Polycrystalline silicon ingot casting process method

Abstract

The invention discloses a polycrystalline silicon ingot casting process method which comprises the following steps: charging, a vacuumizing stage, a heating stage, a melting stage and a crystal growth stage, in the charging step, a silicon raw material is charged into a crucible of an ingot furnace, in the vacuumizing stage, the ingot furnace is subjected to air exhaust, argon is filled into the ingot furnace in the air exhaust process of the ingot furnace, and the ingot furnace is heated to the temperature of 60-80 DEG C; after the vacuumizing stage is finished, the crucible enters a heating stage, the crucible is heated, in the melting stage, the silicon raw material in the crucible is melted to form a silicon melt, and in the crystal growing stage, the silicon melt in the crucible is solidified and grows crystals. According to the polycrystalline silicon ingot casting process method provided by the embodiment of the invention, the content of impurities in the space gas in the ingot casting furnace can be reduced, the pollution of the impurities released by the thermal field atmosphere to the silicon raw material is reduced, the content of the impurities such as boron, phosphorus and metal in the produced polycrystalline silicon is relatively low, and the quality of the produced polycrystalline silicon is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of polysilicon ingot casting process methods, and in particular to a polysilicon ingot casting process method. Background Art

[0002] As single crystal photovoltaic products gradually occupy the photovoltaic market, the cost of single crystal materials has gradually been taken seriously. The price of silicon powder is relatively low, but silicon powder cannot be directly used for Czochralski single crystals. Generally, silicon powder is purified in an ingot furnace. The polycrystalline silicon produced by the purified silicon powder in the ingot furnace is used as the raw material for Czochralski single crystals, thereby reducing the cost of materials for Czochralski single crystals.

[0003] In the related art, the process method for purifying silicon powder in an ingot furnace is to purify silicon powder using an ingot furnace, and the specific steps are: vacuuming, heating, melting, crystal growth, annealing, and cooling. In order to reduce the oxygen content in the ingot furnace during the vacuuming stage, the pressure in the ingot furnace will be pumped to about 0.2mbar, and it can be operated without leakage. Since the temperature in the ingot furnace is about 300-400 degrees during the vacuuming stage, gases containing impurities are released in the hot field atmosphere, resulting in more impurities in the ingot furnace, and the silicon powder will absorb impurities such as boron, phosphorus, and metals therein, so that the silicon powder has been contaminated before entering the heating stage, resulting in a higher content of impurities such as boron, phosphorus, and metals in the produced polysilicon, and lower product quality. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one purpose of the present invention is to propose a polycrystalline silicon ingot casting process method, in which argon gas is filled into the ingot casting furnace during the vacuuming stage, so that the argon gas continuously replaces the gas in the furnace body, thereby reducing the content of impurities in the gas space in the ingot casting furnace, reducing the pollution of silicon raw materials by impurities released from the hot field atmosphere, making the content of impurities such as boron, phosphorus, and metals in the produced polycrystalline silicon less, and ensuring the quality of the produced polycrystalline silicon.

[0005] According to an embodiment of the present invention, the polysilicon ingot casting process method includes: charging, charging silicon raw material into a crucible of an ingot casting furnace; a vacuuming stage, evacuating the ingot casting furnace, and filling argon gas into the ingot casting furnace during the process of evacuating the ingot casting furnace; a heating stage, heating the crucible after the vacuuming stage; a melting stage, melting the silicon raw material in the crucible to form a silicon melt; and a crystal growth stage, solidifying the silicon melt in the crucible to grow crystals.

[0006] According to the polysilicon ingot casting process method of the embodiment of the present invention, during the vacuum stage, argon gas is filled into the casting furnace during the process of evacuating the casting furnace, so that the argon gas continuously replaces the gas in the furnace body, thereby reducing the content of impurities in the gas in the casting furnace, reducing the pollution of impurities released by the hot field atmosphere to the silicon raw material, and reducing the content of boron, phosphorus and metal impurities in the produced polysilicon, thereby ensuring the quality of the produced polysilicon.

