Monocrystalline silicon raw material impurity pretreatment method based on thermal migration effect

Abstract

The invention relates to the technical field of monocrystalline silicon raw material pretreatment, in particular to a monocrystalline silicon raw material impurity pretreatment method based on a thermal migration effect, which comprises the following steps: (1) silicon block pretreatment: ultrasonically cleaning a polycrystalline silicon block to obtain a cleaned polycrystalline silicon block; (2) in an inert gas environment, carrying out gradient heating on the cleaned polycrystalline silicon block to migrate impurities so as to obtain a heat-treated polycrystalline silicon block; (3) carrying out directional gas purging on the heat-treated polycrystalline silicon block to obtain a purged polycrystalline silicon block; and (4) cooling and post-processing: cooling the blown polycrystalline silicon block to below 100 DEG C along with the furnace, and taking out the polycrystalline silicon block. Compared with direct acid pickling, the method has the advantages that the metal impurity removal rate is increased by 30% through the specific monocrystalline silicon raw material impurity pretreatment method based on the thermal migration effect, and the method has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of single crystal silicon raw material pretreatment, and in particular relates to a single crystal silicon raw material impurity pretreatment method based on thermal migration effect. Background Art

[0002] Existing technologies for pre-treating single crystal silicon raw materials for impurities primarily rely on chemical etching, using a hydrofluoric acid / nitric acid mixture to remove metallic impurities from the silicon material's surface. However, these methods present the following challenges: The cost of pickling consumables is high, wastewater disposal is difficult, and excessive pickling can cause micro-damage to the silicon surface, hindering subsequent crystal growth. Other existing technologies utilize heat treatment methods that require high-temperature (>600°C) annealing to remove impurities, which is energy-intensive and prone to silicon oxidation. Therefore, a low-cost, non-destructive impurity pre-treatment method for single crystal silicon is urgently needed. Summary of the Invention

[0003] The object of the present invention is to provide a method for pretreating impurities in single crystal silicon raw materials based on the thermal migration effect, so as to solve the technical problems in the prior art.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for pretreating impurities in a single crystal silicon raw material based on the thermal migration effect, comprising the following steps: Step (1) silicon block pretreatment: ultrasonically cleaning the polycrystalline silicon block to obtain a cleaned polycrystalline silicon block; Step (2) in an inert gas environment, subjecting the cleaned polycrystalline silicon block to gradient heating to migrate impurities, thereby obtaining a heat-treated polycrystalline silicon block; In the above process, metal impurities (Fe, Al, etc.) diffuse and accumulate on the surface.

[0005] Step (3) directional gas purge is performed on the heat-treated polycrystalline silicon block to obtain a purged polycrystalline silicon block; During the above process, argon or nitrogen is introduced to purge the surface enrichment layer.

[0006] Step (4) Cooling and post-processing: The purged polysilicon blocks are cooled to below 100°C in the furnace and taken out.

[0007] Preferably, in step (1), the raw material specifications of the polysilicon block are: particle size 50-100 mm, metal impurity Fe ≤ 200 ppm, and metal impurity Al ≤ 150 ppm.

[0008] Preferably, in step (1), the ultrasonic cleaning conditions are: ultrasonic cleaning time is 10-15 min, ultrasonic cleaning power is 20-40 kHz; and the cleaning reagent is anhydrous ethanol.

[0009] Preferably, in step (2), the heating equipment is a closed tubular resistance furnace; the quartz tube of the closed tubular resistance furnace has a diameter of 300 mm and a length of 2000 mm.

[0010] Preferably, in step (2), the gradient heating method is: heating from room temperature to 230-270°C at a heating rate of 3-7°C / min, keeping warm for 0.5-1.5h, and then heating to 330-370°C at a heating rate of 2-4°C / min, keeping warm for 1.5-2.5h.

[0011] Preferably, in step (2), the inert gas environment is: the inert gas is high-purity argon with a purity of ≥99.999%, which is continuously introduced into the furnace at a flow rate of 5 L / min, and the micro-positive pressure in the furnace is 0.05 MPa.

