Uniform deposition furnace for synthetic quartz glass and deposition preparation method

Abstract

The invention relates to a synthetic quartz glass uniform deposition furnace and a deposition preparation method, the deposition furnace comprises a furnace body and a furnace top, a jet burner is arranged on the furnace top, a concave deposition tank is arranged in a hearth in the furnace body below the furnace top corresponding to the jet burner, and the concave deposition tank is connected with the jet burner. The device is characterized in that the concave sedimentation tank is arranged on the lifting rotary vibration table, extraction openings are formed in the upper part of the furnace body corresponding to the periphery of the concave sedimentation tank at intervals in the circumferential direction, and air inlets are formed in the lower part of the furnace body at intervals in the circumferential direction. According to the device, the lifting rotary vibration table is arranged, the deposition pond moves back and forth on the XY plane along with the rotary vibration table in the deposition process, it is guaranteed that silicon dioxide micro powder can be evenly laid on the whole deposition target surface in the deposition process, and meanwhile flames of the jet combustor can evenly cover the whole deposition surface; the problem that the center area and the edge area of a large-size quartz glass ingot are greatly different in composition and structure is solved, deposition is uniform, airflow in the furnace is stable, and the deposition quality is good.

Description

Technical Field

[0001] The invention relates to a chemical vapor deposition synthetic quartz glass uniform deposition furnace and a deposition preparation method, belonging to the technical field of quartz glass ingot preparation. Background Art

[0002] Due to its many excellent properties, synthetic quartz glass has a large demand and application in the fields of semiconductors, optics, aerospace, etc., among which the optical uniformity of large-diameter synthetic quartz glass is particularly concerned.

[0003] At present, the main method for preparing large-caliber synthetic quartz glass is chemical vapor deposition, which mainly involves introducing volatile liquid silicon compounds into a burner under the drive of a carrier gas, hydrolyzing or oxidizing them in the burner flame to generate amorphous silicon dioxide, which is then deposited on a high-temperature rotating target to form quartz glass. This production method increases the weight of the synthetic quartz glass ingot by increasing the deposition height, and then thermally reshapes it through a trough sinking process to enlarge the quartz glass ingot to the required product size.

[0004] During the deposition process of the vertical chemical vapor deposition method, the centrifugal force of rotation and the gravity of the quartz glass itself are used to diffuse and flow the high-temperature glass liquid at the central feeding point to the entire target surface, while the glass at the edge is cooled and formed under the cooling effect, providing support for the longitudinal growth of the quartz glass. This forming and growth pattern determines that there must be a large temperature gradient between the edge and the center area, resulting in a large gradient change in the internal structure and hydroxyl component composition between the center and the edge of the quartz glass ingot, which will not only increase the stress and striations of the quartz glass, but also directly lead to the uneven distribution of properties such as the density and refractive index of the quartz glass. This refractive index inhomogeneity of the rough quartz glass ingot will also be retained in the later thermal modification process, resulting in unsatisfactory optical uniformity of the product. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a synthetic quartz glass uniform deposition furnace and a deposition preparation method in view of the deficiencies in the above-mentioned prior art, which not only has uniform deposition, but also has stable airflow in the furnace and good deposition quality.

[0006] The technical solution adopted by the present invention to solve the above-mentioned problems is:

[0007] The invention comprises a furnace body and a furnace top, wherein a jet burner is arranged on the furnace top, and a concave sedimentation pool is arranged in a furnace chamber inside the furnace body below the furnace top corresponding to the jet burner. The invention is characterized in that the concave sedimentation pool is arranged on a lifting and rotating vibration table, and exhaust ports are arranged at circumferential intervals on the upper part of the furnace body corresponding to the outer periphery of the concave sedimentation pool, and air inlets are arranged at circumferential intervals on the lower part of the furnace body.

[0008] According to the above scheme, the exhaust ports are arranged at intervals of 4 to 12 along the circumference of the furnace body, the inner ends of the exhaust ports are connected to the furnace, and the outer ends of the exhaust ports are connected to an external exhaust control system to control the exhaust volume at the exhaust ports.

[0009] According to the above scheme, 4 to 12 air inlets are arranged at intervals along the circumference of the furnace body, the inner end of the air inlet is connected to the furnace, and the outer end of the air inlet is connected to an external air intake control system to control the air intake volume at the air inlet.

