Rapid blowing-out cooling process

Abstract

The invention provides a rapid blowing-out cooling process which comprises the following steps: during blowing-out, controlling the furnace pressure to be within a preset high-pressure interval so as to adjust the air flow in the furnace and discharge heat in the furnace out of the furnace body; reducing the pressure in the furnace to a vacuum state, and judging whether the air tightness of the furnace body is qualified; and if qualified, adjusting the furnace pressure to normal pressure, and taking out the single crystal. According to the rapid blowing-out cooling process, the furnace pressure in the furnace is controlled to rise to the high-pressure state, argon convection in the furnace is improved, heat exchange motion between argon molecules and the furnace wall is accelerated, heat in the furnace is transmitted to the furnace wall more rapidly, heat on the furnace wall is taken away by cooling water, and the purpose of rapid cooling is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of single crystal silicon production furnace, and particularly relates to a rapid shutdown and cooling process. BACKGROUND

[0002] At present, in the industry, in the shutdown stage after the single crystal silicon pulling is completed, in order to make the temperature in the furnace drop as soon as possible to be suitable for disassembling the furnace, a decompression process is generally used, that is, after the heating is stopped, the same amount of high-purity argon is continuously filled into the single crystal furnace chamber, and the vacuum pump continuously pumps the gas from the furnace chamber to the outside, and the furnace pressure is kept at 9-12t. Since this shutdown process not only has the characteristics of the vacuum process (the furnace chamber is kept under negative pressure), but also has the characteristics of the flowing atmosphere (continuous filling and continuous exhaust), it has been used for a long time in the industry. However, this shutdown process has two major shortcomings: first, it takes a long time, and with the increase of the size of the hot zone, the shutdown time of the 32-inch hot zone is about 480 minutes, the shutdown time of the 33-inch hot zone is about 540 minutes, and the shutdown time of the 36-inch hot zone is about 600 minutes. Second, since the argon and the vacuum pump are always on, the consumption of high-purity argon and electric energy is large, resulting in high production cost.

[0003] Chinese public patent CN103266348A rapid energy-saving single crystal silicon pulling shutdown process provides a shutdown process for 18-inch and 20-inch hot zones, that is, to raise the furnace pressure to rapidly shut down. However, this process is not suitable for large-size hot zones such as 32-inch, 33-inch and 36-inch hot zones, and the heat dissipation effect is not very significant, especially in the case that the last stage of single crystal growth is not ideal, the last single crystal silicon rod is easily made into a crystal rod without crystal line. If these crystal rods continue to be raised after shutdown, the temperature deviation between the upper and lower furnace cavities will be too large, resulting in the explosion of the crystal rod. SUMMARY

[0004] The application provides a rapid shutdown and cooling process, which solves the technical problems of easy crystal rod explosion, crystal rod tail color affecting the quality of recovered material, and slow heat dissipation of large-size hot zones in the prior art.

[0005] To solve at least one of the above technical problems, the technical solution adopted by the application is:

[0006] A rapid shutdown and cooling process, comprising the following steps:

[0007] During shutdown, the furnace pressure is controlled in a preset high pressure range to adjust the air flow in the furnace, so that the heat in the furnace is discharged outside the furnace body;

[0008] The pressure in the furnace is reduced to a vacuum state to determine whether the air tightness of the furnace body is qualified;

[0009] If qualified, the furnace pressure is adjusted to normal pressure, and the single crystal is taken out.

[0010] Further, the preset high pressure range is 90t-500t, and higher than the initial furnace pressure when the furnace is stopped.

[0011] Further, the furnace pressure is controlled in a preset high pressure range, specifically:

[0012] The furnace pressure is controlled to rise from the initial negative pressure to a first high pressure, and maintained at the first high pressure state for a period of time;

[0013] The furnace pressure is controlled to rise from the first high pressure to a second high pressure, and maintained at the second high pressure state for a period of time;

[0014] The furnace pressure is controlled to drop from the second high pressure to the first high pressure, and maintained at the first high pressure state for a period of time;

[0015] The time maintained at the first high pressure state is shorter than the time maintained at the second high pressure state, and the two times maintained at the first high pressure state are not the same.

[0016] Further, during the process of rising from the initial negative pressure state to the first high pressure state,

[0017] Lower the crucible and stop the crystal rotation and crucible rotation, and gradually reduce the heater power to zero;

[0018] At the same time, control the gas to continuously enter the furnace, and the flow rate is 90-200 slpm, until the furnace pressure rises to the first high pressure.