[0012] Preferably, in step (3), the purging device: a multi-hole nozzle array is provided at the end of the furnace body, with a hole diameter of 1 mm and a spacing of 20 mm.

[0013] Preferably, in step (3), the gas is nitrogen or argon; the purge parameters are: flow rate 7-9 m / s, temperature 140-160°C, and purge angle 45±5°.

[0014] Preferably, in step (3), the purging method is: three pulse purgings, each 10 minutes with an interval of 5 minutes, for a total of 30 minutes.

[0015] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: Compared with direct pickling, the present invention improves the metal impurity removal rate by 30% through a specific single crystal silicon raw material impurity pretreatment method based on the thermal migration effect; the amount of pickling solution used is reduced by more than 40%, while avoiding high-temperature oxidation, and the silicon material loss rate is less than 0.5%, which significantly reduces the amount of subsequent pickling reagents used and solves the problem of oxidation caused by high-temperature heat treatment, solving the problems of high reagent consumption and oxidation caused by high-temperature heat treatment in traditional pickling methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 It is a process flow chart of the method for pretreating impurities of single crystal silicon raw materials of the present invention. DETAILED DESCRIPTION

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

[0019] See Figure 1 As shown, this embodiment discloses a method for pretreating impurities in a single crystal silicon raw material based on the thermal migration effect, comprising the following steps: Step (1) silicon block pretreatment: cleaning the surface of a 10 cm × 10 cm × 5 cm polycrystalline silicon block with an ultrasonic cleaning power of 30 kHz for 13 minutes to obtain a cleaned polycrystalline silicon block; Step (2) Argon gas is continuously introduced at a flow rate of 5 L / min, and the micro-positive pressure in the furnace is 0.05 MPa. The cleaned polysilicon block is then placed in a closed tubular resistance furnace, and the temperature is raised from room temperature to 250°C at a heating rate of 5°C / min, and kept warm for 1 hour. Then, the temperature is raised to 350°C at a heating rate of 3°C / min, and kept warm for 2 hours to migrate impurities and obtain a heat-treated polysilicon block. Step (3) introducing argon or nitrogen to perform a directional gas purge on the heat-treated polycrystalline silicon block to obtain a purged polycrystalline silicon block; Purge parameters: flow rate 8 m / s, temperature 150°C, purge angle 50°; purge mode: 3 pulse purges, each 10 minutes with an interval of 5 minutes, for a total of 30 minutes.

[0020] Step (4) Cooling and post-processing: The purged polysilicon blocks are cooled to below 100°C in the furnace and taken out.

[0021] After cooling, the Fe content dropped from 120 ppm to 75 ppm. Example

[0022] See Figure 1 As shown, this embodiment discloses a method for pretreating impurities in a single crystal silicon raw material based on the thermal migration effect, comprising the following steps: Step (1) silicon block pretreatment: cleaning the surface of a 10 cm × 10 cm × 5 cm polycrystalline silicon block with an ultrasonic cleaning power of 20 kHz for 15 minutes to obtain a cleaned polycrystalline silicon block; Step (2) Argon is continuously introduced at a flow rate of 5 L / min, and the micro-positive pressure in the furnace is 0.05 MPa. Then, the cleaned polysilicon block is placed in a closed tubular resistance furnace, and the temperature is increased from room temperature to 270°C at a heating rate of 3°C / min, and kept warm for 0.5 h. Then, the temperature is increased to 330°C at a heating rate of 4°C / min, and kept warm for 2.5 h to migrate impurities and obtain a heat-treated polysilicon block. Step (3) introducing argon or nitrogen to perform a directional gas purge on the heat-treated polycrystalline silicon block to obtain a purged polycrystalline silicon block; Purge parameters: flow rate 7 m / s, temperature 160°C, purge angle 45°; purge mode: 3 pulse purges, each 10 minutes with an interval of 5 minutes, for a total of 30 minutes.

