Process for preparing monocrystalline silicon by multiple-feeding and multiple-pulling method for quantitative compensation of volatile doping elements in multiple-feeding stage and monocrystalline silicon rod prepared by process

Abstract

The invention provides a process for preparing a silicon single crystal rod by a multi-feeding and multi-pulling method. The invention provides a process for preparing monocrystalline silicon by a multi-feeding and multi-pulling method for quantitatively compensating volatile doping elements in a re-feeding stage, which is a method for measuring and calculating the concentration of a volatile doping agent in a residual silicon melt in the re-feeding stage of the multi-feeding and multi-pulling method. Therefore, the purposes of accurately compensating the concentration of the volatile dopant and guaranteeing the quality consistency between crystal bars are achieved. According to the method, the concentration of the volatile dopant in the residual silicon melt in the re-feeding stage can be accurately measured under the condition that a crystal pulling furnace platform is not changed at all; the compensation amount of the volatile dopant in the re-feeding stage can be accurately obtained, and the stable quality of the crystal bar is ensured; meanwhile, auxiliary equipment is not needed, the method is low in cost, good in economical efficiency, suitable for various volatile dopants, wide in application range and suitable for an existing technology for preparing monocrystalline silicon through a multiple-feeding and multiple-pulling method, the technology does not need to be changed, and the production efficiency is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of single crystal silicon rod materials, and relates to a process for preparing single crystal silicon rods by a multiple-feeding and re-pulling method and the single crystal silicon rods prepared therefrom, and in particular to a process for preparing single crystal silicon by a multiple-feeding and re-pulling method with quantitative compensation of volatile doping elements in the re-feeding stage and the single crystal silicon rods prepared therefrom. Background Art

[0002] The multiple-feed compound pulling method (RCZ method) for producing single crystal silicon refers to adding new silicon material to the small amount of silicon melt remaining in the quartz crucible after the pulling of a single single crystal silicon rod is completed, and then pulling the next single crystal silicon rod. Compared with the earliest batch direct pulling method, the RCZ method shortens the cooling of the crystal rod and saves the time of intake and exhaust, and the quartz crucible can be reused. It is the current mainstream single crystal silicon pulling process.

[0003] After a single single crystal silicon rod (hereinafter referred to as "ingot") is pulled, the next ingot needs to go through the process of ingot cooling, silicon material re-injection, and material melting, which takes 8 to 15 hours. During this process, the volatile dopant is continuously consumed. Therefore, during the ingot pulling process, the concentration of the remaining volatile dopant in the silicon melt cannot be kept constant, and it is difficult to maintain stable quality between ingots without human intervention.

[0004] Antimony (Sb) is a common volatile dopant in the production of single crystal silicon rods. Compared with phosphorus doping, antimony (Sb) doping can shorten the head-to-tail resistance ratio of the crystal rod, improve the mechanical strength of the silicon wafer, and increase the minority carrier lifetime of the silicon wafer. However, the segregation coefficient of antimony in silicon melt is extremely small (0.023) and its solubility is low (the solubility in silicon at 1100°C is only 4.5×10 19 / cm 3 ), the evaporation coefficient is relatively large (about 7×10 -2cm / s), so it needs to be replenished in time when re-feeding to ensure the quality stability between crystal rods. In response to this problem, the existing related technical solutions mainly focus on suppressing the volatilization of dopants, shortening the doping time of volatile dopants, and improving the doping efficiency. For example, patent CN 114574946 A discloses a Sb element doping device and a matching doping process composed of a quartz cover and an inner loading funnel made of graphite plated silicon carbide. The doping device enters the single crystal furnace after the silicon material is melted. By inserting the lower section of the inner loading funnel into the silicon melt, the purpose of reducing the volatilization loss of Sb is achieved. However, this method cannot control the speed at which Sb enters the silicon melt, so it cannot be accurately replenished. In addition, since the single furnace operation time of the photovoltaic RCZ technology has reached more than 500 hours, the lower section of the inner loading funnel is immersed in the silicon melt for a long time, and it is difficult to avoid corrosion, thereby releasing impurities into the silicon melt, affecting the quality of the crystal rod. For example, patent CN109457294A uses seed crystals with Sb sources for doping. Although this solution can control the Sb content in the seed crystals, it cannot accurately measure the residual Sb concentration in the silicon melt after the silicon material is re-doped. For example, patent CN101717993A designs an Sb element doping device consisting of a quartz bell jar and a small quartz crucible, which can achieve accurate doping of the Sb element during initial feeding, but cannot control the Sb doping amount during re-doping.

