Method for improving axial resistance uniformity of antimony-doped silicon single crystal and antimony-doped silicon single crystal

Abstract

The invention relates to the technical field of photovoltaic crystal growth, in particular to a method for improving the axial resistance uniformity of an antimony-doped silicon single crystal and the antimony-doped silicon single crystal. The method provided by the invention comprises the following steps: growing the antimony-doped silicon single crystal by adopting a czochralski method, and at an equal-diameter stage, controlling the furnace pressure to be 4-13torr; in the czochralski method, after leading and releasing are failed or growth of a single antimony-doped silicon single crystal is completed, supplemental doping of an antimony element is carried out according to the volatilization amount of the antimony element. In the method disclosed by the invention, the tail resistance and the head resistance of the prepared antimony-doped silicon single crystal are kept highly consistent by controlling the furnace pressure at the equal-diameter stage, regulating and controlling the volatilization rate of the antimony element, combining the segregation phenomenon of the antimony element in silicon and determining the supplementary doping time of the antimony element.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic crystal growth, and particularly relates to a method for improving the axial resistance uniformity of antimony-doped silicon single crystals and an antimony-doped silicon single crystal. Background Art

[0002] Due to advantages such as high efficiency, low attenuation, and good temperature coefficient, N-type crystalline silicon solar cells are gradually becoming the technical mainstream in the photovoltaic industry. N-type single crystal silicon rods are formed by doping specific elements such as phosphorus, arsenic, antimony, etc. The axial resistance uniformity of the single crystal silicon rod has an important impact on the concentration of the resistance distribution of the silicon wafer. This uniformity can better match the requirements of the battery manufacturing process, thereby effectively improving the photoelectric conversion efficiency of the solar cell. Moreover, as the technology of N-type crystalline silicon solar cells, especially N-type BC cells, tends to be thinner, higher requirements are put forward for the mechanical strength of the silicon wafer.

[0003] In the existing preparation processes of phosphorus- or arsenic-doped single crystal silicon rods, due to the small segregation coefficients of phosphorus and arsenic, the segregation effect of the dopant at the solid-liquid interface is significant during the crystal growth process, resulting in uneven axial doping concentration distribution. To alleviate this problem, a large remaining crucible amount process is usually required for crystal pulling. However, even so, the axial resistivity difference of the obtained silicon rods is still as high as 4 to 7 times, which not only greatly increases the production cost but also leads to poor matching between the resistance distribution of the silicon wafer and the subsequent battery process, affecting the battery performance.

[0004] Compared with phosphorus- or arsenic-doped single crystal silicon rods, antimony-doped single crystal silicon rods exhibit relatively better axial resistance uniformity. And the introduction of antimony elements can enhance the mechanical strength of the silicon wafer, which effectively reduces the fragmentation rate caused by mechanical stress during the thin wafer processing of the silicon wafer. However, the volatility of antimony elements in molten silicon is relatively high, and the volatility coefficient is affected by multiple parameters such as temperature, furnace pressure, time, and argon flow rate, resulting in difficult control of the axial resistance of the single crystal silicon rod. Abnormalities such as the resistance of the tail of the silicon rod being higher than that of the head and the resistance of the middle of the silicon rod being higher than that of the head and tail often occur in the production line, seriously affecting the resistance uniformity, concentration, and yield of the silicon wafer.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for improving the axial resistance uniformity of antimony-doped silicon single crystals and an antimony-doped silicon single crystal. The antimony-doped silicon single crystal obtained by the method of the present invention has a high degree of coincidence between the head resistivity and the target resistivity, and the axial resistance uniformity is significantly improved.

[0007] To achieve the above object of the present invention, in the first aspect of the present invention, a method for improving the axial resistance uniformity of antimony-doped silicon single crystals is provided, including the following steps: growing an antimony-doped silicon single crystal by the Czochralski method, and during the equal-diameter stage, the furnace pressure is 4 to 13 torr;

[0008] In the Czochralski method, when the pulling and feeding fails or after the growth of a single antimony-doped silicon single crystal is completed, antimony element is replenished according to the evaporation amount of the antimony element.

[0009] In a specific embodiment of the present invention, during the isodiameter stage, the furnace pressure gradually increases and the flow rate of the protective gas gradually decreases;

[0010] Set the furnace pressures corresponding to the start and end of the isodiameter stage to be P0 and P1 respectively, and set the flow rates of the protective gas corresponding to the start and end of the isodiameter stage to be Q0 and Q1 respectively, and satisfy: P1 - P0 = 0.5 - 4 torr, Q0 - Q1 = 5 - 30 slpm.

[0011] In a specific embodiment of the present invention, the furnace pressure P0 is 4 - 7 torr, and the furnace pressure P1 is 6 - 10 torr.

[0012] In a specific embodiment of the present invention, the flow rate Q0 of the protective gas is 85 - 115 slpm, and the flow rate Q1 of the protective gas is 55 - 95 slpm.

[0013] In a specific embodiment of the present invention, during the isodiameter stage, the change rate of the furnace pressure does not exceed 0.2%P0 / mm. Further, during the isodiameter stage, the change rate of the furnace pressure is 0.006%P0 / mm - 0.018%P0 / mm.

