JP4438948B2 - Synthetic quartz glass manufacturing burner and synthetic quartz glass ingot manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a burner for manufacturing a synthetic quartz glass ingot which is a raw material for obtaining an optically more homogeneous synthetic quartz glass component or a component for a large scale synthetic quartz glass substrate for a liquid crystal efficiently and easily which are used for optical components such as a lens, a prism and a window used for excimer laser and a quartz glass substrate for a photomask and the like and to provide a method for manufacturing the synthetic quartz glass ingot using the burner. <P>SOLUTION: A main burner comprises a center tube to supply a silica raw material compound, a first surrounding tube to surround the center tube and to supply a combustion supporting gas, a multiple tube having at least a triple tube structure with a second surrounding tube to surround the first surrounding tube and to supply a combustible gas, an outer shell tube to surround the multiple tube and to supply the combustible gas, and to supply the combustible gas and a plurality of nozzles located in the outer shell tube and to supply the combustion supporting gas. The burner for manufacturing synthetic quartz glass is provided with a double tube surrounding at least the head end part side of the main burner. <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

  The present invention is effective as an optical material such as a lens, a prism, a mirror, a window material, a quartz glass substrate for a photomask used for an excimer laser, particularly for an ArF excimer laser, and has high optical uniformity and light transmittance change. Synthetic quartz glass for producing large-diameter synthetic quartz glass ingots used as raw materials for synthetic quartz glass ingots and large photomask substrates for liquid crystals, etc. The present invention relates to a production burner and a method for producing a synthetic quartz glass ingot using the burner.

  In recent years, with the high integration of VLSI, optical lithography technology for drawing an integrated circuit pattern on a wafer demands a drawing technology in submicron units, and in order to perform finer line width drawing, an exposure system The wavelength of light sources has been shortened. For this reason, the KrF excimer laser (wavelength 248 nm) has become the mainstream from the conventional i-line (wavelength 365 nm) as the light source of the lithography stepper apparatus, and in recent years, the ArF excimer laser (wavelength 193 nm) has been put into practical use. A lens used in such a stepper device is required to have excellent ultraviolet transmittance and strong resistance and homogeneity against ultraviolet irradiation.

  Synthetic quartz glass usually introduces high-purity organosilicon compounds such as silicon tetrachloride directly into an oxyhydrogen flame to avoid contamination with metal impurities that cause ultraviolet absorption, and this is hydrolyzed by flame. Thus, silica fine particles are produced, and deposited on a heat-resistant substrate such as quartz glass that directly rotates and melted into glass to produce transparent synthetic quartz glass.

  The transparent synthetic quartz glass produced in this way shows good light transmission up to a short wavelength region of about 190 nm in the LSI field, and in addition to ultraviolet laser light, specifically i-line, KrF (248 nm), It has been used as a transmission material for excimer laser light such as XeCl (308 nm), XeBr (282 nm), XeF (351, 353 nm), ArF (193 nm), and the fourth harmonic (250 nm) of YAG.

  In this case, the absorption of light in the ultraviolet region newly generated by irradiating the synthetic quartz glass with ultraviolet rays having an intense energy like an excimer laser is caused by a paramagnetic defect caused by a photoreaction from an intrinsic defect in the synthetic quartz glass. It is thought to be due to. Many light absorptions due to such paramagnetic defects have been identified in ESR spectra and the like, and examples thereof include an E 'center (Si.) And NBOHC (Si-O.).

  Thus, since paramagnetic defects generally have an optical absorption band, when quartz glass is irradiated with ultraviolet rays, the absorption band that causes problems due to paramagnetic defects in quartz glass in the ultraviolet region is, for example, The E ′ center (Si ·) is 215 nm, which is not yet accurately identified, but is 260 nm. These absorption bands are relatively broad and may cause strong absorption. For example, when used as a transmission material for an ArF excimer laser or a KrF excimer laser, the absorption band may be a serious problem.

Inherent defects in synthetic quartz glass that cause paramagnetic defects include, for example, structures other than SiO ₂ such as Si—OH and Si—Cl, oxygen vacancies such as Si—Si and Si—O—O—Si, oxygen This is due to excessive structure.