[0005] Moreover, the existing related technical research focuses on the precise doping of volatile elements in the initial silicon material injection stage, lacks the calculation and measurement method of the volatile dopants in the remaining silicon melt in the re-injection stage, and cannot accurately control the compensation amount of volatile dopants in the re-injection stage. There is no corresponding technical solution or theoretical research that can effectively characterize the Sb concentration in the silicon melt after the silicon material is re-injected. Or it is necessary to use special feeding equipment, which greatly changes the existing single crystal furnace equipment. The feeding equipment used is usually made of quartz or silicon carbide, which has a limited life, increases the cost of crystal pulling, and there is a risk of introducing impurities into the silicon melt.

[0006] Therefore, how to find a more suitable way to solve the above-mentioned technical problems existing in the existing multiple-feeding re-pulling method and to accurately and quantitatively supplement Sb in the re-feeding process of direct-pull single crystals has become one of the urgent problems to be solved by many front-line researchers in the industry. Summary of the invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a process for preparing single crystal silicon rods by multiple feeding and re-pulling method and the single crystal silicon rods prepared therefrom, in particular, a process for preparing single crystal silicon by multiple feeding and re-pulling method with quantitative compensation of volatile doping elements in the re-feeding stage. The Czochralski single crystal re-feeding process for quantitatively supplementing volatile doping elements provided by the present invention, after the silicon material is re-fed, samples are taken from the silicon melt for detection, and the concentration of the volatile doping elements remaining in the silicon melt is calculated, so that accurate quantitative supplementation of volatile dopants in the re-feeding link can be achieved, which effectively solves the problem that in the preparation of single crystal silicon rods by the Czochralski method, it is difficult to accurately and quantitatively supplement the doping elements in the re-feeding stage due to the strong volatility of the doping elements.

[0008] The present invention provides a process for preparing a single crystal silicon rod by a multiple feeding and pulling method, comprising the following steps:

[0009] 1) After the previous crystal ingot is pulled, the tail resistivity of the previous crystal ingot is measured, and the pulling end time t1 of the previous crystal ingot is obtained;

[0010] Based on the tail resistivity, the concentration of the volatile doping element in the remaining silicon melt is calculated, and then based on the concentration N1 of the volatile doping element in the remaining silicon melt, the total amount M1 of the volatile doping element in the silicon melt is calculated again;

[0011] 2) Based on the consumption of the previous crystal ingot pulling, complete the target re-injection of silicon material for the next crystal ingot, material processing and temperature stabilization operations;

[0012] 3) Add a crystal pulling growth process for the test crystal rod. The test crystal rod undergoes the seeding and shouldering processes. After the shouldering reaches the target diameter, the shoulder is turned to enter the equal diameter growth. After the equal diameter length is controlled to a certain length, the crystal pulling is stopped, the crystal rod is taken out, and the equal diameter end time t2 of the test crystal rod is recorded;

[0013] 4) measuring the resistance of the tail of the test crystal rod with equal diameter, calculating the concentration N2 of the volatile doping element in the silicon melt when the test crystal rod has equal diameter, and the total amount M2 of the volatile doping element in the silicon melt when the test crystal rod has equal diameter;

[0014] 5) Based on the total amount of volatile doping elements M1 and M2 in the silicon melt obtained in the above steps, as well as the end time t1 of the previous crystal ingot pulling and the end time t2 of the test crystal ingot equalization, the average loss rate V of the volatile doping elements from the end of the previous crystal ingot pulling to the end of the test crystal ingot pulling is calculated;

[0015] 6) Based on the average loss rate V obtained in the above steps, calculate the total amount of volatile doping elements that need to be replenished at the beginning of the next crystal rod pulling, compensate the volatile doping elements in the system, complete the re-injection, and carry out the next crystal rod pulling.