[0014] In a specific embodiment of the present invention, during the isodiameter stage, the change rate of the flow rate of the protective gas does not exceed 0.01%Q0 / mm. Further, during the isodiameter stage, the change rate of the flow rate of the protective gas is 0.004%Q0 / mm - 0.01%Q0 / mm.

[0015] In a specific embodiment of the present invention, during the isodiameter stage, the crystal pulling rate is 80 - 120 mm / h.

[0016] In a specific embodiment of the present invention, the Czochralski method for growing antimony-doped silicon single crystals includes: melting raw materials to obtain molten silicon, and then performing seed crystal pulling, shoulder forming, isodiameter and finishing; the preparation of the molten silicon includes: after the silicon material is melted, controlling the temperature to be 1470 ± 10 °C and adding antimony element. Further, the initial doping amount of the antimony element is calculated according to the target resistivity.

[0017] In a specific embodiment of the present invention, the target resistivity is 0.5 - 10 Ω·cm.

[0018] In a specific embodiment of the present invention, the rated length of the isodiameter stage is 3000 - 5000 mm.

[0019] In a specific embodiment of the present invention, the supplementary doping amount of the antimony element is 5% to 20% of the initial doping amount.

[0020] In a specific embodiment of the present invention, when determining the failure of the drawing or the completion of the growth of a single antimony-doped silicon single crystal, the concentration c of the antimony element in the molten silicon is determined according to the following formula, and the volatilization amount of the antimony element is calculated;

[0021]

[0022] In the formula, β is a correction coefficient, T is the theoretical value of the melt temperature calculated from the seeding power, P is the furnace pressure, c0 is the initial concentration of the antimony element, c is the concentration of the antimony element in the molten silicon after t minutes, A is the volatilization area of the molten silicon, E is the evaporation rate constant of the antimony element, and W is the weight of the molten silicon.

[0023] In a specific embodiment of the present invention, in the Czochralski method, the amount of remaining crucible ≤ 30%.

[0024] The second aspect of the present invention provides an antimony-doped silicon single crystal prepared by using the method for improving the axial resistance uniformity of the antimony-doped silicon single crystal provided in the first aspect of the present invention.

[0025] In a specific embodiment of the present invention, the resistivity fluctuation (ρ max -ρ min ) / ρ min ≤ 10%; wherein, ρ max and ρ min are the maximum resistivity and the minimum resistivity of the antimony-doped silicon single crystal in the axial direction, respectively.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) In the preparation of the antimony-doped silicon single crystal of the present invention, by controlling the furnace pressure in the isodiametric stage, regulating the volatilization rate of the antimony element, combining with the segregation phenomenon of the antimony element in silicon, and determining the supplementary doping timing of the antimony element, the tail resistance and the head resistance of the prepared antimony-doped silicon single crystal are kept highly consistent;

[0028] (2) During the growth process from the isodiametric head to the tail in the isodiametric stage of the present invention, the furnace pressure is further regulated to gradually increase, the flow rate of the protective gas is gradually decreased, and the change amount of the furnace pressure and the change amount of the flow rate of the protective gas are synergistically controlled within a certain range to control the volatilization rate of the antimony element, and combining with the segregation phenomenon of the antimony element in silicon, the tail resistance and the head resistance of the prepared antimony-doped silicon single crystal are kept highly consistent;

[0029] (3) The present invention further predicts the volatilization amount of antimony element through a complementary doping model, and performs complementary doping on antimony element according to the volatilization amount, which helps to improve the uniformity of axial antimony element in the silicon single crystal, achieve precise control of the resistivity, and further improve the uniformity of axial resistivity of the silicon single crystal;

[0030] (4) The present invention further adds antimony element after the silicon material is melted, so that the antimony element quickly melts into the melted silicon material, reducing the volatilization amount of antimony element before the equal-diameter stage, which helps to improve the coincidence degree between the resistivity of the head of the silicon single crystal and the target resistivity;

[0031] (5) The antimony-doped silicon single crystal obtained by the method of the present invention has a high coincidence degree between the resistivity of the head and the target resistivity, and the axial resistance uniformity is significantly improved, which helps to improve the photoelectric conversion efficiency of the solar cell. Specific Embodiments

[0032] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0033] The first aspect of the present invention provides a method for improving the axial resistance uniformity of antimony-doped silicon single crystals, including the following steps: growing antimony-doped silicon single crystals by the Czochralski method, and during the equal-diameter stage, the furnace pressure is 4-13 torr;

[0034] In the Czochralski method, when the pulling and releasing fails or after the growth of a single antimony-doped silicon single crystal is completed, complementary doping of antimony element is carried out according to the volatilization amount of antimony element.

[0035] The segregation problem will affect the distribution and uniformity of dopants during the growth of antimony-doped silicon single crystals. The segregation coefficient of antimony element is much less than 1 and it tends to enrich in the liquid phase. For this reason, usually, the antimony-doped silicon single crystal obtained has a situation where the resistance of the head is higher than that of the tail. However, antimony element has a high volatility and is affected by multiple parameters. The present invention found in the research that when the parameters are adjusted improperly and the volatilization amount of antimony element is too large, abnormal situations such as the resistance of the head being lower than that of the tail or the resistance in the middle being higher than that of the head and the tail will occur. Based on this, the present invention controls the furnace pressure during the equal-diameter stage, regulates the volatilization rate of antimony element, combines the segregation phenomenon of antimony element in silicon, and determines the timing of complementary doping of antimony element at the same time, so that the tail resistance of the prepared antimony-doped silicon single crystal is highly consistent with the head resistance.