[0007] According to some embodiments of the present invention, during the vacuum stage, the exhaust speed of the ingot furnace is the exhaust flow rate, the intake speed of argon gas into the ingot furnace is the first intake flow rate, and the exhaust flow rate is greater than the first intake flow rate.

[0008] According to some embodiments of the present invention, during the heating stage and the melting stage, the intake speed of argon gas into the ingot furnace is a second intake flow rate, and during the crystal growth stage, the intake speed of argon gas into the ingot furnace is a third intake flow rate, the second intake flow rate is greater than the first intake flow rate, and the third intake flow rate is greater than the first intake flow rate.

[0009] According to some embodiments of the present invention, the ratio of the first intake air flow rate to the second intake air flow rate is in a range of 10%-40%, and the ratio of the first intake air flow rate to the third intake air flow rate is in a range of 10%-40%.

[0010] According to some embodiments of the present invention, the vacuuming stage ends when the pressure in the ingot casting furnace drops to a first preset pressure, and the first preset pressure ranges from 100 to 300 mbar.

[0011] According to some embodiments of the present invention, during the vacuum pumping stage, the casting furnace is first evacuated until the pressure inside the casting furnace is reduced to a second preset pressure, and then argon is filled into the casting furnace. When the pressure inside the casting furnace is reduced to a first preset pressure, the vacuum pumping stage ends, and the first preset pressure is less than the second preset pressure.

[0012] According to some embodiments of the present invention, the casting furnace is not leak-checked before the vacuuming stage; or, the casting furnace is leak-checked before the charging.

[0013] According to some embodiments of the present invention, the casting furnace is kept filled with argon gas throughout the heating stage.

[0014] According to some embodiments of the present invention, in the heating stage and the melting stage, the intake speed of argon gas into the ingot furnace is a second intake flow rate, in the crystal growth stage, the intake speed of argon gas into the ingot furnace is a third intake flow rate, the speed at which the gas in the ingot furnace is discharged to the outside is an exhaust flow rate, and in the heating stage, the melting stage and the crystal growth stage, the exhaust flow rate is controlled and adjusted to keep the pressure in the ingot furnace within a set range.

[0015] According to some embodiments of the present invention, in the heating stage and the melting stage, the intake speed of argon gas into the ingot furnace is a second intake flow rate, in the crystal growth stage, the intake speed of argon gas into the ingot furnace is a third intake flow rate, and the speed at which the gas in the ingot furnace is discharged to the outside is an exhaust flow rate; the third intake flow rate in the crystal growth stage is smaller than the second intake flow rate in the heating stage and the melting stage.

[0016] According to some embodiments of the present invention, during the heating stage and the melting stage, the intake speed of argon gas into the ingot furnace is a second intake flow rate, and during the crystal growth stage, the intake speed of argon gas into the ingot furnace is a third intake flow rate; wherein, the second intake flow rate is 45L / min-100L / min; and / or, the third intake flow rate is 20L / min-100L / min.

[0017] According to some optional embodiments of the present invention, during the heating stage, the melting stage and the crystal growth stage, the pressure in the ingot casting furnace ranges from 50 to 250 mbar.

[0018] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0020] Figure 1 1 is a schematic flow chart of a polysilicon ingot casting process according to some embodiments of the present invention. DETAILED DESCRIPTION

[0021] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0022] Reference below Figure 1 A polysilicon ingot casting process according to an embodiment of the present invention is described.

[0023] like Figure 1 As shown, the polycrystalline silicon ingot casting process method according to an embodiment of the present invention includes the following steps: charging, vacuuming stage, heating stage, melting stage and crystal growth stage.

[0024] First, the silicon raw material is loaded into the crucible of the ingot casting furnace.

[0025] After the loading is completed, the vacuuming stage begins. During the vacuuming stage, the ingot furnace is evacuated as a whole, and argon is filled into the ingot furnace during the evacuation process. During the vacuuming stage, the ingot furnace will also have a certain temperature, so that the gas containing impurities is released in the hot field atmosphere. The silicon raw material will absorb metal impurities such as boron and phosphorus in the gas, resulting in a high content of impurities such as boron and phosphorus in the produced polysilicon.