  Therefore, as a method for suppressing paramagnetic defects, there is a method in which Si—Cl, which is one of paramagnetic defects, is not contained in glass by using an alkoxysilane such as tetramethoxysilane that does not contain chlorine as a silane compound. It has been proposed (see Patent Document 1: JP-A-6-199532).

  In addition, it is known that when hydrogen molecules having a certain concentration or more are present in quartz glass, defects at the E 'center (Si.), Which are oxygen defects, are less likely to occur, and laser durability is improved.

  Compared with KrF excimer laser light, ArF excimer laser light damages quartz glass several times more intensely. Therefore, quartz glass for ArF use requires a hydrogen molecule concentration several times that for quartz glass for KrF use. Become.

  A method for controlling the concentration of hydrogen molecules in synthetic quartz glass has also been proposed (see Patent Document 2: Japanese Patent Laid-Open No. 6-305736), and the concentration of hydrogen molecules in the glass is adjusted according to the energy usage conditions of the ArF laser. I came.

  As described above, as the light source becomes shorter in wavelength, the glass laser durability in the case where the energy of light becomes more intense with excimer laser light or the like than the conventional i-line light has been intensively studied.

  In addition, for optical components such as lenses, windows, prisms, and quartz glass substrates for photomasks used in exposure apparatuses due to these shorter wavelengths, recently, projection lens materials used in exposure apparatuses are particularly expensive. With the progress of NA, the diameter of the lens material has been increasing year by year, and at the same time, the optical homogeneity of the lens material has been demanded to be highly accurate. In particular, for ArF excimer laser, the initial transmittance of quartz glass and the transmittance of the entire optical member at a wavelength of 193.4 nm are theoretical values; the theoretical value is 99.85% at a wavelength of 193.4 nm when multiple reflection is considered. Close values have been required. This is because the optical system in the exposure apparatus is composed of several to several tens of lenses, so as to suppress the absorption of light energy into the quartz glass by increasing the initial transmittance of the quartz glass as much as possible, It has become important to minimize the possibility of causing a density change by conversion to thermal energy when light energy is absorbed and possibly causing a change in refractive index. In addition to the homogeneity of the original refractive index, reduction of birefringence is also an extremely important issue.

  Conventionally, synthetic quartz glass usually introduces a vapor of a high-purity organosilicon compound such as silicon tetrachloride directly into an oxyhydrogen flame in order to avoid contamination with metal impurities that cause ultraviolet absorption. Silica flame is hydrolyzed to produce fine silica particles, which are deposited on a heat-resistant substrate such as quartz glass that rotates directly, and melted into vitrified glass to produce transparent synthetic quartz glass. At this time, when the manufactured synthetic quartz glass ingot is cut perpendicularly to the growth direction (slicing) and the transmittance distribution at the wavelength of 193.4 nm in the growth direction plane is measured, the distribution occurs in the plane. Usually, the transmittance tends to decrease from the center to the outer periphery. Here, when the value required for the initial transmittance is, for example, 99.7% or more in terms of internal transmittance, the usable portion of the synthetic quartz glass ingot, the so-called yield, is determined here.

  On the other hand, recently, large quartz glass substrates for photomasks have been used in the field of LCDs, in other words the so-called liquid crystal field, apart from the field of LSI, and the increase in diameter of the synthetic quartz glass ingot used as this material This is indispensable in consideration of the yield of the process for manufacturing a large glass substrate. A conventional synthetic quartz glass substrate for an IC is mainly a 6-inch square size, but a large glass substrate size is already required to have a substrate with a side of 1 m or more. To produce this, the diameter of the conventional synthetic quartz glass ingot for IC is required to be, for example, about 100 to 140 mm in diameter. However, in the case of a large quartz glass substrate, the product weight is ensured if the conventional ingot size is used. However, it is necessary to repeat the molding many times in order to adjust the size of the ingot to a desired shape, which is disadvantageous in terms of yield and efficiency.

JP-A-6-199532 JP-A-6-305736

  The present invention has been made in view of the above circumstances, and is an optically high-homogeneous synthetic quartz glass member used for optical members such as lenses, prisms, windows, and photomask quartz glass substrates used for excimer lasers, and large-sized liquid crystal. In order to make it easier to obtain optically more homogeneous synthetic quartz glass members in glass substrate members, or to produce synthetic quartz glass ingots as raw materials for efficiently obtaining large-sized synthetic quartz glass substrate members An object of the present invention is to provide a burner for producing a synthetic quartz glass ingot and a method for producing a synthetic quartz glass ingot using the burner.

