution occurring in the concentration distribution of the hydrogen molecules is flattened and the synthetic quartz member for the excimer laser optical use which is obtained by this manufacturing method and has both of the high laser resistance and homogeneity. SOLUTION: The method for manufacturing the synthetic quartz glass member for the excimer laser includes a process step of incorporating the hydrogen molecules into the quartz glass body by heat treating the quartz glass body at a treatment temperature below 600 deg.C in a hydrogen-containing atmosphere of pressure above 1 atm to below 150 atm. The pressure of the hydrogen-containing gas is continuously or stepwise changed at least partly during the heat treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ultraviolet light, especially KrF,
The present invention relates to an optical synthetic quartz glass member having excellent light transmittance, homogeneity, and stability with respect to high-intensity irradiation of ArF excimer laser light, and a method for manufacturing the same. Specifically, the synthetic quartz glass member according to the present invention is:
In particular, lenses and other optical components of lithography exposure equipment using excimer lasers for semiconductor chip manufacturing,
Also, a prism for narrowing a band used in an excimer laser body, a general optical member used for KrF or ArF excimer laser light, a synthetic quartz glass member suitably used for a lens, a beam splitter, a prism, and the like. It is about.

[0002]

2. Description of the Related Art In recent years, LSIs have been manufactured in earnest by KrF excimer laser lithography, and development is being pursued toward realization of ArF excimer laser lithography as a next-generation exposure technique. The KrF lithography is also being improved as needed, and improvements are being made such as increasing the performance of drawing finer circuit patterns and increasing the processing capacity (throughput) per time. Specifically, for the writing of minute circuit patterns, improved techniques for exposure methods, such as a modified illumination method and a phase shift mask, are used, but basically a higher level of performance of the lens material of the exposure apparatus is required. Is coming. That is, high homogeneity and low birefringence are strongly demanded of lens materials in order to focus accurately. In order to improve the throughput, techniques such as increasing the exposure amount by increasing the repetition frequency or energy of the excimer laser are used. In such a case, since the amount of light transmitted through the lens material of the exposure device increases, optical damage is likely to occur. In any case, the quality required for the quartz glass lens material is increasing year by year with the improvement of the performance of the exposure machine, and the measures to improve the homogeneity and laser resistance by the conventional technology are becoming insufficient. .

Techniques for obtaining highly homogeneous quartz glass have been studied in many fields, and many patents have been filed. In general, the homogeneity of quartz glass for optics means the homogeneity of the refractive index, and the distribution of the refractive index is calculated by measuring the phase lag with an interferometer using a 632.8 nm He-Ne laser. are doing. Since a lens used for lithography is required to have very high imaging performance, a very high uniform quartz glass lens material is required. The refractive index changes depending on impurities in the quartz glass, for example, chlorine and hydroxyl groups, and also changes according to the fictive temperature. If there is a distribution of impurities in the quartz glass, the refractive index also changes with the distribution. For example, a portion having a large amount of SiOH groups has a relatively low refractive index. The fictive temperature depends on the cooling rate when heat-treating the quartz glass, and a fictive temperature distribution is generated in the quartz glass, so that a refractive index distribution is also formed. Japanese Patent Application Laid-Open No. 3-88743 discloses a manufacturing method for obtaining highly homogeneous glass by positively combining the above-mentioned individual factors causing the refractive index fluctuation in order to obtain a highly homogeneous quartz glass material for optical use. Have been. Further, the publication describes that in order to impart high laser resistance, heat treatment is performed in a hydrogen-containing atmosphere to dope hydrogen molecules. That is, the technique is to obtain a highly uniform glass while maintaining high excimer laser properties by doping with hydrogen. As described above, by applying hydrogen doping to highly homogeneous quartz glass obtained by controlling the distribution of impurities such as SiOH and chlorine, high laser resistance can be imparted, and thus it is suitably used as a lens material for excimer laser lithography. Was thought to be possible. However, in practice, 1) higher laser resistance is required in recent years with higher repetition and higher energy of lasers, and 2) larger materials are required due to higher NA. The practical problem that it is difficult to dope uniformly is emerging, and the method described in the above-mentioned publication does not necessarily provide a material that can sufficiently satisfy the current required level. In particular, it is very difficult to obtain a large-sized material in which hydrogen molecules are uniformly doped by heat treatment in a hydrogen-containing atmosphere in consideration of the diffusion coefficient of hydrogen molecules. Actually, there are difficulties such as a very long calculation time required for the calculation and a hydrogen treatment at a considerably high temperature. In addition, previous studies have shown that hydrogen molecules also affect the refractive index distribution, and that the uniform doping of hydrogen molecules is important.

[0004] Uniform hydrogen doping is highly homogeneous,
And it is important to obtain quartz glass with high resistance, but especially in the case of large materials, it takes considerable time for hydrogen to sufficiently diffuse inside, and as a result, productivity deteriorates. There is a big problem. Hydrogen doping at a high temperature, where the diffusion coefficient of hydrogen is large, can shorten the hydrogen diffusion time, but quartz glass exposed to hydrogen at high temperatures tends to cause new defects, which is the laser resistance. It is known to be a factor that worsens. JP 6
Japanese Patent Application Publication No. 166522 discloses that the synthetic quartz glass member prototyped by the indirect method is heat-treated at various temperatures in a hydrogen atmosphere, and the resistance of the hydrogen-doped material to ArF excimer laser irradiation is described. It is shown that the laser resistance was extremely deteriorated even though the heat treatment was performed at a higher temperature. This is because hydrogen molecules introduced at a high temperature cause reducing defects in the quartz glass, and irradiation with an excimer laser induces absorption in the ultraviolet region. This induced absorption is E '
This is due to a paramagnetic defect generally called a center, and has an absorption band having a center wavelength of 210 to 215 nm. Therefore, this publication describes that hydrogen treatment is performed at 600 ° C. or less to suppress generation of E ′ center, that is, to suppress generation of induced absorption. Since the diffusion coefficient is small, when processing a large-sized material, the processing time becomes long and the productivity deteriorates. Therefore, this publication describes that the treatment is performed at a high pressure of 1 atm or more, preferably 50 atm or more in order to introduce more hydrogen molecules into the quartz glass. However, in general, the concentration of hydrogen molecules in the quartz glass obtained in this way is higher at the periphery than at the center, as a result of the principle of diffusion phenomenon. In the case of the treatment with, it is known that the difference is large, so that the uniformity (refractive index distribution) is greatly affected.