[0026] Therefore, during the vacuuming stage, argon is filled into the ingot casting furnace during the process of evacuating the ingot casting furnace. Argon can take out the impurities released by the thermal field atmosphere and continuously replace the gas in the ingot casting furnace. Compared with the vacuuming stage in the related art, the continuous filling of argon keeps the gas flow rate of the ingot casting furnace at a relatively large value during the vacuuming stage, so that more impurities are taken out of the ingot casting furnace, thereby reducing the content of impurities in the gas in the ingot casting furnace, reducing the pollution of silicon raw materials by impurities released by the thermal field, and reducing the content of metal impurities such as boron and phosphorus in the produced polysilicon, thereby ensuring the quality of the produced polysilicon.

[0027] Moreover, argon gas is filled into the ingot furnace during the process of evacuating the ingot furnace, so that the argon gas continuously replaces the air in the ingot furnace, thereby rapidly reducing the oxygen content in the ingot furnace. Compared with the vacuum pumping stage in the related technology, there is no need to pump the pressure in the ingot furnace to a lower value, so that the oxygen content in the ingot furnace can reach a lower level, thereby shortening the overall time of the vacuum pumping stage, and further shortening the time that the silicon raw material is exposed to the hot field atmosphere, reducing the contamination of the silicon raw material by impurities.

[0028] After the vacuuming stage is completed, the heating stage begins, during which the crucible is heated. For example, during the heating stage, the top and sides of the crucible may be heated by a heater, and the heating temperature of the heater is gradually increased, so that the crucible is heated more evenly, thereby preventing the crucible from cracking or being damaged.

[0029] In the melting stage, the silicon raw material in the crucible melts to form a silicon melt. When the crucible is raised to a certain temperature, the silicon raw material in the crucible begins to melt until the silicon raw material in the crucible is completely melted to form a silicon melt.

[0030] After the melting stage, the crystal growth stage begins, during which the silicon melt in the crucible solidifies and grows into crystals. The silicon melt in the crucible continues to solidify to form polycrystalline silicon.

[0031] Specifically, the polysilicon ingot casting process also includes an annealing stage and a cooling stage. After the crystal growth stage, the annealing stage is entered, and after the annealing stage, the cooling stage is entered. After the cooling stage, the produced polysilicon can be taken out from the ingot casting furnace. After the cooling stage, the generated polysilicon can be taken out from the ingot casting furnace. Argon gas is continuously injected during the vacuum stage, heating stage, melting stage, crystal growth stage, annealing stage and cooling stage, so that the content of metal impurities such as boron and phosphorus in the produced polysilicon can be reduced to ensure product quality.

[0032] According to the polysilicon ingot casting process method of the embodiment of the present invention, during the vacuum stage, argon gas is filled into the casting furnace during the process of evacuating the casting furnace, so that the argon gas continuously replaces the gas in the furnace body, thereby reducing the content of impurities in the gas space in the casting furnace, reducing the pollution of impurities released by the hot field atmosphere to the silicon raw material, and making the content of impurities such as boron, phosphorus, and metals in the produced polysilicon less, thereby ensuring the quality of the produced polysilicon.

[0033] According to some embodiments of the present invention, referring to Figure 1 In the vacuum stage, the exhaust speed of the ingot furnace is the exhaust flow rate, the intake speed of argon gas into the ingot furnace is the first intake flow rate, and the exhaust flow rate is greater than the first intake flow rate. This setting can make the oxygen in the ingot furnace flow out of the ingot furnace faster, so that the oxygen content in the ingot furnace quickly reaches a lower value, and at the same time, the pressure in the ingot furnace can be continuously reduced, thereby ensuring that the overall process content meets the vacuum stage.

[0034] According to some embodiments of the present invention, referring to Figure 1 In the heating stage and the melting stage, the intake speed of argon gas into the ingot furnace is the second intake flow rate, and in the crystal growth stage, the intake speed of argon gas into the ingot furnace is the third intake flow rate, the second intake flow rate is greater than the first intake flow rate, and the third intake flow rate is greater than the first intake flow rate. Therefore, in unit time, the intake amount of argon gas in the heating stage, the melting stage and the crystal growth stage is greater than the intake amount of argon gas in the vacuum stage, so that in the heating stage, the melting stage and the crystal growth stage, the argon gas can take more impurities out of the ingot furnace, thereby reducing the impurities in the gas in the ingot furnace and improving the quality of the polysilicon produced. At the same time, the first intake flow rate is less than the second intake flow rate and the third intake flow rate, which can make the pressure in the ingot furnace in the vacuum stage drop faster, thereby reducing the overall time of the vacuum stage.