As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that a burner structure forms a flame when a synthetic silica glass ingot is produced by gas phase hydrolysis or oxidative decomposition of a silica raw material compound with an oxyhydrogen flame. Conventionally, it is composed of a central triple tube structure, an outer shell tube surrounding the triple tube, and a plurality of nozzles provided between the triple tube and the outer shell tube. A synthetic quartz glass manufacturing burner arranged and configured to be positioned at the tip of the main burner was used, but this was composed of at least a central triple tube structure, an outer shell tube surrounding the triple tube, and the triple tube and the outer tube. As a main burner consisting of a plurality of nozzles existing in the outer shell tube between the outer shell tube and a double tube on the outer ring of the main burner, an optically highly homogeneous synthetic quartz glass is provided. And a large glass substrate member for liquid crystal It is obtained by finding the enabling the production of a synthetic quartz glass ingot can.
That is, the present inventors aim to extend the effective portion of the above-described synthetic quartz glass ingot to the entire area of the synthetic quartz glass ingot. The manufacturing factors that determine the initial transmittance of this synthetic quartz glass ingot are the burner (structure, set state), which is an important component of the direct flame method, and the raw material silane compound, hydrogen and other combustible gases, oxygen It is almost determined by the gas supporting gas such as these and the balance of these gases. Among these, it turned out that the place which depends especially on the structure of a burner is very large.

Accordingly, the present invention provides the following burner for producing synthetic quartz glass and a method for producing a synthetic quartz glass ingot using the same.
Claim 1:
A central tube for supplying a silica raw material compound, a first surrounding tube for surrounding the central tube and supplying combustion-supporting gas, and a second surrounding tube for surrounding the first surrounding tube and supplying combustible gas A multiple tube having at least a triple tube structure, an outer shell tube surrounding the multiple tube and supplying a combustible gas, and a plurality of nozzles disposed in the outer tube and supplying a combustion-supporting gas A main burner comprising: an outer tube that surrounds at least the front end portion of the main burner and has a front end projecting forward from the front end portion; and the front end is located at the same position as the front end portion of the main burner Or it consists of an inner tube at a rear position, and the tip of the outer tube protruding forward is a cylindrical shape having a constant inner diameter, and a space between the outer tube and the inner tube is formed as a combustion-supporting gas passage. synthetic silica, characterized in that a double pipe which is Las production for the burner.
Claim 2 :
The total cross-sectional area of the gas ejection portions of the plurality of nozzles arranged in the outer shell tube (the sum of the cross-sectional areas in the hollow portion of the nozzle) is the disconnection of the gas ejection portion between the multiple tube and the outer shell tube. Area (cross-sectional area in the hollow portion between the multiple tube and the outer shell tube (total area of the hollow portion between the multiple tube and the outer shell tube when the first nozzle is not provided)) synthetic quartz glass manufacturing burner according to claim 1, wherein from 5 to 20% by ratio.
Claim 3 :
A central tube for supplying a silica raw material compound, a first surrounding tube for surrounding the central tube and supplying combustion-supporting gas, and a second surrounding tube for surrounding the first surrounding tube and supplying combustible gas A multiple tube having at least a triple tube structure, an outer shell tube surrounding the multiple tube and supplying a combustible gas, and a plurality of nozzles disposed in the outer tube and supplying a combustion-supporting gas A main burner composed of: a cylinder surrounding at least the front end portion of the main burner, the front end projecting forward from the front end, and the front projecting front end having a constant inner diameter A synthetic quartz glass manufacturing burner comprising a double tube consisting of a cylindrical outer tube and an inner tube whose tip is located at the same position as or behind the tip of the main burner, on a rotating substrate Quartz glass target mounted on The silica raw material compound is supplied from the central tube of the burner, the combustion supporting gas is supplied from the first surrounding tube and the nozzle, and the combustible gas is supplied from the second surrounding tube and the outer shell tube. Obtained by gas phase hydrolysis or oxidative decomposition of a silica raw material compound with an oxyhydrogen flame formed from the above-mentioned combustion-supporting gas and combustible gas. A method for producing a synthetic quartz glass ingot, characterized in that silica fine particles to be deposited are deposited on the target and then melted into glass.
Claim 4 :
The production method according to claim 3 , wherein the flow rate of the combustion-supporting gas circulated from the double pipe is 0.5 to 1.3 m / sec.
Claim 5 :
The manufacturing method according to claim 3 or 4 , wherein the diameter of the ingot is 150 mm or more.