Japanese Unexamined Patent Publication No. 2000-95535 discloses a method of doping hydrogen at a high pressure so that the hydrogen concentration distribution is not so formed so as not to affect the homogeneity. In this publication, 10 atm or more, preferably 50 atm
a hydrogen concentration at a pressure of at least m or more (second step) and then a heat treatment (third step) to selectively degas the high-hydrogen-concentration parts in the peripheral region, thereby achieving a uniform hydrogen concentration distribution. This is a method of obtaining a quartz glass material having However, in the method according to the patent, in order to obtain a homogeneous hydrogen-containing molded body, a two-step process is performed in which a heat treatment for doping with hydrogen (second step) is followed by a heat treatment in an atmosphere containing no hydrogen (third step). Heat treatment must be performed. It is also known that, in the latter heat treatment, if the temperature is kept too high, new defects are generated and the laser resistance deteriorates. Therefore, when selectively degassing only the peripheral portion having a high hydrogen concentration, it is necessary to perform the treatment at a relatively low temperature, and as a result, a long-time heat treatment is required. The concentration of hydrogen introduced and its distribution vary considerably depending on the size of the molded body and the conditions of the second step, but the heat treatment in the simple third step only selectively removes hydrogen appropriately only in the peripheral portion. It was quite difficult to gas and obtain a flat hydrogen concentration.
As described above, additional heat treatment after doping with hydrogen was not a very preferable method in terms of laser resistance and productivity.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, the present invention requires that sufficient hydrogen molecules be obtained in quartz glass to obtain high laser resistance while suppressing generation of reducing defects that lower laser resistance. And a method for producing a synthetic quartz glass member for an excimer laser for uniformly introducing hydrogen molecules so that the refractive index distribution caused by the concentration distribution of hydrogen molecules becomes flat, and a high laser obtained by the method. An object of the present invention is to provide a synthetic quartz glass member for an excimer laser having both resistance and homogeneity.

[0007]

The above-mentioned object is achieved by the present invention according to any one of the following (1) to (10). (1) Excimer laser optics including a step of heat-treating a synthetic quartz glass body in a hydrogen-containing atmosphere at a pressure of 1 atm or more and less than 150 atm at a processing temperature of 600 ° C. or less to cause the quartz glass body to contain hydrogen molecules. A method of manufacturing a synthetic quartz glass member for an excimer laser, wherein the pressure of the hydrogen-containing gas is changed continuously or stepwise at least in part during the heat treatment. . (2) The method for producing a synthetic quartz glass member for an excimer laser according to the above (1), wherein a change in the pressure of the hydrogen-containing gas is reduced. (3) heat-treating the synthetic quartz glass body in a hydrogen-containing atmosphere at a first set pressure for a first set time, and then heat-treating the synthetic quartz glass body at a second set pressure lower than the first set pressure for a second set time; (2) The method for producing a synthetic quartz glass member for excimer laser according to the above (2). (4) the hydrogen-containing atmosphere is 100% hydrogen gas;
Alternatively, the method for producing a synthetic quartz glass member for an excimer laser according to any one of the above (1) to (3), which is a mixed gas of nitrogen, argon or helium and hydrogen gas. (5) The synthetic quartz glass member for an excimer laser according to any one of (1) to (4), wherein the synthetic quartz glass body containing hydrogen is prepared by a direct flame hydrolysis method or an indirect flame hydrolysis method. Manufacturing method. (6) A synthetic quartz glass member for excimer laser produced by the method for producing a synthetic quartz glass member for excimer laser according to any one of claims 1 to 5, wherein hydrogen is contained uniformly. (7) The average value of the hydrogen molecule concentration is 1 × 10 ¹⁸ molecules / cm ³
And the difference ΔH ₂ between the maximum value and the minimum value of the hydrogen molecule concentration.
The synthetic quartz glass member for an excimer laser according to the above (6), which has a molecular weight of 1.2 × 10 ¹⁸ molecules / cm ³ or less. (8) 215 n during irradiation when an ArF excimer laser is irradiated at an energy density of ² mJ / cm ² per pulse, a frequency of 200 Hz, and an irradiation number of 2 × 10 ⁵ pulses.
The synthetic quartz glass member for an excimer laser according to the above (6) or (7), wherein the induced absorption amount at m is 0.003 or less in absorbance per 1 cm thickness. (9) A KrF excimer laser was used with an energy density per pulse of 100 mJ / cm ² and a frequency of 200H.
z, 2 during irradiation when 2 × 10 ⁵ pulses are irradiated
(6) or (7) above, wherein the induced absorption amount at 10 nm is 0.0075 or less in absorbance per 1 cm thickness.
The synthetic quartz glass member for an excimer laser according to the above. (10) The homogeneity of the refractive index at 632.8 nm is ±
The synthetic quartz glass member for an excimer laser according to any one of the above (7) to (9), which has a birefringence of 2 × 10 ⁻⁶ (/ cm) or less and a birefringence of 2 nm / cm or less. The member obtained by the present invention is for excimer laser,
Particularly, it is suitably used for various devices for KrF and ArF excimer lasers, and has high laser resistance and homogeneity because hydrogen molecules are introduced into optical members in high concentration and high homogeneity. An optical member that can be stably used for a long period of time in various devices using the above-described excimer laser. For example, it can be suitably used as an optical member of an excimer laser stepper, a laser processing device, a laser annealing device, or the like.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing a synthetic quartz glass member for an excimer laser according to the present invention, a heat treatment is performed at a temperature of 600 ° C. or less in a hydrogen-containing atmosphere of 1 atm or more.
By changing the pressure of the hydrogen atmosphere gas stepwise or continuously during the heat treatment, a high concentration of hydrogen molecules can be uniformly contained in the quartz glass. As a result, a quartz glass material for optics having both excellent properties of homogeneity and laser resistance is obtained. In other words, long-term processing is required to diffuse hydrogen molecules at a relatively low temperature into quartz glass at a high concentration, but high-concentration hydrogen molecules are contained by setting the pressure at 1 atm or higher. The hydrogen concentration distribution in the quartz glass can be positively controlled by changing the pressure, and a uniform hydrogen concentration profile can be obtained.
According to the production method of the present invention, the processing temperature in a hydrogen atmosphere is relatively low, and since the processing time is short, generation of reducing defects that deteriorate laser resistance in quartz glass is not observed, Since high-concentration hydrogen molecules are contained by high-pressure treatment, those that have excellent long-term laser resistance can be obtained. And a laser having extremely uniform and stable laser resistance.