[0016] Preferably, the volatile doping element comprises an element having an evaporation coefficient in the silicon melt greater than or equal to about 1×10 -2 cm / s of volatile elements;

[0017] In the step 1), the formula for calculating the concentration of the volatile doping element in the remaining silicon melt is as shown in formula (1) and formula (2):

[0018] ρ=6.242×10 18 / N1×10 Z’ (1);

[0019] Where ρ is the tail resistivity (Ω·cm), N1 is the atomic concentration of the volatile doping element in the remaining silicon melt (atom / cm 3 ), y=(log 10 N1)-16;

[0020]

[0021] Among them, A'0=-3.0769, A'1=2.2108, A'2=-0.62272, A'3=0.057501, B'1=-0.68157, B'2=0.19833, B'3=-0.018376.

[0022] Preferably, the volatile doping element comprises antimony and / or gallium;

[0023] In the step 1), the formula for recalculating the total amount of volatile doping elements M1 in the silicon melt is shown in formula (3):

[0024] M1=N1×W1 (3);

[0025] Where N1 is the concentration of volatile doping elements in the silicon melt at the end of the previous ingot pulling (atom / cm 3 ), W1 is the remaining silicon melt volume at the end of the previous crystal ingot pulling (cm 3 ).

[0026] Preferably, the lengths of the previous crystal rod and the next crystal rod are independently selected from 10 to 10000 mm;

[0027] The diameters of the previous crystal rod and the next crystal rod are independently selected from 1 to 500 mm;

[0028] The certain length is specifically 5 to 10 mm;

[0029] The tail resistivity is specifically the tail edge resistivity or the tail skin resistivity.

[0030] Preferably, the length of the test crystal rod is 10 to 1000 mm;

[0031] The diameter of the test crystal rod is 1 to 500 mm;

[0032] The target diameter is 250-350 mm.

[0033] Preferably, the formula for calculating the concentration N2 of the volatile doping element in the silicon melt when the test crystal rod reaches the same diameter is as shown in formula (1) and formula (2).

[0034] Preferably, when the test crystal rod reaches the same diameter, the total amount of volatile doping elements M2 in the silicon melt is expressed as follows:

[0035] M2=N2×(W1+W2) (4);

[0036] Where N1 is the concentration of volatile doping elements in the silicon melt when the test ingot is equal in diameter (atom / cm 3 ), W2 is the volume of raw material added in step 2) (cm 3 ).

[0037] The concentration of volatile doping elements in the silicon melt N2, and the total amount of volatile doping elements in the silicon melt M2 when the test crystal rod is equal in diameter

[0038] Preferably, the calculation formula of the average loss rate V of the volatile doping element is as shown in formula (4):

[0039]

[0040] Preferably, the calculation formula for the total amount of volatile doping elements that need to be supplemented is as shown in formula (5):

[0041] Δw=N×W+V×Δt-N1W1 (5);

[0042] Wherein, Δw is the compensation amount of volatile doping elements in the re-injection stage; N is the concentration of volatile doping elements in the silicon melt at the target resistivity; W is the total volume of the silicon melt after re-injection (cm 3 ), V is the average volatilization rate of volatile elements from the end of the previous crystal ingot pulling to the end of the test crystal ingot shouldering; Δt is the interval time (hours) from the end of the previous crystal ingot pulling to the start of the next crystal ingot seeding; N1 is the concentration of volatile doping elements in the silicon melt at the end of the previous crystal ingot pulling; W1 is the volume of the remaining silicon melt at the end of the previous crystal ingot pulling (cm 3 );

[0043] The re-investment stage specifically refers to the process from the end of the previous crystal ingot pulling to the next crystal ingot seeding;

[0044] The average loss rate of the volatile doping element is the average loss rate of the volatile doping element in the reinvestment stage.

[0045] The present invention also provides a process for preparing a single crystal silicon rod according to any one of the above technical solutions, wherein the head-to-tail resistance ratio of the single crystal silicon rod is less than or equal to 1.5;

[0046] The length of the single crystal silicon rod is greater than or equal to 3.5 m;

[0047] The number of single crystal silicon rods pulled from a single furnace is greater than or equal to 6;

[0048] The head resistance hit rate of single-furnace single-crystal silicon rods is greater than or equal to 95%.