[0035] According to some embodiments of the present invention, referring to Figure 1, the ratio of the first air intake flow rate to the second air intake flow rate is in the range of 10%-40%, and the ratio of the first air intake flow rate to the third air intake flow rate is in the range of 10%-40%. If the first air intake flow rate is too large, the pressure drop rate in the ingot furnace during the vacuuming stage will be slow, making the overall time of the vacuuming stage longer; if the first air intake flow rate is too small, the impurities carried away by the argon gas during the vacuuming stage will be less, so that the silicon raw material will absorb more metal impurities such as boron and phosphorus, thereby causing the output of polysilicon to have more impurities.

[0036] Therefore, the ratio of the first air intake flow rate to the second air intake flow rate is in the range of 10%-40%, and the ratio of the first air intake flow rate to the third air intake flow rate is in the range of 10%-40%. This can make the pressure in the ingot furnace drop faster during the vacuum stage, reduce the overall time of the vacuum stage, and at the same time ensure that the argon gas takes away more impurities during the vacuum stage, so that the silicon raw material absorbs less metal impurities such as boron and phosphorus, thereby ensuring the quality of the produced polysilicon.

[0037] For example, the ratio of the first intake air flow rate to the second intake air flow rate can be 10%, 20%, 30%, 40%, etc., and the ratio of the first intake air flow rate to the third intake air flow rate can be 10%, 20%, 30%, 40%, etc. When the ratio of the first intake air flow rate to the second intake air flow rate is 20%, it can better ensure that the argon gas takes away more impurities during the vacuum stage, ensure the quality of the polysilicon produced, and at the same time better reduce the overall time of the vacuum stage.

[0038] According to some embodiments of the present invention, referring to Figure 1 , when the pressure in the ingot furnace is reduced to the first preset pressure, the vacuum stage ends, and the range of the first preset pressure is 100-300mbar. When the pressure in the ingot furnace is reduced to the first preset pressure, the oxygen content in the ingot furnace reaches a relatively low level, and the requirement of the oxygen content in the ingot furnace to enter the next process step is met, and the vacuum stage ends. The value range of the first preset pressure is 100-300mbar. Compared with the pressure value at the end of the vacuum stage in the related art, the value of the first preset pressure is larger, which can shorten the overall time of the vacuum stage, thereby shortening the time that the silicon raw material is exposed to the hot field atmosphere, and reducing the adsorption of impurities by the silicon raw material; at the same time, it can ensure that the oxygen content in the ingot furnace reaches a relatively low level, reduce the oxidation reaction of the silicon raw material, and thus reduce the impact of oxygen in the ingot furnace on the silicon raw material.

[0039] For example, the value of the first preset pressure may be 100 mbar, 200 mbar, 300 mbar, etc. When the value of the first preset pressure is 200 mbar, it can better ensure that the oxygen content in the ingot furnace reaches a lower level, reducing the impact of oxygen in the ingot furnace on the silicon raw material; at the same time, the overall time of the vacuum stage can be shortened, thereby reducing the adsorption of impurities by the silicon raw material.

[0040] According to some embodiments of the present invention, referring to Figure 1 In the vacuuming stage, the ingot furnace is first evacuated until the pressure in the ingot furnace is reduced to the second preset pressure, and then argon is filled into the ingot furnace. When the pressure in the ingot furnace is reduced to the first preset pressure, the vacuuming stage ends, and the first preset pressure is less than the second preset pressure. This arrangement can shorten the time for the pressure in the ingot furnace to be reduced to the second preset pressure, thereby shortening the time of the vacuuming stage, shortening the time that the silicon raw material is exposed to the hot field atmosphere, and reducing the adsorption of impurities by the silicon raw material; at the same time, the impurities released by the hot field atmosphere can be taken out of the ingot furnace by argon, thereby reducing the content of impurities in the gas in the ingot furnace and reducing the pollution of the silicon raw material by impurities released by the hot field.