[0019] Further, the time maintained at the first high pressure state includes maintaining 60-120 min based on the first high pressure state; and continuously controlling the furnace exhaust; wherein the initial furnace pressure is 7-9t, and the first high pressure is 30-120t.

[0020] Further, when the crystal rotation is stopped, it also includes judging whether the crystal rod is raised or not;

[0021] When the crystal line of the crystal rod appears broken or no edge, the crystal rod is not lifted, and the crystal rod is lifted when the furnace pressure is normal;

[0022] When the crystal line of the crystal rod is intact, the crystal rod is lifted to a height of 400-1000mm.

[0023] Further, the furnace pressure is controlled to rise from the first high pressure to a second high pressure, specifically:

[0024] Lift the flow guide cylinder to its upper limit;

[0025] Continuously add the furnace gas, so that the flow rate is 200-300 slpm, until the furnace pressure rises to the second high pressure;

[0026] Stop the gas inlet and exhaust, and maintain the second high pressure state for 30-60 min;

[0027] The second high pressure is 400-500 t.

[0028] Further, the furnace pressure is controlled to decrease from the second high pressure to the first high pressure, specifically:

[0029] First, the exhaust is opened, and when the furnace pressure decreases to the first high pressure, the intake is opened; then the first high pressure state is maintained for 120-150 min.

[0030] Further, the furnace pressure is decreased to a vacuum state to determine whether the furnace body air tightness is qualified, specifically:

[0031] The intake is closed, and the vacuumization treatment is started to determine whether the furnace body air tightness is qualified;

[0032] If not, find the leakage point and re-vacuumize to check the furnace air tightness until the test is qualified.

[0033] Further, after the furnace body air tightness is qualified, the exhaust is closed and the intake is opened, and after 30-60 min of continuous inflation, the furnace pressure becomes normal pressure, the crystal bar is taken out, and the disassembly operation is prepared.

[0034] The rapid shutdown cooling process designed in the application controls the furnace pressure to increase to a high pressure state, improves the argon convection in the furnace, speeds up the heat exchange movement between argon molecules and the furnace wall, makes the heat in the furnace be transferred to the furnace wall more quickly, so that the heat on the furnace wall is taken away by the cooling water, and the purpose of rapid cooling is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is the flow chart of the rapid shutdown cooling process in the application. DETAILED DESCRIPTION

[0036] The application will be described in detail below in combination with the drawings and specific embodiments.

[0037] The embodiment proposes a rapid shutdown cooling process, as shown in Figure 1 The steps include:

[0038] S1, when the furnace is shut down, the furnace pressure is controlled in a preset high pressure interval to adjust the air flow in the furnace, so that the heat in the furnace is discharged out of the furnace body.

[0039] Specifically, the preset high pressure interval is 90 t-500 t, and is higher than the initial furnace pressure when the furnace is shut down, wherein the initial furnace pressure is 7-9 t.

[0040] S11, the furnace pressure is controlled to increase from the initial negative pressure to the first high pressure, and the first high pressure state is maintained for a period of time.

[0041] In this process, when the furnace pressure is raised from the initial negative pressure state to the first high pressure state, the crucible position is first lowered based on the 0 position and the crystal rotation and the crucible rotation are stopped, and the power of the heater is controlled and gradually reduced to zero.

[0042] At the same time, the pipeline connected to the furnace body for charging inert gas into the furnace is opened, and the gas is continuously introduced into the furnace, and the inert gas flow is 90-200 slpm until the furnace pressure is raised to the first high pressure, and the gas introduction is continuously performed at the same time. Among them, the first high pressure is 30-120 t.

[0043] When the first high pressure is reached, the furnace pressure is maintained at the first high pressure state for a period of time, and the holding time is 60-120 min.

[0044] In this process, the furnace exhaust is always continuously controlled, but the flow rate of the furnace exhaust is less than that of the furnace inlet, so that the furnace pressure of the furnace body can be continuously raised.

[0045] Further, when the crystal rotation is stopped, it also includes judging whether the crystal rod needs to be raised. That is, when the system detects that the crystal line of the crystal rod appears broken or no edge, the crystal rod is not lifted, and the crystal rod is lifted when the furnace pressure is normal. This is because if the crystal rod is continuously lifted directly after shutdown, the temperature difference between the upper and lower furnace chambers will be too large, which will cause the crystal rod to burst. If the system detects that the crystal line of the crystal rod is intact, the crystal rod can be lifted, and the crystal rod is lifted to a height of 400-1000 mm.

[0046] S12, control the furnace pressure to rise from the first high pressure to the second high pressure, and maintain the second high pressure state for a period of time.