  According to the present invention, an optical high-homogeneous synthetic quartz glass member used for an excimer laser, particularly an ArF excimer laser, an optical member strong in laser resistance, or other optical member using a light source such as an excimer laser It is possible to provide a burner for producing a synthetic quartz glass for producing a synthetic quartz glass ingot which is a material used for applications, optical fiber applications for ultraviolet rays, and the like.

  Hereinafter, the present invention will be described in more detail. A burner for producing a synthetic quartz glass ingot according to the present invention includes a multiple tube having at least a triple tube structure, an outer shell tube surrounding the multiple tube, and a plurality of tubes provided in the outer tube. A main burner composed of a plurality of nozzles. A double pipe is provided on the outer ring of the main burner.

  1 and 2 show an embodiment of a burner according to the present invention. Reference numeral 1 denotes a central tube 2, a first surrounding tube 3 surrounding the central tube 2, and the first surrounding tube 3. Is a multi-tube having a triple-pipe structure comprising a second envelope tube 4 surrounding the tube. Reference numeral 5 denotes an outer shell that surrounds the multiple tube (triple tube) 1, and a plurality of nozzles 6 are arranged between the outer tube 5 and the triple tube 1 in the outer tube 5. The main burner 7 is configured. Further, 8 is a double pipe disposed so as to surround at least the front end portion of the main burner 7 and comprises an outer tube 9 and an inner tube 10 disposed inside the outer tube 9. It is. At this time, the distal end portion of the outer tube 9 of the double tube 8 surrounds the distal end portion of the main burner 7 and protrudes forward from this, and the gas flow from the main burner 7 does not spread to the side of the outer tube 9. The tip of the inner tube 10 is located at the same position as the tip of the main burner 7. Note that the distal end portion of the inner tube 10 may be located behind the distal end portion of the main burner 7.

  In this case, the silica raw material compound is supplied and circulated in the center tube 2, and oxygen gas or carrier gas is normally supplied and circulated. In addition, a flammable gas such as oxygen is supplied to the double pipe (inside the first surrounding pipe 3), and a flammable gas such as hydrogen is supplied to and distributed from the triple pipe (in the second surrounding pipe 4). . Further, in the nozzle 6 and the double pipe 8 (between the outer pipe 9 and the inner pipe 10), a combustion-supporting gas such as oxygen gas is supplied and circulated, and the outer shell pipe 5 is supplied. Is supplied and circulated so that a combustible gas such as hydrogen gas circulates around the nozzle 6.

  Here, the total cross-sectional area of the gas ejection portions of the plurality of nozzles 6 disposed in the outer shell tube 5 (the sum of the cross-sectional areas in the hollow portions of the nozzles 6) is as follows. The cross-sectional area of the gas jetting part between (the cross-sectional area in the hollow part between the multiple pipe 1 and the outer shell pipe 5 (the multiple pipe 1 and the outer shell pipe 5 when the nozzle 6 is not provided) It is preferable that it is 5% or more as a ratio occupied in the hollow part total area between), More preferably, it is 5 to 20%, More preferably, it is 8 to 13%.

  The double pipe provided in the outer ring of the main burner is particularly preferably made of quartz, and the flow rate of the combustion-supporting gas flowing from here is preferably 0.5 to 1.3 m / sec. This is because if the flow velocity is lower than 0.5 m / sec, a problem occurs in which the flame returns backward. On the other hand, if it exceeds 1.3 m / sec, the flame of the main burner may be disturbed.

