Solar N-type monocrystalline silicon doping method

Abstract

The invention discloses a solar N-type monocrystalline silicon doping method. The method comprises the following steps: S1, determining the target resistivity of czochralski monocrystalline silicon; s2, determining a raw material formula for crystal pulling; s3, determining an arsenic alloy blocking position; s4, the doping amount of the arsenic alloy is calculated according to the segregation theory; s5, adding a second doping agent into the quartz crucible along with the silicon material in the last re-feeding barrel; (S6); after the arsenic alloy enters the quartz crucible, the furnace pressure and the argon flow are adjusted, and volatilization of a doping agent in the material melting process is controlled; and S7, after material melting is completed, normal subsequent crystal growth is carried out. According to the solar N-type monocrystalline silicon doping method, the monocrystalline silicon rod with excellent resistivity range and resistance concentration ratio is obtained by changing the use of the dopant, and the growth length of the crystal can be greatly improved on the premise of keeping the resistivity range of the growth head and the growth tail of the crystal unchanged, so that the non-silicon cost of the crystal growth is greatly reduced; therefore, higher energy conversion efficiency of the photovoltaic cell is obtained.

Description

Technical Field

[0001] The invention relates to the field of solar Czochralski single crystals, and in particular to a solar N-type single crystal silicon doping method. Background Art

[0002] Improving the photoelectric conversion efficiency is an eternal theme in the photovoltaic industry. With the development of high-efficiency battery structures such as HJT and TOPcon, the crystalline silicon photovoltaic market has rapidly transformed from P-type to N-type, and the market demand for N-type silicon wafers has increased rapidly. The main process parameters of the battery diffusion process at the battery end - diffusion source concentration, temperature, pressure, time, are basically stable and consistent. Under this premise, in order to further improve the photoelectric conversion efficiency of solar cells, it is necessary to further confirm the optimal matching range between the resistivity of silicon wafers and the battery process. The higher resistivity of silicon wafers will lead to an increase in the series resistance of the battery, while the lower resistivity will lead to a significant increase in carrier Auger recombination, both of which will reduce the photoelectric conversion efficiency of solar cells. Currently, the dopants used in solar N-type monocrystalline silicon are mostly P elements, but the segregation coefficient of P elements is small, which will lead to poor resistance concentration of the produced silicon wafers, resulting in poor concentration of the overall photoelectric conversion efficiency of the battery. At the same time, more defective products will be produced, which will further increase the production cost. Summary of the invention

[0003] The main purpose of the present invention is to provide a solar N-type single crystal silicon doping method, which can effectively solve the problems in the background technology.

[0004] To achieve the above object, the technical solution adopted by the present invention is: A solar N-type single crystal silicon doping method comprises the following steps: S1: Determine the target resistivity of CZ single crystal silicon: the resistivity is 0.200Ω·m, 0.400Ω·m, 0.600Ω·m, 0.800Ω·m, 1.000Ω·m and 1.200Ω·m; S2: Determine the raw material formula for crystal pulling: including two raw materials, one raw material including but not limited to group V elements phosphorus, arsenic, and antimony, and the other raw material is arsenic, one of the raw materials is used as the first dopant, and the arsenic is used as the second dopant; S3: Determine the arsenic alloy barrier: Determine the arsenic alloy barrier according to the target resistivity of the CZ silicon single crystal of S1 and the raw material formula used in S2; S4: Calculating the doping amount of the arsenic alloy according to the segregation theory: Calculating the doping amount of the arsenic alloy according to the arsenic alloy blocking position obtained in step S3 and based on the segregation theory, the impurity concentration of the arsenic alloy is 4.0E+14-1.8E+16atoms / cm³; S5: Adding the second dopant with the silicon material into the quartz crucible in the last bucket of re-feeding: When preparing solar N-type monocrystalline silicon, adding the first dopant with the silicon material into the quartz crucible in the second-to-last bucket of re-feeding, and adding the second dopant with the silicon material into the quartz crucible in the last bucket of re-feeding; S6; after the arsenic alloy enters the quartz crucible, the furnace pressure and argon flow rate are adjusted to control the volatilization of the dopant during the chemical process: wherein the furnace pressure is 1.9-2.9 MPa, and the argon flow rate is 4-6 degrees; S7: After the chemical reaction is completed, the subsequent crystal growth will proceed normally: After the first dopant and the second dopant are poured, the subsequent crystal growth can be carried out. After the chemical reaction is completed, 25μm of each upper and lower surfaces of the material are ground with 20-mesh boron carbide, and then ultrasonically cleaned three times with high-purity water. The conductivity type of the single crystal silicon is detected by the hot and cold probe method. After the crystal growth is completed, the doping of solar N-type single crystal silicon can be completed.

