JP3228676B2 - High purity silica glass for far ultraviolet rays and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-purity silica glass for deep ultraviolet rays and a method for producing the same, and more particularly to a lamp, an optical fiber, a lens, and a prism having a high transmittance for excimer laser and excimer lamp light in the far ultraviolet region. High-purity synthetic silica glass for glass, windows and mirrors and a method for producing the same.

[0002]

2. Description of the Related Art Heretofore, ultraviolet rays from a mercury lamp such as a g-line or an i-line have been used as light rays used in photolithography for drawing an electronic circuit pattern on a wafer.
However, in recent years, the miniaturization of semiconductor devices has increased, and today, mass production of ultra LSI using a fine pattern of quarter micron or less (0.25 μm or less) is about to begin. In order to form such an ultrafine pattern, the resolution of the currently used g-line and i-line is limited, and light of shorter wavelength is attracting attention. In particular, the most complete excimer laser attracts attention. Have been. The excimer laser is a high-power laser, and is conventionally known from KrF (248 nm) and XeCl (308 n) in terms of oscillation efficiency and gas life.
m) and XeF (351, 353 nm) were suitably used. However, the wavelength for forming a fine pattern of the quarter micron or less is insufficient, and the wavelength is 165 to 165 μm.
Xe ₂ excimer laser (172 nm), ArCl excimer laser (175 nm), ArF excimer laser (193 nm) oscillating at 195 nm (hereinafter referred to as far ultraviolet)
nm), Xe ₂ excimer lamp (172 nm) or Ar
The use of a Cl excimer lamp (175 nm) has been considered. Accordingly, a member which is not damaged by the far ultraviolet ray has been required for the optical member.

[0003]

As the silica glass which is not damaged by the far ultraviolet rays, the present applicant has
Silica glass with virtually no oxygen deficiency defects
No. 197343. The silica glass has about 20
It exhibited high durability against ultraviolet rays in the range of 0 to 400 nm, but was inferior in durability to ultraviolet rays having shorter wavelengths. Therefore, a silica glass containing an OH group and a hydrogen molecule at a high concentration and having a content of a transition metal element or the like of 10 wtppb or less was proposed in Japanese Patent Publication Nos. 6-24997 and 6-48734. However, when a member for far-ultraviolet rays was prepared and used using the silica glass, the transmittance of far-ultraviolet rays having a wavelength of 200 nm or less was lowered, the absolute refractive index was increased, and the amount of birefringence was increased. The life was short.

Accordingly, far ultraviolet rays having a wavelength of 200 nm or less,
As a result of intensive studies to develop silica glass having high durability even with respect to far ultraviolet rays having a wavelength of 165 to 195 nm, the concentration of oxygen-deficient defects and the concentration of oxygen-excess defects are reduced to specific ranges or less. At the same time, they have found that by lowering the fictive temperature of the silica glass, a silica glass with less damage to far ultraviolet rays having the above wavelength can be obtained. Further, the present inventors have found a novel production method for producing the silica glass and completed the present invention.

An object of the present invention is to provide a silica glass having high durability against irradiation of far ultraviolet rays having a wavelength of 165 to 195 nm.

Further, the present invention provides a method for controlling a wavelength of 165 to 195 nm.
It is an object of the present invention to provide a stable silica glass having a high transmittance with respect to irradiation of far ultraviolet rays and a small change in absolute refractive index and birefringence.

Another object of the present invention is to provide a method for producing the above silica glass.

[0008]

According to the present invention, which achieves the above object, a set virtual temperature is 500 to 1000 ° C., an oxygen deficiency type defect concentration is 5 × 10 ¹⁶ / cm ³ or less, and an oxygen excess type defect concentration is 5 × 10 ¹⁶ / cm ³ or less. The present invention relates to a high-purity silica glass for far-ultraviolet rays characterized by being at most 10 ¹⁶ / cm ³ and a method for producing the same.

The silica glass of the present invention has a wavelength of 165-1.
Stable silica glass with high transmittance to 95nm far ultraviolet rays, especially excimer laser and excimer lamp light, little change in absolute refractive index and little change in birefringence, YAG harmonic laser, Ar gas harmonic laser Is a useful silica glass. The silica glass is made of an ultra-high purity silicon compound, and is made of aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, nickel,
Each transition metal element concentration such as copper or gallium is 1wt
It is a silica glass having a ppb or less.

