JP2000063128A - Method and apparatus for producing synthetic quartz glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for producing a synthetic quartz glass by which a high homogeneity of the ingot is kept and the yield is improved. SOLUTION: A raw material gas, a combustion-supporting gas and combustible gas are ejected from a burner 7 installed in the upper part of a furnace 2 to produce flame. A synthetic quartz glass ingot IG is formed at the upper part of a target 5 installed in the space of the furnace 2. The gas jetting angle of the burner 7 is changed periodically in the prescribed plane. The flame is regulated so as to strike the synthetic face S of the ingot IG thoroughly to uniform the temperature profile on the synthetic face S.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a photolithography technique of 400 nm or less, preferably 300 nm.
The present invention relates to a method and an apparatus for producing synthetic quartz glass used in optical systems such as lenses and mirrors in the following specific wavelength bands.

[0002]

2. Description of the Related Art Conventionally, an exposure apparatus called a stepper has been used in an optical lithography technique for exposing and transferring a fine pattern of an integrated circuit on a wafer such as silicon. The light source of this stepper is a g-line (436 nm) to an i-line (365 n) with the recent high integration of LSI.
m), and further KrF (248 nm) and ArF (193n)
m) Shorter wavelengths are being promoted to excimer lasers. Optical glass used as an illumination system or a projection lens of such an excimer laser stepper has a low light transmittance in a wavelength region shorter than the i-line. Therefore, synthetic quartz glass or fluorite (CaF It has been proposed to use fluoride single crystals such as ₂ ).

Quartz glass used as an optical element for this ultraviolet lithography is required to have a high transmittance of ultraviolet rays, a high homogeneity of a refractive index, and a large diameter. Generally, in the production of synthetic quartz glass, a silicon compound gas and a combustion-supporting gas / combustible gas are ejected from a burner installed with the ejection port facing the upper surface of the target to generate a flame, and the synthetic quartz glass ingot is formed on the upper surface of the target. The flame hydrolysis method of depositing and forming is used. Further, in order to form an ingot having a highly uniform refractive index in such a flame hydrolysis method, it is necessary to make the temperature distribution on the synthesis surface uniform. For this reason, it is common practice to swing the ingot in a plane perpendicular to the central axis of the burner during synthesis so that the flame hits the synthesis surface evenly.

Further, during synthesis, the SiO ₂ powder which is not taken in by the formation of the ingot and is scattered in the furnace adheres to the inner wall of the furnace and grows, so that the distance between the ingot and the inner wall of the furnace gradually decreases. When swinging the ingot as described above, the distance is further reduced, but in order to prevent interference between the two, it is necessary to lower the temperature in the furnace during the synthesis to drop the deposits (manual work). There is.

[0005]

However, when the deposits are removed during the synthesis, the homogeneity of the refractive index of the ingot may be deteriorated because the synthesis conditions change during the synthesis. In addition, the powder of the deposits scattered in the furnace due to the work of removing the deposits often falls on the synthetic surface to form bubbles, and the part containing such bubbles cannot be used as the glass material of the lens. Since it disappeared, the yield rate of ingots was reduced.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a synthetic quartz glass manufacturing method and apparatus capable of maintaining a high homogeneity of an ingot and improving a good product rate. And

[0007]

In order to achieve the above object, a method of manufacturing synthetic quartz glass according to the present invention is directed from a burner installed at the top of a furnace toward a target arranged in a space inside the furnace. In the method for producing synthetic quartz glass, in which a silicon compound gas, a combustion-supporting gas, and a flammable gas are ejected to generate a flame, and a synthetic quartz glass ingot is formed on the upper surface of the target, the gas ejection angle of the burner is changed. While forming the ingot. Here, the gas ejection angle of the burner may be changed within a predetermined plane (for example, the tilting plane in the embodiment), but it is more preferable if the tilt angle of this predetermined plane can be set arbitrarily.