[0005] Preferably, the single crystal silicon, the first dopant and the second dopant need to be pretreated before use, and the pretreatment includes ultrasonically cleaning the first dopant and the second dopant with high-purity water for 3 minutes and then taking them out, ultrasonically cleaning them with acetone for 5 minutes and then taking them out, ultrasonically cleaning them with methanol for 3 minutes and then taking them out, cleaning them with APM cleaning solution at 75°C for 15 minutes and then taking them out, soaking them in 2.0wt.% HF for 2 minutes and then taking them out, and then ultrasonically cleaning them with high-purity water.

[0006] Preferably, after the single crystal silicon is cleaned, it is placed in a diffusion furnace for heating at a temperature of 1200°C for 2 hours. After the diffusion is completed, it is quickly cooled to room temperature, and the cooling water rate needs to be greater than 300K / s. The surface of the single crystal silicon is polished with boron nitride. After it is ultrasonically cleaned for 3 minutes, the resistivity of the single crystal silicon is measured with a four-probe tester at room temperature in the dark.

[0007] Compared with the prior art, the present invention has the following beneficial effects: The present invention obtains a single crystal silicon rod with an excellent resistivity range and resistance concentration by changing the use of dopants. The crystal growth length can be greatly increased while maintaining the resistivity range of the head and tail of the crystal growth unchanged, thereby greatly reducing the non-silicon cost of the crystal growth. The resistance concentration of the crystal output can be greatly increased while maintaining the crystal growth crucible ratio unchanged, thereby obtaining a higher energy conversion efficiency for the photovoltaic cell. DETAILED DESCRIPTION

