JP2002154827A - Method for producing synthetic quartz glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce synthetic quartz glass having good UV resistance and high transmittance by maintaining the surface temperature in a growth section for a quartz glass ingot at >=2,000 deg.C. SOLUTION: This method for producing the synthetic quartz glass by supplying gaseous oxygen, gaseous hydrogen and a gaseous silica making raw material from burners to a reaction area, forming silica particulates in the reaction area by flame hydrolysis of the gaseous silica making raw material, depositing the silica particulates on the synthetic quartz glass ingot rotatably arranged in the reaction area and growing the quartz glass by melting the silica particulates, in which the surface temperature in the growth section for the synthetic quartz glass ingot is maintained at >=2,000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a synthetic quartz glass having a high transmittance to ultraviolet rays such as a KrF or ArF excimer laser and suppressing a decrease in transmittance due to the irradiation of ultraviolet rays.

[0002]

2. Description of the Related Art LSI
In the manufacture of highly integrated circuits such as those described above, a stepper device for transferring a fine circuit pattern onto a wafer has become indispensable for manufacturing semiconductor devices.

The stepper device includes an illumination system, a projection lens unit, and a wafer driving unit. The illumination system supplies light emitted from a light source onto the reticle (photomask) as light of uniform illuminance, and projects the light. The lens unit has a role of accurately and shrinking the circuit pattern on the reticle to form an image on the wafer.

[0004] The quality required of these illumination / projection system materials is, first, that the light from the light source is highly transmissive, and second, that the intensity of the transmitted light is uniform.

In recent years, the miniaturization of circuit patterns in the manufacture of semiconductor devices has progressed, and the shortening of the wavelength of a light source irradiated from a stepper has been accelerated.
m), i-line (365 nm) to KrF (248 nm),
It has shifted to ArF (193 nm).

[0006] In the current mainstream KrF, the use of optical glass is impossible due to the problem of transmittance. Therefore, synthetic quartz glass is very important as a material constituting a stepper.

As a method for producing synthetic quartz glass, alkoxysilane is hydrolyzed in the presence of an acid or ammonia catalyst to obtain silica fine particles, which are then sintered to form a synthetic quartz glass, a sol-gel method, Silica compounds such as silicon are hydrolyzed or thermally decomposed in an oxyhydrogen flame to deposit silica fine particles on a rotating carrier (ingot) to produce a porous silica matrix, which is melted and synthesized. There are known a soot method using quartz glass and a direct method using the ingot directly melted to obtain synthetic quartz glass.

Among them, synthetic quartz glass as a material for a photolithography apparatus such as a stepper is manufactured by a direct method which can obtain a high-purity quartz glass having the lowest impurity content among the above methods.

The synthetic quartz glass obtained in this way has high transmittance to KrF and ArF excimer lasers, but when comprehensively evaluated as a stepper material, from the viewpoint of the life of the material. You have to consider it.

[0010] This is because, even with quartz glass having relatively high transparency, energy is accumulated inside the quartz glass due to slight absorption of irradiation ultraviolet rays, and a change in the internal structure occurs. Is a problem.

When compaction occurs, not only the uniformity of the refractive index is lost, but also the state of the surface polished with high precision changes, and the performance designed as a stepper can no longer be exhibited. The effect of this compaction becomes more pronounced as the irradiation wavelength becomes shorter or the irradiation energy increases.However, the shortening of the light source is unavoidable to improve the functionality of the device. This is necessary to improve the throughput of the stepper. Therefore, this UV resistance is a very important physical property, although it is a factor that greatly contributes to the life of the stepper.

As an evaluation method of the ultraviolet light resistance, an accelerated test method of excimer laser irradiation at a used wavelength is generally used.
Universal Dos representing irradiation energy
The evaluation is based on the degree of decrease in transmittance with respect to the amount of e.
The Universal Dose amount is specifically represented by the square of the energy density times the number of pulses, and is obtained by converting the energy density of the excimer laser actually used and the required useful life.

Various studies have been conducted on the decrease in transmittance caused by irradiation with ultraviolet rays, that is, on the absorption of ultraviolet irradiation. It has a defect structure, and has a structure such as Si. And Si-O. The presence of these defects has been confirmed by analysis of electron spin resonance (ESR) spectra. These include KrF (248 nm) and ArF (193).
nm), the center wavelength is 215 nm at the E 'center and 2 at NBOHC.
60 nm.