The apparatus for carrying out the above method includes a furnace, a target arranged in a space inside the furnace (for example, the furnace inner space 3 in the embodiment), and a gas jet supported by an upper portion of the furnace. A synthetic quartz that has a burner whose outlet is directed to a target, ejects a silicon compound gas, a combustion-supporting gas, and a flammable gas from the burner to generate a flame, and forms an ingot of synthetic quartz glass on the upper surface of the target. A glass manufacturing apparatus includes burner supporting means (for example, the burner supporting apparatus 6 in the embodiment) that is attached to an upper portion of a furnace to support a burner and change a gas ejection angle of the burner.

According to such a method and apparatus, the temperature of the composite surface is controlled by periodically changing the gas ejection angle of the burner and uniformly applying the flame generated by the gas ejected from the burner to the composite surface. Since the distribution can be made uniform, it is possible to form an ingot having a highly uniform refractive index without rocking the ingot as in the conventional case. Since there is no need to swing the ingot in this way, the distance between the ingot and the deposit on the inner wall of the furnace can be maintained sufficiently, and the work of removing the deposit is unnecessary. As a result, the temperature in the furnace is not lowered and the synthesis conditions do not change during the synthesis, so that the homogeneity of the ingot can be improved. Also, since the work of removing the adhered material itself is not required, there is no need to interrupt the synthesis, improving workability, and since the powder of the adhered material is not scattered and the ingot is not defective, the yield rate of the ingot is good. Is improved. In addition,
It is preferable to rotate the target in the horizontal plane while changing the gas ejection angle of the burner because the effect of making the temperature distribution on the combined surface uniform is improved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a synthetic quartz glass manufacturing apparatus (hereinafter simply referred to as a manufacturing apparatus) 1 according to the present invention. The furnace 2 of the manufacturing apparatus 1 is configured to have a furnace frame 2a and a fireproof wall 2b attached to the inside thereof, and a furnace space 3 surrounded by the fireproof wall 2b is a cylinder extending vertically. I am in a shape. Inside the cylindrical furnace space 3, there is provided a turntable 4 including a vertically extending support rod 4a and a horizontal disk 4b attached to the upper end of the support rod 4a. It is attached so as to substantially coincide with the central axis AX of 3. By rotating the support bar 4a around the axis, the horizontal disk 4b can be rotated in the horizontal plane. On the upper surface of the horizontal disc 4b is placed a target 5 which is made by vertically stacking several vertically extending ceramic cylinders.

A burner support device 6 is provided above the furnace 2, and the burner support device 6 causes the burner 7 to operate.
Are supported with the gas ejection port facing the furnace interior space 3. Although not shown, the burner 7 has a multi-tube structure having a plurality of concentric circular ejection ports. The raw material ejection pipe located at the center of the burner 7 dilutes the raw material silicon tetrachloride (SiCl ₄ ). A silicon compound gas containing a carrier gas (usually oxygen gas) is ejected, and a combustion-supporting gas (eg oxygen gas) and a flammable gas (eg hydrogen gas) are emitted from a plurality of ejection pipes located outside the raw material ejection pipe. ) Is to be spouted.

The burner supporting device 6 comprises a slider supporting portion 1 mounted above a furnace 2 as shown in FIGS.
0, and a lower slider 20 and an upper slider 30 provided above the slider supporting portion 10. The hemispherical slider support portion 10 is fixed to the upper portion of the furnace frame 2a, and the outer peripheral surface 11 is formed in a spherical shape centered on a fixed point P in the furnace space 3 (therefore, the slider support portion). The central axis of 10 is on the central axis AX of the furnace space 3).
Further, the slider support portion 10 has a vertical through hole 12 (the through hole 12 also penetrates the furnace 2) in the vertical direction, and the outer peripheral surface 11 has two curved parallel shapes. The rails 13 are provided at symmetrical positions with an arc passing through the apex on the outer peripheral surface 11 interposed therebetween (however, the rails 13 have through holes 12).
Has been divided by the middle).