[0047] Further, the time maintained at the first high pressure state is shorter than the time maintained at the second high pressure state, that is, the furnace pressure is raised in steps to avoid sudden rise affecting the furnace pressure change too much, and the rise is performed intermittently, which can not only stabilize the continuity and persistence of the furnace pressure rise.

[0048] In this process, the draft tube is first lifted to its upper limit, the gas inlet is continuously opened and the exhaust is closed; the gas inlet flow is increased and the flow is increased to 200-300 slpm until the furnace pressure is raised to the second high pressure; wherein the second high pressure is 400-500 t.

[0049] Then stop the gas inlet and exhaust, and maintain the second high pressure state for 30-60 min.

[0050] The flow of the argon gas filled in is increased to control the increase of the furnace pressure, and part of the heat is taken away by the argon gas, and the other part of the heat is taken away by the high-purity argon gas filled in the furnace at a high flow rate to increase the convection of the gas in the furnace and accelerate the heat exchange movement between the argon gas molecules and the furnace wall, so that the heat in the furnace is transferred to the furnace wall more quickly, and the heat can be taken away by the cooling water in the furnace wall in time, the furnace shutdown process time can be shortened, and the purpose of rapid cooling is achieved.

[0051] S13, controlling the furnace pressure to decrease from the second high pressure to the first high pressure, and keeping the first high pressure state for a period of time.

[0052] The time for keeping the first high pressure state is different from the time for keeping the first high pressure state in step S11. This is because the first time for keeping the first high pressure state is to increase to the second high pressure, and a stage-like increase is needed, and a long time is not needed to wait. This time is to prepare for the pressure reduction process before the air tightness check, and a long time is needed to wait here, so that more buffer time is left, and the hot gas flow in the furnace body is gradually discharged outside the furnace body.

[0053] In this process, the exhaust is first opened, and the gas inlet pipeline is temporarily closed at this time. The first exhaust will make the furnace pressure gradually decrease from the high second furnace pressure, and the gas inlet is opened again when the furnace pressure decreases to the first high pressure. When the furnace pressure is the first high pressure, the first high pressure state is kept for 120-150 minutes.

[0054] S2, reducing the pressure in the furnace to a vacuum state, judging whether the air tightness of the furnace body is qualified or not; if qualified, adjusting the furnace pressure to normal pressure, and taking out the single crystal.

[0055] After keeping the furnace pressure in the first high pressure state for a period of time, the gas inlet is prepared to be closed, and the vacuumization process in the furnace is started to judge whether the air tightness of the furnace body is qualified or not, that is, the air tightness of the furnace body is checked, and whether it leaks is observed.

[0056] If qualified, the furnace pressure is adjusted to normal pressure, and the single crystal is taken out. If the air tightness of the furnace body is checked to be qualified, the exhaust is closed, and the gas inlet is opened. Inert gas is filled in for 30-60 minutes, the furnace pressure becomes normal pressure, the crystal rod is taken out, and the dismounting operation is prepared.

[0057] If not qualified, the leak point is found, and the vacuumization is re-started. The air tightness in the furnace is checked until the test is qualified.

[0058] In order to enable those skilled in the art to further understand the method of the present application, the technical solutions of the present application will be explained in detail below in combination with specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments.

[0059] Embodiment 1:

[0060] Take 32-inch hot field as an example

[0061] First, execute the shutdown process to control the crucible to drop 50 mm, and reduce the seed crystal rotation speed to 0 rpm; determine the constant diameter stage, the crystal rod has a ridge line, control the crystal rod to rise, and the rising speed is 200 mm / hr; and reduce the crucible rotation speed to 0 rpm, while controlling the heating power of the heater to reduce from 5 min to 0 kw.

[0062] Control the inert gas filled into the furnace body, and the commonly used inert gas is argon, and the argon flow is 150 slpm, the first furnace pressure is set to 40 t, and the throttle valve is adjusted to 25%.

[0063] Keep the furnace at a first furnace pressure of 40 t, continuously fill high-flow argon based on the high pressure state, and continuously pump gas from the furnace to the outside (the feature of the vacuum process, the furnace chamber is kept at high pressure) for 90 min, and the flow guide cylinder is lifted to the upper limit.

[0064] After the flow guide cylinder is lifted to the upper limit, the main pump ball valve is closed, the furnace pressure is raised to the second furnace pressure of 450 t, and the argon filling is stopped, and the second furnace pressure is kept for 30 min.

[0065] Continue to discharge the exhaust gas in the furnace body, and continue to fill argon into the furnace body, so that the furnace pressure decreases from the second furnace pressure of 450 t to the first furnace pressure of 40 t, and the first furnace pressure is kept for 150 min.