Hereinafter, one embodiment of the production method of the present invention will be described in detail. The quartz glass used in the present invention may be generally any kind, and a typical one is a synthetic quartz glass produced by an indirect flame hydrolysis method (soot method) or a direct flame hydrolysis method (direct method). It is suitable. It is important to perform a thermal annealing treatment before the treatment in the hydrogen gas-containing atmosphere to degas the hydrogen gas remaining in the quartz glass. Generally, almost no hydrogen molecules are present in the quartz glass obtained by the soot method (in most cases, 1 × 10 ¹⁶ molecules / cm ³ or less).
However, hydrogen molecules often remain in the quartz glass obtained by the direct method. Since hydrogen molecules do not remain uniformly, annealing before hydrogen doping treatment in a hydrogen-containing atmosphere of the present invention to degas hydrogen molecules in quartz glass requires uniform hydrogen. Necessary for doping. In general, the hydrogen gas contained in the direct method is often introduced in a high temperature state, and it is highly likely that many reducing defects are generated. Therefore, when using quartz glass manufactured by the direct method, heat treatment and degassing are performed before hydrogen doping.

The hydrogen atmosphere treatment may be performed in a hydrogen-containing atmosphere mixed with 100% hydrogen gas or He or nitrogen gas. The size and shape of the quartz glass to be subjected to the hydrogen atmosphere treatment are not particularly limited, but if the thickness is too large, it takes a long time to diffuse hydrogen molecules from the surface into the quartz glass. Actually, the thickness is preferably 50 mm or less, but is not limited to this size.

The hydrogen treatment pressure is 1 atm or more. The pressure is adjusted so that a desired hydrogen concentration can be obtained in the quartz glass. If the desired hydrogen concentration is high, the processing pressure will necessarily also be high. But if the pressure gets too high,
It is difficult to control the transformation and it is difficult to obtain a uniform hydrogen concentration distribution. Although it depends on the shape and size of the quartz glass body to be treated, generally a condition of about 5 to 100 atm is often selected. In the hydrogen treatment, hydrogen molecules are diffused from the surface to the inside of the quartz glass by holding for a certain period of time, but if the time is short, the hydrogen concentration near the surface is set higher than the inside. The shape of the difference between the maximum value and the minimum value of the hydrogen molecule concentration in the quartz glass depends on conditions such as the shape of the sample to be processed, the processing temperature, and the processing time. In general, when the shape of quartz glass is a parallel plate (such as the disk shape shown in FIG. 1), hydrogen diffusion from the side surface also occurs particularly in the vicinity of the outer peripheral portion. The diffusion of hydrogen molecules in the thickness direction becomes dominant. Therefore, distribution of hydrogen molecules generally occurs significantly in the thickness direction. As described above, when the difference between the maximum value and the minimum value of the hydrogen molecule concentration occurs in the thickness direction and the hydrogen concentration near the parallel plate surface increases, the refractive index generally also increases, and the refraction only from the side surface is performed. The rate distribution is no longer flat. When such a material is used for a prism or various lenses that require high precision, it is not preferable because it affects the optical characteristics. Therefore, it is preferable to highly uniformly dope the optical quartz glass with hydrogen molecules. However, it is necessary to perform the treatment for a sufficiently long time in order to uniformly dope the hydrogen molecules at a constant pressure, and the treatment time becomes longer in proportion to the square of the thickness of the quartz glass. The present invention does not perform the process until the hydrogen molecule concentration is diffused to a certain extent, and when the hydrogen concentration distribution during the hydrogen process is large, the hydrogen molecule in the quartz glass is actively changed by appropriately changing the hydrogen process pressure. The concentration is flattened, hydrogen molecules are uniformly doped in a short processing time, and a quartz glass body for optics having high homogeneity and high laser resistance is obtained.

The pressure of the hydrogen-containing atmosphere gas is changed continuously or stepwise. It is possible to control the hydrogen concentration distribution more finely by changing it continuously,
In the case of quartz glass having a general thickness, hydrogen is uniformly doped at a level that does not substantially cause a problem by a pressure change in two or three steps.