[0036] In different embodiments, the furnace pressure can be 4 torr, 5 torr, 6 torr, 8 torr, 10 torr, 12 torr, 13 torr, or a range composed of any two of them. When the furnace pressure is lower than the above range, the volatilization of antimony element slows down, resulting in the head resistance of the antimony-doped silicon single crystal being higher than the tail resistance; when the furnace pressure is higher than the above range, the volatilization of antimony element speeds up, resulting in the head resistance of the antimony-doped silicon single crystal being lower than the tail resistance. By regulating the furnace pressure within the above range in the present invention, it is more conducive to combining the segregation phenomenon of antimony element in silicon and improving the axial distribution uniformity of antimony element in the silicon single crystal.

[0037] The pulling and feeding failures of the present invention include seeding failure, shoulder formation failure, and wire breakage before the equal-diameter stage reaches the target length. After the pulling and feeding failures, it is necessary to add materials and supplementary doping to make the contents of silicon and antimony elements in the molten silicon the same as those in the initial molten silicon, and then perform seeding, shoulder formation, equal-diameter stage, and ending. For example, the proportion of pulling and feeding failures in the production line is about 10%, and the equal-diameter wire breakage rate is about 20%. Precise supplementary doping helps to improve the accuracy of controlling the resistivity of the antimony-doped silicon single crystal and the uniformity of the axial resistivity.

[0038] In a specific embodiment of the present invention, during the equal-diameter stage, the furnace pressure gradually increases, and the flow rate of the protective gas gradually decreases;

[0039] Let the furnace pressures corresponding to the start and end of the equal-diameter stage be P0 and P1 respectively, and let the flow rates of the protective gas corresponding to the start and end of the equal-diameter stage be Q0 and Q1 respectively, and satisfy: P1 - P0 = 0.5 - 4 torr, Q0 - Q1 = 5 - 30 slpm.

[0040] In the preparation of the antimony-doped silicon single crystal of the present invention, during the growth process from the equal-diameter head to the tail in the equal-diameter stage, the furnace pressure gradually increases, and the flow rate of the protective gas gradually decreases. And the change amount of the furnace pressure and the change amount of the flow rate of the protective gas are synergistically controlled within a certain range to control the volatilization rate of the antimony element, and combined with the segregation phenomenon of the antimony element in silicon, so that the tail resistance of the prepared antimony-doped silicon single crystal is highly consistent with the head resistance. Herein, the start and end of the equal-diameter stage refer to when entering the equal-diameter stage and when ending the equal-diameter stage for finishing.

[0041] The difference P1 - P0 between the furnace pressures corresponding to the start and end of the equal-diameter stage can be 0.5 torr, 1 torr, 1.5 torr, 2 torr, 2.5 torr, 3 torr, 3.5 torr, 4 torr, or a range composed of any two of them. The difference Q0 - Q1 between the flow rates Q0 and Q1 of the protective gas corresponding to the start and end of the equal-diameter stage can be 5 slpm, 10 slpm, 15 slpm, 20 slpm, 25 slpm, 30 slpm, or a range composed of any two of them. In the equal-diameter stage of the present invention, the furnace pressure of the single crystal furnace gradually increases, while the flow rate of the protective gas gradually decreases. By controlling the difference in the head and tail furnace pressures and the difference in the flow rate of the protective gas within a certain range, combined with the segregation phenomenon of antimony in silicon, the tail resistance and the head resistance of the antimony-doped silicon single crystal obtained are kept highly consistent. In the growth of the silicon single crystal of the present invention, the protective gas is argon.

[0042] In a specific embodiment of the present invention, the furnace pressure P0 is 4 - 7 torr, and the furnace pressure P1 is 6 - 10 torr. In different embodiments, the furnace pressure P0 corresponding to the start of the equal-diameter stage can be 4 torr, 4.5 torr, 5 torr, 5.5 torr, 6 torr, 6.5 torr, 7 torr, or a range composed of any two of them; the furnace pressure P1 corresponding to the end of the equal-diameter stage can be 6 torr, 6.5 torr, 7 torr, 7.5 torr, 8 torr, 8.5 torr, 9 torr, 9.5 torr, 10 torr, or a range composed of any two of them. Controlling the furnace pressures P0 and P1 within the above ranges is more conducive to improving the coincidence degree of the head resistivity of the silicon single crystal with the target resistivity and the axial resistance uniformity.