[0066] Start to close the argon inlet valve and the fast filling valve, that is, close the gas inlet, simultaneously pump the furnace to vacuum, and perform gas tightness detection.

[0067] After the furnace gas tightness detection is qualified, the large pump ball valve of the furnace body is closed, the large pump power is turned off, all power equipment is turned off, and argon is filled. When the furnace pressure rises to normal pressure, stop filling argon, and wait for 30 min, and then perform the furnace disassembly operation after the single crystal silicon rod is taken out.

[0068] In this embodiment, the whole process takes about 5 hours.

[0069] Example 2

[0070] Take 33-inch hot field as an example

[0071] First, execute the shutdown process to control the crucible to drop 80 mm, and reduce the seed crystal rotation speed to 0 rpm; determine the constant diameter stage, the crystal rod has a ridge line, control the crystal rod to rise, and the rising speed is 200 mm / hr; and reduce the crucible rotation speed to 0 rpm, while controlling the heating power of the heater to reduce from 5 min to 0 kw.

[0072] Control the inert gas filled into the furnace body, and the commonly used inert gas is argon, and the argon flow is 150 slpm, the first furnace pressure is set to 60 t, and the throttle valve is adjusted to 25%.

[0073] The furnace is kept stable at the first furnace pressure of 60 t, and high-flow argon is continuously filled based on the high-pressure state while the vacuum pump continuously pumps gas out of the furnace (a feature of the vacuum process, the furnace is kept at high pressure) for 120 min, and the flow guide cylinder is lifted to the upper limit.

[0074] After the flow guide cylinder is lifted to the upper limit, the main pump ball valve is closed, the furnace pressure is raised to the second furnace pressure of 480 t, and the argon filling is stopped. Based on the second furnace pressure, it is kept for 50 min.

[0075] The exhaust gas in the furnace body is continuously discharged, and argon is continuously filled into the furnace body, so that the furnace pressure is reduced from the second furnace pressure of 450 t to the first furnace pressure of 40 t, and the first furnace pressure is kept for 150 min.

[0076] The upper argon valve and the fast filling valve are started to be closed, that is, the gas inlet is closed, the furnace body is vacuumed, and the gas tightness test is qualified.

[0077] After the furnace body gas tightness test is qualified, the large pump ball valve of the furnace body is closed, the large pump power is turned off, all power equipment is turned off, and argon is filled. When the furnace pressure rises to normal pressure, the argon filling is stopped, and 30 min is waited after the single crystal silicon rod is taken out for dismounting operation.

[0078] In this embodiment, the whole process takes about 5.8 hours.

[0079] Example 3:

[0080] Take the 36-inch hot field as an example

[0081] First, the shutdown process is performed to control the crucible to drop 120 mm, and the seed crystal speed is reduced to 0 rpm; the equal diameter stage is judged, the crystal rod has a ridge line, the crystal rod is controlled to rise, and the rising speed is 200 mm / hr; and the crucible speed is reduced to 0 rpm, and the heating power of the heater is reduced from 5 min to 0 kw.

[0082] The inert gas filled into the furnace body is commonly argon, and the argon flow is 250 slpm. The first furnace pressure is set to 100 t, and the throttle valve is adjusted to 25%.

[0083] The furnace is kept stable at the first furnace pressure of 100 t, and high-flow argon is continuously filled based on the high-pressure state while the vacuum pump continuously pumps gas out of the furnace (a feature of the vacuum process, the furnace is kept at high pressure) for 120 min, and the flow guide cylinder is lifted to the upper limit.

[0084] After the flow guide cylinder is lifted to the upper limit, the main pump ball valve is closed, the furnace pressure is raised to the second furnace pressure of 520 t, and the argon filling is stopped. Based on the second furnace pressure, it is kept for 60 min.

[0085] The exhaust gas in the furnace is continuously discharged, and the argon gas is continuously filled into the furnace, so that the furnace pressure is reduced from the second furnace pressure 520t to the first furnace pressure 100t, and the first furnace pressure is waited for 150min.

[0086] The upper argon valve and the fast filling valve are started to be closed, that is, the gas inlet is closed, the furnace is vacuumized, and the air tightness is detected.

[0087] After the air tightness of the furnace is qualified, the large pump ball valve of the furnace is closed, the power supply of the large pump is closed, all power supply equipment is closed, and the argon gas is filled. When the furnace pressure rises to the normal pressure, the filling of the argon gas is stopped, and 60min is waited for, and the furnace is disassembled after the single crystal silicon rod is taken out.