The temperature of the hydrogen atmosphere treatment is 600 ° C. or less, preferably 200 ° C. to 400 ° C. or less. If the processing temperature is too high, many reducing defects are generated and the laser resistance is deteriorated. If the processing temperature is too low, the processing time is prolonged and productivity is extremely deteriorated. Irradiation of ArF or KrF laser causes 215 nm
An absorption band is induced in the vicinity, which significantly reduces the transmittance. The amount of reducing defects generated is related to the temperature and time of the hydrogen atmosphere treatment. Generally, it is preferable to perform the treatment at a temperature as low as possible for a short time, but the setting of the treatment conditions for each sample should be appropriately selected depending on the sample size and the desired hydrogen molecule concentration.

According to the manufacturing method described above, the uniform
Synthetic quartz glass for excimer laser containing hydrogen
The resulting member is obtained. Excimer laser according to the present invention
The average value of the hydrogen molecule concentration of the synthetic quartz glass member is 1 × 10
¹⁸Number of molecules / cm^ThreeThe maximum and minimum of the hydrogen molecule concentration
Value difference ΔH ₂Is 1.2 × 10¹⁸Number of molecules / cm^ThreeIs below
Preferably. Above hydrogen molecule concentration and hydrogen content
Difference ΔH between maximum and minimum values₂By satisfying
High excimer laser resistance and high homogeneity
Synthetic quartz glass for excimer laser
can get. That is, according to the present invention, the ArF excimer
The laser has an energy density per pulse of 2 mJ /
cm², Frequency 200Hz, irradiation number 2 × 10^FivePulse illumination
Induced absorption at 215 nm during irradiation
Is less than 0.003 in absorbance per 1 cm thickness
A synthetic quartz glass member for excimer laser is obtained. Ma
In addition, the KrF excimer laser is
Lugie density 100mJ / cm², Frequency 200Hz, illumination
Shot number 2 × 10^Five210n during pulsed irradiation
The induced absorption at m is the absorbance per 1 cm thickness
Synthetic quartz gas for excimer laser of 0.0075 or less
A lath member is obtained. And the excimer laser of the present invention
For synthetic quartz glass members for
± 4 × 10 in refractive index homogeneity^-6(/ cm) or less
Folding can achieve 2 nm / cm or less.

The methods for evaluating the various physical properties of the quartz glass obtained by this production method are described below. 1) Measurement of Hydrogen Concentration In the present invention, the concentration of hydrogen contained in quartz glass is determined by Zhurma
l Prikladonoi Spektroskopii Vol. 46 No.6 pp987 to
It was measured by the method shown in 991 June 1987. This method uses a Raman scattering spectrum, and uses SiO ₂
Raman shift of 800 cm ^-1 for band intensity and 4137 cm for hydrogen molecules contained in quartz glass
^The hydrogen concentration is obtained from the intensity ratio of the band of ⁻¹ , and the hydrogen molecule concentration C (number of molecules / cm ³ ) is calculated by the following equation. C = K × (I ₍₄₁₃₇₎ / I ₍₈₀₀₎ ) where K is a coefficient used to match the hydrogen molecular weight with the absolute value measured by gas mass spectroscopy. In this experiment, 1.22 × 10 ²¹ was used. Used. I
₍₄₁₃₇₎ and _{I (800)} is 4137Cm ^-1 and 800 cm ^- is the area strength of ¹ Raman band.
The hydrogen molecule concentration calculated from this equation is the number of hydrogen molecules contained in the quartz glass per volume of 1 cm ³ . The equipment used was an NR-1100 double monochromator manufactured by JASCO and an Ar ion laser with a wavelength of 488 nm was output.
Used at 00mW, R943-02 manufactured by Hamamatsu Photonics
A photomultiplier tube is used.

2) Refractive index distribution Measurement method using Fizeau interferometer. The maximum value and the minimum value (Δn) of the refractive index at 632.8 nm are measured. As shown in FIG. 1, when the quartz glass body has a disk shape, the refractive index distribution in the thickness direction is measured when measured from the side surface, and the refractive index distribution in the diameter direction is measured when measured from the upper and lower surfaces. I do. In addition, the measurement from the side of the disk-shaped quartz glass body
As shown in FIG. 1, the cutting is performed by cutting a hatched portion and grinding both surfaces in parallel.

3) Birefringence amount Oak Manufacturing Co., Ltd. Automatic birefringence measuring device ADR-100 used

4) Method and apparatus for evaluating laser resistance FIG. 2 shows a schematic view of an apparatus for evaluating ArF and KrF laser resistance. When excimer laser is applied to quartz glass in which reducing defects have been generated by the hydrogen atmosphere treatment, an absorption band having a center at about 215 nm (210 nm in the case of KrF) is generated, and the tail of this band is 193 nm (Ar
F) or the wavelength of 248 nm (KrF), so that the laser transmittance is reduced. That is, the laser resistance can be evaluated by measuring the absorption at 215 nm. The absorption band appears during laser irradiation,
If the irradiation is interrupted, it will be relaxed, so measurement must be performed simultaneously during laser irradiation. FIG. 2 schematically shows a transmittance measuring device for evaluating laser resistance. In the figure, reference numeral 2 denotes an evaluation sample, usually 10 mm × 10 mm × 5.
It has a size of 0 mm and the entire side surface (10 mm × 50 mm surface) is polished to a mirror surface. While irradiating the sample 2 with an excimer laser beam having a predetermined energy density, the laser irradiation site is simultaneously 215 nm from a direction orthogonal to the laser beam.
By passing through the light for measuring the transmittance, the absorbance at 215 nm can be measured simultaneously with the laser irradiation. A deuterium lamp 3 as a light source for ultraviolet rays,
First monochromator 6 for dispersing into monochromatic light of 15 nm
1. A first photomultiplier 51 for measuring the amount of incident light via the beam splitter 4, and a second monochromator 62 for measuring the amount of light transmitted through the sample with the sample 2 interposed therebetween. The photomultiplier 52 is used. The light emitted from the deuterium lamp 3 is monochromatized by the first monochromator 61 into light of 215 nm,
The 215 nm monochromatic light partially enters the photomultiplier 52 via the beam splitter 4, and the other light passes through the sample 2 and is received by the photomultiplier 52 via the monochromator 62. Here, the transmittance can be measured from the ratio of the amount of light measured by the photomultipliers 51 and 52. Here Photomaru 51
Since the measurement of the amount of received light is synchronized with the oscillation pulse of the excimer laser, the transmittance can be simultaneously measured while irradiating the laser. In addition, 2
The amount of 15 nm induced absorption is represented by the value of the induced absorbance per 1 cm of the sample. That is, the induced absorption amount D can be calculated by D = -Log (transmittance during laser irradiation / transmittance before laser irradiation). As for the induced absorption, in the case of ArF, when the irradiation energy density per pulse is ² mJ / cm ² , the absorbance is stabilized at about 2 × 10 ⁵ shots. Therefore, the value of the absorbance at this time is measured. In the case of KrF, the irradiation energy density per pulse is set to 100 mJ / cm ² because damage is smaller than that of ArF.

