JPH11171561A - Apparatus for producing synthetic quartz glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an apparatus for producing synthetic quartz glass capable of producing an ingot of synthetic quartz glass having quality stable from the beginning to the end of synthesis and lessening the state change during synthesis. SOLUTION: A revolving shaft 22 is supported by a revolving shaft supporting member 27 held on a freely liftable stage 30. This revolving shaft supporting member 27 is so formed that the angle of inclination of the revolving shaft supporting member 27 with respect to the stage 30 may be adjusted by turning upper adjusting screws 36a, 26b... by upper inclination controllers 25a, 25b.... The adjustment of the angle of inclination is executed in accordance with the angle of inclination of the revolving shaft 22. The detection of the angle of inclination is executed by irradiating a mirror 28 mounted at the revolving shaft 22 with a laser emitted from a laser irradiation device 19 and detecting the position of the reflected laser beam by a two-dimensional position detector 29.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a quartz glass optical member for ultraviolet lithography used in an optical system such as a lens or a mirror in a specific wavelength band of 400 nm or less, preferably 300 nm or less in an optical lithography technique. The present invention relates to a synthetic quartz glass manufacturing apparatus.

[0002]

2. Description of the Related Art Conventionally, in an optical lithography technique for exposing and transferring a fine pattern of an integrated circuit on a wafer such as silicon, an exposure apparatus called a stepper is used.
The light source of this stepper has been shortened in wavelength from g-line (436 nm) to i-line (365 nm) and further to KrF (248 nm) and ArF (193 nm) excimer lasers with the recent high integration of LSIs. I have.

VLSI (ultra LSI) which is a kind of LSI
Among them, DRAM is an example, LSI to VLSI
1K → 256K → 1M → 4
The capacity increases in the order of M → 16M → 64M → 256M → 1G. With such an increase in capacitance, the processing line width of the pattern is 10 μm → 2 μm → 1 μm → 0.8 μm →
There has been a demand for a stepper capable of exposing a fine line width of 0.5 μm → 0.35 μm → 0.25 μm → 0.18 μm.

For this reason, a projection lens of a stepper requires a high resolution and a large depth of focus. In general, a multi-component optical glass having a high transmittance is mainly used for i-line as a lens material used for illumination or a projection optical system of a stepper, and a conventional optical glass is used for a stepper using a KrF or ArF excimer laser as a light source. Instead, a single crystal of fluoride such as synthetic quartz glass or CaF ₂ (fluorite) is used.

[0005] In particular, a mass production line for a macro processor or the like used as a large-capacity VRAM of 16 M or more has a capacity of 0.3.
A stepper using an excimer laser capable of performing exposure with a line width of 25 μm has been introduced. Ultraviolet lithography optical elements (lens materials used for illumination or projection optics) used in steppers capable of such fine line width exposure require high purity in order to achieve high transmittance in the ultraviolet region. Synthetic quartz glass is used.

[0006] As one of useful methods for producing this synthetic quartz glass, a flame hydrolysis method is known. The flame hydrolysis method is a synthesis method in which a silicon compound, which is a raw material of synthetic quartz glass, is supplied together with an oxyhydrogen flame into a flame from a combustion burner, and a hydrolysis reaction is performed to synthesize and deposit silica fine particles, and at the same time, a fusion vitrification is performed. It is.

The apparatus for producing synthetic quartz glass which realizes this synthesis method has a structure similar to a so-called Bernoulli furnace, in which the outer wall is double-walled so that heat is not released, the exhaust is passed, and the furnace temperature is set to 1000 ° C. or higher. The synthesis is carried out while maintaining the temperature at a high level. This manufacturing apparatus is configured by assembling a refractory (refractory member) inside a furnace (furnace frame), and a target for forming an ingot installed on the refractory (a refractory member). And a burner.