The lower slider 20 has an inner peripheral surface 21 and an outer peripheral surface 22 formed in a spherical shape having a fixed point P as a center, and is formed in a circular arc passing through the apex of the outer peripheral surface 22 so as to penetrate the front and back surfaces. It has a long hole 23. Two curved rails 24 parallel to each other are provided on the outer peripheral surface 22 at symmetrical positions with the elongated hole 23 interposed therebetween, while on the inner peripheral surface 21, the rails 24 are parallel to each other so as to be orthogonal to the rail 24. Two curved rail grooves 25 are formed at symmetrical positions across an arc passing through the apex of the inner peripheral surface 21 (however, the rail groove 25 is divided in the middle by the elongated hole 23). The lower slider 20 is attached by fitting the rail groove 25 to the rail 13 of the slider support portion 10, and can be slid along the rail 13 of the slider support portion 10 by being driven by a servo mechanism (not shown). There is.

The upper slider 30 has an inner peripheral surface 31 and an outer peripheral surface 32 formed in a spherical shape centered on a fixed point P. The inner peripheral surface 31 has two curved rail grooves parallel to each other. 33 are formed at symmetrical positions with an arc passing through the apex on the inner peripheral surface 31 being sandwiched. The upper slider 30 is attached by fitting the rail groove 33 to the rail 24 of the lower slider 20, and can be slid along the rail 24 of the lower slider 20 by being driven by a servo mechanism (not shown) ( Therefore, the slide movement locus of the upper slider 30 is always orthogonal to the slide movement locus of the lower slider 20).

The burner 7 is attached to the upper slider 30 so as to penetrate therethrough. There is. Since the central axis 7a of the burner 7 is attached so as to be perpendicular to the outer peripheral surface 32 (or the inner peripheral surface 31) of the upper slider 30, the central axis 7a is attached to the lower slider 20 and the upper slider 3.
It always passes through the fixed point P regardless of the position of 0.

The lower slider 20 can be slid from the neutral position to any tilt angle, and the upper slider 30 can be reciprocally slid around the neutral position at any tilt angle. It has become. Here, the neutral position of the lower slider 20 is a position where the central axis of the lower slider 20 coincides with the central axis AX in the furnace, and the neutral position of the upper slider 30 is the lower slider 2.
Regardless of the position of 0, the center axis 7a of the burner 7 is located in the vertical plane. Therefore, the lower slider 20 is slid to a predetermined tilt angle and fixed, and in this state, the upper slider 30 is reciprocally slid at a predetermined tilt angle so that the gas ejection direction of the burner 7 always includes a fixed point P. It is possible to periodically change the tilt in a plane (hereinafter referred to as a tilting surface). Further, the tilt angle of the tilt surface can be set to an arbitrary angle by changing the tilt angle of the lower slider 20.

The upper slider 30 and the lower slider 20
Although the range of the tilting angle depends on the shapes of the slider support portion 10 and the upper and lower sliders 20 and 30, etc., in the present embodiment,
The tilt angle of the lower slider 20 is 20 degrees on each side from the neutral position (of the lower slider 20) (shown in FIG. 1, displacement in the plane of the drawing),
Further, the tilt angle of the upper slider 30 is configured to be 20 degrees on each side from the neutral position (of the upper slider 30) (not shown, but displaced in a plane perpendicular to the paper surface in FIG. 1). FIG. 3 shows a state in which the tilt angle of the upper slider 30 is 0 degree and the lower slider 20 is tilted to a tilt angle of 20 degrees.

When the synthetic quartz glass is manufactured using the manufacturing apparatus 1 having the above-mentioned structure, the silicon compound gas, the combustion-supporting gas and the combustible gas are jetted from the burner 7 toward the upper surface of the target 5 to generate a flame. A synthetic quartz glass ingot IG is formed on the upper surface of the target 5 by generating and causing a hydrolysis reaction. Here, the lower slider 20 is slid and fixed to an arbitrary tilt angle (however, within 20 degrees from one side of the neutral position of the lower slider 20) and fixed, and the upper slider 30 is tilted to an arbitrary predetermined tilt angle (however, the neutral position of the upper slider 30 is neutral). Make a reciprocating slide motion within 20 degrees from one side)
The gas ejection angle of the burner 7 is periodically changed. During the formation of the ingot IG, the turntable 4 is rotated in the horizontal plane at a constant speed, and the ingot I
It is pulled down at a speed commensurate with the amount of G formed in the vertical direction.