[0008] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0009] The present invention relates to a solar N-type single crystal silicon doping method, comprising the following steps: S1: Determine the target resistivity of CZ single crystal silicon: the resistivity is 0.200Ω·m, 0.400Ω·m, 0.600Ω·m, 0.800Ω·m, 1.000Ω·m and 1.200Ω·m; S2: Determine the raw material formula for crystal pulling: including two raw materials, one raw material includes but is not limited to group V elements phosphorus, arsenic, and antimony, and the other raw material is arsenic, one of the raw materials is used as the first dopant, and arsenic is used as the second dopant; The single crystal silicon, the first dopant and the second dopant need to be pretreated before use. The pretreatment includes ultrasonic cleaning the first dopant and the second dopant with high-purity water for 3 minutes and then taking them out, ultrasonic cleaning them with acetone for 5 minutes and then taking them out, ultrasonic cleaning them with methanol for 3 minutes and then taking them out, cleaning them with APM cleaning solution at 75°C for 15 minutes and then taking them out, soaking them with 2.0wt.% HF for 2 minutes and then taking them out, and then ultrasonic cleaning them with high-purity water; After cleaning, the single crystal silicon is placed in a diffusion furnace for heating at 1200°C for 2 hours. After diffusion, it is quickly cooled to room temperature. The cooling rate must be greater than 300K / s. The surface of the single crystal silicon is polished with boron nitride. After ultrasonic cleaning for 3 minutes, the resistivity of the single crystal silicon is measured with a four-probe tester at room temperature in the dark. S3: Determine the arsenic alloy barrier: Determine the arsenic alloy barrier according to the target resistivity of the CZ silicon single crystal of S1 and the raw material formula used in S2; S4: Calculating the doping amount of the arsenic alloy according to the segregation theory: According to the arsenic alloy blocking position obtained in step S3 and based on the segregation theory, the doping amount of the arsenic alloy is calculated, and the impurity concentration of the arsenic alloy is 4.0E+14-1.8E+16atoms / cm³; S5: Adding the second dopant with the silicon material into the quartz crucible in the last bucket of re-feeding: When preparing solar N-type monocrystalline silicon, adding the first dopant with the silicon material into the quartz crucible in the second-to-last bucket of re-feeding, and adding the second dopant with the silicon material into the quartz crucible in the last bucket of re-feeding; S6; after the arsenic alloy enters the quartz crucible, the furnace pressure and argon flow rate are adjusted to control the volatilization of the dopant during the chemical process: the furnace pressure is 1.9-2.9 MPa, and the argon flow rate is 4-6 degrees; S7: After the chemical reaction is completed, the subsequent crystal growth will proceed normally: After the first dopant and the second dopant are poured, the subsequent crystal growth can be carried out. After the chemical reaction is completed, 25μm of each upper and lower surfaces of the material are ground with 20-mesh boron carbide, and then ultrasonically cleaned three times with high-purity water. The conductivity type of the single crystal silicon is detected by the hot and cold probe method. After the crystal growth is completed, the doping of solar N-type single crystal silicon can be completed. Specific embodiment one: A solar N-type single crystal silicon doping method comprises the following steps: S1: Determine the target resistivity of CZ single crystal silicon: the resistivity is 0.200Ω·m; S2: Determine the raw material formula for crystal pulling: including two raw materials, one raw material is phosphorus, and the other raw material is arsenic, wherein one raw material is used as a first dopant, and arsenic is used as a second dopant; The single crystal silicon, the first dopant and the second dopant need to be pretreated before use. The pretreatment includes ultrasonic cleaning the first dopant and the second dopant with high-purity water for 3 minutes and then taking them out, ultrasonic cleaning them with acetone for 5 minutes and then taking them out, ultrasonic cleaning them with methanol for 3 minutes and then taking them out, cleaning them with APM cleaning solution at 75°C for 15 minutes and then taking them out, soaking them with 2.0wt.% HF for 2 minutes and then taking them out, and then ultrasonic cleaning them with high-purity water; After cleaning, the single crystal silicon is placed in a diffusion furnace for heating at 1200°C for 2 hours. After diffusion, it is quickly cooled to room temperature. The cooling rate must be greater than 300K / s. The surface of the single crystal silicon is polished with boron nitride. After ultrasonic cleaning for 3 minutes, the resistivity of the single crystal silicon is measured with a four-probe tester at room temperature in the dark. S3: Determine the arsenic alloy barrier: Determine the arsenic alloy barrier according to the target resistivity of the CZ silicon single crystal of S1 and the raw material formula used in S2; S4: Calculating the doping amount of the arsenic alloy according to the segregation theory: According to the arsenic alloy blocking position obtained in step S3 and based on the segregation theory, the doping amount of the arsenic alloy is calculated, and the impurity concentration of the arsenic alloy is 4.0E+14-1.8E+16atoms / cm³; S5: Adding the second dopant with the silicon material into the quartz crucible in the last bucket of re-feeding: When preparing solar N-type monocrystalline silicon, adding the first dopant with the silicon material into the quartz crucible in the second-to-last bucket of re-feeding, and adding the second dopant with the silicon material into the quartz crucible in the last bucket of re-feeding; S6; after the arsenic alloy enters the quartz crucible, the furnace pressure and argon flow rate are adjusted to control the volatilization of the dopant during the chemical process: the furnace pressure is 1.9-2.9 MPa, and the argon flow rate is 4-6 degrees; S7: After the chemical reaction is completed, the subsequent crystal growth will proceed normally: After the first dopant and the second dopant are poured, the subsequent crystal growth can be carried out. After the chemical reaction is completed, 25μm of each upper and lower surfaces of the material are ground with 20-mesh boron carbide, and then ultrasonically cleaned three times with high-purity water. The conductivity type of the single crystal silicon is detected by the hot and cold probe method. After