[0019]

EXAMPLES The measured values of various physical properties and simple manufacturing conditions of the quartz glass bodies described in the respective examples and comparative examples are summarized in the table of FIG. Example 1 Silicon tetrachloride was introduced into an oxygen / hydrogen flame, and synthetic silica fine particles obtained by flame hydrolysis were directly deposited on a rotating substrate to prepare a porous silica base material. ). Next, the porous silica base material is placed in a vacuum furnace for 1 hour.
The mixture was heated to 1600 ° C. or higher under a high vacuum of 0 ⁻⁴ torr to obtain a transparent ingot. Next, the obtained ingot was placed in an electric furnace using a carbon heater in nitrogen for 1800 hours.
C., and was melted and formed into a disk shape. The size of the molded body is 260 mm in diameter and 60 mm in thickness. The outer surface of the molded body was ground to a depth of 10 mm to obtain a quartz glass body having a diameter of 240 mm and a thickness of 40 mm. Next, in order to remove the distortion of the quartz glass body and homogenize, the material was heated at 1150 ° C. for 50 hours in an electric furnace in an air atmosphere, and then gradually cooled to 900 ° C. at a temperature reduction rate of 5 ° C./hour. Thereafter, the power supply to the furnace was stopped, and natural cooling was performed. The hydrogen concentration at this time is below the detection limit, and the homogeneity of the refractive index in the thickness direction (measured from the side)
± 1.2 × 10 as the difference (Δn) between the maximum value and the minimum value of the refractive index
^-6 , homogeneity of refractive index in the diameter direction (measurement from upper and lower surfaces)
Was ± 0.7 × 10 ⁻⁶ in Δn.

In order to introduce hydrogen molecules into the above-mentioned molded product,
Heat treatment was performed in a hydrogen treatment furnace. The processing conditions are hydrogen molecule 1
In an atmosphere of 00%, the heating and holding temperature is maintained at 350 ° C. and a pressure (p1) of 30 atm for 600 hours (t1). Subsequently, the heating and holding temperature is 350 ° C. and the pressure (p2) is reduced to 8 atm and reduced to 550. The time (t2) was maintained. The hydrogenated molded product was taken out, and the homogeneity of the refractive index was measured in the thickness direction and the diameter direction. The difference (Δn) between the maximum value and the minimum value of the refractive index in the thickness direction is ± 1.5 × 10 ⁻⁶ and ± in the diameter direction.
0.9 × 10 ⁻⁶ , and high homogeneity was maintained even after the introduction of hydrogen molecules. When the birefringence was measured in the thickness direction, it was <1.5 nm / cm.

Next, water is applied from the center of the hydrogen-treated molded body.
Sample for elemental molecular concentration distribution measurement and laser resistance evaluation
Cut out samples for Raman spectroscopy and
Distribution of hydrogen molecules using a laser
And laser resistance evaluation. Hydrogen molecules in the thickness direction
The concentration distribution is small and the average hydrogen molecule concentration is 4.5 × 10 ¹⁸
(Number of molecules / cm³), Difference between maximum and minimum values of hydrogen molecule concentration
(ΔH₂) Is 5.0 × 10¹⁷(Number of molecules / cm³)
Was.

In order to evaluate the laser resistance, a sample for evaluation was cut out from a portion near the center of the above-mentioned molded body, and the ArF and KrF laser irradiation resistance were evaluated by the evaluation method described above. An ArF laser is applied at an energy density of ² mJ / cm ² per pulse at a frequency of 200 Hz and 2 × 10 2
The induced absorbance at 215 nm when irradiated with ⁵ shots was 0.0015 (/ cm). FIG. 4 shows a change in absorbance at 215 nm due to ArF laser irradiation. Further, a KrF laser is used at an energy density of 100 mJ / cm ² per pulse and a frequency of 200 Hz.
The induced absorbance at 210 nm upon irradiation with × 10 ⁵ shots was 0.0035 (/ cm). This level is sufficiently small as a quartz glass material for excimer laser optics, and can be said to have high laser resistance.

As described above, by changing the processing pressure during the high-pressure hydrogen atmosphere processing, the doping is performed uniformly without causing the concentration distribution of the hydrogen molecules, so that the refractive index has high homogeneity, and An optical quartz glass having excellent laser resistance can be obtained. The evaluation results of the examples and the comparative examples are collectively shown in the table of FIG.

