CN114657629A - Crystal bar drawing method - Google Patents
Crystal bar drawing method Download PDFInfo
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- CN114657629A CN114657629A CN202210329332.9A CN202210329332A CN114657629A CN 114657629 A CN114657629 A CN 114657629A CN 202210329332 A CN202210329332 A CN 202210329332A CN 114657629 A CN114657629 A CN 114657629A
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/20—Controlling or regulating
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Abstract
The invention provides a crystal bar drawing method, which comprises the following steps: material melting: introducing argon into a single crystal furnace, starting a dry pump, and smelting the raw materials in the single crystal furnace to obtain molten liquid; cooling: reducing the temperature of the molten liquid to obtain the molten liquid after temperature reduction; a crystal pulling step: drawing the cooled molten liquid to obtain a crystal bar; when the material melting step enters the temperature reduction step, the flow of argon is reduced and the furnace pressure is reduced along with the reduction of the temperature. According to the crystal bar drawing method provided by the embodiment of the invention, impurities in the molten liquid can be effectively reduced by reducing the flow of argon and the furnace pressure in the cooling stage, so that oxygen in the molten liquid is separated out as much as possible, the oxygen content in the molten liquid is further reduced before seeding, and the crystallization rate of the crystal bar is further improved.
Description
Technical Field
The invention relates to the technical field of crystal pulling methods, in particular to a crystal bar drawing method.
Background
During the crystal bar drawing process, the cleanliness in the furnace and the impurity concentration of the solution affect the crystallization condition of the crystal bar, and the impurity concentration is high, for example, the oxygen content is too high, so that tiny impurity regions are easily formed, and the regions can affect the stability of a crystallization interface. Therefore, the 'impurity removing' method in the crystal bar drawing process is the key point.
In the conventional crystal pulling method, impurities are removed only by increasing the opening degree of a dry pump in a material melting stage, and impurity removal treatment is not performed by other measures, so that the crystal forming rate of a single crystal is not substantially improved. And the existing oxygen in the melt is not effectively removed, so that the oxygen content of the crystal bar is difficult to control, and the quality of the crystal bar is poor.
Disclosure of Invention
In view of the above, the present invention provides a method for pulling a crystal rod, which can further effectively reduce the oxygen content in a melt.
In order to solve the technical problems, the invention adopts the following technical scheme:
the crystal bar drawing method comprises the following steps:
material melting: introducing argon into a single crystal furnace, starting a dry pump, and smelting the raw materials in the single crystal furnace to obtain molten liquid;
cooling: reducing the temperature of the molten liquid to obtain the cooled molten liquid;
a crystal pulling step: drawing the cooled molten liquid to obtain a crystal bar;
when entering the temperature reduction step from the material melting step, the flow of argon is reduced and the furnace pressure is reduced along with the reduction of the temperature.
Further, in the material melting step, the flow rate of the argon is 60-80L/min, and the pressure in the single crystal furnace is 900-1000 Pa.
Further, in the material melting step, the melting temperature is 1500-1650 ℃, and the melting time is 5-10 h.
Further, in the temperature reduction step, the flow rate of the argon is 40-50L/min, and the pressure in the single crystal furnace is 300-600 Pa.
Further, when the material melting step enters the temperature reduction step, the opening degree of the dry pump is kept unchanged so as to improve the flow rate of argon in the single crystal furnace.
Further, in the cooling step, the cooling time is 12-16 min, and the temperature of the cooled molten liquid is 1400-1500 ℃.
Further, in the drawing step, the flow rate of the argon is 60-80L/min, and the pressure in the single crystal furnace is 1400-1600 Pa.
Further, when the temperature reduction step enters the drawing step, the flow rate of the argon gas is fixed, and the opening degree of the dry pump is reduced to control the pressure in the furnace.
Further, in the temperature lowering step, argon gas is blown from above the sub-chamber of the single crystal furnace and argon gas is also blown from below the main chamber of the single crystal furnace at a flow rate of 20L/min or less.
Further, the method can further comprise the following steps before the material melting step:
a pretreatment step: cleaning the single crystal furnace, putting the pretreated raw materials into the single crystal furnace, and vacuumizing.
The technical scheme of the invention at least has one of the following beneficial effects:
according to the crystal bar drawing method provided by the embodiment of the invention, the effective impurity removing effect is achieved by controlling the flow of argon in the cooling period. In the material melting stage, the environment in the furnace can be effectively improved and the crystallization condition can be improved by introducing argon and starting a dry pump; impurities in the molten liquid can be effectively reduced by reducing the flow of argon and the furnace pressure in the cooling stage, so that oxygen in the molten liquid is separated out as much as possible, the oxygen content in the molten liquid is further reduced before seeding, and the crystallization rate of the crystal bar is further improved.