The silica glass of the present invention has, in addition to the above-mentioned high purity, a set fictive temperature of 500 to 1000 ° C., an oxygen deficiency type defect concentration of 5 × 10 ¹⁶ / cm ³ or less, and an oxygen excess type defect concentration of 5 × 10 ¹⁶ / cm ³ or less. It is silica glass of 10 ¹⁶ pieces / cm ³ or less. Although the fictive temperature of ordinary silica glass exceeds 1000 ° C., by setting the fictive temperature at 1000 ° C. or lower while keeping the oxygen-deficient defect concentration and the oxygen-excess type defect concentration in the above ranges, far-ultraviolet rays, particularly at a wavelength of 165 ° C. ~ 195n
Even with ultraviolet light of m, the damage is small and the service life is prolonged. The lower the set virtual temperature of silica glass is, the less damage to far ultraviolet rays is required. On the other hand, to set the virtual temperature of silica glass low requires a long heat treatment. For example, a virtual temperature of 500 ° C.
To do so, it is necessary to heat-treat the silica glass at 500 ° C. for about 2000 hours or more. Therefore, the limit is to set the set virtual temperature to 500 ° C. from the viewpoint of manufacturing cost. Further, when a large number of oxygen-deficient defects are present in the silica glass, the absorption strongly appears around 7.6 eV (163 nm),
The transmittance of far ultraviolet rays decreases. Therefore, the concentration of oxygen-deficient defects is preferably set to 5 × 10 ¹⁶ defects / cm ³ or less. Further, the concentration of oxygen-excess type defects is 5 × 1.
If it exceeds 0 ¹⁶ / cm ³ , the light transmittance in the vicinity of the ultraviolet absorption edge is remarkably reduced, which is not preferable. Further, the silica glass has a birefringence of 10 nm / cm or less and a chlorine content of 10 nm / cm.
When the content is 0 wtppm or less, silica glass with less distortion can be obtained, and the shift of the ultraviolet absorption end to the longer wavelength side due to chlorine is reduced, and the durability is further improved. Especially YA
When producing a member for a G harmonic laser or an Ar gas harmonic laser, it is important to regulate the birefringence to 10 nm / cm or less and the chlorine content to 100 wtppm or less.

The silica glass of the present invention is manufactured by the following manufacturing method. Ie

(I) Production of silica glass (a) Soot method SiCl ₄ , HSiCl ₃ , which has been highly purified by means such as distillation,
(CH ₃ ) ₂ SiCl ₂ , CH ₃ SiCl ₃ , CH ₃ Si (O
A silicon compound such as CH ₃ ) ₃ and Si (OCH ₃ ) ₄ is formed in soot by a flame hydrolysis method, and the soot is deposited to produce a white opaque soot body. As the flame hydrolysis method, an oxyhydrogen flame hydrolysis method, a propane flame hydrolysis or the like is used.
The obtained soot body is placed in an electric furnace under a vacuum of 100 Pa or less, preferably 10 Pa or less, at 1300 to 1700 ° C.,
A transparent glass ingot without bubbles can be produced by heating slowly from below to above by a zone heating method, preferably at a temperature of 1400 to 1600 ° C. (B) Direct method or plasma method In addition, a transparent silica glass can be directly produced by a direct method or a plasma method using the silicon compound used as a main raw material.

(Ii) Processing of Silica Glass The silica glass ingot obtained by the above manufacturing method is heat-treated to remove internal strain in the silica glass ingot, and then cut, ground and polished to obtain silica glass of a predetermined size. Process into members. For example, if it is a member for a lamp tube, the outer diameter is 200 mm, the inner diameter is 100 mm, and the length is 1000 m.
The tube can be manufactured by preparing a tube having an outer diameter of 5 to 50 mm from a large cylinder of m by a hot-melt drawing method, and then cutting the tube to an arbitrary length. Also, if it is a lens member,
It can be prepared by grinding a large ingot having a diameter of 100 mm and a length of 2000 mm into a columnar object having a diameter of 10 to 100 mm and a thickness of 10 to 100 mm. It is preferable to employ a temperature of about 1100 ° C. as the internal strain removal temperature.