Therefore, the number of the plurality of nozzles 6 may be determined according to the above conditions. The flow rate of the combustion-supporting gas flowing from the double tube 8 may be determined by the clearance between the outer tube 9 and the inner tube 10 and the flow rate of the combustion-supporting gas.
That is, in contrast to the conventional burner structure, by providing a double tube around the outer shell tube of the main burner, when manufacturing a synthetic quartz glass ingot directly by the flame method, from the center to the outer periphery of the ingot growth surface. When the melt surface temperature distribution is observed, the high temperature region at the center extends to the outer peripheral portion and becomes a uniform state. As a result, the silica structure in the process of deposition, melting, and vitrification of silica fine particles on the ingot growth melt surface is formed under the same conditions from the center to the outer periphery, and the initial transmittance of the ingot outer periphery is the center. The difference between the initial transmittance at the outer peripheral portion and the initial transmittance at the central portion can be suppressed as much as possible without lowering. At the same time, it is possible to increase the diameter of the synthetic quartz glass ingot by increasing the melting area.

  This is because the double-tube is newly provided around the outer shell tube of the main burner of the conventional structure, so that the high temperature region is expanded from the inner flame to the outer flame in the formed flame, and this outer flame portion is The outer peripheral portion of the ingot melt growth surface is irradiated. In addition, the structure is such that the combustion-supporting gas can flow from between the outer shell pipe and the double pipe of the main burner, and the cross-sectional area of a plurality of nozzle groups provided between the multiple pipe and the outer shell pipe. By setting the ratio to 5% or more, the combustion efficiency of the combustible gas such as hydrogen gas supplied from the periphery of the plurality of nozzle groups is increased, and the high temperature region can be expanded in the entire flame. Furthermore, by surrounding the tip of the main burner with the outer shell tube of a double tube, flame disturbance due to the airflow in the furnace can be prevented and the thermal power can be concentrated.

  Next, a method for producing a synthetic quartz glass ingot when using the synthetic quartz glass production burner of the present invention will be described.The burner is disposed toward a quartz glass target mounted on a rotating substrate, Each of the silica raw material compound, a flammable gas such as hydrogen gas, and a combustion-supporting gas such as oxygen gas is supplied to the burner of the present invention, and gas phase hydrolysis or oxidative decomposition is performed on the target by an oxyhydrogen flame. And a synthetic quartz glass ingot is produced by melting it into a molten glass.

In this case, an organic silicon compound is used as a raw material silica raw material compound, and a silane compound or a siloxane compound represented by the following general formula (1), (2) or (3) is preferably used.
(R ¹ ) _n Si (OR ² ) _4-n (1)
(In the formula, R ¹ and R ² each represent the same or different aliphatic monovalent hydrocarbon group, hydrogen atom or halogen atom, and n represents an integer of 0 to 4.)

（式中、Ｒ³は水素原子又は脂肪族一価炭化水素基を示し、ｍは１以上、特に１又は２である。また、ｐは３〜５の整数である。）

(Wherein R ³ represents a hydrogen atom or an aliphatic monovalent hydrocarbon group, m is 1 or more, particularly 1 or 2, and p is an integer of 3 to 5)

Here, the aliphatic monovalent hydrocarbon group for R ¹ , R ² , and R ³ is an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group. And a cycloalkyl group having 3 to 6 carbon atoms such as a cyclohexyl group, an alkenyl group having 2 to 4 carbon atoms such as a vinyl group and an allyl group.

Specific examples of the silane compound represented by the general formula (1) include SiCl ₄ , CH ₃ SiCl ₃ , Si (OCH ₃ ) ₄ , Si (OCH ₂ CH ₃ ) ₄ , and CH ₃ Si (OCH ₃ ) _3. Examples of the siloxane compound represented by the general formulas (2) and (3) include hexamethyldisiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and the like.

  The synthetic quartz glass production burner of the present invention that forms an oxyhydrogen flame includes a silane or siloxane compound as a raw material, a combustible gas such as hydrogen, carbon monoxide, methane, and propane, and a combustion-supporting gas such as oxygen. Supply each one.

  Here, as a device for producing the synthetic quartz glass ingot, either a saddle type or a horizontal type can be used.