By periodically changing the gas ejection angle of the burner 7 (the tilt angle of the central axis 7a) as described above, the flame produced by the gas ejected from the burner 7 is evenly distributed on the synthetic surface S. As it hits, the composite surface S
The temperature distribution can be made uniform. Therefore, an ingot IG having a highly uniform refractive index can be obtained without rocking the ingot IG as in the conventional case. In the present invention, since it is not necessary to swing the ingot IG in this way, the ingot IG and the refractory wall 2b in the furnace 2 are
It is possible to keep a sufficient distance from the adhered matter 8 that has reached the surface, and the work of removing the adhered matter is unnecessary. As a result, the temperature in the furnace 2 is not lowered and the synthesis conditions do not change during the synthesis, so that the homogeneity of the ingot IG can be improved. Further, since the work of removing the adhered matter itself is not required, it is not necessary to interrupt the synthesis, the workability is improved, and the powder of the adhered matter 8 is not scattered to cause the ingot IG to be defective. The rate of non-defective products is improved. As described above, it is preferable to rotate the target 5 in the horizontal plane while changing the gas ejection angle of the burner 7 because the effect of making the temperature distribution of the combined surface S uniform can be improved.

The above-described manufacturing apparatus 1 has the lower slider 2
Since there are two sliders, 0 and the upper slider 30, it is possible to set the inclination angle of the tilting surface of the burner 7 to any angle, but for example, the lower slider 20 is not provided and the burner is not provided. It does not matter even if the tilting surface of 7 is fixed.

Next, an example in which a synthetic quartz glass ingot IG is formed by using the manufacturing method according to the present invention will be described.
A comparative example using the conventional manufacturing method is also shown. From these examples and comparative examples, it is understood that the non-defective product rate is improved by the present invention. The manufacturing apparatus 1 described above is used in both the example and the comparative example, but in the comparative example, the central axis 7a of the burner 7 is aligned with the central axis AX (vertical axis) of the furnace space 3 and fixed. The rotary table 4 was made swingable in the horizontal direction, and the rotary table 4 was set to be equivalent to a conventional manufacturing apparatus.

[0022]

EXAMPLE In the manufacturing apparatus 1 in which the inner diameter of the furnace space 3 is 600 mm, the central axis of the support rod 4a of the turntable 4 is aligned with the central axis AX of the furnace space 3, and the lower slider 20 is moved from its neutral position. In a state where the upper slider 30 is slid at a tilt angle of 3.4 degrees and is fixed, the upper slider 30 is tilted with a tilt angle of ± from the neutral position.
The silica glass ingot IG was synthesized by the flame hydrolysis method while performing reciprocal sliding movement at 13.5 degrees for one cycle of 90 seconds and periodically changing the ejection direction of the burner 7. As a result, a synthetic quartz glass ingot IG having a diameter of 400 mm and a length of 500 mm was formed, and the distance between the ingot IG and the deposit 8 on the fireproof wall 2b after the synthesis was 100 mm at the shortest. It should be noted that it was not necessary to perform the work of removing the adhering substances once from the start to the end of synthesis.
The yield rate of the ingot IG was 68.0%.