[0049] The present invention provides a process for preparing a single crystal silicon rod by a multiple feeding and re-pulling method, comprising the following steps: first, after completing the pulling of the previous crystal rod, measuring the tail resistivity of the previous crystal rod, and obtaining the pulling end time t1 of the previous crystal rod; calculating the concentration of volatile doping elements in the remaining silicon melt based on the tail resistivity, and then calculating the total amount M1 of volatile doping elements in the silicon melt again based on the concentration N1 of the volatile doping elements in the remaining silicon melt; then completing the target re-feeding amount of silicon material for the next crystal rod, re-feeding, material treatment and temperature stabilization operations based on the consumption of the previous crystal rod pulling; then adding a test crystal rod pulling growth process, the test crystal rod undergoes a seeding and shouldering process, after the shoulder is released to a target diameter, the shoulder is turned to enter equal diameter growth, after the equal diameter length is controlled to a certain length, the crystal pulling is stopped, the crystal rod is taken out, and the equal diameter structure of the test crystal rod is recorded beam time t2; then measure the resistance of the test crystal rod equal diameter tail, calculate the volatile doping element concentration N2 in the silicon melt when the test crystal rod equal diameter ends, and the total amount of volatile doping elements M2 in the silicon melt when the test crystal rod equal diameter ends; then based on the total amount of volatile doping elements M1 in the silicon melt, the total amount of volatile doping elements M2 in the silicon melt, and the end time t1 of the previous crystal rod pulling and the end time t2 of the test crystal rod equal diameter obtained in the above steps, calculate the average loss rate V of the volatile doping elements from the end of the previous crystal rod pulling to the end of the test crystal rod pulling; finally, combined with the average loss rate V obtained in the above steps, calculate the total amount of volatile doping elements that need to be supplemented at the beginning of the next crystal rod pulling, compensate the volatile doping elements in the system, complete the re-investment, and carry out the next crystal rod pulling. Compared with the prior art, the process for preparing single crystal silicon rods by multiple feeding and re-pulling method provided by the present invention is a method for measuring and calculating the concentration of volatile dopants in the remaining silicon melt in the re-feeding stage of the multiple feeding and re-pulling method, thereby achieving the purpose of accurately compensating the concentration of volatile dopants and ensuring the consistency of quality between crystal rods. After the silicon material is re-fed, the present invention takes samples from the silicon melt for detection and calculates the concentration of volatile doping elements remaining in the silicon melt, thereby achieving accurate quantitative replenishment of volatile dopants in the re-feeding link, effectively solving the problem of difficulty in accurate quantitative replenishment in the re-feeding stage of preparing single crystal silicon rods by the direct pulling method due to the strong volatility of the doping elements.

[0050] The Czochralski single crystal re-throwing process for quantitatively supplementing volatile doping elements provided by the present invention can accurately measure the concentration of volatile dopants in the remaining silicon melt in the re-throwing stage without making any changes to the crystal pulling furnace; it can also accurately obtain the compensation amount of volatile dopants in the re-throwing stage to ensure the stability of the crystal rod quality; at the same time, no auxiliary equipment is required, the cost is low, the economy is good, it is suitable for a variety of volatile dopants, the scope of use is wide, and it is suitable for the existing multi-time feeding re-throwing method for preparing single crystal silicon, without changing the process, and the production efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1The present invention provides a schematic diagram of the process flow of preparing single crystal silicon rods by the multiple feeding and pulling method. DETAILED DESCRIPTION

[0052] In order to further understand the present invention, the technical solution of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all 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.

[0053] All raw materials of the present invention have no particular limitation on their sources, and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0054] There is no particular restriction on the purity of all raw materials in the present invention. The present invention preferably uses analytically pure materials or materials with conventional purity in the field of preparing single crystal silicon rods by multiple feeding and pulling methods.