[0041] The value range of the second preset pressure may be 800-900 mbar, that is, the second preset pressure may be 800 mbar, 850 mbar, 900 mbar, etc.

[0042] According to some embodiments of the present invention, referring to Figure 1 Before the vacuum stage, the ingot furnace is not leak-checked. During the vacuum stage, argon is filled into the ingot furnace during the process of evacuating the ingot furnace. The continuous filling of argon can continuously remove impurities and oxygen in the gas in the ingot furnace. When the oxygen content in the ingot furnace reaches a low level, the leak detection step can be omitted and the heating stage can be entered directly, thereby shortening the overall time of the vacuum stage, shortening the time that the silicon raw material is exposed to the hot field atmosphere, and reducing the adsorption of impurities by the silicon raw material.

[0043] Alternatively, leak detection of the ingot furnace before loading can shorten the overall time of the vacuum stage, shorten the time that the silicon raw material is exposed to the hot field atmosphere, reduce the adsorption of impurities by the silicon raw material, and better ensure the sealing effect of the ingot furnace. In addition, leak detection of the ingot furnace before loading ensures that there is no silicon raw material in the ingot furnace during the leak detection process, which can avoid the silicon raw material from being contaminated during the leak detection process, thereby reducing the impurity content in the silicon raw material.

[0044] According to some embodiments of the present invention, referring to Figure 1During the entire heating stage, keep filling the ingot furnace with argon. During the heating stage, as the temperature continues to rise, more impurities in the hot field atmosphere are continuously released, and the silicon raw material will absorb more impurities. If argon is filled after heating to a certain temperature, the silicon raw material will absorb more impurities in the process before argon is filled, resulting in a higher content of metal impurities such as boron and phosphorus in the silicon raw material, reducing the quality of the produced polysilicon.

[0045] Therefore, during the entire heating stage, argon gas is kept filled into the ingot furnace to carry out impurities through argon gas, which can prevent the silicon raw material from absorbing more impurities during the heating stage, thereby reducing the content of metal impurities such as boron and phosphorus in the silicon raw material and ensuring the quality of the produced polysilicon.

[0046] According to some embodiments of the present invention, referring to Figure 1 In the heating stage and the melting stage, the intake speed of argon gas into the ingot furnace is the second intake flow rate. In the crystal growth stage, the intake speed of argon gas into the ingot furnace is the third intake flow rate. The speed at which the gas in the ingot furnace is discharged outward is the outlet flow rate. In the heating stage and the melting stage, argon gas first flows into the ingot furnace at the speed of the second intake flow rate, and then flows out of the ingot furnace at the speed of the outlet flow rate. In the crystal growth stage, argon gas first flows into the ingot furnace at the speed of the third intake flow rate, and then flows out of the ingot furnace at the speed of the outlet flow rate. During the flow of argon gas, impurities in the gas in the ingot furnace can be taken out of the ingot furnace, thereby reducing the content of impurities in the gas in the ingot furnace and reducing the contamination of silicon raw materials and silicon melt by impurities.

[0047] In the heating stage, melting stage and crystal growth stage, the gas outlet flow rate is controlled and adjusted to keep the pressure in the ingot casting furnace within the set range. Compared with controlling the pressure in the ingot casting furnace by changing the second gas inlet flow rate and the third gas inlet flow rate, this arrangement can ensure the continuous filling of argon gas in the heating stage, melting stage and crystal growth stage, avoiding the situation where no argon gas is filled, thereby better reducing the adsorption of impurities by silicon raw materials and silicon melt, reducing the content of metal impurities such as boron and phosphorus in silicon melt, and ensuring the quality of the produced polysilicon.