The generation of these defects is considered by many research reports as follows. First, the E ′ center is considered to be generated because oxygen-deficient defects such as Si—Si bonds present in quartz glass are broken by ultraviolet irradiation.

[0015] For NBOHC, Si-OH is considered as a precursor.

[0016] Such ultraviolet irradiation absorption includes ultraviolet irradiation initial absorption (RDP), which occurs at the initial stage of irradiation with ultraviolet light and whose transmittance rapidly decreases with respect to the irradiation amount, and transmittance which occurs when irradiation is further continued. There is long-term radiation absorption (SDP) with a relatively modest decline in UV resistance, and UV resistance is assessed for both.

According to conventional research, effective means has not yet been established for RDP, and it has been possible to suppress SDP by doping hydrogen molecules.

In this method, a high concentration of hydrogen molecules in quartz glass is used to complement the generated absorption defect as shown in the following formula, and to convert the absorption defect in the case where the absorption does not appear near the light source wavelength of the stepper. .

2Si · + H ₂ → 2Si-H (Formula 3) 2Si—O · + H ₂ → 2Si-OH (Formula 4) Here, the H ₂ molecule concentration in the quartz glass is 1 × 10 ¹⁸ molecules / cm ³ or more is preferred.

However, in this method, only the structural defect caused by the irradiation of ultraviolet rays is converted into another bond, the generation of the structural defect itself cannot be suppressed, and a high concentration of hydrogen molecules is contained in the quartz glass. For this reason, it is necessary to make the gas balance during the production of quartz glass an excess hydrogen condition. Under this condition, oxygen-deficient defects Si—Si are easily generated.

An object of the present invention is to provide a method for producing a synthetic quartz glass having improved ultraviolet transmittance and ultraviolet resistance, which meets the above-mentioned demands.

[0022]

Means for Solving the Problems and Embodiments of the Invention The present inventors have conducted intensive studies in order to achieve the above object, and as a result, have found that the surface temperature of the growth portion of the quartz glass ingot in the synthetic quartz glass manufacturing process is reduced. It has been found that by maintaining the temperature at a higher temperature than in the past, a synthetic quartz glass having excellent UV resistance, particularly good RDP, and high UV transmittance can be obtained.
That is, conventionally, the surface temperature of the growth portion of the quartz glass ingot was maintained at about 1900 to 1950 ° C. from the viewpoint of reducing the amount of the raw material gas and reducing the manufacturing cost. It has been found that manufacturing a quartz glass by setting the surface temperature of the growth portion of the glass ingot to 2000 ° C. or higher has high UV transmittance and excellent UV resistance. Furthermore, by making the surface temperature uniform, it is possible to obtain quartz glass having a uniform ultraviolet transmittance in quartz glass, and to obtain KrF or ArF
The inventors have found that a synthetic quartz glass suitable as a material for photolithography can be obtained, and have accomplished the present invention.

That is, the present invention provides the following method for producing synthetic quartz glass. (1) Oxygen gas, hydrogen gas and raw material gas for silica production are supplied from a burner to a reaction zone, and in this reaction zone, silica fine particles are generated by flame hydrolysis of the raw material gas for silica production and rotatably disposed in the reaction zone. In the method for producing a synthetic quartz glass in which the silica fine particles are deposited and melted on the synthetic quartz glass ingot, and the quartz glass is grown, a surface temperature of a growth portion of the synthetic quartz glass ingot is set to 2000 ° C. or more. Method for producing synthetic quartz glass. (2) Oxygen gas, hydrogen gas and raw material gas for silica production are supplied from a burner to a reaction zone, and in this reaction zone, silica fine particles are generated by flame hydrolysis of the raw material gas for silica production and rotatably disposed in the reaction zone. A method for producing a synthetic quartz glass in which the silica fine particles are deposited and melted on the synthetic quartz glass ingot thus obtained, wherein the surface temperature of a growth portion of the synthetic quartz glass ingot is maintained uniformly ( 1) A method for producing a synthetic quartz glass. (3) The method for producing synthetic quartz glass according to (1) or (2), wherein the surface temperature of the growth portion of the synthetic quartz glass ingot is controlled using a secondary heat source such as an auxiliary burner. (4) The method for producing synthetic quartz glass according to any one of (1) to (3), wherein a fluorine compound gas is supplied from the raw material supply section together with the silica production raw material gas.