[0023] Step (4) Cooling and post-processing: The purged polysilicon blocks are cooled to below 100°C in the furnace and taken out.

[0024] After cooling, the Fe content dropped from 120 ppm to 80 ppm. Example

[0025] See Figure 1 As shown, this embodiment discloses a method for pretreating impurities in a single crystal silicon raw material based on the thermal migration effect, comprising the following steps: Step (1) silicon block pretreatment: cleaning the surface of a 10 cm × 10 cm × 5 cm polycrystalline silicon block with an ultrasonic cleaning power of 40 kHz for 10 minutes to obtain a cleaned polycrystalline silicon block; Step (2) Argon is continuously introduced at a flow rate of 5 L / min, and the micro-positive pressure in the furnace is 0.05 MPa. Then, the cleaned polysilicon block is placed in a closed tubular resistance furnace, and the temperature is raised from room temperature to 230°C at a heating rate of 7°C / min, and kept warm for 1.5 hours. Then, the temperature is raised to 370°C at a heating rate of 2°C / min, and kept warm for 1.5 hours to migrate impurities and obtain a heat-treated polysilicon block. Step (3) introducing argon or nitrogen to perform a directional gas purge on the heat-treated polycrystalline silicon block to obtain a purged polycrystalline silicon block; Purge parameters: flow rate 9 m / s, temperature 140°C, purge angle 40°; purge mode: 3 pulse purges, each 10 minutes with an interval of 5 minutes, for a total of 30 minutes.

[0026] Step (4) Cooling and post-processing: The purged polysilicon blocks are cooled to below 100°C in the furnace and taken out.

[0027] After cooling, the Fe content dropped from 120 ppm to 85 ppm. Example

[0028] See Figure 1 As shown, this embodiment discloses a method for pretreating impurities in a single crystal silicon raw material based on the thermal migration effect, comprising the following steps: Step (1) silicon block pretreatment: the surface of a 10 cm × 10 cm × 5 cm polycrystalline silicon block was ultrasonically cleaned for 12 minutes at a power of 25 kHz to obtain a cleaned polycrystalline silicon block; Step (2) Argon is continuously introduced at a flow rate of 5 L / min, and the micro-positive pressure in the furnace is 0.05 MPa. Then, the cleaned polysilicon block is placed in a closed tubular resistance furnace, and the temperature is raised from room temperature to 260°C at a heating rate of 4°C / min, and kept warm for 0.8 h. Then, the temperature is raised to 340°C at a heating rate of 3°C / min, and kept warm for 2 h to migrate impurities and obtain a heat-treated polysilicon block. Step (3) introducing argon or nitrogen to perform a directional gas purge on the heat-treated polycrystalline silicon block to obtain a purged polycrystalline silicon block; Purge parameters: flow rate 8 m / s, temperature 160°C, purge angle 40°; purge mode: 3 pulse purges, each 10 minutes with an interval of 5 minutes, for a total of 30 minutes.

[0029] Step (4) Cooling and post-processing: The purged polysilicon blocks are cooled to below 100°C in the furnace and taken out.

[0030] After cooling, the Fe content dropped from 120 ppm to 80 ppm. Example

[0031] See Figure 1 As shown, this embodiment discloses a method for pretreating impurities in a single crystal silicon raw material based on the thermal migration effect, comprising the following steps: Step (1) silicon block pretreatment: cleaning the surface of a 10 cm × 10 cm × 5 cm polycrystalline silicon block by ultrasonic cleaning at a power of 20-40 kHz for 10-15 minutes to obtain a cleaned polycrystalline silicon block; Step (2) Argon is continuously introduced at a flow rate of 5 L / min, and the micro-positive pressure in the furnace is 0.05 MPa. Then, the cleaned polysilicon block is placed in a closed tubular resistance furnace, and the temperature is increased from room temperature to 240°C at a heating rate of 6°C / min, and kept warm for 1.5 hours. Then, the temperature is increased to 360°C at a heating rate of 2°C / min, and kept warm for 1.5 hours to migrate impurities and obtain a heat-treated polysilicon block. Step (3) introducing argon or nitrogen to perform a directional gas purge on the heat-treated polycrystalline silicon block to obtain a purged polycrystalline silicon block; Purge parameters: flow rate 9 m / s, temperature 150°C, purge angle 45°; purge mode: 3 pulse purges, each 10 minutes with an interval of 5 minutes, for a total of 30 minutes.