Example 2 Silicon tetrachloride was introduced into an oxygen / hydrogen flame, and synthetic silica fine particles obtained by flame hydrolysis were melted and deposited on a rotating substrate as it was to produce an ingot of a transparent glass body ( Direct flame hydrolysis method). Next, the transparent glass ingot was placed in an electric furnace using a carbon heater in nitrogen for 1 hour.
It was kept at 800 ° C., melted and shaped into a disk. The size of the molded body is 260 mm in diameter and 65 mm in thickness. In order to temporarily degas the hydrogen molecules contained from the beginning of the molded body, a temperature of 1150.degree.
Hold for 0 hr, and subsequently, at a temperature lowering rate of 5 ° C./min.
Slow cooling was performed until the temperature reached 00 ° C., and thereafter, power supply to the furnace was stopped, and natural cooling was performed. Next, the outer surface of the molded body was
To obtain a quartz glass body having a diameter of 240 mm and a thickness of 40 mm. The hydrogen concentration of this quartz glass body is below the detection limit, and the refractive index homogeneity in the thickness direction (measured from the side)
Was ± 1.0 × 10 ⁻⁶ in Δn, and ± 0.7 × 10 ⁻⁶ in Δn in the diameter direction (measured from the upper and lower surfaces).

In order to introduce hydrogen molecules into the above molded product,
Heat treatment was performed in a hydrogen treatment furnace. The processing conditions are hydrogen molecule 1
In an atmosphere of 00%, the heating and holding temperature is 400 ° C., and the pressure is
(P1) Hold at 10 atm for 350 hours (t1), then
The heating and holding temperature is 400 ° C. and the pressure (p2) is 2.5
The pressure was reduced to and maintained for 300 hours (t2). Hydrogen treated
Take out the molded body and adjust the homogeneity of the refractive index in the thickness direction and
The measurements were taken in the diametric direction. Refractive index homogeneity in the thickness direction
(Measured from the side) is ± 1.2 × 10 in Δn^-6,diameter
Direction (measured from upper and lower surfaces) is ± 0.9 × 10 in Δn^-6so
And high uniformity is maintained even after the introduction of hydrogen molecules.
Was. When birefringence was measured in the thickness direction, it was found that <1.5.
nm / cm. As in Example 1, the hydrogen molecule concentration
Evaluation of excimer laser resistance of cloth, ArF and KrF
went. Average hydrogen molecule concentration of 1.7 × 10 ¹⁸(Number of molecules /
cm³), The difference between the maximum and minimum values of the hydrogen molecule concentration (Δ
H₂) Is 3.5 × 10¹⁷(Number of molecules / cm³)Met. Ma
Also, the 215 nm induced absorbance upon ArF laser irradiation is
When irradiated with KrF laser at 0.002 (/ cm)
The induced absorbance at 210 nm is 0.0045 (/ cm).
there were. FIG. 4 shows the 215 nm wavelength accompanying ArF laser irradiation.
A change in absorbance was indicated. This level is excimer laser
A sufficiently small quartz glass material for optical use
High laser resistance as in the case of Example 1.
It can be said that.

Example 3 A disk-shaped transparent glass having a diameter of 240 mm and a thickness of 25 mm was obtained from the quartz glass ingot obtained by the direct flame hydrolysis method to the thermal annealing treatment for dehydrogenation in the same manner as described in Example 2. Created body. The hydrogen concentration of the quartz glass body below the detection limit, uniformity in the thickness direction of the refractive index (measured from the side) is, ± at Δn 1.2 × 10 - ^6, (measured from the upper and lower surfaces) diameter direction at ± 0 0.9 × 10 ⁻⁶ .

In order to introduce hydrogen molecules into the above molded product,
Heat treatment was performed in a hydrogen treatment furnace. The processing conditions are hydrogen molecule 1
In a 00% atmosphere, the heating and holding temperature was maintained at 350 ° C. and a pressure (p1) of 100 atm for 120 hours (t1). Subsequently, the heating and holding temperature was reduced to 350 ° C. and a pressure (p2) of 50 atm and reduced for 85 hours (T2) Hold, then heat hold temperature 35
At 0 ° C., the pressure (p3) was reduced to 25 atm and maintained for 135 hours (t3). Take out the hydrogenated molded body,
The homogeneity of the refractive index was measured in the thickness direction and the diameter direction. The difference (Δn) between the maximum value and the minimum value of the refractive index in the thickness direction (measured from the side surface) is ± 1.8 × 10 ⁻⁶ , and the difference in the diameter direction (measured from the upper and lower surfaces) is ± 1.5 × 10 ⁻⁶ . High homogeneity was maintained even after the introduction of hydrogen molecules. When the birefringence was measured in the thickness direction, it was <2 nm / cm. As in Example 1, the hydrogen molecule concentration distribution and the excimer laser resistance of ArF and KrF were evaluated. The average hydrogen molecule concentration was 1.6 × 10 ¹⁹ (number of molecules / cm ³ ), and the difference (ΔH ₂ ) between the maximum value and the minimum value of the hydrogen molecule concentration was 1.2 × 10 ¹⁸ (number of molecules / cm ³ ). Was. The 215 nm-induced absorbance at the time of ArF laser irradiation was 0.0023 (/ cm), and Kr
The induced absorbance at 210 nm when irradiated with the F laser was 0.0050 (/ cm). FIG. 4 shows a change in absorbance at 215 nm due to ArF laser irradiation. This level is sufficiently small as a quartz glass material for excimer laser optics, and as in the case of Example 1,
It can be said that it has high laser resistance.