the crystal growth is completed, the doping of solar N-type single crystal silicon can be completed. Specific embodiment 2: A solar N-type single crystal silicon doping method comprises the following steps: S1: Determine the target resistivity of CZ single crystal silicon: the resistivity is 0.400Ω·m; S2: Determine the raw material formula for crystal pulling: including two raw materials, one raw material is antimony, and the other raw material is arsenic, wherein one raw material is used as a first dopant, and arsenic is used as a second dopant; The single crystal silicon, the first dopant and the second dopant need to be pretreated before use. The pretreatment includes ultrasonic cleaning the first dopant and the second dopant with high-purity water for 3 minutes and then taking them out, ultrasonic cleaning them with acetone for 5 minutes and then taking them out, ultrasonic cleaning them with methanol for 3 minutes and then taking them out, cleaning them with APM cleaning solution at 75°C for 15 minutes and then taking them out, soaking them with 2.0wt.% HF for 2 minutes and then taking them out, and then ultrasonic cleaning them with high-purity water; After cleaning, the single crystal silicon is placed in a diffusion furnace for heating at 1200°C for 2 hours. After diffusion, it is quickly cooled to room temperature. The cooling rate must be greater than 300K / s. The surface of the single crystal silicon is polished with boron nitride. After ultrasonic cleaning for 3 minutes, the resistivity of the single crystal silicon is measured with a four-probe tester at room temperature in the dark. S3: Determine the arsenic alloy barrier: Determine the arsenic alloy barrier according to the target resistivity of the CZ silicon single crystal of S1 and the raw material formula used in S2; S4: Calculating the doping amount of the arsenic alloy according to the segregation theory: According to the arsenic alloy blocking position obtained in step S3 and based on the segregation theory, the doping amount of the arsenic alloy is calculated, and the impurity concentration of the arsenic alloy is 4.0E+14-1.8E+16atoms / cm³; S5: Adding the second dopant with the silicon material into the quartz crucible in the last bucket of re-feeding: When preparing solar N-type monocrystalline silicon, adding the first dopant with the silicon material into the quartz crucible in the second-to-last bucket of re-feeding, and adding the second dopant with the silicon material into the quartz crucible in the last bucket of re-feeding; S6; after the arsenic alloy enters the quartz crucible, the furnace pressure and argon flow rate are adjusted to control the volatilization of the dopant during the chemical process: the furnace pressure is 1.9-2.9 MPa, and the argon flow rate is 4-6 degrees; S7: After the chemical reaction is completed, the subsequent crystal growth will proceed normally: After the first dopant and the second dopant are poured, the subsequent crystal growth can be carried out. After the chemical reaction is completed, 25μm of each upper and lower surfaces of the material are ground with 20-mesh boron carbide, and then ultrasonically cleaned three times with high-purity water. The conductivity type of the single crystal silicon is detected by the hot and cold probe method. After the crystal growth is completed, the doping of solar N-type single crystal silicon can be completed. Specific embodiment three: A solar N-type single crystal silicon doping method comprises the following steps: S1: Determine the target resistivity of CZ single crystal silicon: the resistivity is 0.600Ω·m; S2: Determine the raw material formula for crystal pulling: including two raw materials, one raw material is phosphorus, and the other raw material is arsenic, wherein one raw material is used as a first dopant, and arsenic is used as a second dopant; The single crystal silicon, the first dopant and the second dopant need to be pretreated before use. The pretreatment includes ultrasonic cleaning the first dopant and the second dopant with high-purity water for 3 minutes and then taking them out, ultrasonic cleaning them with acetone for 5 minutes and then taking them out, ultrasonic cleaning them with methanol for 3 minutes and then taking them out, cleaning them with APM cleaning solution at 75°C for 15 minutes and then taking them out, soaking them with 2.0wt.% HF for 2 minutes and then taking them out, and then ultrasonic cleaning them with high-purity water; After cleaning, the single crystal silicon is placed in a diffusion furnace for heating at 1200°C for 2 hours. After diffusion, it is quickly cooled to room temperature. The cooling rate must be greater than 300K / s. The surface of the single crystal silicon is polished with boron nitride. After ultrasonic cleaning for 3 minutes, the resistivity of the single crystal silicon is measured with a four-probe tester at room temperature in the dark. S3: Determine the arsenic alloy barrier: Determine the arsenic alloy barrier according to the target resistivity of the CZ silicon single crystal of S1 and the raw material formula used in S2; S4: Calculating the doping amount of the arsenic alloy according to the segregation theory: According to the arsenic alloy blocking position obtained in step S3 and based on the segregation theory, the doping amount of the arsenic alloy is calculated, and the impurity concentration of the arsenic alloy is 4.0E+14-1.8E+16atoms / cm³; S5: Adding the second dopant with the silicon material into the quartz crucible in the last bucket of re-feeding: When preparing solar N-type monocrystalline silicon, adding the first dopant with the silicon material into the quartz crucible in the second-to-last bucket of re-feeding, and adding the second dopant with the silicon material into the quartz crucible in the last bucket of re-feeding; S6; after the arsenic alloy enters the quartz crucible, the furnace pressure and argon flow rate are adjusted to control the volatilization of the dopant during the chemical process: the furnace pressure is 1.9-2.9 MPa, and the argon flow rate is 4-6 degrees; S7: After the chemical reaction is completed, the subsequent crystal growth will proceed normally: After the first dopant and the second dopant are poured, the subsequent crystal growth can be carried out. After the chemical reaction is completed, 25μm of each upper and lower surfaces of the material are ground with 20-mesh boron carbide, and then ultrasonically cleaned three times with high-purity water. The conductivity type of the single crystal silicon is detected by the hot and cold probe method. After the crystal growth is completed, the doping of solar N-type single crystal silicon can be completed.