  The internal transmittance at a wavelength of 193.4 nm of the synthetic quartz glass ingot produced by the synthetic quartz glass production burner of the present invention is preferably 99.70% or more. This is because when this synthetic quartz glass ingot is finally used as a raw material as an optical member, the wavelength used at this time is, for example, ArF excimer laser, and the transmittance at a wavelength of 193.4 nm is 99 as internal transmittance. This is because 70% or more may be required. When the internal transmittance is less than 99.70%, when ArF excimer laser light passes through the quartz glass member, the light energy is absorbed and changed to thermal energy, thereby causing a change in the density of the glass and further changing the refractive index. May also occur. For example, when a synthetic quartz glass ingot having an internal transmittance of less than 99.70% is used as a lens material of an exposure apparatus whose light source is ArF excimer laser light, the image plane is distorted due to a change in the refractive index of light of the lens material. May cause problems.

Therefore, as described above, it is necessary to have the burner structure of the present invention. In addition, in order to use this burner more optimally, the silica raw material compound and oxygen to be supplied to the central tube of the burner , for example, oxygen can be mixed to be a 1.15-fold molar oxygen stoichiometry required by the silica raw material compound.

Furthermore, the gas flow rate of the silica raw material compound supplied to the central tube is preferably 0.3 to 0.7 Nm ³ / hr, particularly 0.4 to 0.5 Nm ³ / hr. In this case, this center tube, 2.0～4.0Nm a combustion-supporting gas such as oxygen ³ / hr, particularly preferably be distributed in 2.5~3.5Nm ³ / hr, also such as Ar An inert gas can be circulated.
It said first combustion assisting gas flow through the surrounding tubes of 0.3~2.5Nm ³ / hr, the combustible gas flow rate through the second surrounding tube combustible flowing 12~15Nm ³ / hr, tubular shell The gas flow rate is 20 to 25 Nm ³ / hr, the total flow rate of the combustion-supporting gas flowing through the nozzle is 10 to 16 Nm ³ / hr, and the double pipe is supplied at a combustion-supporting gas flow rate of 2 to 5 Nm ³ / hr. The gas flow rate is preferably 0.5 to 1.3 m / sec.

  By supplying the required gas to the burner as described above, the silica raw material compound is vapor-phase hydrolyzed or oxidatively decomposed by an oxyhydrogen flame to produce silica fine particles, which are deposited on the target. And this is melt vitrified, and the vitrification temperature on the growth surface has a temperature distribution on the growth surface, and the minimum temperature at this time is 1,800 ° C. or higher, preferably 2,000 ° C. or higher ( The upper limit is 2,500 ° C. or lower, preferably 2,400 ° C. or lower) to widen the region where the internal transmittance of synthetic quartz glass at a wavelength of 193.4 nm is maintained at 99.70% or higher. Is possible. As described above, the use of the burner for producing the synthetic quartz glass according to the present invention contributes to the optimum gas balance of oxyhydrogen, etc., which greatly contributes to the melting vitrification temperature of the growth surface.

That is, the present inventors have an influence on the transmittance at the melting surface temperature shorter than the wavelength of 200 nm, particularly at the wavelength of ArF (193.4 nm), in the relationship between the melt vitrification temperature of the growth surface and the transmittance. I found out that That is, if the melting glassification temperature is higher, the internal transmittance can be maintained at 99.70% or more. Similarly, the hydrogen molecule content contained in the synthetic quartz glass within this condition range can be kept at 3 × 10 ¹⁸ molecules / cm ³ or more, and long-term stability during excimer laser irradiation ( (Transmission deterioration suppression) can be sufficiently maintained. In addition, synthetic quartz glass ingots can also be manufactured with large diameter ingots having a diameter of 150 mm or more, particularly 150 to 500 mm, especially 200 to 300 mm.

Here, the synthetic quartz glass ingot produced using the burner for producing the synthetic quartz glass of the present invention has an internal transmittance at a wavelength of 193.4 nm, for example, 99.70% of the entire surface in a state where the ingot is cut. The above is preferable. Further, the amount of OH groups in the glass is preferably 500 to 1,300 ppm, particularly preferably 800 to 900 ppm. Furthermore, the hydrogen molecule concentration is 3 × 10 ¹⁸ molecules / cm ³ or more, particularly 3 × 10 ^{18 to} 6 × 10 ¹⁸ molecules / cm ³ , especially 3 × 10 ^{18 to} 5 × 10 ¹⁸ molecules / cm ³ . It is more preferable from the viewpoint of laser resistance. Moreover, since a large-diameter synthetic quartz glass ingot can be produced by using the burner of the present invention, it can be used as a member for a large glass substrate for liquid crystal, which is preferable.