[0043] In a specific embodiment of the present invention, the flow rate Q0 of the protective gas is 85 - 115 slpm, and the flow rate Q1 of the protective gas is 55 - 95 slpm. In different embodiments, the flow rate Q0 of the protective gas corresponding to the start of the equal-diameter stage can be 85 slpm, 90 slpm, 95 slpm, 100 slpm, 105 slpm, 110 slpm, 115 slpm, or a range composed of any two of them; the flow rate Q1 of the protective gas corresponding to the end of the equal-diameter stage can be 55 slpm, 60 slpm, 65 slpm, 70 slpm, 75 slpm, 80 slpm, 85 slpm, 90 slpm, 95 slpm, or a range composed of any two of them. Controlling the flow rates Q0 and Q1 of the protective gas within the above ranges and cooperating with the furnace pressure in the equal-diameter stage to improve the coincidence degree of the head resistivity of the silicon single crystal with the target resistivity and the axial resistance uniformity.

[0044] In a specific embodiment of the present invention, during the equal-diameter stage, the change rate of the furnace pressure does not exceed 0.2% P0 / mm. Further, during the equal-diameter stage, the change rate of the furnace pressure is 0.006% P0 / mm to 0.018% P0 / mm.

[0045] The change rate of the furnace pressure in the present invention refers to the change rate of the furnace pressure with respect to the equal-diameter growth length. During the equal-diameter stage, the change rate of the furnace pressure can be 0.006% P0 / mm, 0.008% P0 / mm, 0.01% P0 / mm, 0.012% P0 / mm, 0.014% P0 / mm, 0.015% P0 / mm, 0.018% P0 / mm, or any range composed of any two of them. Controlling the change rate of the furnace pressure in the equal-diameter stage of the present invention within the above range, while cooperating with the protective gas flow rate to control the volatilization rate of antimony elements, maintaining the melt stability, and significantly reducing the wire breakage rate, etc.

[0046] In a specific embodiment of the present invention, during the equal-diameter stage, the change rate of the flow rate of the protective gas does not exceed 0.01% Q0 / mm. Further, during the equal-diameter stage, the change rate of the flow rate of the protective gas is 0.004% Q0 / mm to 0.01% Q0 / mm.

[0047] The change rate of the flow rate of the protective gas in the present invention refers to the change rate of the flow rate of the protective gas with respect to the equal-diameter growth length. During the equal-diameter stage, the change rate of the flow rate of the protective gas can be 0.004% Q0 / mm, 0.005% Q0 / mm, 0.006% Q0 / mm, 0.007% Q0 / mm, 0.008% Q0 / mm, 0.009% Q0 / mm, 0.01% Q0 / mm, or any range composed of any two of them. Controlling the change rate of the flow rate of the protective gas in the equal-diameter stage of the present invention within the above range can further cooperate with the furnace pressure to control the volatilization rate of antimony elements, so as to better match the segregation phenomenon of antimony elements in silicon and improve the consistency of the tail resistance and head resistance of the antimony-doped silicon single crystal.

[0048] It can be understood that only the numerical magnitude is considered in the calculation process of the change rate of the furnace pressure and the change rate of the flow rate of the protective gas in the present invention, and the positive and negative are not considered.

[0049] In a specific embodiment of the present invention, during the equal-diameter stage, the crystal pulling rate is 80 to 120 mm / h. For example, in different embodiments, the crystal pulling rate during the equal-diameter stage can be 80 mm / h, 90 mm / h, 100 mm / h, 110 mm / h, 120 mm / h, or any range composed of any two of them.

[0050] In a specific embodiment of the present invention, the Czochralski method for growing antimony-doped silicon single crystals includes: melting raw materials to obtain molten silicon, and then performing seed crystal pulling, shoulder release, constant diameter growth, and tailing; the preparation of molten silicon includes: after the silicon material is melted, controlling the temperature to be 1470 ± 10 °C and adding antimony element.

[0051] The traditional method of adding antimony element is to add it to the quartz crucible together with the silicon material during charging. Since the melting point of antimony is about 630 °C, which is much lower than that of silicon, adding antimony element too early will cause a large amount of evaporation of antimony element. The present invention adopts a suitable timing for adding antimony element and precisely controls the temperature after the silicon material is melted, shortening the time for antimony element to be at high temperature, reducing the evaporation amount of antimony before the constant diameter stage, and being more conducive to improving the coincidence degree between the resistivity of the head of the silicon single crystal and the target resistivity.

[0052] In a specific embodiment of the present invention, the initial doping amount of antimony element is calculated according to the target resistivity. Among them, the initial doping amount of antimony element is obtained by converting the target resistivity of the antimony-doped silicon single crystal into the doping amount of antimony element in the molten silicon according to GB / T 13389-2014 "Conversion Regulations for Resistivity and Dopant Concentration of Boron-Doped, Phosphorus-Doped, and Arsenic-Doped Silicon Single Crystals".

[0053] In a specific embodiment of the present invention, the target resistivity is 0.5 to 10 Ω·cm, for example, it can be 0.5 Ω·cm, 1 Ω·cm, 2 Ω·cm, 3 Ω·cm, 4 Ω·cm, 5 Ω·cm, 6 Ω·cm, 7 Ω·cm, 8 Ω·cm, 9 Ω·cm, 10 Ω·cm or the range composed of any two of them. The method of the present invention is applicable to the preparation of low-resistance and high-resistance antimony-doped silicon single crystals with the target resistivity within the above range.