The target is provided on a stage which is vertically movable in a vertical direction, and the stage is lowered at the same speed as the growth speed of the quartz glass to keep the distance between the burner and the synthetic surface of the quartz glass constant. To keep it. Further, in order to uniformly supply the flame temperature (heat supply amount) from the burner to the synthetic surface of the quartz glass, the target is rotated and rocked during the synthesis of the quartz glass.

[0009] Quartz glass synthesized using the synthetic quartz glass manufacturing apparatus configured as described above is manufactured under various synthesizing conditions.
There are a supply gas amount, a raw material supply amount, a target swing pattern, a rotation speed, and the like. Then, when synthesizing quartz glass, the synthesis is started under the optimum synthesis conditions obtained based on past results. Maintaining the synthesis conditions at the start of synthesis during synthesis is an important factor for obtaining an optical glass usable as an optical element for ultraviolet lithography.

[0010] The synthetic quartz glass manufacturing apparatus comprises a furnace and an elevating system, and the furnace and the elevating system are configured to be separable and are separately installed on the floor. The lifting system supports the stage so as to be able to move up and down, and the target is rotatably arranged on the stage in the lifting system. For this reason, at the start of the synthesis, the furnace and the elevating system are aligned, and various conditions for the synthesis are set to be in an optimum state, so that the quartz glass to be synthesized does not have a non-uniform refractive index.

In the synthetic quartz glass manufacturing apparatus, maintenance may be performed by separating the furnace and the elevating system after synthesizing the quartz glass, but after such separation, alignment of the furnace and the elevating system is performed again. Need to do. For this reason, in order to easily perform the re-alignment, a tray having a V-shaped groove on which the support legs for supporting the lifting / lowering system can be placed is fixed to the floor surface, and the support legs are placed on the tray. By doing so, the furnace and the elevating system are aligned.

The applicant has been disclosed in Japanese Patent Application Laid-Open No. 7-53226 so that such alignment can be performed more appropriately and promptly, and the vertical alignment of the rotating shaft can be easily performed. The proposed apparatus for manufacturing quartz glass is as follows. In order to accurately align the burner with the target rotation axis, this quartz glass manufacturing device irradiates a laser to a mirror fixed to the burner and measures the position of the reflected laser to determine the position of the burner. The burner and the rotation axis of the target are aligned using an optical axis of a laser fixed to a floor supporting the furnace.

[0013]

However, during the synthesis of quartz glass, the weight of the ingot IG changes (increases in weight) as the synthetic quartz glass is deposited. As shown in FIG. 3, when the stage 30 is configured to be supported on one side with respect to the elevating system 8, the amount of deflection of the stage 30 due to the difference in weight generated in the ingot between the start of synthesis and the end of synthesis. ω changes. For this reason, the rotating shaft 2
2 changes, and the rotation axis of the rotation shaft 22 is no longer coaxial with the start of the synthesis, so that the relative positional relationship between the burner 7 and the ingot IG in the horizontal direction is shifted.

In the synthetic quartz glass manufacturing apparatus configured to hold the stage 30 on one side as described above, the load is set to W, the Young's modulus of the material is set to E, the distance from the end point to the load point is set to L, Is the second moment of area of I, the deflection amount ω is ω = WL ³ / 24EI. The tilt angle δ of the rotation axis (target) 22 is
δ = WL ² / 8EI.

That is, since the magnitude of δ in one-sided support is proportional to the load W, the inclination angle δ of the rotating shaft 22 increases as the weight of the ingot increases, and the relative position of the burner and the target in the horizontal direction at the start of the synthesis is increased. Even if is adjusted to optimal conditions,
In the latter half, synthesis was performed under different conditions, and there was a problem that the refractive index homogeneity was changed between the upper and lower portions of the synthesized ingot.

The present invention has been made in view of such problems and circumstances, and has reproducibility of conditions for synthesizing quartz glass, and provides a synthetic quartz glass of stable quality from the start to the end of synthesis. It is an object of the present invention to provide a synthetic quartz glass manufacturing apparatus capable of manufacturing an ingot and reducing a change in state during synthesis.