[0048] According to some embodiments of the present invention, referring to Figure 1In the heating stage and the melting stage, the intake speed of argon gas into the ingot furnace is the second intake flow rate. In the crystal growth stage, the intake speed of argon gas into the ingot furnace is the third intake flow rate. The speed at which the gas in the ingot furnace is discharged outward is the outlet flow rate. In the heating stage and the melting stage, argon gas first flows into the ingot furnace at the speed of the second intake flow rate, and then flows out of the ingot furnace at the speed of the outlet flow rate. In the crystal growth stage, argon gas first flows into the ingot furnace at the speed of the third intake flow rate, and then flows out of the ingot furnace at the speed of the outlet flow rate. During the flow of argon gas, impurities in the gas in the ingot furnace can be taken out of the ingot furnace, thereby reducing the content of impurities in the gas in the ingot furnace and reducing the contamination of silicon raw materials and silicon melt by impurities.

[0049] The third gas flow rate in the crystal growth stage is smaller than the second gas flow rate in the heating stage and the melting stage. If the third gas flow rate in the crystal growth stage is larger, the argon gas will cause a greater disturbance to the silicon melt liquid level, affecting the quality of the polysilicon produced.

[0050] Therefore, during the heating stage, melting stage and crystal growth stage, the gas inlet speed of the third gas inlet flow rate during the crystal growth stage is the smallest, which can reduce the disturbance of the silicon melt liquid surface by argon gas and ensure the quality of the output polysilicon.

[0051] According to some embodiments of the present invention, referring to Figure 1 In the heating stage and the melting stage, the intake speed of argon gas into the ingot furnace is the second intake flow rate, and in the crystal growth stage, the intake speed of argon gas into the ingot furnace is the third intake flow rate. Among them, the second intake flow rate is 45L / min-100L / min. This arrangement can make the intake speed of argon gas in the heating stage and the melting stage larger, so as to better reduce the impurity content in the ingot furnace, reduce the contamination of impurities in the gas and the silicon melt, thereby ensuring the quality of the produced polysilicon. For example, the second intake flow rate can be 45L / min, 50L / min, 60L / min, 80L / min, 100L / min, etc.

[0052] According to some embodiments of the present invention, referring to Figure 1 The third air intake flow rate is 20L / min-100L / min, which can reduce the disturbance of argon gas on the silicon melt liquid surface, ensure the quality of the produced polysilicon, and at the same time ensure the intake speed of argon gas, reduce the content of impurities in the gas in the ingot furnace, and reduce the contamination of impurities in the gas to the silicon melt, thereby ensuring the quality of the produced polysilicon.

[0053] For example, the third air intake flow rate can be set to 20 L / min, 40 L / min, 60 L / min, 80 L / min, 100 L / min, etc. When the third air intake flow rate can be set to be gradually reduced from 40 L / min to 20 L / min, it can better ensure that the argon gas has less disturbance on the silicon melt liquid level, ensure the quality of the produced polysilicon, and at the same time reduce the content of impurities in the gas in the ingot furnace, thereby ensuring the quality of the produced polysilicon.

[0054] According to some optional embodiments of the present invention, referring to Figure 1 , in the heating stage, melting stage and crystal growth stage, the pressure range in the ingot furnace is 50-250mbar. In a low-pressure environment, boron, phosphorus and oxygen in the silicon melt are more easily volatilized, reducing the carbon entering the silicon melt, and reducing the content of boron, phosphorus, oxygen and carbon in the silicon melt. In the heating stage, melting stage and crystal growth stage, the pressure range in the ingot furnace is 50-250mbar. Compared with the pressure in the ingot furnace in the corresponding stage in the related art, the pressure in the ingot furnace can be lower, which can be more conducive to the volatilization of boron, phosphorus and oxygen in the silicon melt, reduce the carbon entering the silicon melt, and better reduce the content of boron, phosphorus, oxygen and carbon in the silicon melt, thereby making the content of impurities in the output polysilicon less, ensuring product quality. For example, in the heating stage, melting stage and crystal growth stage, the pressure in the ingot furnace can be 50mbar, 100mbar, 200mbar, 250mbar, etc.

[0055] For example, the pressure in the ingot furnace during the crystal growth stage is greater than that in the heating and melting stages, so as to avoid the problem of the crucible and the silicon melt being adhered to each other due to the decomposition of silicon nitride, thereby ensuring the normal use of the crucible. For example, the pressure in the ingot furnace during the heating and melting stages can be 50 mbar, and the pressure in the ingot furnace during the crystal growth stage can be 250 mbar.