According to the present invention, by utilizing the above method, it is possible to suppress the generation of structural defects induced by ultraviolet irradiation and to produce a synthetic quartz glass having good ultraviolet resistance and high transmittance. Becomes possible.

Although the reason for this is not yet clear,
At the present stage, the present inventors consider as follows.

Conventionally, precursors of defects due to ultraviolet irradiation are:
It is thought to be due to bonds such as Si-Si or Si-OH, but in fact the main cause is an unstable structure in quartz glass, for example, those having unstable angles due to Si-O-Si bonds. It is considered that the bond is broken by the irradiation of the ultraviolet rays to generate Si and Si-O.

[0027] Quartz glass has, as a basic structural unit, a tetrahedron in which O atoms are bonded in a tetrahedral shape around Si atoms, and these are connected in a mesh to form a network. This network unit is called a cluster, and the clusters collectively constitute quartz glass. Average Si in this cluster
The —O—Si bond angle is 144 °, and a bond having an angle smaller than this is considered to be energetically unstable and easily broken by irradiation with ultraviolet light. Further, a planar three-membered ring and a four-membered ring structure exist in the quartz glass, and the Si—O—Si bond angle in the planar three-membered ring is 130.5 °.
Which is also considered an unstable bond.

On the other hand, by setting the surface temperature of the growth portion of the quartz glass ingot to 2000 ° C. or higher in the present invention, Si—O—S that is energetically stable in the quartz glass can be obtained.
It is considered that the molecular motion for obtaining the i-bond angle is promoted, and the generation of a narrow bond angle is suppressed. As a result, the UV resistance is improved, and Si and Si-
It is possible to obtain a synthetic quartz glass in which the generation of absorption defects such as O. is reduced, the UV transmittance is high, and the transmittance is hardly reduced by UV irradiation.

Hereinafter, the present invention will be described in more detail.

In the method for producing synthetic quartz glass according to the present invention, oxygen gas, hydrogen gas and raw material gas for producing silica are supplied from a burner to a reaction zone, and silica fine particles are generated by flame hydrolysis of the raw material gas for producing silica in this reaction zone. At the same time, a method is employed in which the silica fine particles are deposited and melted on a synthetic quartz glass ingot rotatably arranged in the reaction zone to grow quartz glass.

This method itself is known, and various conditions and the like are set so that the set surface temperature is obtained.

As a raw material gas for producing silica, a known silicon compound such as chlorosilane such as silicon tetrachloride or alkoxysilane such as tetramethoxysilane is used. Cl is considered in consideration of ultraviolet absorption by Si-Cl bond. Alkoxysilanes that do not contain are preferred.

According to the present invention, in the above method, the surface temperature of the growth portion of the synthetic quartz glass ingot is set to 2000 ° C. or more,
Preferably 2000 to 2200 ° C, more preferably 20 ° C
The temperature is set to 00 to 2100 ° C., which makes it possible to produce a synthetic quartz glass having good ultraviolet resistance and high transparency.

Further, by keeping the surface temperature of the growth portion of the quartz glass ingot uniform, the ultraviolet transmittance of the synthetic quartz glass is high and its value is made uniform in the radial direction of the ingot and in the growth axis direction. Can be. In this case, the surface temperature of the growth portion of the quartz glass ingot is set to an average of 2000 ° C. or more, preferably 2000 to 2200 ° C.,
More preferably, the temperature is set to 2000 to 2100 ° C.

Means for raising the surface temperature of the growth portion of the synthetic quartz glass ingot to 2000 ° C. or higher include oxygen gas,
Methods such as selecting the flow rates of the hydrogen gas and the raw material gas for producing silica, adjusting the gas balance of the burner, and using a secondary heat source such as an auxiliary burner and a heater can be adopted.