[0017]

In order to achieve the above object, a synthetic quartz glass manufacturing apparatus according to the present invention comprises a furnace, a target for manufacturing a synthetic quartz glass, and a horizontally rotatable target. And a burner for synthesizing quartz glass, and a lifting mechanism.
The target is held by the elevating stage and located in the space inside the furnace, the rotating shaft extends vertically and is rotatably supported by the elevating stage, and the burner for synthesizing quartz glass is installed with the spout facing the target. ing. The lifting mechanism raises and lowers the lifting stage to raise and lower the target with respect to the burner in the vertical direction.

Further, the synthetic quartz glass manufacturing apparatus is provided with a positioning mechanism, which adjusts the inclination angle of the elevating mechanism with respect to the vertical direction and the inclination angle of the rotating shaft with respect to the elevating stage, thereby controlling the center axis of the burner. And the center axis of the rotary shaft. Note that this alignment is performed based on the inclination angle of the rotation axis with respect to the vertical direction detected by the rotation axis inclination detector.

According to the synthetic quartz glass manufacturing apparatus configured as described above, when the rotating shaft is inclined together with the elevating stage due to the bending and the like of the elevating stage, the rotating shaft is moved with respect to the elevating stage. By adjusting the inclination angle, the rotation axis can be maintained vertically.

In the apparatus for manufacturing synthetic quartz glass according to the present invention, a rotation axis tilting mechanism is provided to detect the tilt angle detector so that the rotation axis always extends in the vertical direction regardless of the tilt of the elevating stage. It is preferable that the rotation axis is inclined with respect to the lifting stage based on the value. In such a configuration, if the vertical movement of the elevating mechanism is adjusted at the start of the synthesis, even if the elevating stage is bent during the synthesis, the rotation axis tilt mechanism tilts the rotating shaft with respect to the elevating stage. Since the angle is adjusted, it is possible to always keep the rotation axis vertical during the synthesis and maintain the relative positional relationship between the burner and the synthesis surface constant.

In the above synthetic quartz glass manufacturing apparatus, the laser irradiator, the reflecting mirror for reflecting the laser light emitted from the laser irradiator, and the light receiving position for receiving the laser light reflected by the reflecting mirror are provided. It is preferable to detect the inclination angle of the rotation axis with respect to the vertical direction using a rotation axis inclination detector constituted by a detector. Here, the laser irradiator irradiates the laser beam in the vertical direction, and the reflecting mirror is fixed to the rotation axis and reflects the laser beam. The light receiving position detector detects the displacement of the two-dimensional position of the received laser light to detect the inclination angle of the rotation axis.

By using the rotary shaft tilt detector having the above-described structure, the tilt angle of the rotary shaft can be detected without contact with the rotary shaft. Even in the case of ascending and descending, accurate detection of the inclination angle of the rotating shaft can be performed.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the synthetic quartz glass manufacturing apparatus of the present invention will be described below with reference to FIG. The synthetic quartz glass manufacturing apparatus 1 has a furnace including a furnace frame 3, a refractory 4 provided in the furnace frame 3, and a hearth plate 2 on which the furnace frame 3 and the refractory 4 are placed. It is configured. Inside the refractory 4, a target 5 for forming an ingot IG and a burner 7 for synthesizing quartz glass which is installed with the ejection port 6 facing the target 5 are provided. Are synthesized and deposited.

The furnace frame 3 is provided with an exhaust port 12 for discharging exhaust gas generated in the inner peripheral space 11 of the furnace frame 3 during synthesis of quartz glass to the outside.
An exhaust pipe 13 is connected to 2. In the exhaust pipe 13,
Scrubber and other abatement equipment, exhaust fan (both not shown)
And is configured to discharge exhaust gas to the atmosphere.