Example 4 A molded article was prepared under the same conditions as in Example 1 except that a mixed gas of helium gas and hydrogen gas was used in the heat treatment for doping hydrogen molecules. The heat treatment conditions for introducing hydrogen molecules are as follows: the processing temperature is 350 ° C.
The pressure (p1) was maintained at 30 atm for 600 hours (t1) in a 100% hydrogen gas atmosphere. Next, in the second stage treatment, a mixed gas of helium gas and hydrogen gas was used. The partial pressure of the helium gas in the mixed gas was set at 22 atm, the partial pressure of the hydrogen gas was set at 8 atm, and the mixture was maintained at 350 ° C. for 550 hours in the 30 atm mixed gas. As in the case of Example 1, the homogeneity, the hydrogen molecule concentration distribution, and the laser resistance were evaluated. The homogeneity of the refractive index in the thickness direction is ± 1.5 × 10 ^{−6 as} the difference (Δn) between the maximum value and the minimum value, and ± 1.
0 × 10 ⁻⁶ , indicating that high homogeneity was maintained even after the introduction of hydrogen molecules. When the birefringence was measured in the thickness direction, it was <1.5 nm / cm. Mean concentration of hydrogen molecules is 4.0 × 10 ¹⁸ (molecules / cm ^3), the difference between the maximum value and the minimum value of the hydrogen molecule concentration ([Delta] H ₂₎ is 4.0 × 10 ¹⁷ (molecules /
cm ³ ). In addition, 21 when ArF laser irradiation
The induced absorbance at 5 nm was 0.0015 (/ cm), and the induced absorbance at 210 nm when irradiated with a KrF laser was 0.15 (/ cm).
0035 (/ cm), a result similar to that of Example 1 was obtained. FIG. 4 shows a change in absorbance at 215 nm due to ArF laser irradiation.

Example 5 In the same manner as in Example 1, the diameter was 240 nm and the thickness was 50 m.
m was formed. Heat treatment to introduce molecular hydrogen
The process pressure is changed in three stages, the third stage processing pressure
Was set higher than the processing pressure in the second stage. Specific processing
The conditions are as follows.
In a 0% hydrogen gas atmosphere, a pressure (p1) of 30 atm.
It was kept for 50 hours (t1). Then the second stage processing is
The processing temperature was maintained at 350 ° C, and the pressure (p2) was set at 4 atm.
And held for 500 hours (t2). Further processing in the third stage
In principle, the pressure (p3) is set to 10 atm and
The time (t3) was maintained. Homogeneity as in Example 1,
The hydrogen molecule concentration distribution and laser resistance were evaluated. thickness
The homogeneity of the refractive index in the direction is the difference between the maximum value and the minimum value (Δn)
± 1.2 × 10^-6± 0.9 × 10 in the diameter direction
^-6High homogeneity is maintained even after the introduction of hydrogen molecules.
I was By setting the pressure of hydrogen treatment in three stages
Even if the thickness is relatively large, dope hydrogen molecules uniformly
Quartz can therefore be sufficiently homogeneous
It was found that glass was obtained. Bifurcated in the thickness direction
The fold was measured to be <2 nm / cm. Average water
Elemental molecule concentration is 3.0 × 10¹⁸(Number of molecules / cm³), Hydrogen content
Difference between the maximum value and the minimum value of the ₂) Is 3.0 × 10
¹⁷(Number of molecules / cm³)Met. ArF laser irradiation
215 nm induced absorbance at the time is 0.0012 (/ cm),
Induced absorption at 210 nm when irradiated with KrF laser
The degree is as low as 0.0032 (/ cm).
Was. FIG. 4 shows the absorption at 215 nm due to ArF laser irradiation.
Degrees of change were indicated.

Comparative Example 1 In the same manner as in Example 1, a molded article having the same size was produced. This molded body was produced by exactly the same method as that obtained before the hydrogen atmosphere treatment in Example 1.
In order to dope the molded body with hydrogen molecules, a treatment temperature of 400 ° C. is applied in an atmosphere of hydrogen gas 100% at a pressure of 30 atm.
For 600 hours. The homogeneity, hydrogen molecule concentration distribution, and laser resistance of the obtained molded body were measured. Homogeneity in the diameter direction (measured from the upper and lower surface), ± 2.5 × 10 difference between the maximum value and the minimum value of the refractive index ([Delta] n) ^- was the extent which is somewhat poor in ^6, thickness The direction homogeneity is 1.
8 × 10 ⁻⁵ , which is a very large refractive index distribution as compared with the example. The average hydrogen molecule concentration is 7.5 × 1
Although the concentration was relatively high at 0 ¹⁸ (number of molecules / cm ³ ), the difference (ΔH ₂ ) between the maximum value and the minimum value of the concentration of hydrogen molecules was 1.1 × 10 ¹⁹ (number of molecules / cm ³ ), which was very high. Bigger,
In particular, the concentration of hydrogen molecules near the outer surface is high, so that the distribution of the refractive index is also rapidly increasing near the surface. The 215 nm induced absorbance upon ArF laser irradiation was 0.1.
003 (/ cm), 2 when irradiated with KrF laser
The induced absorbance at 10 nm is 0.007 (/ cm), which is not extremely bad. Since the pressure of the atmosphere gas was not changed during the hydrogen molecule doping process, if the processing time was insufficient,
Hydrogen molecules do not diffuse into the quartz glass, and an extreme concentration distribution of hydrogen molecules occurs, and as a result, the distribution of the refractive index becomes extremely large.

Comparative Example 2 Except that the heat treatment conditions for hydrogen molecule doping were different,
A molded body was prepared in the same manner as in Example 1. That is, a quartz glass molded body having a diameter of 240 mm and a thickness of 40 mm was prepared by an indirect method, and a heat treatment was performed in a hydrogen gas atmosphere to introduce hydrogen molecules into the molded body. The conditions of the heat treatment are as follows.
0 ° C., processing pressure (p1) at 30 atm for 130 hours (t1)
After holding, then, while maintaining the temperature at 650 ° C,
The pressure (p2) of the hydrogen gas was set to 8 atm, and heat treatment was performed for 120 hours (t2).