(Iii) Virtual temperature setting treatment The silica glass member is then heated at 500 to 1000 ° C. for 1 hour.
Heat treatment is performed for 00 to 2000 hours to set the fictive temperature of the silica glass to 500 to 1000 ° C. As the atmosphere during the fictive temperature setting process, an oxygen-containing gas atmosphere or a hydrogen-containing gas atmosphere can be employed. Preferably, when the silica glass has an oxygen-deficient defect, the oxygen-containing gas atmosphere is used. In some cases, a hydrogen-containing gas atmosphere is preferably used.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to specific examples, but the present invention is not limited thereto.

[0017]

【Example】

Example 1-5 (1) the soot body creating purity 99.9999% of silicon tetrachloride (SiCl ₄₎
The gas is fixed at 2 liters / minute, and oxygen and hydrogen gas are supplied to the burner at a rate of 2 to 20 liters / minute and 6 to 60 liters / minute, respectively, and a soot body containing an OH group is deposited by a soot method. I let it. Argon is preferred as the carrier gas used.

(2) Production of Silica Glass Ingot The above white opaque soot body was placed in a stainless steel electric furnace equipped with a cylindrical high-purity graphite heater, and the inside of the electric furnace was evacuated to about 8 Pa and about
It was heated and melted while slowly moving from below to above in a zone at a temperature of 50 ° C. to produce a transparent silica glass ingot. The concentrations of transition metal elements such as aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper or gallium in the manufactured silica glass ingot are each 1 wtppb or less, and the presence of bubbles cannot be confirmed visually. Was. Further, the concentration of the OH group was 300 wtppm in Examples 1 to 4, and 50 wt% in Example 5.
ppm and chlorine concentration were all 20 wtppm.

Examples 6 to 9 The high-purity silicon tetrachloride (SiC) used in Examples 1 to 5 was used.
Using l ₄ ), high-purity silica glass was manufactured by the direct method in Examples 6 and 7, and by the plasma method in Examples 8 and 9.

The contents of impurities in the silica glasses of Examples 1 to 9 were measured, and the results are as shown in Table 1.

[0021]

[Table 1] Note) Al, Ti and Fe are measured by flameless atomic absorption spectrometry, and other elements are measured by plasma mass spectrometry (IC
P-MS method).

(3) Processing of Silica Glass Ingot A sample was cut from the above silica glass, ground, and both surfaces thereof were mirror-polished to obtain an OH group-containing concentration analysis sample, an oxygen deficiency type defect concentration and an oxygen excess type. A sample for defect concentration measurement, a sample for virtual temperature measurement, a sample for chlorine concentration analysis, a sample for birefringence measurement, a sample for Xe ₂ excimer lamp irradiation, and a sample for ArF excimer laser irradiation are formed. A measurement was made. Table 2 shows the results.

[0023]

[Table 2]

Comparative Examples 1 to 5 Silica glass was formed by the CVD soot method (Comparative Examples 1 to 4) and the plasma method (Comparative Example 5). Defect concentration,
Oxygen excess defect concentration, fictive temperature, OH group concentration, chlorine concentration, birefringence, 165n after Xe ₂ excimer lamp irradiation
m, 165 after irradiation with ArF excimer laser
The transmittance of nm light was measured. Table 3 shows the results.

[0025]

[Table 3]

As is clear from Tables 2 and 3, the silica glass of the present invention shows excellent transmittance at a wavelength of 165 nm even after irradiation with far ultraviolet rays, and the silica glasses of Examples 4 and 5 have a transmittance of more than 80%. Is shown. On the other hand, silica glass having a virtual temperature exceeding 1000 ° C. shows a low transmittance. Even when the fictive temperature is 1000 ° C. or lower, silica glass having a transition metal element content of more than 1 wtppm in silica glass has a low transmittance at 165 nm after irradiation with far ultraviolet rays.

The methods for measuring the physical properties of the above Examples and Comparative Examples are as follows. (I) Method for measuring OH group content M. DODD and D. B. FRASE
R, Optical determination o
f OH in fused silica, Jour
nal of Applied Physics, Vo
l. 37 (1966) p. Measurement method described in 3911 document.

(Ii) Method of Measuring Oxygen-Deficient Defects HOSONO, et al. , Experime
ntal evidence for the Si-
Si bond model of the 7.6 eV
band in SiO ₂ glass, Phys
ical Review B, Vol. 44, No.
21 pp. 12043-45 (1991) Measurement method described in the literature.