[0056] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0057] Although the 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 the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A polycrystalline silicon ingot casting process, characterized in that: include: Charging, charging silicon raw materials into the crucible of the ingot casting furnace; In the vacuuming stage, the ingot casting furnace is evacuated, and argon gas is filled into the ingot casting furnace during the process of evacuating the ingot casting furnace; A heating stage, heating the crucible after the vacuuming stage is completed; In the melting stage, the silicon raw material in the crucible is melted to form a silicon melt; In the crystal growth stage, the silicon melt in the crucible solidifies and grows crystals.

2. The polycrystalline silicon ingot casting process according to claim 1, characterized in that: During the vacuuming stage, the exhaust speed for exhausting the ingot furnace is the exhaust flow rate, the intake speed of argon gas into the ingot furnace is the first intake flow rate, and the exhaust flow rate is greater than the first intake flow rate.

3. The polysilicon ingot casting process according to claim 2, characterized in that: During the heating stage and the melting stage, the intake speed of argon gas into the ingot furnace is a second intake flow rate. During the crystal growth stage, the intake speed of argon gas into the ingot furnace is a third intake flow rate. The second intake flow rate is greater than the first intake flow rate, and the third intake flow rate is greater than the first intake flow rate.

4. The polysilicon ingot casting process according to claim 3, characterized in that: The ratio of the first intake air flow rate to the second intake air flow rate is in a range of 10%-40%, and the ratio of the first intake air flow rate to the third intake air flow rate is in a range of 10%-40%.

5. The polysilicon ingot casting process according to claim 1, characterized in that: The vacuuming stage ends when the pressure in the ingot casting furnace drops to a first preset pressure, and the first preset pressure ranges from 100 to 300 mbar.

6. The polycrystalline silicon ingot casting process according to claim 1, characterized in that: During the vacuum pumping stage, the casting furnace is first evacuated until the pressure inside the casting furnace is reduced to a second preset pressure, and then argon is filled into the casting furnace. When the pressure inside the casting furnace is reduced to a first preset pressure, the vacuum pumping stage ends, and the first preset pressure is less than the second preset pressure.

7. The polycrystalline silicon ingot casting process according to claim 1, characterized in that: Before the vacuuming stage, the casting furnace is not leak-checked; alternatively, the casting furnace is leak-checked before the charging.

8. The polysilicon ingot casting process according to claim 1, characterized in that: Throughout the heating phase, the casting furnace is kept filled with argon.

9. The polysilicon ingot casting process according to claim 1, characterized in that: In the heating stage and the melting stage, the intake speed of argon gas into the ingot furnace is the second intake flow rate, in the crystal growth stage, the intake speed of argon gas into the ingot furnace is the third intake flow rate, the speed at which the gas in the ingot furnace is discharged to the outside is the exhaust flow rate, and in the heating stage, the melting stage and the crystal growth stage, the exhaust flow rate is controlled and adjusted to keep the pressure in the ingot furnace within a set range.

10. The polysilicon ingot casting process according to claim 1, characterized in that: In the heating stage and the melting stage, the gas intake speed of argon gas into the ingot casting furnace is a second gas intake flow rate, in the crystal growth stage, the gas intake speed of argon gas into the ingot casting furnace is a third gas intake flow rate, and the speed at which the gas in the ingot casting furnace is discharged to the outside is an exhaust gas flow rate; The third gas intake flow rate in the crystal growth stage is smaller than the second gas intake flow rates in the heating stage and the melting stage.

11. The polysilicon ingot casting process according to claim 1, characterized in that: In the heating stage and the melting stage, the gas intake rate of argon gas into the ingot casting furnace is a second gas intake rate, and in the crystal growth stage, the gas intake rate of argon gas into the ingot casting furnace is a third gas intake rate; Wherein, the second air intake flow rate is 45L / min-100L / min; and / or, the third air intake flow rate is 20L / min-100L / min.

12. The polycrystalline silicon ingot casting process according to any one of claims 1 to 11, characterized in that: During the heating stage, the melting stage and the crystal growth stage, the pressure in the ingot casting furnace ranges from 50 to 250 mbar.

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