Drawings
FIG. 1 is a flow chart of a method for drawing a crystal rod according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It should be apparent that the described embodiments are only some of the embodiments of the present invention, and not all of them. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention, are within the scope of the invention.
Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. Also, the use of the terms "a" or "an" and the like do not denote a limitation of quantity, but rather denote the presence of at least one.
First, a method for drawing a crystal rod according to an embodiment of the present invention is described in detail, including the following steps:
material melting: introducing argon into the single crystal furnace, starting a dry pump, and smelting the raw materials in the single crystal furnace to obtain molten liquid;
cooling: reducing the temperature of the molten liquid to obtain the cooled molten liquid;
a crystal pulling step: drawing the cooled molten liquid to obtain a crystal bar;
when the material melting step enters the temperature reduction step, the flow of argon is reduced and the furnace pressure is reduced along with the reduction of the temperature.
That is, the flow rate of argon gas and the pressure in the furnace are higher in the melting step than in the temperature reduction step. In the material melting stage, volatile matters and impurities are easily generated in the furnace along with the rise of the temperature in the furnace, and the volatile matters and the impurities generated at high temperature can be effectively taken away by introducing argon and starting a dry pump, so that the cleanliness in the single crystal furnace is improved, and the improvement of the crystallization condition is facilitated; and in the cooling stage, along with the reduction of the temperature of the molten liquid in the single crystal furnace, volatile matters are reduced, impurities overflowing from the molten liquid are reduced, if the same argon flow and furnace pressure as in the melting stage are kept, the impurities and the like are not beneficial to overflowing from the molten liquid, and at the moment, the partial pressure of each impurity and gas in the furnace is reduced by reducing the argon flow and the furnace pressure, so that oxygen and impurities in the molten liquid are further precipitated, the oxygen content in the molten liquid is further reduced before seeding, and the crystallization rate of the crystal bar is further improved.
Further, when the temperature reduction step is completed and the crystal pulling step is carried out, the flow rate of argon can be increased again and the furnace pressure can be controlled. Preferably, in the pulling step, the furnace pressure of the single crystal furnace is controlled again when the level of the melt is settled from a slightly shaken state. That is, the furnace pressure is adjusted after the melt is stabilized. Therefore, instability caused by the fluctuation of the liquid level of the molten liquid due to the change of the furnace pressure can be avoided, and the subsequent crystal pulling operation can be smoothly carried out. The furnace pressure can be controlled by automatically controlling the opening of the dry pump by the system.
According to the crystal bar drawing method provided by the embodiment of the invention, the effective impurity removing effect is achieved by controlling the flow of argon in the cooling time period. In the material melting stage, the environment in the furnace can be effectively improved and the crystallization condition can be improved by introducing argon and starting a dry pump; impurities in the molten liquid can be effectively reduced by reducing the flow of argon and the furnace pressure in the cooling stage, so that oxygen in the molten liquid is separated out as much as possible, the oxygen content in the molten liquid is further reduced before seeding, and the crystallization rate of the crystal bar is further improved.
Particularly, in the material melting step, the flow of argon can be set to 60-80L/min, the pressure in the single crystal furnace is 900-1000 Pa, argon is introduced and a dry pump is started in the material melting stage, namely, the opening degree of the dry pump reaches the maximum, so that volatile matters and impurities generated at high temperature can be effectively taken away in the material melting process, the environment in the furnace can be effectively improved, the cleanliness in the furnace is ensured, and the crystallization condition is improved.
In addition, in the material melting step, the melting temperature can be set to be 1500-1650 ℃ and the melting time can be 5-10 h by combining the characteristics of the raw materials, so that the material melting is fully performed.
And after the material melting is finished, cooling the melt, namely entering a cooling step. As described above, when the temperature is decreased from the melting step to the temperature decreasing step, the flow rate of argon gas is also decreased and the furnace pressure is also decreased. Specifically, in the temperature reduction step, the flow rate of the argon can be reduced to 40-50L/min, and the pressure in the single crystal furnace is 300-600 Pa. Thus, the partial pressure of each impurity and gas in the furnace can be reduced, which contributes to further precipitation of oxygen and impurities in the melt, further reduces the oxygen content in the melt before seeding, and further improves the crystallization rate of the ingot.
In addition, when the material melting step enters the temperature reduction step, for example, the opening degree of the dry pump can be kept unchanged, and the flow rate of argon in the single crystal furnace can be increased by increasing the flow rate of argon, so that impurities and oxygen can be more quickly taken away from the furnace chamber.
In addition, in the cooling step, the cooling time may be set to 12 to 16min, for example, and the temperature of the melt after cooling may be 1400 to 1500 ℃, depending on impurities contained in the raw material. At this temperature, the subsequent crystal pulling is not affected, and the precipitation of impurities and the like is facilitated.
