Czochralski single crystal isolation process
By filling the first and second isolation gases in the straight-pull single crystal isolation process to achieve a specific pressure, the problem of high production costs in the prior art due to the large amount of argon gas used in the prior art is solved, and the maintenance of the isolation effect and the reduction of the cost are achieved.
Patent Information
- Application Number
- CN202311502334.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-10
- Publication Date
- 2025-05-13
AI Technical Summary
In the existing direct pull single crystal isolation process, the use of argon is large, resulting in an increase in production costs.
A straight-pull single crystal isolation process is adopted, by filling the first isolation gas and the second isolation gas into the sub-room of the single crystal furnace, the pressures of the first threshold and the second threshold are respectively reached to achieve the isolation effect and reduce the amount of argon gas usage.
It effectively reduces the use of argon, reduces production costs, and ensures the isolation effect between the main furnace chamber and the secondary chamber of the single crystal furnace.
Smart Images
Figure CN119980459A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of Czochralski single crystals, and in particular relates to a Czochralski single crystal isolation process. Background Art
[0002] The direct pulling method is the main method for producing single crystal silicon, and single crystal furnaces are widely used. In the process of pulling single crystals, the removal of sticky slag, the removal of lifting heads, the removal of single crystals, and the re-injection of silicon materials all require the use of an isolation valve to isolate the main furnace chamber and the auxiliary chamber of the single crystal furnace, so that the main furnace chamber is in a closed state. In the process of pulling single crystals, argon gas is filled into the single crystal furnace to make the pressure in the furnace about 5-20Torr. After closing the isolation valve to complete the isolation of the main furnace chamber and the auxiliary chamber, the auxiliary chamber needs to be inflated to normal pressure. In the isolation process in the prior art, argon gas is usually used to inflate the auxiliary chamber of the single crystal furnace. The amount of argon gas used is large. With the continuous increase in the unit price of argon gas, the production cost is greatly increased. Summary of the invention
[0003] In order to solve the above technical problems, the present invention provides a Czochralski single crystal isolation process, which effectively solves the problem of large amount of argon gas usage and increased production costs, and overcomes the shortcomings of the prior art.
[0004] The technical solution adopted by the present invention is: a Czochralski single crystal isolation process, comprising the following steps:
[0005] When the single crystal furnace sub-chamber is isolated from the main furnace chamber, a first isolation gas is filled into the single crystal furnace sub-chamber so that the pressure in the single crystal furnace sub-chamber reaches a first threshold;
[0006] A second insulating gas is filled into the single crystal furnace sub-chamber so that the pressure in the single crystal furnace sub-chamber reaches a second threshold value.
[0007] Optionally, the first insulating gas is of the same type and concentration as the gas in the main furnace chamber.
[0008] Optionally, the first isolation gas is argon.
[0009] Optionally, the second isolation gas is compressed air or nitrogen.
[0010] Optionally, before the first isolation gas is filled, the isolation valve is closed to isolate the single crystal furnace sub-chamber from the main furnace chamber.
[0011] Optionally, the value range of the first threshold is 100-200 Torr.
[0012] Optionally, the value range of the second threshold is 670-700 Torr.
[0013] Optionally, the inflation flow rate of the first isolation gas and the second isolation gas is greater than 200 slpm.
[0014] Optionally, the first isolation gas and the second isolation gas are switched for inflation by setting a switching valve on the inflation pipeline.
[0015] The advantages and positive effects of the present invention are: by setting the first isolation gas, the pollution of the gas environment in the main furnace chamber is avoided; by setting the second isolation gas, the isolation effect between the main furnace chamber and the auxiliary chamber of the single crystal furnace is ensured, the use of argon gas is effectively reduced, and the production cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 This is a process flow chart of a Czochralski single crystal isolation process according to an embodiment of the present invention. DETAILED DESCRIPTION
[0017] An embodiment of the present invention provides a Czochralski single crystal isolation process, and the embodiment of the present invention is described below with reference to the accompanying drawings.