Further, the refractory 4 and the furnace frame 3 include:
A furnace monitoring window 41 for observing the inside of the inner peripheral space 11 from outside is formed. Outside the furnace monitoring window 41, a heat-resistant glass 42 is attached with a gap that can maintain the temperature inside the furnace so as not to decrease. Further, a furnace monitoring camera 14 such as a CCD camera is provided behind (outside) the heat-resistant glass 42 so as to capture an image of the inner peripheral space 11, in particular, a distance between the burner 7 and a synthetic surface of synthetic quartz glass. It is configured so that it is possible to take a picture that can be grasped.

The target 5 is raised / lowered (only lowered during synthesis) by a lifting / lowering system (raising / lowering mechanism) 8. This lifting / lowering system 8 is formed separately from the furnace and separated from the furnace. It is configured to be possible. The elevating system 8 includes a base 25
A pillar 23 extending vertically (up and down) above
And a rail 16 composed of two rail members attached to the column 23, and an elevating member 33 arranged to be vertically movable by the rail 16.

The elevating member 33 is connected to the center axis (2
Precision ball screw 17 installed between two rail members)
It is configured to be able to move up and down by rotating
The precision ball screw 17 is rotationally driven by a lifting / lowering motor 18 attached to a column 23.

The lifting system 8 is configured so that the inclination angle can be adjusted. This adjustment is performed by adjusting the inclination angle of the base 25 by moving the lower adjustment screws (support legs) 21a, 21b,... The lower adjustment screws 21a, 21b are rotated by lower inclination controllers 24a, 24b.

The lower adjustment screws 21a, 21b,.
It is arranged at four places in front, back, left and right of the base 25, and is set on a tray 20 ... mounted on a floor (not shown),
In FIG. 2, for convenience of explanation, lower adjustment screws 21 a and 21 b and tray 20,
Only 20 is shown. And this lower adjustment screw 21
The a and 21b are rotated by the lower tilt controllers 24a and 24b, and extend and retract with respect to the base 25.

A stage (elevation stage) 30 is disposed on the elevating member 33 in the elevating system 8. The rotating shaft 22 is provided on the stage 30 so as to freely rotate, swing and move horizontally in the X and Y directions. The rotating shaft 22 is rotated by the rotating motor 9 and the swing is performed by the swing motor. 1
Done by 0. The rotating shaft 22 is supported by a rotating bearing (not shown) at two or more points in the vertical direction, and is rotated with the number of rotations controlled by the rotating motor 9.

Further, the rotation axis 22 can change the inclination angle with respect to the stage 30. On the upper surface of the stage 30, a rotating shaft support member 27 supported by upper adjustment screws 26a, 26b. This upper adjustment screw 26a,
26b also extend and contract with respect to the rotating shaft support member 27 by being rotated by the upper tilt controllers 25a, 25b. Therefore, the upper tilt controllers 25a, 25
By controlling the expansion and contraction of each of the upper adjustment screws 26a, 26b,... By 5b, the inclination angle of the rotation shaft support member 27 with respect to the stage 30 can be adjusted.

A rotary shaft holding hole 27a is formed at the center of the rotary shaft support member 27, and the rotary shaft 22 is held through the rotary shaft holding hole 27a. Therefore, by changing the inclination angle of the rotation shaft support member 27 with respect to the stage 30, the rotation shaft 2 with respect to the stage 30 is changed.
2 can change the falling angle.

The upper adjustment screws 26a, 26b...
The rotary shaft support member 27 is provided at four positions in front, back, left and right of the rotary shaft support member 27. However, in FIG.
, Only the upper adjustment screws 26a, 26b provided on one side of the upper tilt controller 25a, and the upper tilt controllers 25a, 25b... Also represent only the corresponding upper tilt controllers 25a, 25b.