[0054] In a specific embodiment of the present invention, the rated length of the constant diameter stage is 3000 to 5000 mm, for example, it can be 3000 mm, 3200 mm, 3500 mm, 3800 mm, 4000 mm or the range composed of any two of them. When the method of the present invention is used to prepare antimony-doped silicon single crystals with the rated length of the constant diameter stage within the above range, the axial resistance uniformity of the antimony-doped silicon single crystal can be ensured.

[0055] In a specific embodiment of the present invention, the supplementary doping amount of antimony element is 5% to 20% of the initial doping amount. Usually, the supplementary doping amount of antimony element in different seed crystal pulling and shoulder release failure stages is controlled within the range of 5% to 20% of the initial doping amount, for example, it can be 5%, 6%, 8%, 10%, 12%, 15%, 18%, 20% or the range composed of any two of them. When seed crystal pulling and shoulder release failure occurs, as the time for the melt to experience at high temperature during seed crystal pulling and shoulder release failure increases, the supplementary doping amount increases.

[0056] In a specific embodiment of the present invention, the concentration c of antimony element in the molten silicon when the ingot drawing fails or the growth of a single antimony-doped silicon single crystal is completed is determined according to the following formula, and the volatilization amount of the antimony element is calculated.

[0057]

[0058] In Formula I, β is a correction coefficient; T is the theoretical value of the melt temperature calculated from the seeding power, with the unit of °C; P is the furnace pressure, with the unit of torr; c0 is the initial concentration of the antimony element, with the unit of atoms / cm 3 ; c is the concentration of the antimony element in the molten silicon after t minutes (t is counted from the addition of the antimony element), with the unit of atoms / cm 3 ; A is the volatilization area of the molten silicon, with the unit of cm 2 ; E is the evaporation rate constant of the antimony element, with the unit of g·cm -2 ·m -1 (grams per square centimeter per minute); W is the weight of the molten silicon, with the unit of kg.

[0059] The correction coefficient β of the present invention is obtained by summarizing multiple experiments. The correction coefficient β of the present invention is 0.678; the volatilization area A of the molten silicon is the volatilization area corresponding to the addition of the antimony element; the specific value of E is 1.7×10 -2 . In the specific embodiments of the present invention, unless otherwise specified, the additional doping amount is calculated according to the above Formula I of the present invention for additional doping.

[0060] After the addition of the antimony element in the present invention, the seeding power, furnace pressure, and weight of the molten silicon of the single crystal furnace are monitored in real time. The monitoring is carried out through the conventional real-time monitoring system of the single crystal furnace, and the theoretical value T of the melt temperature is converted according to the seeding power. According to the above formula, the change of the concentration c of the antimony element in the molten silicon with time t is calculated. According to the time t corresponding to the failure of ingot drawing or the completion of the growth of a single antimony-doped silicon single crystal, the volatilization amount of the antimony element is calculated, and additional doping is carried out accordingly to make the contents of silicon and antimony elements in the molten silicon after additional doping the same as those in the initial molten silicon. By carrying out additional doping in the above manner, not only can the resistivity of the product be highly consistent with the target resistivity, but also it helps to improve the uniformity of the axial resistivity of the silicon single crystal and ensure the consistency of the quality of the subsequent silicon wafer products.

[0061] In a specific embodiment of the present invention, in the Czochralski method, the remaining crucible amount ≤ 30%. For example, it can be 30%, 25%, 20%, 15% or the range composed of any two of them. The method of the present invention supports a lower remaining crucible amount, thereby reducing costs.

[0062] By deeply coupling the doping timing of the antimony element with the crystal growth kinetic parameters, the present invention breaks through the technical bottleneck that the axial resistance of N-type antimony-doped silicon single crystal is difficult to control due to the volatilization of antimony during the preparation process, and has significant industrialization value.

[0063] The present invention mainly studies the doping timing of antimony element, the furnace pressure in the isodiameter stage, the flow rate of the protective gas, and the compensation doping model. It can be understood that for other growth parameters involved in crystal seeding, shoulder release, isodiameter, and tailing, if not mentioned in the embodiments, they can be carried out according to conventional crystal growth parameters and will not be elaborated here and in subsequent embodiments.

[0064] The second aspect of the present invention provides an antimony-doped silicon single crystal prepared by using the method for improving the axial resistance uniformity of antimony-doped silicon single crystal provided in the first aspect of the present invention.

[0065] In a specific embodiment of the present invention, the resistivity fluctuation of the antimony-doped silicon single crystal in the axial direction (ρ max -ρ min ) / ρ min ≤10%, for example, it can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3% or the range composed of any two of them; wherein, ρ max and ρ min are respectively the maximum resistivity and the minimum resistivity of the antimony-doped silicon single crystal in the axial direction.

[0066] The antimony-doped silicon single crystal product obtained by using the method of the present invention has small resistivity fluctuation in the axial direction and high uniformity; it can better match the requirements of the battery manufacturing process, thereby effectively improving the photoelectric conversion efficiency of the solar cell. Compared with the antimony-doped silicon single crystal products of the same specification prepared by the current conventional methods, the battery conversion efficiency can be increased by 0.03% - 0.05% (about 0.04% for N-type 210 and about 0.03% for N-type 182).