[0032] Step (4) Cooling and post-processing: The purged polysilicon blocks are cooled to below 100°C in the furnace and taken out.

[0033] After cooling, the Fe content dropped from 120 ppm to 85 ppm. Example

[0034] Compared with Example 1: Direct pickling group: 30% HF solution soaking for 20 minutes is required to achieve the same effect as Example 1.

[0035] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

[0036] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for pretreating impurities in single crystal silicon raw materials based on the thermal migration effect, characterized in that: The following steps are involved: Step (1) silicon block pretreatment: ultrasonically cleaning the polycrystalline silicon block to obtain a cleaned polycrystalline silicon block; Step (2) in an inert gas environment, subjecting the cleaned polycrystalline silicon block to gradient heating to migrate impurities, thereby obtaining a heat-treated polycrystalline silicon block; Step (3) directional gas purge is performed on the heat-treated polycrystalline silicon block to obtain a purged polycrystalline silicon block; Step (4) Cooling and post-processing: The purged polysilicon blocks are cooled to below 100°C in the furnace and taken out.

2. The method for pretreating impurities in single crystal silicon raw materials based on the thermal migration effect according to claim 1, characterized in that: In the step (1), the raw material specifications of the polysilicon block are: particle size 50-100 mm, metal impurity Fe ≤ 200 ppm, metal impurity Al ≤ 150 ppm.

3. The method for pretreating impurities in single crystal silicon raw materials based on the thermal migration effect according to claim 1, characterized in that: In the step (1), the ultrasonic cleaning conditions are as follows: the ultrasonic cleaning time is 10-15 minutes, the ultrasonic cleaning power is 20-40 kHz; and the cleaning reagent is anhydrous ethanol.

4. The method for pretreating impurities in single crystal silicon raw materials based on the thermal migration effect according to claim 1, characterized in that: In the step (2), the heating equipment is a closed tubular resistance furnace; the quartz tube of the closed tubular resistance furnace has a diameter of 300 mm and a length of 2000 mm.

5. The method for pretreating impurities in single crystal silicon raw materials based on the thermal migration effect according to claim 1, characterized in that: In step (2), the gradient heating method is: heating from room temperature to 230-270°C at a heating rate of 3-7°C / min, keeping warm for 0.5-1.5h, and then heating to 330-370°C at a heating rate of 2-4°C / min, keeping warm for 1.5-2.5h.

6. The method for pretreating impurities in single crystal silicon raw materials based on the thermal migration effect according to claim 1, characterized in that: In step (2), the inert gas environment is: the inert gas is high-purity argon with a purity of ≥99.999%, which is continuously introduced into the furnace at a flow rate of 5 L / min, and the micro-positive pressure in the furnace is 0.05 MPa.

7. The method for pretreating impurities in single crystal silicon raw materials based on the thermomigration effect according to claim 1, characterized in that: In the step (3), the purging device: a multi-hole nozzle array is provided at the end of the furnace body, with a hole diameter of 1 mm and a spacing of 20 mm.

8. The method for pretreating impurities in single crystal silicon raw materials based on the thermal migration effect according to claim 1, characterized in that: In step (3), the gas is nitrogen or argon; the purge parameters are: flow rate 7-9 m / s, temperature 140-160°C, and purge angle 45±5°.

9. The method for pretreating impurities in single crystal silicon raw materials based on the thermal migration effect according to claim 1, characterized in that: In the step (3), the purging method is: 3 pulse purgings, each 10 minutes with an interval of 5 minutes, for a total of 30 minutes.

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