[0010] According to the above scheme, the air inlet is opened from outside to inside and tilted upward, and the angle θ between the air inlet and the vertical direction is 30° to 60°.

[0011] According to the above scheme, the air extraction ports and air inlets are symmetrically distributed with equal distances in the circumferential direction, the number of the air extraction ports is the same as the number of the air inlets, and there is an air inlet corresponding to each air extraction port.

[0012] According to the above solution, the distance h2 between the lower edge of the air exhaust port and the upper edge of the air inlet is 300 mm to 500 mm.

[0013] According to the above scheme, the distance h1 between the upper edge of the air extraction port and the upper edge of the sedimentation tank is 100 mm to 200 mm.

[0014] According to the above scheme, each of the air inlets is connected to a gas flow meter and a throttle valve respectively, and the gas flow meter and the throttle valve are connected to an air intake control system to control the air intake volume of each air inlet respectively.

[0015] According to the above scheme, the furnace top is provided with a temperature sensor and an air pressure sensor, and the air exhaust port is also provided with a temperature sensor and an air pressure sensor.

[0016] According to the above scheme, the lifting and rotating vibration table drives the concave sedimentation pool to vibrate back and forth along the XY direction parallel to the horizontal plane while keeping rotating around the center.

[0017] According to the above scheme, the distance between the outer peripheral wall of the concave sedimentation pool and the furnace wall is 200-300 mm, and the amplitude of the concave sedimentation pool along the XY directions in the furnace is 100-200 mm respectively.

[0018] According to the above scheme, the vibration frequency of the concave sedimentation pool is 1×10 -3 ~1×10 -2 HZ.

[0019] According to the above scheme, the material of the concave sedimentation pool is refractory material, and the material of the refractory material is zirconium oxide, aluminum oxide or silicon carbide. The inner wall of the concave sedimentation pool has an outward angle with the vertical direction, and the angle ranges from 0° to 30°.

[0020] According to the above scheme, 6 or more jet burners are provided, the angle between the jet burner and the vertical line is 0° to 15°, and the distance between the jet burner and the target surface during deposition is 300mm to 450mm.

[0021] The technical solution of the method for preparing quartz glass using the above deposition furnace of the present invention is:

[0022] A quartz glass ingot is prepared by chemical vapor deposition (CVD). The deposition target is placed in a concave deposition pool. The deposition pool is adjusted to a suitable height by lifting and lowering a rotary vibration table. The rotary vibration table is turned on so that the concave deposition pool follows the rotary vibration table to perform a compound motion of rotation and vibration. The jet burner is ignited. After the temperature in the furnace rises to a preset temperature value, the raw material is driven by the carrier gas and sprayed into the concave deposition pool through the jet burner placed on the top of the furnace. A chemical reaction occurs in the combustion environment of the hydrogen-oxygen flame to generate silicon dioxide particles and deposit on the deposition target. As the deposition process proceeds, the glass melt covers the entire deposition target. At this time, the glass melt formed by the deposition serves as a new collection target surface. During the entire deposition process, the concave deposition pool rises slowly to keep the distance between the deposition target surface and the jet burner constant. The exhaust port is always controlled by an external exhaust control system to discharge the exhaust gas generated in the furnace out of the furnace chamber and maintain the temperature balance in the furnace chamber until the deposition process is completed.

[0023] According to the above scheme, as the lifting and rotating vibration table oscillates in the XY plane, the distance between the deposition pool wall and the furnace wall will change periodically, causing the amount of air entering the furnace from all directions at the bottom of the furnace to change continuously, resulting in periodic fluctuations in the temperature and pressure of the deposition pool in the furnace. At this time, the temperature and pressure sensors located on the top of the furnace will detect this change and transmit it to the external controller. The controller will adjust the air intake of each air inlet under the furnace wall through the air intake control system to balance the fluctuation of the bottom air intake caused by the oscillating movement, so that the temperature and air pressure of the deposition pool inside the furnace remain in a relatively stable range until the deposition process is completed.

[0024] According to the above scheme, when the pressure at the furnace top pressure sensor fluctuates, the controller can control the air intake system to adjust the increase or decrease of the air intake amount at each air inlet according to the increase or decrease of the pressure at the pressure sensor.

[0025] According to the above scheme, the air extraction port is connected to the tail gas treatment system, and the air pressure at the air extraction port is controlled by the tail gas treatment system at a preset value P0, preferably P0≤1000 Pa. The temperature of the sedimentation tank is 1600℃~1800℃.

[0026] According to the above scheme, the inlet gas is air or nitrogen, and nitrogen can reduce the influence of oxygen contained in the inlet gas on the flame combustion in the furnace.

[0027] According to the above scheme, the raw material is SiCl4 or an organic compound of silicon.

[0028] The beneficial effects of the present invention are as follows: 1. A lifting and rotating vibration table is set, and the deposition pool moves back and forth in the XY plane following the rotating vibration table during the deposition process, ensuring that the silica powder can be evenly laid on the entire deposition target surface during the deposition process, and at the same time, the flame of the jet burner can evenly cover the entire deposition surface, solving the problem that there are large differences in composition and structure between the center and edge areas of large-sized quartz glass ingots, and improving the uniformity of synthetic quartz glass deposition. 2. An air inlet is set below the furnace wall, and each air inlet is connected to a gas flow meter and a throttle valve respectively. By controlling the air intake of each air inlet, the influence of the air extraction port caused by the XY vibration table during the oscillation process on the air extraction volume in the furnace is balanced, ensuring the stability of the temperature and air pressure in the deposition pool during the deposition process, solving the problems of stripes and bubbles caused by temperature and air pressure fluctuations in large-sized quartz glass ingots during the deposition process, and further enhancing the uniformity and stability of deposition. 3. Multiple temperature sensors and pressure sensors are placed on the furnace top and exhaust port to accurately monitor and feedback the changes in temperature and air pressure in the entire deposition pool during the deposition process, so as to accurately control and adjust the air intake and exhaust volumes to ensure the stability of temperature and air pressure in the entire deposition pool. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of a front cross-sectional structure of an embodiment of the present invention.

[0030] Figure 2 It is a schematic diagram of the radial cross-sectional structure of the air inlet according to one embodiment of the present invention.

[0031] Figure 3 The figure is a schematic diagram of the relative relationship between the components of an embodiment of the present invention.

[0032] Figure 4 It is a schematic diagram of the layout of the temperature sensor and the air pressure sensor on the top of a deposition furnace according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0034] A deposition furnace according to an embodiment of the present invention is as follows Figure 1-4As shown, it comprises a cylindrical furnace body 13 and a furnace top 1, on which a jet burner 2 with a nozzle facing downward is arranged, and the furnace top is also provided with a temperature sensor 3 and an air pressure sensor 4, the horizontal distance r1 between the temperature sensor and the air pressure sensor and the center of the furnace top is 700mm, and 4 temperature sensors and air pressure sensors are arranged, which are staggered with the furnace top in the circumferential direction; below the furnace top, a concave sedimentation pool 5 is arranged in the furnace chamber inside the furnace body corresponding to the jet burner, and the radius r2 of the sedimentation pool is 800mm, which is located between the sedimentation pool and the jet burner The space between the devices is a deposition chamber 6, the concave deposition pool is mounted on a lifting and rotating vibration table 7, and exhaust ports 8 are provided at circumferential intervals corresponding to the outer periphery of the concave deposition pool above the furnace body, the exhaust ports 12 are evenly spaced along the circumference of the furnace body, the inner end of the exhaust port is communicated with the furnace, and the outer end of the exhaust port is connected to an external exhaust control system 12, the external exhaust control system 12 controls the pressure P0 at the exhaust port 8 to be stable at around 1000 Pa, so as to control the exhaust volume at the exhaust port, and a temperature sensor and an air pressure sensor are also provided at the exhaust port. The distance h1 between the upper edge of the air extraction port and the upper edge of the sedimentation pool is 150mm. An air inlet 11 is provided at intervals in the circumferential direction below the furnace body. The distance h2 between the lower edge of the air extraction port 8 and the upper edge of the air inlet 11 is 400mm. Twelve air inlets are provided at intervals in the circumferential direction of the furnace body. The inner end of the air inlet communicates with the furnace, and the outer end of the air inlet is connected to the external air intake control system 9. The air inlet is opened upwardly from the outside to the inside, and the angle θ between the air inlet and the vertical direction is 60°. Each of the air inlets is connected to a gas flow meter and a throttle valve 10, respectively. The gas flow meter and the throttle valve are connected to the air intake control system to control the air intake of each air inlet. The distance between the outer peripheral wall of the concave sedimentation pool and the furnace wall is 300mm, and the amplitude of the concave sedimentation pool along the XY direction in the furnace is 100mm respectively.

[0035] The deposition preparation process of this embodiment is as follows: place the deposition target in a concave deposition pool 5, adjust the height of the deposition pool so that the deposition target surface is 450mm away from the jet burner, ignite the jet burner 2, and turn on the lifting and rotating vibration table 7 at the same time, so that it can make a rotational oscillation motion with the deposition pool. When the oscillation is turned on, the gap between the furnace wall and the deposition pool wall will be different in different directions, resulting in different amounts of air entering the furnace from different directions below the furnace. The pressure sensors located in different directions on the top of the furnace will show differences in readings, which will be transmitted to the air intake control system 9. At this time, the air intake control system will increase or decrease the air volume at the air inlet according to the increase or decrease of the pressure sensor data, and adjust the gas flow meter and the throttle valve through the air intake control system to increase or decrease the air volume at the air intake, and finally reach a stable pressure sensor reading in each direction at the same level until the deposition is completed. During the deposition process, the air pressure fluctuation in the deposition chamber is less than 10pa, and the temperature fluctuation is less than 5°C. The quartz glass ingot obtained by deposition has a diameter of 1600mm and a height of 200mm. It has no macroscopic defects such as bubble streaks, and its optical uniformity is less than 5×10-6 , stress is less than 5×10 -6 .

[0036] The second embodiment of the deposition preparation process of the present invention is as follows: Different from the first embodiment, when the oscillation is turned on, the gap between the furnace wall and the periphery of the deposition pool will appear in different sizes in different directions. At this time, the air intake control system will adjust the gas volume of the air inlet on the same side to increase or decrease according to the size of the gap between the furnace wall and the deposition pool wall through the air intake control system; when the gap increases, the air intake of the air inlet on the same side is reduced, and when the gap decreases, the air intake of the air inlet on the same side is increased, and finally the pressure sensor readings in all directions are stabilized at the same level until the deposition is completed. During the deposition process, the air pressure fluctuation in the deposition chamber is less than 8pa, and the temperature fluctuation is less than 3°C. The quartz glass ingot obtained by deposition has a diameter of 1600mm and a height of 200mm, without macroscopic defects such as bubble streaks, and an optical uniformity of less than 4×10 -6 , stress is less than 4×10 -6 .

Claims

1. A synthetic quartz glass uniform deposition furnace, comprising a furnace body and a furnace top, wherein a jet burner is arranged on the furnace top, and a concave deposition pool is arranged in a furnace chamber in the furnace body below the furnace top corresponding to the jet burner, characterized in that The concave sedimentation pool is arranged on a lifting and rotating vibration platform, air exhaust ports are arranged at intervals in the circumferential direction corresponding to the outer circumference of the concave sedimentation pool above the furnace body, and air inlets are arranged at intervals in the circumferential direction below the furnace body.

2. The synthetic quartz glass uniform deposition furnace according to claim 1, characterized in that The exhaust ports are arranged at intervals of 4 to 12 along the circumference of the furnace body, the inner ends of the exhaust ports are communicated with the furnace, and the outer ends of the exhaust ports are connected to an external exhaust control system to control the exhaust volume at the exhaust ports; the air inlets are arranged at intervals of 4 to 12 along the circumference of the furnace body, the inner ends of the air inlets are communicated with the furnace, and the outer ends of the air inlets are connected to an external air intake control system to control the air intake volume at the air inlets.

3. The synthetic quartz glass uniform deposition furnace according to claim 2, characterized in that The air extraction ports and air inlets are symmetrically distributed circumferentially and equidistantly, the number of the air extraction ports is the same as the number of the air inlets, and there is an air inlet directly below each of the air extraction ports; the air inlets are opened from the outside to the inside and tilted upward, and the angle θ between the air inlets and the vertical direction is 30° to 60°.

4. The synthetic quartz glass uniform deposition furnace according to claim 2 or 3, characterized in that The distance h2 between the lower edge of the air extraction port and the upper edge of the air inlet is 300 mm to 500 mm, and the distance h1 between the upper edge of the air extraction port and the upper edge of the sedimentation pool is 100 mm to 200 mm.

5. The synthetic quartz glass uniform deposition furnace according to claim 2 or 3, characterized in that Each of the air inlets is connected to a gas flow meter and a throttle valve respectively, and the gas flow meter and the throttle valve are connected to an air intake control system to respectively control the air intake volume of each air inlet.

6. The synthetic quartz glass uniform deposition furnace according to claim 1 or 2, characterized in that The furnace top is provided with a temperature sensor and an air pressure sensor, and the air exhaust port is also provided with a temperature sensor and an air pressure sensor.

7. The synthetic quartz glass uniform deposition furnace according to claim 1 or 2, characterized in that The lifting and rotating vibration table drives the concave sedimentation pool to vibrate back and forth along the XY direction parallel to the horizontal plane while rotating around the center. The distance between the outer peripheral wall of the concave sedimentation pool and the furnace wall is 200-300 mm. The amplitude of the concave sedimentation pool along the XY direction in the furnace is 100-200 mm respectively. The vibration frequency of the concave sedimentation pool is 1×10 -3 ~1×10 -2 HZ.

8. The synthetic quartz glass uniform deposition furnace according to claim 1 or 2, characterized in that The concave sedimentation pool is made of refractory material, which is zirconium oxide, aluminum oxide or silicon carbide. The inner wall of the concave sedimentation pool has an outward angle with the vertical direction, and the angle ranges from 0° to 30°.

9. The synthetic quartz glass uniform deposition furnace according to claim 1 or 2, characterized in that The number of the jet burners is 6 or more, the angle between the jet burner and the vertical line is 0° to 15°, and the distance between the jet burner and the target surface during deposition is 300mm to 450mm.

10. A method for uniformly depositing synthetic quartz glass, characterized in that Using any deposition furnace in claims 1-9, A quartz glass ingot is prepared by chemical vapor deposition. The deposition target is placed in a concave deposition pool. The deposition pool is adjusted to a suitable height by lifting and lowering a rotary vibration table. The rotary vibration table is turned on so that the concave deposition pool follows the rotary vibration table to perform a compound motion of rotation and vibration. The jet burner is ignited. After the temperature in the furnace rises to a preset temperature value, the raw material is driven by the carrier gas and sprayed into the concave deposition pool through the jet burner placed on the top of the furnace. A chemical reaction occurs in the combustion environment of the hydrogen-oxygen flame to generate silicon dioxide particles and deposit on the deposition target. As the deposition process proceeds, the glass melt covers the entire deposition target. At this time, the glass melt formed by the deposition serves as a new collection target surface. During the entire deposition process, the concave deposition pool rises slowly to keep the distance between the deposition target surface and the jet burner constant. The exhaust port is always controlled by an external exhaust control system to discharge the exhaust gas generated in the furnace out of the furnace chamber and maintain the temperature balance in the furnace chamber until the deposition process is completed.

11. The method for uniformly depositing synthetic quartz glass according to claim 10, characterized in that As the lifting and rotating vibration table oscillates in the XY plane, the distance between the deposition pool wall and the furnace wall will change periodically, causing the amount of air entering the furnace from all directions at the bottom of the furnace to change continuously, resulting in periodic fluctuations in the temperature and pressure of the deposition pool in the furnace. At this time, the temperature and pressure sensors located on the top of the furnace will detect this change and transmit it to the external controller. The controller will adjust the air intake of each air inlet under the furnace wall through the air intake control system to balance the fluctuation of the bottom air intake caused by the oscillating movement, so that the temperature and air pressure of the deposition pool inside the furnace remain in a relatively stable range until the deposition process is completed.

12. The method for uniformly depositing synthetic quartz glass according to claim 10 or 11, characterized in that When the pressure at the furnace top pressure sensor fluctuates, the controller can control the air intake system to adjust the increase or decrease of the air intake amount at each air inlet according to the increase or decrease of the pressure at the pressure sensor.

13. The method for uniformly depositing synthetic quartz glass according to claim 10 or 11, characterized in that The air extraction port is connected to the tail gas treatment system, and the air pressure at the air extraction port is controlled by the tail gas treatment system at a preset value P0≤1000Pa. The temperature of the sedimentation tank is 1600℃~1800℃, and the air inlet gas is air or nitrogen.

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