(Iii) Method for measuring oxygen-excess type defects E. FIG. SHELBY, Reaction of h
ydogen with hydroxyyl-fre
e vitroous silica, Journa
l of Applied Physics, Vo
l. 51, No. 5, pp. 2589-93 (19
80) and D.I. M. DODD and D. B. FRA
SER, Optical determination
no ofh om fused silica, J
own of Applied Physic
s, Vol. 37, p. 3911 (1966).

(Iv) Measurement method of virtual temperature E. FIG. GEISSBERGER and F. L. G
ALEENER, Raman studies of
vitruous SiO ₂ versus fiction
ne temperature, PhysicalR
view B, Vol. 28, No. 6, p
p. 3266-71.

(V) Method for measuring chlorine concentration Measurement by turbidimetry.

(Vi) A method for measuring the amount of birefringence. A retardation measurement method using a polarizing plate strain meter.

(Vii) Measurement of transmittance at 165 nm Measurement by a vacuum ultraviolet transmittance meter.

(Viii) A method for measuring the transmittance at a wavelength of 165 nm after irradiation with a Xe ₂ excimer lamp. Transmittance when irradiating silica glass for 300 hours using a Xe ₂ excimer lamp having a wavelength of 172 nm, a half width of 14 nm, and a lamp energy density of 10 mW / cm ² , on a sample having a size of 30 × 20 × thickness 10 mm and a double-side mirror polishing finish. How to measure.

(V) 16 after irradiation with ArF excimer laser
Method for measuring 5 nm transmittance. A sample having a size of 30 × 20 × thickness 10 mm, a mirror-polished double-sided surface, a wavelength of 193 nm, a half width of 3 nm, a pulse life of 17 nsec, and an energy density of 50 mJ / cm ² . s
A method for measuring the transmittance when irradiating an ArF excimer laser having a number of shots of 1 × 10 ⁶ shots (however, 100 Hz).

[0036]

The silica glass of the present invention has a wavelength of 165 to 165.
It retains excellent transmittance with respect to the irradiation of far-ultraviolet light of 195 nm and is useful as an optical material for far-ultraviolet light. Moreover, the silica glass can be easily produced by subjecting silica glass produced from a high-purity silicon compound as a raw material by a conventionally known production method to a fictive temperature setting treatment, and its industrial value is high.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-58667 (JP, A) JP-A-7-215735 (JP, A) JP-A-5-186234 (JP, A) 88742 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C03B 20/00 C03B 8/04 C03C 3/06 CA (STN)

Claims (5)

(57) [Claims] 1. A flame hydrolysis method from a high-purity silicon compound.
Create a more opaque white soot body and vacuum the soot body
100Pa or less, band at 1300-1700 ° C
After heating and melting to form a transparent glass, oxygen-containing gas or
100 at 500-1000 ° C in a hydrogen-containing gas atmosphere
The set virtual temperature obtained by performing the virtual temperature setting process of heating up to 2000 hours is 500 to 1000 ° C., the oxygen deficiency type defect concentration is 5 × 10 ¹⁶ defects / cm ³ or less, and the oxygen excess type defect concentration is 5
× 10 ¹⁶ / cm ³ or less high-purity silica glass for deep ultraviolet rays. 2. The method according to claim 1, wherein the high purity silicon compound is directly
After creating a transparent silica glass block by the plasma method, oxygen
500 to 100 in an atmosphere of a gas containing hydrogen or a gas containing hydrogen
Virtual temperature setting process for heating at 0 ° C for 100 to 2000 hours
Set hypothetical temperature obtained from 500 to 1000 ° C, oxygen deficiency
Mold defect concentration of 5 × 10 ¹⁶ / cm ³ or less, oxygen-excess mold defect
High purity for deep ultraviolet rays with a fall concentration of 5 × 10 ¹⁶ / cm ³ or less
Silica glass . Wherein aluminum transition metal elements, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, deep ultraviolet rays according to claim 1, wherein each concentration of copper and gallium is equal to or less than 1wtppb For high purity silica glass. Wherein birefringence is 10 nm / cm or less claims 1 to 3 of any one high-purity silica glass for far ultraviolet rays, wherein it is. 5. A method according to claim 1 to 4 of any one of far ultraviolet high-purity synthetic silica glass, wherein the chlorine content is not more than 100 wtppm.