[0018] In the description of the embodiments of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "set" and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood by specific circumstances.
[0019] In an embodiment of the present invention, a CZ single crystal isolation process is provided. When a single crystal furnace sub-chamber is isolated from a main furnace chamber, the isolation valve is first closed to isolate the single crystal furnace sub-chamber from the main furnace chamber, and a first isolation gas is filled into the single crystal furnace sub-chamber to make the pressure in the single crystal furnace sub-chamber reach a first threshold value, and then a second isolation gas is filled into the single crystal furnace sub-chamber to make the pressure in the single crystal furnace sub-chamber reach a second threshold value. The first isolation gas is introduced first to increase the pressure difference between the single crystal furnace sub-chamber and the main furnace chamber to make the isolation state more stable, and then the second isolation gas is introduced to make the gas pressure in the sub-chamber reach normal pressure.
[0020] In order to avoid the secondary chamber being connected to the main furnace chamber due to the isolation valve not being completely closed, which pollutes the gas environment of the main furnace chamber. The first isolation gas uses the same gas as that in the main furnace chamber of the single crystal furnace. In the process of pulling single crystals in the single crystal furnace, argon is usually introduced into the furnace to ensure the stability of the inert gas environment pressure for single crystal growth, and the argon gas flow can promptly take away the impurity volatiles generated by high temperature. In order to avoid destroying the argon environment in the main furnace chamber, the first isolation gas usually selects argon of the same concentration, and argon with a concentration greater than 99.999% is selected. After closing the isolation valve, argon is first filled into the secondary chamber, and after the pressure in the secondary chamber reaches the first threshold and the isolation state is stable, the second isolation gas is filled into the secondary chamber. In order to reduce production costs, low-cost inert gas or compressed air can be selected. Nitrogen can be selected as the inert gas, thereby reducing the use of argon and reducing the use of argon each time it is isolated. During the entire single crystal pulling process, the single crystal furnace needs to be isolated 50-80 times, so the use of argon can be greatly reduced. The first isolation gas and the second isolation gas filling flow rate are usually greater than 200slpm.
[0021] There is no restriction on the type of isolation valve, which may be a flap valve or a rotary valve, as long as it can isolate the auxiliary chamber and the main chamber of the single crystal furnace. This is existing technology and will not be elaborated here.
[0022] In order to ensure that the isolation state is stable and does not cause pollution to the main furnace chamber, the value range of the first threshold is 100-200Torr. Before isolation, the sub-chamber of the single crystal furnace is connected to the main furnace chamber, and the pressure is the same, both 5-20Torr. Entering the isolation process, after the sub-chamber is filled with the first isolation gas, the pressure of the sub-chamber must reach 100-200Torr, so as to ensure that the pressure difference between the sub-chamber and the main furnace chamber makes the isolation state stable. After the isolation state is stable, the second isolation gas is filled into the sub-chamber so that the pressure in the sub-chamber reaches the second threshold. The value range of the second threshold is 670-700Torr, that is, normal pressure.
[0023] Optionally, the first isolation gas and the second isolation gas are switched and inflated by providing a switching valve on the inflation pipeline. To facilitate the switching between the first isolation gas and the second isolation gas, a switching valve is provided on the inflation pipeline of the single crystal furnace sub-chamber.
[0024] Comparative Example: A CZ single crystal isolation process. Before isolation, the single crystal furnace auxiliary chamber is connected to the main furnace chamber, and the pressure is 10 Torr. Close the isolation valve to isolate the single crystal furnace auxiliary chamber from the main furnace chamber. Open the charging valve, and introduce argon into the auxiliary chamber until the pressure in the auxiliary chamber reaches 680 Torr, and then close the charging valve. The single crystal furnace is isolated once, and the argon usage is 2.3m 3 During the single crystal pulling process, the single crystal furnace was isolated 60 times, and the total amount of argon used was 138m 3 .