In the lifting system 8 configured as described above, the vertical alignment of the rotary shaft 22 and the like (burner 7
Of the rotating shaft 22 with the center axis of the rotating shaft 22). In this alignment, first, a weight (not shown) is vertically dropped from above, and a laser beam is emitted from a He-Ne laser irradiator (hereinafter, referred to as “laser irradiator”) 19 so as to be parallel to the weight. To set the vertical reference. The tilt angle of the lifting system 8 is adjusted so that the laser beam from the laser irradiator 19 passes through the center of the target 5 and the center of the through-hole 22c provided at the center of the disk 22a.

The adjustment of the inclination angle of the lifting system 8 is performed by adjusting the lower adjustment screw 2 which is configured to be vertically expandable and contractable with respect to the base 25.
.. Are moved in the vertical direction to adjust the inclination angle of the base 25. That is, the laser beam emitted from the laser irradiator 19 is
And lower tilt controllers 24a, 24a so as to pass through the center of a through hole 22c provided at the center of the disk 22a.
.. are performed to adjust the inclination angle of the base 25.

The center of rotation of the rotating shaft 22 is the stage 3
The rotation shaft 22 is adjusted to X-
The alignment is performed by moving in the Y direction. Further, the laser beam from the laser irradiator 19 is used to align the central pipe of the burner 7, which is a straight pipe for injecting the raw material, so as to be coaxial and vertical. As described above, by performing each alignment, the target 5 can be vertically lowered with the deposition of the synthetic quartz glass.

In the synthetic quartz glass manufacturing apparatus 1 configured as described above, the Si compound gas as the raw material of the quartz glass and the combustion gas for heating are ejected from the ejection port of the burner 7 to thereby set the target in the flame. 5 can be synthesized and deposited on quartz glass. Here, at the time of synthesizing the quartz glass, the target 5 is lowered by rotating and swinging the target 5 and lowering the entire stage 30.

At the time of synthesizing such quartz glass, the weight of the ingot IG increases as the synthetic quartz glass accumulates as described above.
Changes, and the relative positional relationship between the burner 7 and the ingot IG in the horizontal direction shifts. Therefore, in the synthetic quartz glass manufacturing apparatus 1, as shown in FIG. 1, a mirror (reflecting mirror) 28 is disposed behind a disk portion 22a formed at the upper end of the rotating shaft 22, and the mirror 28 is provided with a laser. Irradiator 19
The two-dimensional position detector (light receiving position detector) 29 detects the position of the reflected light by irradiating a laser beam from the laser beam to detect the tilt angle δ of the rotating shaft 22.

As the mirror 28, a so-called half mirror is used. Half of the laser light emitted from the laser irradiator 19 passes through the mirror 28 and reaches the central tube of the burner 7, and the other half is reflected. Then, it reaches the two-dimensional position detector 29. This two-dimensional position detector 29
For example, a semiconductor position detector (PSD), a four-division photodiode, or the like is used to detect a two-dimensional position of incident laser light. Further, since the inclination angle of the half mirror is ≒ 0 and the thickness is very thin, the shift of the transmitted light enters the error region and can be regarded as linear light.

The laser beam emitted from the laser irradiator 19 is used to align the burner 7 and the elevating system 8 with each other.
It is irradiated vertically upward through 2c. The mirror 28 has a reflecting surface obliquely disposed so that the reflected laser beam is directed to the two-dimensional position detector 29. The mirror 28 is vertically aligned and the rotation axis with respect to the lifting system 8. The reflected light arrives in a state where the alignment in the vertical direction 22 is performed.

Here, when the rotation axis 22 is inclined, the incident angle and the reflection angle of the laser light with respect to the mirror 28 change, and the incident position of the laser light on the two-dimensional position detector 29 changes. Therefore, when the quartz glass is synthesized after the vertical alignment of the lifting / lowering system 8 itself and the vertical alignment of the rotary shaft 22 with respect to the lifting / lowering system 8, the incident position of the laser beam on the two-dimensional position detector 29 is obtained. Is changed, it can be determined that the stage 30 bends due to the weight of the combined ingot IG and the rotary shaft 22 is tilted (falls down).