[0023]

[Comparative Example] In the same manufacturing apparatus 1 as the above embodiment (inner diameter of the furnace space 3 is 600 mm), the central axis 7a of the burner 7 is fixed to the central axis AX of the furnace space 3 and fixed, and the rotary table 4
The center axis of the support rod 4a was set to be offset from the center axis 7a of the burner 7 by an offset amount (offset amount) of 15 mm. Then, the quartz glass ingot IG was synthesized by the flame hydrolysis method while swinging the target 5 with a swing width of 120 mm and a swing cycle of 90 seconds. As a result, the diameter is 400m
A synthetic quartz glass ingot IG having a length of m and a length of 500 mm was formed, and the distance between the ingot IG and the deposit 8 on the fireproof wall 2b after the synthesis was 38 mm at the shortest. It should be noted that the first deposit removal was performed when the quartz glass had grown 182 mm from the start of the synthesis, and then the second deposit removal was performed when the quartz glass had grown 365 mm. In this case, the distance between the ingot IG and the deposit is about 5 mm.
I went when. The silica glass with a total length of 168 mm became defective due to bubbles and strong striae that were mixed in the two times of dropping the adhered material, and the non-defective product ratio for the ingot IG length was 3
It was 4.4%.

[0024]

As described above, according to the method and apparatus for manufacturing synthetic quartz glass according to the present invention, the flame generated by the gas ejected from the burner by periodically changing the gas ejection angle of the burner. Since the temperature distribution on the composite surface can be made uniform by evenly applying to the composite surface, it is possible to form an ingot having a highly uniform refractive index without swinging the ingot as in the conventional case. . Since there is no need to swing the ingot in this way, the distance between the ingot and the deposit on the inner wall of the furnace can be maintained sufficiently, and the work of removing the deposit is unnecessary. This will not lower the temperature in the furnace,
Since the synthesis conditions do not change during the synthesis, the homogeneity of the ingot can be improved. Also, since the work of removing the adhered material itself is not required, there is no need to interrupt the synthesis, improving workability, and since the powder of the adhered material is not scattered and the ingot is not defective, the yield rate of the ingot is good. Is improved. It is preferable to rotate the target in the horizontal plane while changing the gas ejection angle of the burner because the effect of making the temperature distribution on the combined surface uniform can be improved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the configuration of a synthetic quartz glass manufacturing apparatus according to the present invention.

FIG. 2 is a perspective view showing a configuration of a burner support device.

FIG. 3 is a schematic cross-sectional view of the vicinity of a burner support device showing a state where the lower slider is slid to tilt the burner.

[Explanation of symbols]

1 Synthetic quartz glass manufacturing equipment 2 furnaces 3 In-furnace space 4 turntable 5 targets 6 Burner support device (burner support means) 7 burners IG Ingot

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroki Jimbo             Marunouchi 3 2-3 No. 3 shares, Chiyoda-ku, Tokyo             Ceremony Company Nikon F-term (reference) 4G014 AH15

Claims (6)

[Claims] 1. A target produced by injecting a silicon compound gas, a combustion-supporting gas and a combustible gas from a burner installed in the upper part of a furnace toward a target arranged in the space inside the furnace to generate a flame. A method for producing synthetic quartz glass, which comprises forming an ingot of synthetic quartz glass on an upper surface of the substrate, wherein the ingot is formed while changing a gas ejection angle of the burner. 2. The method for producing synthetic quartz glass according to claim 1, wherein the gas ejection angle of the burner is changed within a predetermined plane. 3. The method for producing synthetic quartz glass according to claim 2, wherein the inclination angle of the predetermined plane can be set arbitrarily. 4. The method for producing synthetic quartz glass according to claim 1, wherein the target is rotated in a horizontal plane. 5. A furnace comprising a furnace, a target disposed in a space inside the furnace, and a burner supported by an upper portion of the furnace and having an ejection port directed toward the target. In a synthetic quartz glass manufacturing apparatus for generating a flame by ejecting a combustion-supporting gas and a combustible gas, and forming an ingot of synthetic quartz glass on the upper surface of the target, the burner attached to the upper portion of the furnace An apparatus for producing synthetic quartz glass, comprising burner supporting means for supporting and changing a gas ejection angle of the burner. 6. The apparatus for manufacturing synthetic quartz glass according to claim 5, wherein the target is rotated in a horizontal plane.