And after the temperature reduction step is finished, entering a drawing step. Specifically, in the drawing step, for example, the flow rate of argon gas may be set to be 60 to 80L/min, and the pressure in the single crystal furnace may be 1400 to 1600 Pa. That is, after the temperature reduction is completed, the pressure in the furnace and the flow rate of argon gas are further increased.
For example, when the temperature reduction step is performed to the drawing step, the flow rate of argon gas is fixed and the opening degree of the dry pump is reduced to control the pressure in the furnace. When the melt liquid level is calm from a slightly jittered state, the furnace pressure control stage is started, the argon flow is fixed in the stage, the furnace pressure is controlled by automatically controlling the opening of the dry pump through the system, and the subsequent crystal pulling operation is stably carried out.
In the temperature lowering step, in addition to the blowing of argon gas from above the sub-chamber of the single crystal furnace, for example, argon gas may be simultaneously blown from below the main chamber of the single crystal furnace at a flow rate of 20L/min or less. Therefore, impurities and oxygen deposited below the furnace chamber can be smoothly taken out of the furnace chamber, and the impurities in the molten metal can be further reduced.
Further, in order to further improve the cleanliness of the single crystal furnace and reduce impurities, a pretreatment step can be included before the material melting step. Specifically, the single crystal furnace is subjected to furnace disassembly, cleaning and furnace loading, and the pretreated raw material is placed into the single crystal furnace and vacuumized.
Hereinafter, the method of pulling a crystal ingot according to the present invention will be described in further detail by way of specific examples.
Example 1
Material melting: introducing argon gas with the flow rate of 60L/min from the upper part of an auxiliary chamber of the single crystal furnace, starting a dry pump, adjusting the opening of a ball valve of the dry pump to 100%, controlling the pressure in the single crystal furnace to be 900Pa, controlling the smelting temperature to be 1600 ℃, and smelting for 5 hours, and smelting the raw materials in the single crystal furnace to obtain molten liquid;
cooling: reducing the temperature of the molten liquid to 1400 ℃, wherein the temperature reduction time is 16min, keeping the opening of a ball valve of a dry pump unchanged to improve the flow rate of argon in the single crystal furnace, reducing the flow rate of the argon, blowing the argon with the flow rate of 40L/min from the upper part of a secondary chamber of the single crystal furnace, blowing the argon with the flow rate of 20L/min from the lower part of a main chamber of the single crystal furnace, and the pressure in the single crystal furnace is 600 Pa;
a crystal pulling step: argon gas with the flow rate of 60L/min is blown from the upper part of the auxiliary chamber of the single crystal furnace, the flow rate of the argon gas is fixed, the opening degree of a ball valve of a dry pump is adjusted to 30 percent, and the pressure in the furnace is controlled at 1400 Pa.
Example 2
Material melting: introducing argon gas with the flow rate of 80L/min from the upper part of an auxiliary chamber of the single crystal furnace, starting a dry pump, adjusting the opening of a ball valve of the dry pump to 100%, controlling the pressure in the single crystal furnace to be 1000Pa, controlling the smelting temperature to be 1500 ℃ and the smelting time to be 10 hours, and smelting the raw materials in the single crystal furnace to obtain molten liquid;
cooling: reducing the temperature of the molten liquid to 1500 ℃, wherein the temperature reduction time is 12min, keeping the opening degree of a ball valve of a dry pump unchanged to improve the flow rate of argon in the single crystal furnace, reducing the flow rate of the argon, blowing the argon with the flow rate of 50L/min from the upper part of a sub-chamber of the single crystal furnace, and the pressure in the single crystal furnace is 300 Pa;
a crystal pulling step: argon gas with the flow rate of 80L/min is blown from the upper part of the auxiliary chamber of the single crystal furnace, the flow rate of the argon gas is fixed, the opening degree of a ball valve of a dry pump is adjusted to 70 percent, and the pressure in the furnace is controlled to be 1600 Pa.
Comparative example 1
Material melting and cooling steps: introducing argon gas with the flow rate of 80L/min from the upper part of an auxiliary chamber of the single crystal furnace, starting a dry pump, adjusting the opening of a ball valve of the dry pump to 100%, controlling the pressure in the single crystal furnace to be 1000Pa, controlling the smelting temperature to be 1500 ℃ and the smelting time to be 10 hours, and smelting the raw materials in the single crystal furnace to obtain molten liquid;
a crystal pulling step: argon gas with the flow rate of 80L/min is blown from the upper part of the auxiliary chamber of the single crystal furnace, the flow rate of the argon gas is fixed, the opening degree of a ball valve of a dry pump is adjusted to 70 percent, and the pressure in the furnace is controlled to be 1600 Pa.