FIG. 1 shows silica obtained by hydrolyzing a raw material gas for silica production (for example, a silicon compound such as tetraalkoxysilane) in an oxyhydrogen flame using a burner 2 disposed in a chamber 1. This shows an apparatus for manufacturing synthetic quartz glass by depositing fine particles on an ingot 3 which is receding in the axial direction while rotating, and directly melting this.

In the chamber 1, an ingot passage 4 is formed on one wall facing the ingot 3 in the axial direction, and the ingot 3 passes through the passage 4 airtightly and retreats. A window 5 for temperature measurement is provided on the other wall surface facing the ingot 3 in the axial direction, and an infrared radiation thermometer 6 is provided outside the window 5;
The surface temperature of the growth part of the ingot 3 is measured through the window 5.

The surface temperature of the growth part is measured from the direction shown in FIG. 1 when measuring the distribution of the ingot 3 in the radial direction, and 90 ° from the axis of the ingot when measuring the distribution of the ingot 3 in the axial direction. Measure from the direction in which In the case of measurement in the axial direction, a measurement window is provided on the wall surface of the chamber in the same manner as in the radial direction, and measurement is performed with an infrared radiation thermometer through the window.

The window 5 is made of a material having a high infrared transmittance, such as calcium fluoride, to be measured.

In the method for producing synthetic quartz glass using such an apparatus, in order to achieve the above-mentioned surface temperature condition, as described above, the gas balance of the burner 2 is adjusted or the secondary burner such as the auxiliary burner 7 is used. The surface temperature of the ingot growth section is controlled using a suitable heat source. An oxyhydrogen flame is supplied from the auxiliary burner 7. As the secondary heat source, a heater may be installed in addition to the auxiliary burner.

These series of operations are automated by an automatic control device that feeds back the measured values of the infrared radiation thermometer, and automatically changes and controls the position of the burner, the secondary heat source, the gas balance, the gas amount, etc. May be controlled to a predetermined temperature. A mass flow controller may be used for the flow rate control.

The raw material gas for producing silica is supplied from the center of the burner 2 during the production of the synthetic quartz glass. The gas balance near the raw material supply nozzle is preferably set to an oxygen excess condition. This is because the reaction of the raw materials becomes insufficient and the surface temperature tends to decrease unless the raw material supply section is made to have an excessive amount of oxygen.

Further, by keeping the surface temperature of the growth portion of the quartz glass ingot at a high temperature of 2000 ° C. or more and making the balance of the entire gas supplied from the burner excessive in oxygen, the oxygen-deficient defect Si—Si Generation can be suppressed, and conversely, by making hydrogen excess, the concentration of hydrogen molecules in the quartz glass can be increased, and structural defects generated by irradiation with ultraviolet light can be complemented. In this case, the concentration of hydrogen molecules in the quartz glass is preferably 1 × 10 ¹⁷ molecules / cm ³ or more, and more preferably 1 × 10 ¹⁸ molecules / cm ³ or more.

In addition to the above-mentioned method, when the synthetic quartz glass ingot is manufactured, the fluorine compound gas is supplied from the burner together with the raw material gas from the burner to manufacture the fluorine-containing synthetic quartz glass, whereby the ultraviolet resistance can be further improved. In this case, CF ₄ , C
HF ₃ , SiF _{4 and the} like can be selected. When these fluorine compound gases are supplied from the burner, S
Form an i-F bond.

This Si—F bond has a bond energy of 5
Since the bond is 41 kJ / mol, which is a very strong bond, the bond is cleaved and an E ′ center is hardly generated even when irradiated with ultraviolet rays. In addition, an Si-O-Si bond having an unstable angle due to generation of a Si-F bond is reduced.

[0046]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples. Further, the manufacturing conditions such as gas flow rates described in the embodiments do not mean that the present invention is limited to the scope.

Example 1 30.0 Nm ³ / H of H ₂ gas
r, O ₂ gas was supplied from a burner at a flow rate of 13.0 Nm ³ / Hr, and tetramethoxysilane as a raw material at a flow rate of 2500 g / Hr, and synthetic quartz glass was produced by hydrolysis in an oxyhydrogen flame.

The surface temperature of the growth portion of the ingot during manufacture was measured from the axial direction of the ingot with an infrared radiation thermometer (thermo tracer TH3104MR NEC manufactured by San-Ei Co., Ltd.).
50 ° C was indicated.