The homogeneity, hydrogen molecule concentration distribution and laser resistance of the obtained molded product were measured. The homogeneity in the diametric direction (measured from the upper and lower surfaces) is determined by the difference between the maximum value and the minimum value of the refractive index (Δ
n) was ± 1.0 × 10 ⁻⁶ , and the uniformity in the thickness direction was Δn, which was as good as 1.5 × 10 ⁻⁶ . The average hydrogen molecule concentration was 4.0 × 10 ¹⁸ (number of molecules / cm ³ ), and the difference (ΔH ₂ ) between the maximum value and the minimum value of the hydrogen molecule concentration was 4.5 × 1.
It was confirmed that hydrogen molecules were introduced fairly uniformly at 0 ¹⁷ (number of molecules · cm ³ ). However, the 215 nm induced absorbance upon ArF laser irradiation was 0.013 (/
cm) and the induced absorbance at 210 nm when irradiated with a KrF laser is extremely deteriorated to 0.031 (/ cm). FIG. 4 shows the change in the absorbance at 215 nm due to the irradiation with the ArF laser. It can be seen that the sample of Comparative Example 2 shows a sharp increase in absorption. This is because the heat treatment for doping hydrogen molecules was performed at a high temperature, so that reducing defects were generated in the quartz glass, and the absorption was increased by laser irradiation. Although there is no problem in the difference between the maximum value and the minimum value of the hydrogen molecule concentration and the homogeneity, it is unsuitable for optical use of excimer laser due to poor laser resistance.

[0033]

As described above, according to the present invention, it is possible to uniformly dope hydrogen molecules introduced to improve the resistance of quartz glass to excimer laser, so that the refractive index uniformity and birefringence can be improved. A quartz glass member having high laser resistance can be obtained without impairing optical characteristics such as the above. Therefore, the quartz glass manufactured according to the present invention has laser resistance that can be stably used for a long time even with a high-energy ultraviolet pulse laser such as an excimer laser while maintaining excellent optical characteristics, and a semiconductor. It can be suitably used for a manufacturing lithography apparatus and other ultraviolet optical systems.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a method of measuring a refractive index distribution and its direction.

FIG. 2 is a schematic diagram of a transmittance measuring device for evaluating laser resistance.

FIG. 3 is a view showing a table of evaluation results of various physical properties of Examples and Comparative Examples.

FIG. 4 shows the results of ArF laser irradiation in Examples and Comparative Examples.
It is a figure which shows the change of the absorbance of 15 nm.

[Explanation of symbols]

 Reference Signs List 1 excimer laser 2 sample 3 deuterium lamp 4 beam splitter 51 monochromator 52 monochromator 61 photomultiplier 62 photomultiplier 7 excimer laser beam

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akira Fujinoki 88, Kawakubo, Kanaya, Tamura-cho, Koriyama-shi, Fukushima Shin-Etsu Quartz Co., Ltd. Quartz Research Laboratory F-term (reference) 4G014 AH15 AH21 5F071 AA06 FF07 FF09 JJ03

Claims (10)

[Claims] A synthetic quartz glass body is treated at a processing temperature of 600 ° C. in a hydrogen-containing atmosphere at a pressure of 1 to 150 atm.
A method for producing a synthetic quartz glass member for excimer laser optics comprising a step of performing a heat treatment below to cause the quartz glass body to contain hydrogen molecules, wherein at least a part of the heat treatment includes reducing the pressure of the hydrogen-containing gas. A method for producing a synthetic quartz glass member for an excimer laser, wherein the member is changed continuously or stepwise. 2. The method for producing a synthetic quartz glass member for an excimer laser according to claim 1, wherein a change in the pressure of the hydrogen-containing gas is reduced. 3. After subjecting the synthetic quartz glass body to a heat treatment at a first set pressure for a first set time in a hydrogen-containing atmosphere, a second set pressure is set at a second set pressure lower than the first set pressure. The method for producing a synthetic quartz glass member for an excimer laser according to claim 2, wherein the heat treatment is performed for a time. 4. The synthetic quartz glass for an excimer laser according to claim 1, wherein the hydrogen-containing atmosphere is 100% hydrogen gas or a mixed gas of nitrogen, argon, or helium and hydrogen gas. Manufacturing method of the member. 5. The synthetic quartz glass member for an excimer laser according to claim 1, wherein the synthetic quartz glass body containing hydrogen is produced by a direct flame hydrolysis method or an indirect flame hydrolysis method. Production method. 6. A synthetic quartz glass member for an excimer laser, which is produced by the method for producing a synthetic quartz glass member for an excimer laser according to claim 1 and which contains hydrogen uniformly. 7. An average value of hydrogen molecule concentration is 1 × 10 ¹⁸ molecules / cm ³ or more, and a difference ΔH ₂ between a maximum value and a minimum value of hydrogen molecule concentration is 1.2 × 10 ¹⁸ molecules / cm ^3. Claim 6 which is
The synthetic quartz glass member for an excimer laser according to the above. 8. An ArF excimer laser having an energy density per pulse of ² mJ / cm ² and a frequency of 200H
z, 2 during irradiation when 2 × 10 ⁵ pulses are irradiated
8. The synthetic quartz glass member for an excimer laser according to claim 6, wherein an induced absorption amount at 15 nm is 0.003 or less as an absorbance per 1 cm thickness. 9. A KrF excimer laser having an energy density per pulse of 100 mJ / cm ² and a frequency of 20 mJ / cm ² .
8. The synthetic quartz glass member for an excimer laser according to claim 6, wherein the induced absorption amount at 210 nm during irradiation at 0 Hz and irradiation number of 2 × 10 ⁵ pulses is 0.0075 or less as an absorbance per 1 cm thickness. . 10. The homogeneity of the refractive index at 632.8 nm is ± 4 × 10 ⁻⁶ (/ cm) or less, and the birefringence is 2 nm /
The synthetic quartz glass member for an excimer laser according to any one of claims 7 to 9, which has a diameter of not more than 10 cm.