[0025] Embodiment 1: A CZ single crystal isolation process. Before isolation, the sub-chamber of the single crystal furnace is connected to the main furnace chamber at a pressure of 10 Torr. Close the isolation valve to isolate the sub-chamber of the single crystal furnace from the main furnace chamber. Use a switching valve to connect the inflation pipeline to the first isolation gas argon. Open the inflation valve to introduce the first isolation gas argon into the sub-chamber. When the pressure in the sub-chamber reaches 150 Torr, use a switching valve to connect the inflation pipeline to the second isolation gas compressed air. When the pressure in the sub-chamber reaches 680 Torr, close the inflation valve. The single crystal furnace is isolated once, and the argon usage is 0.51m 3 , compressed air usage is 1.79m 3 During the single crystal pulling process, the single crystal furnace was isolated 60 times, and the total amount of argon used was 30.6m 3 The total amount of compressed air used is 107.4m 3 The production cost of compressed air is very low, which greatly reduces the use of argon and reduces production costs.
[0026] Embodiment 2: A CZ single crystal isolation process. Before isolation, the sub-chamber of the single crystal furnace is connected to the main furnace chamber at a pressure of 10 Torr. Close the isolation valve to isolate the sub-chamber of the single crystal furnace from the main furnace chamber. Use a switching valve to connect the inflation pipeline to the first isolation gas, argon. Open the inflation valve to introduce the first isolation gas, argon, into the sub-chamber. When the pressure in the sub-chamber reaches 150 Torr, use a switching valve to connect the inflation pipeline to the second isolation gas, nitrogen. When the pressure in the sub-chamber reaches 680 Torr, close the inflation valve. The single crystal furnace is isolated once, and the amount of argon used is 0.51m 3 , the amount of nitrogen used is 1.79m 3 During the single crystal pulling process, the single crystal furnace was isolated 60 times, and the total amount of argon used was 30.6m 3 The total amount of nitrogen used is 107.4m 3 The production cost of nitrogen is lower than that of argon, which reduces the production cost relative to the comparative example.
[0027] The advantages and positive effects of the present invention are:
[0028] By setting the first isolation gas, the pollution of the gas environment in the main furnace chamber is avoided. By setting the second isolation gas, the isolation effect between the main furnace chamber and the auxiliary chamber of the single crystal furnace is ensured, which effectively reduces the use of argon gas and reduces production costs.
[0029] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.
Claims
1. A Czochralski single crystal isolation process, characterized in that: The following steps are involved: When the single crystal furnace sub-chamber is isolated from the main furnace chamber, a first isolation gas is filled into the single crystal furnace sub-chamber so that the pressure in the single crystal furnace sub-chamber reaches a first threshold; A second insulating gas is filled into the single crystal furnace sub-chamber so that the pressure in the single crystal furnace sub-chamber reaches a second threshold value.
2. The Czochralski single crystal isolation process according to claim 1, characterized in that: The first insulating gas is of the same type and concentration as the gas in the main furnace chamber.
3. The Czochralski single crystal isolation process according to claim 1 or 2, characterized in that: The first isolation gas is argon gas, and the concentration of the argon gas is greater than 99.999%.
4. The Czochralski single crystal isolation process according to claim 3, characterized in that: The second isolation gas is compressed air or nitrogen.
5. The Czochralski single crystal isolation process according to any one of claims 1-2 and 4, characterized in that: Before filling the first isolation gas, the isolation valve is closed to isolate the single crystal furnace sub-chamber from the main furnace chamber.
6. The Czochralski single crystal isolation process according to claim 1, characterized in that: The value range of the first threshold is 100-200 Torr.
7. The Czochralski single crystal isolation process according to claim 1, characterized in that: The value range of the second threshold is 670-700 Torr.
8. The Czochralski single crystal isolation process according to claim 1, characterized in that: The filling flow rates of the first isolation gas and the second isolation gas are greater than 200 slpm.
9. The Czochralski single crystal isolation process according to claim 1, characterized in that: The first isolation gas and the second isolation gas are switched and inflated by setting a switching valve on the inflation pipeline.