  Further, the obtained synthetic quartz glass ingot was subjected to cylindrical grinding or the like, and then hot-melted in a range of 1,700 to 1,800 ° C. for a mask substrate and hot-molded into a square block shape. A synthetic quartz glass substrate can be formed by slicing and polishing after annealing for removing strain within a range of ˜1,300 ° C. In addition, when the optical lens material is used, a synthetic quartz glass free from striae in three directions can be obtained by homogenizing the synthetic quartz glass ingot. That is, after welding both ends of the obtained synthetic quartz glass ingot to a synthetic quartz glass rod (scaffolding tube) held by a lathe and extending to a diameter of 80 mm, one end of the synthetic quartz glass ingot is 1,700 ° C. or higher with an oxyhydrogen burner. Preferably, after igniting at 1,800 ° C. or higher to form a melting zone, the rotation speed of the left and right chucks is changed and shear stress is applied to the melting zone to homogenize the quartz glass ingot, By moving from one end to the other end, the OH group concentration and hydrogen concentration in the ingot growth surface are homogenized (homogenization by zone melting method). After the obtained synthetic quartz glass is molded into a desired size, it is preferable to add an annealing treatment to obtain a uniform fictive temperature (FT). The annealing process can be performed by a conventional method.

  Synthetic quartz glass members obtained in this way include excimer laser lenses in the LSI field, synthetic quartz glass substrates for photomasks, stepper illumination lenses, projection optics lenses, window materials, mirrors, beam splitters, It is also used as an optical quartz glass member such as a prism, and a large quartz glass substrate member in the field of liquid crystal for LCD, for example, a color filter substrate, a dustproof glass substrate, a counter glass substrate, and the like.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. In the following example, the internal transmittance is measured as follows.
Internal transmittance: measured by ultraviolet spectrophotometry (Varian, Cary 400).

[Examples and Comparative Examples]
Methyltrimethoxysilane is supplied as a raw material to the burner for producing synthetic quartz glass of the present invention (FIG. 1) and the conventional burner for producing synthetic quartz glass (FIG. 3), and is oxidized or combusted in an oxyhydrogen flame to produce silica. Fine particles were generated and deposited on a rotating quartz target, and at the same time melted into glass to obtain a synthetic quartz glass member.

  In this case, as shown in FIG. 4, the quartz glass target 12 is mounted on the rotating heat-resistant substrate 11, while the argon gas 15 is introduced into the methyltrimethoxysilane 14 placed in the raw material evaporator 13. A mixed gas obtained by allowing the vapor of methyltrimethoxysilane 14 to accompany the argon gas 15 and mixing the oxygen gas 16 to the argon gas 15 is supplied to the central nozzle of the main burner 17, and the main burner 17 is further supplied with the mixed gas. Oxygen gas 18, hydrogen gas 19, hydrogen gas 20, oxygen gas 21, and oxygen gas 22 are supplied sequentially from the inside to the outside center, and the raw material methyltrimethoxysilane 14 and oxyhydrogen flame 23 are supplied from the main burner 17 to the target 12 The silica fine particles 24 are deposited on the target 12 and simultaneously melted into a transparent glass to produce synthetic quartz. To obtain a Las ingot 25. The size of the resultant synthetic quartz glass ingot was 150 mm × 500 mm in diameter. In addition, the flow velocity of the combustion-supporting gas circulated from the double pipe is 0.6 m / sec. Table 1 shows the nozzle cross-sectional area, the cross-sectional area ratio, and the gas supply conditions of the burners of Examples and Comparative Examples.

注：断面積比は、第２の包囲管と外殻管との間の中空部面積に対するノズル群の中空部総
面積の割合を示す。

Note: The cross-sectional area ratio indicates the ratio of the total area of the hollow part of the nozzle group to the area of the hollow part between the second envelope tube and the outer shell tube.

  Next, the synthetic quartz glass ingot produced from this example and the comparative example was cut into round slices, and after mirror finishing, the initial transmittance distribution at 193.4 nm from the central part to the outer peripheral part of this glass body was measured by ultraviolet spectrophotometry. (Cary 400, manufactured by Varian). This is shown in FIG.