[0067] In a specific embodiment of the present invention, the diameter of the antimony-doped silicon single crystal is 256 - 300 mm. The method of the present invention is applicable to the preparation of large-diameter and small-diameter antimony-doped silicon single crystals and has good universality.

[0068] Example 1

[0069] This example provides a method for improving the axial resistance uniformity of antimony-doped silicon single crystal, including the following steps:

[0070] (1) Add high-purity polysilicon raw materials into a quartz crucible (36-inch single crystal furnace). Under the protection of argon, gradually heat up to above 1420 °C to completely melt the high-purity polysilicon, and then control the melt temperature to 1470 °C and add antimony to melt it. Among them, the total amount of high-purity polysilicon raw materials and antimony is 980 kg, and the dosage of antimony is calculated according to GB / T 13389-2014 "Conversion Rules for Resistivity and Dopant Concentration of Boron-Doped, Phosphorus-Doped, and Arsenic-Doped Silicon Single Crystals" to make the target resistivity of the head of the antimony-doped silicon single crystal be 1.2 Ω·cm.

[0071] (2) Seed crystal and shoulder release are carried out according to conventional crystal growth parameters, enter the isodiametric stage, control the crystal pulling rate in the isodiametric stage to be 90 mm / h ± 3 mm / h, the diameter of the crystal bar is 300 mm, the rated length is 4000 mm, the remaining crucible amount is 20%, and the supplementary doping amount is calculated by formula Ⅰ for supplementary doping (in the experimental process of this embodiment, no seed crystal and shoulder release failure occurred, and the supplementary doping was carried out after the growth of a single antimony-doped silicon single crystal was completed; the same applies to subsequent embodiments); pull 3 antimony-doped silicon single crystal bars;

[0072] Among them, the furnace pressures P0 and P1 corresponding to the start and end of the isodiametric stage are 5 torr and 7 torr respectively, the furnace pressure gradually increases during the isodiametric stage, and the change rate of the furnace pressure is 0.0005 torr / mm; the flow rates Q0 and Q1 of argon corresponding to the start and end of the isodiametric stage are 110 slpm and 80 slpm respectively, the flow rate of argon gradually decreases during the isodiametric stage, and the change rate of the flow rate of argon is 0.0075 slpm / mm.

[0073] Example 2

[0074] This embodiment provides a method for improving the axial resistance uniformity of antimony-doped silicon single crystals, including the following steps:

[0075] (1) Add high-purity polysilicon raw materials into a quartz crucible (36-inch single crystal furnace), under the protection of argon, gradually heat up to above 1420 °C to completely melt the high-purity polysilicon, and then control the melt temperature to be 1465 °C, and add antimony to melt it. Among them, the total amount of high-purity polysilicon raw materials and antimony is 980 kg, and the dosage of antimony is calculated according to GB / T 13389-2014 "Conversion Regulations for Resistivity and Dopant Concentration of Boron-Doped, Phosphorus-Doped, and Arsenic-Doped Silicon Single Crystals" to make the target resistivity of the head of the antimony-doped silicon single crystal be 8 Ω·cm.

[0076] (2) Seed crystal and shoulder release are carried out according to conventional crystal growth parameters, enter the isodiametric stage, control the crystal pulling rate in the isodiametric stage to be 90 mm / h ± 3 mm / h, the diameter of the crystal bar is 300 mm, the rated length is 4000 mm, the remaining crucible amount is 20%, and the supplementary doping amount is calculated by formula Ⅰ for supplementary doping; pull 3 antimony-doped silicon single crystal bars;

[0077] Among them, the furnace pressures P0 and P1 corresponding to the start and end of the isodiametric stage are 6 torr and 8 torr respectively, the furnace pressure gradually increases during the isodiametric stage, and the change rate of the furnace pressure is 0.0005 torr / mm; the flow rates Q0 and Q1 of argon corresponding to the start and end of the isodiametric stage are 95 slpm and 70 slpm respectively, the flow rate of argon gradually decreases during the isodiametric stage, and the change rate of the flow rate of argon is 0.00625 slpm / mm.

[0078] Example 3

[0079] This embodiment provides a method for improving the axial resistance uniformity of antimony-doped silicon single crystals, including the following steps:

[0080] (1) Add high-purity polysilicon raw materials into a quartz crucible (36-inch single crystal furnace). Under argon protection, gradually heat up to above 1420 °C to completely melt the high-purity polysilicon, and then control the melt temperature at 1470 °C, and add antimony to melt it. Among them, the total amount of high-purity polysilicon raw materials and antimony is 980 kg, and the dosage of antimony is calculated according to GB / T 13389-2014 "Conversion Regulations for Resistivity and Dopant Concentration of Boron-Doped, Phosphorus-Doped, and Arsenic-Doped Silicon Single Crystals" to make the target resistivity of the head of the antimony-doped silicon single crystal 1.1 Ω·cm.