When the rotating shaft 22 is tilted in this manner, the conditions for synthesizing the quartz glass change, which causes a difference in the quality of the quartz glass to be synthesized. For this reason, in the synthetic quartz glass manufacturing apparatus 1, the two-dimensional position detector 2 during synthesis is used.
When the incident position of the laser beam in 9 is displaced from the incident position (origin) at the time of alignment adjustment, the inclination angle of the rotating shaft 22 is adjusted so that the incident light is again incident on the origin.

The adjustment of the tilt angle is performed by adjusting the tilt angle of the rotary shaft support member 27 with respect to the stage 30. This inclination angle adjustment is performed by controlling the expansion and contraction of each of the upper adjustment screws 26a, 26b... As described above.
The operation control of the upper tilt controllers 25a, 25b... for expanding and contracting the a, 26b.
This is performed based on the detection position (incident position) of the reflected light due to.

For example, in FIG. 1, when the rotary shaft 22 falls to the right due to the stage 30 bending downward to the right, the left upper tilt controller 25a is operated to reduce the left upper adjustment screw 26a. , Shortening the distance Ha between the stage 30 and the rotating shaft support member 27,
By operating the right upper tilt controller 25b to extend the right upper adjusting screw 26b to increase the distance Hb between the stage 30 and the rotary shaft support member 27, the tilt angle of the rotary shaft support member 27 is increased. After the adjustment, the rotating shaft 22 is returned vertically so that the reflected light is located at the origin of the two-dimensional position detector 29, and the rotating shaft 22 always extends in the vertical direction.

In the synthetic quartz glass manufacturing apparatus 1, the rotation shaft 22 is rocked during the synthesis by rocking the rotation shaft support member 27 by the rocking motor 10. The dynamic speed is low, and in FIG. 1, the through-hole 22c formed in the rotary shaft 22 is exaggerated for convenience of explanation. However, since the through-hole 22c is a so-called pinhole, 22
The inclination of the rotating shaft 22 can be detected even if the oscillating motion occurs.

In the synthetic quartz glass manufacturing apparatus 1 described above, when the two-dimensional position detector 29 is arranged so as to move up and down as the stage 30 moves up and down, the incident light at the two-dimensional position detector 29 is increased. The displacement of the light from the origin can be directly obtained as the inclination angle of the rotating shaft 22. Further, when the two-dimensional position detector 29 is mounted on a place such as a floor that does not move up and down with the up and down movement of the stage 30, the two-dimensional position detector 29 is moved with the up and down movement of the stage 30 even if the rotating shaft 22 is not inclined. Since the light receiving position changes, the displacement is determined in advance, and the rotation axis 2 is determined based on the deviation from the displacement.
What is necessary is just to obtain the inclination angle of 2.

In the above embodiment, the laser irradiator 19, the mirror 28 and the two-dimensional position detector 29 constitute a rotation axis tilt detector described in claims.
The upper adjustment screws 26a, 26b,... And the upper tilt controllers 25a, 25b,... Constitute a rotating shaft tilting mechanism described in the claims, and the rotating shaft tilting mechanism, the lower adjusting screws 21a, 21b. 24
a, 24b,... constitute a positioning mechanism described in the claims.

Therefore, in the apparatus for manufacturing synthetic quartz glass according to the present invention, it is not always necessary to use a rotation axis tilt detector using laser light, but a so-called gravity type tilt angle detection in which a potentiometer is operated by a weight. A container or the like may be used. Also, the lift stage 30 is not necessarily required.
The rotating shaft 2 is always rotated by the rotating shaft
There is no need to adjust the tilt angle of 2. For example, in a case where the stage 30 is not merely a flexure but is permanently deformed with respect to the elevating system 8 and the rotating shaft 22 is inclined,
The adjustment of the inclination angle of the rotary shaft 22 with respect to the stage 30 may be performed only at the time of alignment before the start of the synthesis.