The cross-sectional view of the gas injection opening of the burner for synthetic quartz glass manufacture which concerns on the Example by this invention is shown. The longitudinal cross-sectional view of the burner for synthetic quartz glass manufacture which concerns on the Example by this invention is shown. The cross-sectional view of the gas ejection port of the conventional synthetic quartz glass manufacturing burner according to the comparative example is shown. It is the schematic which shows an example of the manufacturing apparatus of the synthetic quartz glass of this invention. The initial transmittance distribution in the radial direction surface of the synthetic quartz glass ingot obtained in the examples and comparative examples is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multiple tube 2 Center tube 3 1st surrounding tube 4 2nd surrounding tube 5 Outer shell tube 6 Nozzle 7 Main burner 8 Quartz double tube 9 Quartz double tube outer tube 10 Quartz double tube inner tube DESCRIPTION OF SYMBOLS 11 Heat resistant base material 12 Synthetic quartz glass target 13 Raw material evaporator 14 Methyltrimethoxysilane 15 Argon gas 16 Oxygen gas 17 Main burner 18 Oxygen gas 19 Hydrogen gas 20 Hydrogen gas 21 Oxygen gas 22 Oxygen gas 23 Oxyhydrogen flame 24 Silica Fine particle 25 synthetic quartz glass ingot

Claims (5)

A central tube for supplying a silica raw material compound, a first surrounding tube for surrounding the central tube and supplying combustion-supporting gas, and a second surrounding tube for surrounding the first surrounding tube and supplying combustible gas A multiple tube having at least a triple tube structure, an outer shell tube surrounding the multiple tube and supplying a combustible gas, and a plurality of nozzles disposed in the outer tube and supplying a combustion-supporting gas A main burner comprising: an outer tube that surrounds at least the front end portion of the main burner and has a front end projecting forward from the front end portion; and the front end is located at the same position as the front end portion of the main burner Or it consists of an inner tube at a rear position, and the tip of the outer tube protruding forward is a cylindrical shape having a constant inner diameter, and a space between the outer tube and the inner tube is formed as a combustion-supporting gas passage. synthetic silica, characterized in that a double pipe which is Las manufacturing burner. The total cross-sectional area of the gas ejection portions of the plurality of nozzles arranged in the outer shell tube (the sum of the cross-sectional areas in the hollow portion of the nozzle) is the disconnection of the gas ejection portion between the multiple tube and the outer shell tube. Area (cross-sectional area in the hollow portion between the multiple tube and the outer shell tube (total area of the hollow portion between the multiple tube and the outer shell tube when the first nozzle is not provided)) synthetic quartz glass manufacturing burner according to claim 1, wherein from 5 to 20% by ratio. A central tube for supplying a silica raw material compound, a first surrounding tube for surrounding the central tube and supplying combustion-supporting gas, and a second surrounding tube for surrounding the first surrounding tube and supplying combustible gas A multiple tube having at least a triple tube structure, an outer shell tube surrounding the multiple tube and supplying a combustible gas, and a plurality of nozzles disposed in the outer tube and supplying a combustion-supporting gas A main burner composed of: a cylinder surrounding at least the front end portion of the main burner, the front end projecting forward from the front end, and the front projecting front end having a constant inner diameter A synthetic quartz glass manufacturing burner comprising a double tube consisting of a cylindrical outer tube and an inner tube whose tip is located at the same position as or behind the tip of the main burner, on a rotating substrate Quartz glass target mounted on The silica raw material compound is supplied from the central tube of the burner, the combustion supporting gas is supplied from the first surrounding tube and the nozzle, and the combustible gas is supplied from the second surrounding tube and the outer shell tube. Obtained by gas phase hydrolysis or oxidative decomposition of a silica raw material compound with an oxyhydrogen flame formed from the above-mentioned combustion-supporting gas and combustible gas. A method for producing a synthetic quartz glass ingot, characterized in that silica fine particles to be deposited are deposited on the target and then melted into glass. The production method according to claim 3 , wherein the flow rate of the combustion-supporting gas circulated from the double pipe is 0.5 to 1.3 m / sec. The manufacturing method according to claim 3 or 4 , wherein the diameter of the ingot is 150 mm or more.

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