[0081] (2) Seed and shoulder according to conventional crystal growth parameters, enter the constant diameter stage, control the pulling rate in the constant diameter stage at 110 mm / h ± 3 mm / h, the diameter of the crystal rod is 256 mm, the rated length is 4000 mm, and the remaining crucible amount is 30%. Calculate the supplementary doping amount using formula Ⅰ for supplementary doping; pull 3 antimony-doped silicon single crystal rods;

[0082] Among them, the furnace pressures P0 and P1 corresponding to the start and end of the constant diameter stage are 6 torr and 9 torr respectively. The furnace pressure gradually increases during the constant diameter stage, and the change rate of the furnace pressure is 0.00075 torr / mm; the flow rates Q0 and Q1 of argon corresponding to the start and end of the constant diameter stage are 90 slpm and 60 slpm respectively. The flow rate of argon gradually decreases during the constant diameter stage, and the change rate of the flow rate of argon is 0.0075 slpm / mm.

[0083] Example 4

[0084] This embodiment provides a method for improving the axial resistance uniformity of antimony-doped silicon single crystals, including the following steps:

[0085] (1) Add high-purity polysilicon raw materials into a quartz crucible (36-inch single crystal furnace). Under argon protection, gradually heat up to above 1420 °C to completely melt the high-purity polysilicon, and then control the melt temperature at 1470 °C, and add antimony to melt it. Among them, the total amount of high-purity polysilicon raw materials and antimony is 980 kg, and the dosage of antimony is calculated according to GB / T 13389-2014 "Conversion Regulations for Resistivity and Dopant Concentration of Boron-Doped, Phosphorus-Doped, and Arsenic-Doped Silicon Single Crystals" to make the target resistivity of the head of the antimony-doped silicon single crystal 8 Ω·cm.

[0086] (2) Seed and shoulder according to conventional crystal growth parameters, enter the constant diameter stage, control the pulling rate in the constant diameter stage at 110 mm / h ± 3 mm / h, the diameter of the crystal rod is 256 mm, the rated length is 4000 mm, and the remaining crucible amount is 30%. Calculate the supplementary doping amount using formula Ⅰ for supplementary doping; pull 3 antimony-doped silicon single crystal rods;

[0087] Among them, the furnace pressures P0 and P1 corresponding to the start and end of the equal-diameter stage are 5 torr and 7 torr respectively, the furnace pressure gradually increases during the equal-diameter stage, and the change rate of the furnace pressure is 0.0005 torr / mm; the flow rates Q0 and Q1 of argon corresponding to the start and end of the equal-diameter stage are 110 slpm and 90 slpm respectively, the flow rate of argon gradually decreases during the equal-diameter stage, and the change rate of the flow rate of argon is 0.005 slpm / mm.

[0088] Example 5

[0089] This example refers to the method of Example 1, the only difference being that: in step (2), the furnace pressure P1 at the end of the equal-diameter stage and the change rate of the furnace pressure are different.

[0090] In this example, the furnace pressure P1 corresponding to the end of the equal-diameter stage is 6 torr, and the change rate of the furnace pressure is 0.00025 torr / mm.

[0091] Example 6

[0092] This example refers to the method of Example 1, the only difference being that: in step (2), the furnace pressure P1 at the end of the equal-diameter stage and the change rate of the furnace pressure are different.

[0093] In this example, the furnace pressure P1 corresponding to the end of the equal-diameter stage is 9 torr, and the change rate of the furnace pressure is 0.001 torr / mm.

[0094] Example 7

[0095] This example refers to the method of Example 1, the only difference being that: in step (2), the flow rate Q1 of argon at the end of the equal-diameter stage and the change rate of the flow rate of argon are different.

[0096] In this example, the flow rate Q1 of argon corresponding to the end of the equal-diameter stage is 95 slpm, and the change rate of the furnace pressure is 0.00375 slpm / mm.

[0097] Example 8

[0098] This example refers to the method of Example 1, the only difference being that: in step (2), the calculation method of the additional doping amount is different.

[0099] In this example, when the growth of a single antimony-doped silicon single crystal is completed, additional doping is carried out, and the additional doping amount of antimony element is 20% of the initial doping amount.

[0100] Example 9

[0101] Example 9 refers to the method of Example 1, the only difference being that: in step (2), the furnace pressure and the flow rate of argon in the equal-diameter stage remain unchanged.

[0102] In this embodiment, the furnace pressure in the equal-diameter stage is 5 torr, and the flow rate of argon is 110 slpm.

[0103] Example 10

[0104] Example 10 refers to the method of Example 2, with the only difference being that in step (2), the furnace pressure and the flow rate of argon in the equal-diameter stage remain unchanged.

[0105] In this embodiment, the furnace pressure in the equal-diameter stage is 6 torr, and the flow rate of argon is 95 slpm.

[0106] Example 11

[0107] Example 11 refers to the method of Example 3, with the only difference being that in step (2), the furnace pressure and the flow rate of argon in the equal-diameter stage remain unchanged.

[0108] In this embodiment, the furnace pressure in the equal-diameter stage is 6 torr, and the flow rate of argon is 90 slpm.

[0109] Example 12

[0110] Example 12 refers to the method of Example 4, with the only difference being that in step (2), the furnace pressure and the flow rate of argon in the equal-diameter stage remain unchanged.

[0111] In this embodiment, the furnace pressure in the equal-diameter stage is 5 torr, and the flow rate of argon is 110 slpm.