[0049]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a synthetic quartz glass manufacturing apparatus 1 according to the present invention will be described below with reference to FIGS. In the synthetic quartz glass manufacturing apparatus 1, SiCl ₄ is used as a Si compound as a raw material.
O is used as a carrier gas for sending out the i-compound gas.
₂ gas and H ₂ gas is used. These are burned in a refractory 4 made of a material of 99.9% or more of alumina and heated to deposit synthetic quartz glass on a target 5 located in the refractory 4.

The openings on the lower surface of the furnace frame 3 and the refractory 4 on which the target 5 moves up and down are formed in a circular shape and are open. Further, in order to avoid contamination of the synthetic quartz glass with impurities, a plurality of discs having a diameter of 320 mm and made of a refractory material of 99.9% or more alumina are used as in the case of the refractory 4. And is mounted on a disk portion 22 a formed at the upper end of the rotating shaft 22 so that the rotating shaft 22 can receive the load.

The vertical adjustment of the lifting / lowering system 8 itself and the vertical alignment of the rotating shaft 22 with respect to the lifting / lowering system 8 are performed by expanding and contracting the lower adjusting screws 21a, 21b... And the upper adjusting screws 26a, 26b. Thereafter, while the rotation shaft 22 is rotated by the rotation motor 9 disposed on the stage 30, the swing motor 10 swings in a predetermined width in one axial direction, and the target 5 is rotated at the same speed as the synthetic speed of quartz glass. Lower at the speed of.

Thereafter, the position of the synthetic surface is confirmed from the furnace monitoring window 41, and the amount of gas from the burner 7 is changed to control the position of the synthetic surface to be constant, thereby synthesizing quartz glass. At this time, when the stage 30 is bent due to the weight of the synthesized quartz glass and the rotating shaft 22 is inclined, the upper adjustment screws 26a, 26b,.
Is expanded and contracted to perform vertical alignment of the rotating shaft 22 so that the synthesizing conditions are constant.

In the quartz glass ingot IG synthesized by performing the alignment of the rotating shaft 22 even during the synthesis as described above, a sample was taken after the synthesis and the homogeneity was measured by the oil-on-plate method. The homogeneity distribution in the radial direction between the lower part and the upper part of the ingot IG is Δn (difference in refractive index) = 1.4 to 1.6 × 1.
0 ^-6 , with little difference.

Also, after removing the synthesized ingot IG and performing each alignment again, the homogeneity of the synthesized ingot IG was measured in the same manner as described above. As a result, Δn = 1.5 to 1.8. × 10 ^-6 . Therefore, if the synthetic quartz glass manufacturing apparatus 1 according to the present invention is used, quartz glass that can be used as an optical element for ultraviolet lithography can be stably synthesized.

Note that Δn indicates a cylindrical member cut out from the ingot IG, or a lens-shaped optical member obtained by further processing the cylindrical member, viewed from the optical axis direction (growth direction of the ingot IG). The variation of the refractive index in the radial direction at that time is indicated by the difference between the maximum value and the minimum value.

[0056]

As described above in detail, the apparatus for manufacturing synthetic quartz glass of the present invention uses the rotation axis inclination angle with respect to the vertical direction detected by the rotation axis inclination detector.
The alignment mechanism adjusts the inclination angle of the lifting mechanism with respect to the vertical direction, and adjusts the inclination angle of the rotating shaft with respect to the lifting stage, thereby aligning the center axis of the burner with the center axis of the rotating shaft. .

Thus, when the weight of the combined ingot causes deflection or the like in the elevating stage and the rotating shaft is tilted together with the elevating stage, the tilt angle of the rotating shaft with respect to the elevating stage is adjusted. , The axis of rotation can be returned vertically. Therefore, since the alignment accuracy between the burner and the rotation axis of the target can be improved, the reproducibility of the alignment after separating the furnace and the elevating system after the synthesis of quartz glass can be improved, It is possible to repeatedly and efficiently produce stable, high-quality synthetic quartz glass having good homogeneity.