[0088] In the embodiment, the whole process takes about 6.5 hours.

[0089] By using the rapid shutdown and cooling process designed in the application, the furnace pressure in the furnace is controlled to rise to a high pressure state, the convection of the argon gas in the furnace is improved, the heat exchange movement between the argon gas molecules and the furnace wall is accelerated, the heat in the furnace is more quickly transferred to the furnace wall, so that the heat on the furnace wall is taken away by the cooling water, and the purpose of rapid cooling is achieved.

[0090] The embodiments of the application are described in detail above, and the content is only the preferred embodiments of the application, and cannot be considered to limit the scope of the application. Any equivalent changes and improvements made within the scope of the application should still belong to the patent coverage range of the application.

Claims

1. A rapid shutdown cooling process characterized by the steps of The application relates to a method for taking out a single crystal from a single crystal furnace. When the furnace is stopped, the furnace pressure is controlled in a preset high pressure range to adjust the air flow in the furnace, so that the heat in the furnace is discharged out of the furnace body; The pressure in the furnace is reduced to a vacuum state to determine whether the air tightness of the furnace body is qualified; If qualified, the furnace pressure is adjusted to normal pressure, and the single crystal is taken out.

2. A rapid shutdown and cooling process according to claim 1, characterized in that, The preset high pressure range is 90t-500t, and the furnace pressure is higher than the initial furnace pressure when the furnace is stopped.

3. A process according to claim 1 or 2, c h a r a c t e r i s e d in that The furnace pressure is controlled in the preset high pressure range, specifically as follows: The furnace pressure is controlled from the initial negative pressure to a first high pressure, and the first high pressure state is maintained for a period of time; The furnace pressure is controlled from the first high pressure to a second high pressure, and the second high pressure state is maintained for a period of time; The furnace pressure is controlled from the second high pressure to the first high pressure, and the first high pressure state is maintained for a period of time; The time for maintaining the first high pressure state is shorter than the time for maintaining the second high pressure state, and the time for maintaining the first high pressure state twice is not the same.

4. A rapid shutdown and cooling process according to claim 3, characterized in that, When the furnace pressure is increased from the initial negative pressure state to the first high pressure state, The crucible is lowered, and the crystal rotation and the crucible rotation are stopped, and the heater power is gradually reduced to zero; At the same time, the gas is continuously introduced into the furnace, and the flow rate is 90-200 slpm, until the furnace pressure is increased to the first high pressure.

5. A rapid shutdown and cooling process according to claim 4, characterized in that, The first high pressure state is maintained for 60-120 min based on the first high pressure state, and the furnace body is continuously exhausted; wherein the initial furnace pressure is 7-9t, and the first high pressure is 30-120t.

6. A process according to claim 4 or 5, wherein When the crystal rotation is stopped, it is also determined whether the crystal rod is lifted; When the crystal line of the crystal rod is broken or has no edge, the crystal rod is not lifted, and the crystal rod is lifted when the furnace pressure is normal pressure; When the crystal line of the crystal rod is intact, the crystal rod is lifted by 400-1000 mm.

7. A rapid shutdown and cooling process according to claim 6, characterized in that, The furnace pressure is controlled from the first high pressure to the second high pressure, specifically as follows: The flow guide cylinder is lifted to the upper limit position; The gas is continuously introduced into the furnace, and the flow rate is 200-300 slpm, until the furnace pressure is increased to the second high pressure; The gas is stopped, and the second high pressure state is maintained for 30-60 min; The second high pressure is 400-500t.

8. A rapid shutdown and cooling process according to claim 7, characterized in that, The furnace pressure is controlled from the second high pressure to the first high pressure, specifically as follows: First, the exhaust is opened, and the furnace pressure is lowered to the first high pressure, and then the gas is introduced; and then the first high pressure state is maintained for 120-150 min.

9. A process for rapid shutdown and cooling of a furnace as claimed in any one of claims 1-2, 4-5, 7-8, characterized in that, The furnace pressure is reduced to a vacuum state to determine whether the air tightness of the furnace body is qualified, specifically as follows: The gas is stopped, and the vacuum treatment is started to determine whether the air tightness of the furnace body is qualified; if not, the leakage point is found, and the vacuum is re-pumped to check the air tightness in the furnace until the test is qualified.

10. A rapid shutdown and cooling process according to claim 9, characterized in that, After the air tightness of the furnace body is qualified, the exhaust is closed, and the gas is introduced, and the furnace pressure is changed to normal pressure after the gas is continuously filled for 30-60 min, the crystal rod is taken out, and the dismounting operation is prepared.

Images