A synthetic quartz glass ingot produced under the above conditions was taken out, and a sample having a thickness of 10 mm and subjected to optical polishing on both sides was prepared.

When the ultraviolet transmittance at 193.4 nm was measured at the position of the sample corresponding to the portion showing 2050 ° C., the internal transmittance was 99.60%. The measurement was performed using a spectrophotometer Cary400 manufactured by Varian.
Type used.

Next, an ArF excimer laser was applied at the same position on the sample at an energy density of 20 mJ / cm ² p to 2 × 1.
0 ⁷ pulses were measured at the same time transmission and irradiation. As a result, the decrease in the internal transmittance at 193.4 nm was 0.09% at the maximum. Table 1 shows the above results.

Example 2 Synthetic quartz glass was produced by hydrolysis in an oxyhydrogen flame, with the addition of an auxiliary burner to the same gas conditions of the burner as in Example 1. Gas flow rate of the auxiliary burner, and the H ₂ gas 5.0 nm ³ / Hr, the O ₂ gas was 3.0 Nm ³ / Hr.

The surface temperature of the growth portion of the ingot during manufacture was measured by an infrared radiation thermometer from the axial direction of the ingot, and the temperature at the center of the ingot was 2195 ° C.

When a sample was evaluated in the same manner as in Example 1, the internal transmittance before the ArF excimer laser irradiation was 99.65%, and the decrease in the internal transmittance due to the irradiation was 0.5% at the maximum. . Table 1 shows the above results.

Example 3 Synthetic quartz glass was produced by hydrolysis in an oxyhydrogen flame by supplying 900 g / Hr of SiF ₄ gas together with the raw materials under the same burner gas conditions as in Example 1, and adding an auxiliary burner. did.

[0056] Gas flow rate of the auxiliary burner, and the H ₂ gas 5.0 nm ³ / Hr, the O ₂ gas was 2.5 Nm ³ / Hr. When the surface temperature of the growth portion of the ingot during manufacture was measured from the axial direction of the ingot with an infrared radiation thermometer, the temperature at the center of the ingot was 2082 ° C.

When a sample was evaluated in the same manner as in Example 1, the internal transmittance before the irradiation with the ArF excimer laser was 99.70%, and the decrease in the internal transmittance due to the irradiation was 0.1% at the maximum. . The fluorine concentration in the quartz glass was 300 ppm. Table 1 shows the above results.

Example 4 H ₂ gas was used at 30.0 Nm ³ / H
r and O ₂ gas were supplied from a burner at a flow rate of 15.5 Nm ³ / Hr and a raw material of tetramethoxysilane at a flow rate of 2500 g / Hr, and synthetic quartz glass was produced by hydrolysis with an oxyhydrogen flame.

The surface temperature of the growing portion of the ingot during manufacture was measured by an infrared radiation thermometer from the axial direction of the ingot.
The temperature at the portion corresponding to 0 mm is 2089 ° C. and 2
082 ° C and 2080 ° C.

The synthetic quartz glass ingot produced under the above conditions was taken out, and a sample having a thickness of 10 mm and subjected to optical polishing on both surfaces was prepared.

When the internal transmittance was measured at a portion corresponding to the above-mentioned temperature measurement point, the central portion of the ingot, and 30 mm and 60 mm from the central portion, all showed a uniform transmittance of 99.70%.

FIG. 2 shows the surface temperature, and FIG. 3 shows the internal transmittance.

Comparative Example 1 Synthetic quartz glass was produced by hydrolysis in an oxyhydrogen flame while changing the gas flow rate of each nozzle of the burner at the same total gas flow rate as in Example 1.

When the surface temperature of the growing portion of the ingot during manufacture was measured from the axial direction of the ingot with an infrared radiation thermometer, the temperature at the center of the ingot was 1910 ° C.

When a sample was evaluated in the same manner as in Example 1, the internal transmittance before the irradiation with the ArF excimer laser was 99.20%, and the decrease in the internal transmittance due to the irradiation was 2.0% at the maximum. . Table 1 shows the above results.