In the synthetic quartz glass manufacturing apparatus according to the present invention, a rotating shaft tilting mechanism is provided so that the rotating shaft always extends in the vertical direction regardless of the tilt of the lifting stage. It is preferable that the shaft is inclined. In such a configuration, if the vertical movement of the elevating mechanism is adjusted at the start of the synthesis, even if the elevating stage is bent during the synthesis, the rotation axis tilt mechanism tilts the rotating shaft with respect to the elevating stage. Since the angle is adjusted, it is possible to always keep the rotation axis vertical during the synthesis and maintain the relative positional relationship between the burner and the synthesis surface constant. Therefore, the difference in homogeneity between the upper and lower portions of the synthesized ingot can be reduced.

In the above synthetic quartz glass manufacturing apparatus, the rotation axis tilt detector is provided with a laser irradiator for irradiating laser light in the vertical direction, and a reflection means for fixing the rotation axis to reflect the irradiated laser light. A mirror and a light-receiving position detector that receives the laser light reflected by the reflecting mirror. The light-receiving position detector detects displacement of the two-dimensional position of the received laser light and detects the displacement angle of the rotation axis. Preferably, the detection is performed. With this configuration, it is possible to detect the inclination angle of the rotating shaft without contact with the rotating shaft, so that even when the rotating shaft is moved up and down by the elevating operation of the elevating system, accurate rotation of the rotating shaft can be performed. The inclination angle can be detected, and the occurrence of a detection error due to heat can be prevented.

[Brief description of the drawings]

FIG. 1 is a partially enlarged view showing the vicinity of a rotation axis in an elevating system of a synthetic quartz glass manufacturing apparatus of the present invention.

FIG. 2 is a schematic view showing the whole of the synthetic quartz glass manufacturing apparatus.

FIG. 3 is a schematic diagram showing an elevating system of the synthetic quartz glass manufacturing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Synthetic quartz glass manufacturing apparatus 3 Furnace frame 4 Refractory 5 Target 7 Burner 8 Lifting system 20 Receiving tray 21 Lower adjusting screw 22 Rotating shaft 26 Upper adjusting screw 30 Stage 33 Lifting member

Claims (3)

[Claims] A furnace, a target for producing synthetic quartz glass located in an inner space of the furnace, and a rotatably supported by an elevating stage extending in a vertical direction,
A rotating shaft that holds the target so that it can rotate horizontally, a burner for synthesizing quartz glass with a spout installed toward the target, and a vertical stage that moves the target vertically with respect to the burner by moving the lifting stage up and down. An elevating mechanism for raising and lowering, a rotation axis inclination detector for detecting an inclination angle of the rotation axis with respect to a vertical direction, and adjusting an inclination angle of the elevation mechanism with respect to the vertical direction based on a detection result of the rotation axis inclination detector; A synthetic quartz glass manufacturing apparatus, comprising: a positioning mechanism for adjusting an inclination angle of the rotation shaft with respect to a lifting stage. 2. The rotation axis is tilted with respect to the lift stage based on a detection value of the rotation axis tilt detector so that the rotation axis always extends in a vertical direction regardless of the tilt of the lift stage. The synthetic quartz glass manufacturing apparatus according to claim 1, further comprising a rotating shaft tilting mechanism. 3. A laser irradiator that irradiates a laser beam in a vertical direction, wherein the rotation axis inclination detector includes: a laser irradiator that is fixed to the rotation axis and reflects a laser beam emitted from the laser irradiator; A light receiving position detector for receiving the laser light reflected by the reflecting mirror, detecting a displacement of a two-dimensional position of the received laser light, and detecting an inclination angle of the rotation axis. The synthetic quartz glass manufacturing apparatus according to claim 1 or 2, wherein: