External low-disturbance gas circulating filtration system of Czochralski method crystal growth single crystal furnace

Abstract

The invention discloses an external low-disturbance gas circulating filtration system of a Czochralski method crystal growth single crystal furnace, which comprises a filtration unit arranged on the outer side of the hearth of the single crystal furnace, and the gas inlet end and the gas outlet end of the filtration unit are respectively communicated with the hearth through pipelines. The external filtering unit is adopted, efficient gas purification can be achieved on the premise that the stability of airflow in the hearth is not affected, the external mode facilitates replacement and maintenance of the filtering unit, meanwhile, the service life of the filtering unit is effectively prolonged, airflow disturbance in the hearth is reduced, and it is ensured that a crystal growth interface is stable and free of turbulence interference; meanwhile, the filtering unit adopts multi-stage filtering, crystal pollution is effectively avoided, and the optical performance of the crystal is improved.

Description

Technical Field

[0001] The invention relates to the technical field of crystal growth equipment, in particular to an external low-disturbance gas circulation filtration system for a single crystal furnace for crystal growth using a Czochralski method. Background Art

[0002] The Czochralski crystal growth furnace is a device used to manufacture single crystal materials. Existing single crystal furnaces use a gas circulation filtration system, but the existing gas circulation filtration system has the following defects: Traditional single crystal furnace gas filtration systems are mostly integrated inside the furnace, and filter replacement requires shutdown and cooling, which affects production efficiency. Built-in filters are easily affected by high temperatures, have a short lifespan, and may cause instability in the crystal growth interface due to airflow disturbances; During crystal growth, rare earth elements (such as Nd 3+ 、Yb 3+ ) Volatile substances and volatile components in thermal insulation materials are easily deposited in the furnace, contaminating the crystal and reducing optical properties.

[0003] To this end, we proposed an external low-disturbance gas circulation filtration system for the Czochralski crystal growth single crystal furnace. Summary of the Invention

[0004] The object of the present invention is to provide an external low-disturbance gas circulation filtration system for a single crystal growth furnace using the Czochralski method, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: The invention discloses an external low-disturbance gas circulation filtration system for a single crystal furnace for crystal growth by a Czochralski method, comprising a filtration unit arranged outside the furnace of the single crystal furnace, wherein the air inlet and the air outlet of the filtration unit are connected to the furnace through pipelines respectively.

[0006] A further improvement is that the filter unit comprises a main filter element and a secondary filter element connected in parallel to the pipeline, and the air inlet end and the air outlet end of the main filter element and the secondary filter element are both provided with valve bodies.

[0007] A further improvement is that a gas flow meter electrically connected to an external controller is provided on the pipe at the air outlet of the filter unit, the gas flow meter is used to detect the air flow velocity in the pipe, and the external controller is connected to an alarm.

[0008] A further improvement is that the main filter element and the auxiliary filter element both include a coarse filter module and a fine filter module arranged in series.

[0009] A further improvement is that the filter element of the coarse filter module is a detachable sintered metal filter element, and the filter element of the fine filter module is a detachable ceramic fiber filter element.

[0010] A further improvement is that the pore size of the filter element of the coarse filtration module is 8-11 μm, and the pore size of the filter element of the fine filtration module is 0.1-0.2 μm.

[0011] A further improvement is that a regulating fan is provided on the pipeline at the air inlet end of the filter unit, and the regulating fan is used to control the fluctuation of the gas flow speed in the pipeline.

[0012] A further improvement is that the filter unit is detachably connected to the pipeline.

[0013] A further improvement is that one end of the pipeline away from the filter unit extends into the furnace and is connected to a flow guide cover.

[0014] A further improvement is that the air guide cover is a tapered air guide cover.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention adopts an external filter unit, which can achieve efficient gas purification without affecting the stability of the airflow in the furnace. The external approach facilitates the replacement and maintenance of the filter unit, while effectively extending the service life of the filter unit, reducing the airflow disturbance in the furnace, ensuring the stability of the crystal growth interface without turbulent interference, and at the same time, the filter unit adopts multi-stage filtration to filter out rare earth element volatiles in the furnace gas, which can reduce the deposition of volatiles in the furnace, effectively avoid crystal contamination, and improve the optical performance of the crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic structural diagram of the external low-disturbance gas circulation filtration system of the present invention.

[0017] In the figure: 100, filter unit; 101, coarse filter module; 102, fine filter module; 103, valve body; 200, pipeline; 300, furnace; 400, air guide cover; 500, regulating fan; 600, gas flow meter. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] Please see the attached Figure 1, the external low disturbance gas circulation filtering system of the Czochralski crystal growth single crystal furnace, the system is particularly suitable for the crystal which needs to be grown in inert atmosphere, including YAG, GGG, TGG and other pure or doped oxide crystals, also including single crystal silicon, single crystal germanium and other semiconductor crystals grown by Czochralski method, the system comprises a filtering unit 100 arranged outside the furnace chamber 300, the gas inlet end and the gas outlet end of the filtering unit 100 are communicated with the furnace chamber 300 through pipelines 200, for example, the pipeline 200 is a stainless steel bellows; The system adopts the external filtering unit 100, which can realize efficient gas purification without affecting the stability of the airflow in the furnace chamber 300, the external mode is convenient for replacement and maintenance of the filtering unit 100, and effectively prolongs the service life of the filtering unit 100 and reduces the airflow disturbance in the furnace chamber 300.

[0020] Further, the filtering unit 100 comprises a main filter and a secondary filter connected in parallel to the pipeline 200, the main filter and the secondary filter are the same structure, the gas inlet end and the gas outlet end of the main filter and the secondary filter are provided with valve bodies 103, for example, the valve body 103 is an electromagnetic valve, which is convenient for controlling the gas to pass through the main filter or the secondary filter.

[0021] Further, the pipeline 200 at the gas outlet end of the filtering unit 100 is provided with a gas flow meter 600 electrically connected with an external controller (for example, a PID controller), the gas flow meter 600 is used for detecting the airflow speed in the pipeline 200, in the initial use, the gas in the furnace chamber 300 enters the main filter through the pipeline 200, and then circulates to the furnace chamber 300 from the gas outlet end of the main filter and the pipeline 200, as the main filter filters the gas and gradually blocks, the airflow speed in the pipeline 200 decreases, when the gas flow meter 600 detects that the flow rate decreases to a set threshold, the gas flow meter 600 sends a signal to the external controller, the external controller can control the valve body 103 on the main filter to close and the valve body 103 on the secondary filter to open, so as to switch to the secondary filter, so that the entering gas is filtered by the secondary filter, at this time, the main filter can be maintained and replaced without damaging the vacuum of the furnace body and stopping the machine, in addition, the gas flow meter 600 can also be used for automatically calibrating the airflow parameters after replacement, the external controller is connected with an alarm, and when the external controller receives the signal of the gas flow meter 600, the alarm also alarms, so as to remind the user to replace.

[0022] Further, the main filter and the secondary filter each comprise a coarse filter module 101 and a fine filter module 102 arranged in series, multi-stage filtration (coarse filtration + fine filtration) is adopted, and different particle sizes and volatile impurities are filtered respectively.

[0023] Furthermore, the filter element of the coarse filter module 101 is a detachable sintered metal filter element, and the filter element of the fine filter module 102 is a detachable ceramic fiber filter element, for example, it can be detachably installed using a bolt-like structure. The pore size of the filter element of the coarse filter module 101 is 8-11 μm, and the pore size of the filter element of the fine filter module 102 is 0.1-0.2 μm. Preferably, the pore size of the filter element of the coarse filter module 101 is 10 μm, and the pore size of the filter element of the fine filter module 102 is 0.1 μm. Preferably, when adapting to fluoride crystal growth (such as LiCAF), a polytetrafluoroethylene filter element can be used instead for corrosion resistance.

[0024] Furthermore, a regulating fan 500 is provided on the pipe 200 at the air inlet end of the filter unit 100. The regulating fan 500 is used to control the fluctuation of the gas flow velocity in the pipe 200. The regulating fan 500 is electrically connected to an external controller, and the rotation speed of the regulating fan 500 is PID controlled by the external controller (PID controller, etc.) to avoid crystal defects caused by sudden pressure changes. The regulating fan 500 maintains the gas flow velocity in the pipe 200 unchanged. If the flow velocity remains unchanged, the disturbance in the furnace 300 will also remain unchanged. In addition, the gas flow velocity and disturbance in the furnace 300 can be estimated through the diameters of the pipe 200 and the furnace 300 and the gas flow velocity and fluctuation of the pipe 200, and the appropriate pipe airflow velocity can be determined according to the upper limit of the airflow disturbance in the furnace 300.

[0025] Furthermore, the filter unit 100 and the pipe 200 are detachably connected, for example, by a flange connection, which improves the replacement time of the filter element, shortening the replacement time by 90%, without destroying the vacuum of the furnace body, and can be replaced and maintained without stopping the machine.

[0026] Furthermore, one end of the pipe 200 away from the filter unit 100 extends into the furnace 300 and is connected to a flow guide hood 400. The flow guide hood 400 is a tapered flow guide 400 (a fluid guiding structure in which the cross-sectional area gradually decreases along the airflow direction), ensuring that the gas enters the growth zone in a laminar flow (Re < 2000), thereby reducing the impact of turbulence on the crystal interface.

[0027] Taking Nd:YAG crystal growth as an example, the above system has the following advantages: 1. The external filter unit 100 is installed outside the single crystal furnace and connected through a stainless steel bellows. The filter element replacement time is less than 10 minutes (the traditional method takes more than 2 hours); 2. The air flow velocity in the furnace 300 is less than 0.02 m / s, and the crystal dislocation density is reduced to 102 cm-2 (103 cm-2 in the traditional method); 3. The filter element life is extended to 300 hours (built-in type is only 100 hours); 4. The 1064nm transmittance of Nd:YAG crystal is increased to >78% (traditional method is 70-78%).

[0028] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. External low-disturbance gas circulation filtration system for single crystal growth furnace using Czochralski method, characterized by: The invention comprises a filter unit (100) arranged outside a furnace (300) of a single crystal furnace, wherein an air inlet end and an air outlet end of the filter unit (100) are respectively connected to the furnace (300) through a pipeline (200).

2. The external low-disturbance gas circulation filtration system according to claim 1, characterized in that: The filter unit (100) comprises a main filter element and a secondary filter element connected in parallel to a pipeline (200), and the air inlet end and the air outlet end of the main filter element and the secondary filter element are both provided with a valve body (103).

3. The external low-disturbance gas circulation filtration system according to claim 2, characterized in that: A gas flow meter (600) electrically connected to an external controller is provided on the pipe (200) at the gas outlet end of the filter unit (100). The gas flow meter (600) is used to detect the air flow velocity in the pipe (200). The external controller is connected to an alarm.

4. The external low-disturbance gas circulation filtration system according to claim 2, characterized in that: The main filter element and the auxiliary filter element both comprise a coarse filter module (101) and a fine filter module (102) arranged in series.

5. The external low-disturbance gas circulation filtration system according to claim 4, characterized in that: The filter element of the coarse filter module (101) is a detachable sintered metal filter element, and the filter element of the fine filter module (102) is a detachable ceramic fiber filter element.

6. The external low-disturbance gas circulation filtration system according to claim 4, characterized in that: The filter element pore size of the coarse filter module (101) is 8-11 μm, and the filter element pore size of the fine filter module (102) is 0.1-0.2 μm.

7. The external low-disturbance gas circulation filtration system according to claim 1, characterized in that: A regulating fan (500) is provided on the pipeline (200) at the air inlet end of the filter unit (100), and the regulating fan (500) is used to control the fluctuation of the gas flow speed in the pipeline (200).

8. The external low-disturbance gas circulation filtration system according to claim 1, characterized in that: The filter unit (100) is detachably connected to the pipeline (200).

9. The external low-disturbance gas circulation filtration system according to claim 1, characterized in that: One end of the pipe (200) away from the filter unit (100) extends into the furnace (300) and is connected to a flow guide cover (400).

10. The external low-disturbance gas circulation filtration system according to claim 1, characterized in that: The air guide cover (400) is a tapered air guide cover.

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