[0112] Example 13

[0113] Example 13 refers to the method of Example 1, with the only difference being that in step (2), the furnace pressure in the equal-diameter stage remains unchanged, both being 5 torr.

[0114] Example 14

[0115] Example 14 refers to the method of Example 1, with the only difference being that in step (2), the flow rate of argon in the equal-diameter stage remains unchanged, both being 110 slpm.

[0116] Example 15

[0117] Example 15 refers to the method of Example 1, with the only difference being that in step (2), the furnace pressure P1 at the end of the equal-diameter stage and the change rate of the furnace pressure are different.

[0118] In Example 15, the furnace pressure P1 corresponding to the end of the equal-diameter stage is 10 torr, and the change rate of the furnace pressure is 0.00125 torr / mm.

[0119] Example 16

[0120] Example 16 Refer to the method of Example 1, with the difference that: in step (2), the flow rate Q1 of argon at the end of the equal-diameter stage and the change rate of the flow rate of argon are different.

[0121] In Example 16, the flow rate Q1 of argon corresponding to the end of the equal-diameter stage is 75 slpm, and the change rate of argon is 0.00875 slpm / mm.

[0122] Experimental Example

[0123] For the equal-diameter sections of the antimony-doped silicon single crystals grown in different examples, wafer sampling is carried out (the sampling positions correspond to the starting end of the head-equal-diameter section, the ending end of the tail-equal-diameter section, and the central position of the middle-equal-diameter section respectively). The wafers are cut into slices perpendicular to the crystal growth direction and the resistivity is measured using a four-probe resistivity meter. The test results are shown in Table 1.

[0124] Table 1 Resistivity test results of antimony-doped silicon single crystals in different examples and comparative examples

[0125]

[0126]

[0127] From the above test results, it can be seen that the method of the present invention can improve the axial resistivity uniformity in the growth of large-diameter, small-diameter, high-resistivity, and low-resistivity antimony-doped silicon single crystals, can better meet the requirements of the battery manufacturing process, thereby effectively improving the photoelectric conversion efficiency of solar cells; and can support a lower crucible retention amount and thus reduce costs.

[0128] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the axial resistance uniformity of antimony-doped silicon single crystals, characterized in that, It includes the following steps: growing antimony-doped silicon single crystal by the Czochralski method, and during the constant diameter stage, the furnace pressure is 4 - 13 torr; In the Czochralski method, when the pulling and feeding fails or after the growth of a single antimony-doped silicon single crystal is completed, antimony element is replenished according to the volatilization amount of the antimony element.

2. The method according to claim 1, wherein During the constant diameter stage, the furnace pressure gradually increases and the flow rate of the protective gas gradually decreases; Set the furnace pressures corresponding to the start and end of the constant diameter stage as P0 and P1 respectively, and set the flow rates of the protective gas corresponding to the start and end of the constant diameter stage as Q0 and Q1 respectively, and satisfy: P1 - P0 = 0.5 - 4 torr, Q0 - Q1 = 5 - 30 slpm.

3. The method according to claim 2, wherein It has at least one of the following characteristics: (1) The furnace pressure P0 is 4 - 7 torr and the furnace pressure P1 is 6 - 10 torr; (2) The flow rate Q0 of the protective gas is 85 - 115 slpm and the flow rate Q1 of the protective gas is 55 - 95 slpm.

4. The method according to claim 2, wherein It has at least one of the following characteristics: (1) During the constant diameter stage, the change rate of the furnace pressure does not exceed 0.2%P0 / mm; (2) During the constant diameter stage, the change rate of the flow rate of the protective gas does not exceed 0.01%Q0 / mm.

5. The method according to claim 4, wherein During the constant diameter stage, the change rate of the furnace pressure is 0.006%P0 / mm - 0.018%P0 / mm, and the change rate of the flow rate of the protective gas is 0.004%Q0 / mm - 0.01%Q0 / mm.

6. The method according to claim 1, wherein The growth of the antimony-doped silicon single crystal by the Czochralski method includes: melting the raw materials to obtain molten silicon, and then performing seeding, necking, constant diameter and tailing; the preparation of the molten silicon includes: after the silicon material is melted, controlling the temperature to be 1470 ± 10 °C and adding antimony element.

7. The method according to claim 1, characterized in that, The replenishment amount of the antimony element is 5% - 20% of the initial doping amount.

8. The method according to claim 1 or 7, characterized in that Determine the concentration c of the antimony element in the molten silicon when the pulling and feeding fails or after the growth of a single antimony-doped silicon single crystal is completed according to the following formula, and calculate the volatilization amount of the antimony element; In the formula, β is the correction coefficient, T is the theoretical value of the melt temperature calculated from the seeding power, P is the furnace pressure, c0 is the initial concentration of the antimony element, c is the concentration of the antimony element in the molten silicon after t minutes, A is the volatilization area of the molten silicon, E is the evaporation rate constant of the antimony element, and W is the weight of the molten silicon.

9. The method according to claim 1, characterized in that, In the Czochralski method, the remaining crucible amount ≤ 30%.

10. Antimony-doped silicon single crystal, characterized in that, It is obtained by using the method for improving the axial resistance uniformity of the antimony-doped silicon single crystal according to any one of claims 1 - 9.

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