[Comparative Example 2] H ₂ gas was used at 26.5 Nm ³ / H
r, O ₂ gas was supplied from a burner at a flow rate of 12.0 Nm ³ / Hr, and tetramethoxysilane as a raw material at a flow rate of 2500 g / Hr, and synthetic quartz glass was produced by hydrolysis or thermal decomposition in an oxyhydrogen flame.

The surface temperature of the growing portion of the ingot during manufacture was measured by an infrared radiation thermometer from the axial direction of the ingot.
The temperature of the part corresponding to 0 mm is 2002 ° C. and 1
967 ° C and 1906 ° C.

The synthetic quartz glass ingot produced under these conditions was taken out, and a sample having a thickness of 10 mm and subjected to optical polishing on both surfaces was prepared.

When the internal transmittance was measured at a portion corresponding to the above-mentioned temperature measurement point, 99.50%, 9 mm, 30 mm and 60 mm from the center of the ingot, respectively.
9.40% and 99.10%.

FIG. 2 shows the surface temperature, and FIG. 3 shows the internal transmittance.

[0071]

[Table 1]

[0072]

According to the present invention, by setting the surface temperature of the growth portion of the quartz glass ingot to 2000 ° C. or higher, a synthetic quartz glass having good ultraviolet resistance and high transmittance can be produced.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a synthetic quartz glass manufacturing apparatus.

FIG. 2 is a graph showing a surface temperature distribution of synthetic quartz glass in Example 4 and Comparative Example 2.

FIG. 3 is a graph showing the internal transmittance at 193.4 nm of the synthetic quartz glass obtained in Example 4 and Comparative Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chamber 2 Burner 3 Synthetic quartz glass ingot 4 Ingot passage 5 Window for surface temperature measurement 6 Infrared radiation thermometer 7 Auxiliary burner

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[Procedure amendment]

[Submission date] December 6, 2000 (200.12.
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

By incorporating hydrogen molecules at a high concentration in quartz glass, the generated absorption defects are complemented by the following formula, and converted into bonds that do not show absorption near the light source wavelength of the stepper. .

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

According to the present invention, it is possible to produce a synthetic quartz glass having good ultraviolet resistance and high transmittance by utilizing the above method.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0051

[Correction method] Change

[Correction contents]

Next, an ArF excimer laser was applied at the same position on the sample at an energy density of 20 mJ / cm ² p to 2 × 1.
0 ⁷ pulses were measured at the same time transmission and irradiation. As a result, the decrease in internal transmittance at 193.4 nm was 1.0% at the maximum. Table 1 shows the above results.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03F 1/14 G03F 1/14 B (72) Inventor Kazuo Shiroda 28 Nishifukushima, Kazagusuku-mura, Nakakushiro-gun, Niigata Prefecture -1 Shin-Etsu Chemical Co., Ltd. Precision Functional Materials Laboratory F-term (reference) 2H095 BC27 4G014 AH11 AH12

Claims (4)

[Claims] An oxygen gas, a hydrogen gas and a raw material gas for producing silica are supplied from a burner to a reaction zone. In this reaction zone, silica fine particles are generated by flame hydrolysis of the raw material gas for producing silica, and can be rotated into the reaction zone. In the method for producing a synthetic quartz glass in which the silica fine particles are deposited and melted on a synthetic quartz glass ingot arranged in the above, a surface temperature of a growth portion of the synthetic quartz glass ingot is set to 2000 ° C. or more. Characteristic method for producing synthetic quartz glass. 2. An oxygen gas, a hydrogen gas, and a raw material gas for producing silica are supplied from a burner to a reaction zone. In this reaction zone, silica fine particles are generated by flame hydrolysis of the raw material gas for producing silica, and the reaction zone can be rotated. In the method for producing a synthetic quartz glass in which the silica fine particles are deposited on a synthetic quartz glass ingot disposed in the above and melted to grow the quartz glass, the surface temperature of a growth portion of the synthetic quartz glass ingot is maintained uniformly. The method for producing a synthetic quartz glass according to claim 1. 3. The method for producing synthetic quartz glass according to claim 1, wherein the surface temperature of the growth portion of the synthetic quartz glass ingot is controlled using a secondary heat source such as an auxiliary burner. 4. The method for producing synthetic quartz glass according to claim 1, wherein a fluorine compound gas is supplied from the raw material supply section together with the raw material gas for producing silica.