[0013] The performance of the doping method of the present invention is compared with that of the prior art doping method, wherein the specific embodiments 1 to 3 of the present invention are recorded as embodiments 1-3, and the method of the prior art is recorded as comparative example 1. The following is a comparison table: Electrical performance parameters (R25 (Ω)) Efficiency before illumination (%) Efficiency after illumination (%) Attenuation ratio (%) Example 1 44.3976 21.71 21.53 0.83 Example 2 43.4794 21.79 21.64 0.73 Example 3 43.7756 21.77 21.53 0.68 Comparative Example 1 41.0035 20.52 18.11 11.74 This shows that the doping method of the present invention has higher performance.

[0014] The present invention obtains a single crystal silicon rod with an excellent resistivity range and resistance concentration by changing the use of dopants. The crystal growth length can be greatly increased while maintaining the resistivity range of the head and tail of the crystal growth unchanged, thereby greatly reducing the non-silicon cost of the crystal growth. The resistance concentration of the crystal output can be greatly increased while maintaining the crystal growth crucible ratio unchanged, thereby obtaining a higher energy conversion efficiency for the photovoltaic cell.

[0015] Although 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 appended claims and their equivalents.

Claims

1. A solar N-type single crystal silicon doping method, characterized in that: The steps include: S1: Determine the target resistivity of CZ single crystal silicon: the resistivity is 0.200Ω·m, 0.400Ω·m, 0.600Ω·m, 0.800Ω·m, 1.000Ω·m and 1.200Ω·m; S2: Determine the raw material formula for crystal pulling: including two raw materials, one raw material including but not limited to group V elements phosphorus, arsenic, and antimony, and the other raw material is arsenic, one of the raw materials is used as the first dopant, and the arsenic is used as the second dopant; S3: Determine the arsenic alloy barrier: Determine the arsenic alloy barrier according to the target resistivity of the CZ silicon single crystal of S1 and the raw material formula used in S2; S4: Calculating the doping amount of the arsenic alloy according to the segregation theory: Calculating the doping amount of the arsenic alloy according to the arsenic alloy blocking position obtained in step S3 and based on the segregation theory, the impurity concentration of the arsenic alloy is 4.0E+14-1.8E+16atoms / cm³; S5: Adding the second dopant with the silicon material into the quartz crucible in the last bucket of re-feeding: When preparing solar N-type monocrystalline silicon, adding the first dopant with the silicon material into the quartz crucible in the second-to-last bucket of re-feeding, and adding the second dopant with the silicon material into the quartz crucible in the last bucket of re-feeding; S6; after the arsenic alloy enters the quartz crucible, the furnace pressure and argon flow rate are adjusted to control the volatilization of the dopant during the chemical process: wherein the furnace pressure is 1.9-2.9 MPa, and the argon flow rate is 4-6 degrees; S7: After the chemical reaction is completed, the subsequent crystal growth will proceed normally: After the first dopant and the second dopant are poured, the subsequent crystal growth can be carried out. After the chemical reaction is completed, 25μm of each upper and lower surfaces of the material are ground with 20-mesh boron carbide, and then ultrasonically cleaned three times with high-purity water. The conductivity type of the single crystal silicon is detected by the hot and cold probe method. After the crystal growth is completed, the doping of solar N-type single crystal silicon can be completed.

2. A solar N-type single crystal silicon doping method according to claim 1, characterized in that: The single crystal silicon, the first dopant and the second dopant need to be pretreated before use. The pretreatment includes ultrasonic cleaning the first dopant and the second dopant with high-purity water for 3 minutes and then taking them out, ultrasonic cleaning with acetone for 5 minutes and then taking them out, ultrasonic cleaning with methanol for 3 minutes and then taking them out, cleaning with APM cleaning solution at 75°C for 15 minutes and then taking them out, soaking them in 2.0wt.% HF for 2 minutes and then taking them out, and then ultrasonic cleaning with high-purity water.

3. A solar N-type single crystal silicon doping method according to claim 1, characterized in that: After the single crystal silicon is cleaned, it is placed in a diffusion furnace for heating at a temperature of 1200°C for 2 hours. After the diffusion is completed, it is quickly cooled to room temperature. The cooling water rate needs to be greater than 300K / s. The surface of the single crystal silicon is polished with boron nitride. After ultrasonic cleaning for 3 minutes, the resistivity of the single crystal silicon is measured with a four-probe tester at room temperature in the dark.