The results (shown as example 1 and example 2) of calculating the crystal growth rate of the ingot by drawing the ingot using the production methods of example 1 and example 2 are shown in table 1 below, and the results (shown as comparative example 1 and comparative example 1) of calculating the crystal growth rate of the ingot by drawing the ingot using the production method of comparative example 1 are shown in table 1 below.
TABLE 1 Crystal growth Rate for Crystal bars under different production methods
| / | Example 1 | Example 2 | Comparative example 1 |
| Number of crystal pulls | 20 | 20 | 20 |
| Number of formed crystals | 7 | 8 | 4 |
| Crystal forming rate | 35％ | 40％ | 20％ |
As can be seen from table 1, the crystal yield of the ingot was improved by using the ingot drawing method of the present example.
While the foregoing is directed to the preferred embodiment of the present invention, it will be appreciated by those skilled in the art that various changes and modifications may be made therein without departing from the principles of the invention as set forth in the appended claims.
Claims (10)
1. A method of pulling a crystal rod, comprising the steps of:
material melting: introducing argon into a single crystal furnace, starting a dry pump, and smelting the raw materials in the single crystal furnace to obtain molten liquid;
a cooling step: reducing the temperature of the molten liquid to obtain the cooled molten liquid;
a crystal pulling step: drawing the cooled molten liquid to obtain a crystal bar;
when the material melting step enters the temperature reduction step, the flow of argon is reduced and the furnace pressure is reduced along with the reduction of the temperature.
2. The method of pulling a crystal ingot according to claim 1, wherein in the melting step, the flow rate of the argon gas is 60 to 80L/min, and the pressure in the single crystal furnace is 900 to 1000 Pa.
3. The method for drawing the crystal rod according to claim 2, wherein in the melting step, the melting temperature is 1500-1650 ℃ and the melting time is 5-10 hours.
4. The method of pulling an ingot according to claim 2, wherein in the step of reducing the temperature, the flow rate of the argon gas is 40 to 50L/min, and the pressure in the single crystal furnace is 300 to 600 Pa.
5. The method of claim 4, wherein the opening of the dry pump is maintained to increase the flow rate of argon gas in the single crystal furnace during the cooling step from the melting step.
6. The method according to claim 2, wherein in the step of cooling, the cooling time is 12 to 16min, and the temperature of the melt after cooling is 1400 to 1500 ℃.
7. The method as claimed in claim 2, wherein in the drawing step, the flow rate of the argon gas is 60 to 80L/min, and the pressure in the single crystal furnace is 1400 to 1600 Pa.
8. The ingot pulling method as set forth in claim 7, wherein the flow rate of the argon gas is fixed and the opening degree of the dry pump is decreased to control the furnace pressure at the time of the pulling step from the temperature decreasing step.
9. The method of pulling an ingot according to claim 1, wherein in the temperature lowering step, in addition to the argon gas blown from above the sub-chamber of the single crystal furnace, argon gas is simultaneously blown from below the main chamber of the single crystal furnace at a flow rate of 20L/min or less.
10. The method of claim 1, further comprising, prior to the melting step:
a pretreatment step: cleaning the single crystal furnace, putting the pretreated raw materials into the single crystal furnace, and vacuumizing.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20020157600A1 (en) * | 2000-02-28 | 2002-10-31 | Izumi Fusegawa | Method for preparing silicon single crystal and silicon single crystal |
| CN105113003A (en) * | 2015-10-14 | 2015-12-02 | 江苏华盛天龙光电设备股份有限公司 | Crystal pulling process for single crystal silicon |
| CN107338474A (en) * | 2017-08-03 | 2017-11-10 | 晶科能源有限公司 | One kind reduces polycrystalline silicon ingot casting oxygen content method |
| CN113981525A (en) * | 2021-11-05 | 2022-01-28 | 双良硅材料(包头)有限公司 | Oxygen reduction crystal pulling process and quartz crucible |
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- 2022-03-31 CN CN202210329332.9A patent/CN114657629A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20020157600A1 (en) * | 2000-02-28 | 2002-10-31 | Izumi Fusegawa | Method for preparing silicon single crystal and silicon single crystal |
| CN105113003A (en) * | 2015-10-14 | 2015-12-02 | 江苏华盛天龙光电设备股份有限公司 | Crystal pulling process for single crystal silicon |
| CN107338474A (en) * | 2017-08-03 | 2017-11-10 | 晶科能源有限公司 | One kind reduces polycrystalline silicon ingot casting oxygen content method |
| CN113981525A (en) * | 2021-11-05 | 2022-01-28 | 双良硅材料(包头)有限公司 | Oxygen reduction crystal pulling process and quartz crucible |
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