[0055] The present invention provides a process for preparing a single crystal silicon rod by a multiple feeding and pulling method, comprising the following steps:

[0056] 1) After the previous crystal ingot is pulled, the tail resistivity of the previous crystal ingot is measured, and the pulling end time t1 of the previous crystal ingot is obtained;

[0057] Based on the tail resistivity, the concentration of the volatile doping element in the remaining silicon melt is calculated, and then based on the concentration N1 of the volatile doping element in the remaining silicon melt, the total amount M1 of the volatile doping element in the silicon melt is calculated again;

[0058] 2) Based on the consumption of the previous crystal ingot pulling, complete the target re-injection of silicon material for the next crystal ingot, material processing and temperature stabilization operations;

[0059] 3) Add a crystal pulling growth process for the test crystal rod. The test crystal rod undergoes the seeding and shouldering processes. After the shouldering reaches the target diameter, the shoulder is turned to enter the equal diameter growth. After the equal diameter length is controlled to a certain length, the crystal pulling is stopped, the crystal rod is taken out, and the equal diameter end time t2 of the test crystal rod is recorded;

[0060] 4) measuring the resistance of the tail of the test crystal rod with equal diameter, calculating the concentration N2 of the volatile doping element in the silicon melt when the test crystal rod has equal diameter, and the total amount M2 of the volatile doping element in the silicon melt when the test crystal rod has equal diameter;

[0061] 5) Based on the total amount of volatile doping elements M1 and M2 in the silicon melt obtained in the above steps, as well as the end time t1 of the previous crystal ingot pulling and the end time t2 of the test crystal ingot equalization, the average loss rate V of the volatile doping elements from the end of the previous crystal ingot pulling to the end of the test crystal ingot pulling is calculated;

[0062] 6) Based on the average loss rate V obtained in the above steps, calculate the total amount of volatile doping elements that need to be replenished at the beginning of the next crystal rod pulling, compensate the volatile doping elements in the system, complete the re-injection, and carry out the next crystal rod pulling.

[0063] The present invention firstly measures the tail resistivity of the previous crystal rod after the previous crystal rod pulling is completed, and obtains the crystal pulling end time t1 of the previous crystal rod;

[0064] Based on the tail resistivity, the concentration of the volatile doping element in the remaining silicon melt is calculated, and then based on the concentration N1 of the volatile doping element in the remaining silicon melt, the total amount M1 of the volatile doping element in the silicon melt is calculated again.

[0065] In the present invention, the volatile doping element preferably includes an element having an evaporation coefficient in the silicon melt greater than or equal to about 1×10 -2 cm / s of volatile elements.

[0066] In the present invention, in step 1), the formula for calculating the concentration of the volatile doping element in the remaining silicon melt is as shown in formula (1) and formula (2):

[0067] ρ=6.242×10 18 / N1×10 Z’ (1);

[0068] Wherein, ρ is preferably the tail resistivity (Ω·cm), N1 is preferably the atomic concentration of the volatile doping element in the remaining silicon melt (atom / cm 3 ), y=(log 10 N1)-16;

[0069]

[0070] Among them, A'0=-3.0769, A'1=2.2108, A'2=-0.62272, A'3=0.057501, B'1=-0.68157, B'2=0.19833, B'3=-0.018376.

[0071] In the present invention, the volatile doping element preferably includes antimony and / or gallium, and more preferably antimony or gallium.

[0072] In the present invention, in the step 1), the formula for recalculating the total amount of volatile doping elements M1 in the silicon melt is preferably as shown in formula (3):

[0073] M1=N1×W1 (3);

[0074] Wherein, N1 is preferably the concentration of volatile doping elements in the silicon melt at the end of the previous crystal ingot pulling, in units of atom / cm 3 W1 is preferably the remaining silicon melt volume at the end of the previous crystal ingot pulling, in cm 3 .

[0075] The present invention completes the target re-feeding amount of silicon material in the next crystal ingot, the material chemical reaction and the temperature stabilization operation based on the consumption of the previous crystal ingot pulling. In the present invention, the test crystal ingot is not considered as a normal pulled crystal ingot, but is only a crystal ingot used for calculation and testing.

[0076] In the present invention, the lengths of the previous crystal rod and the next crystal rod are independently preferably selected from 10 to 10000 mm, more preferably 100 to 6000 mm, and more preferably 1000 to 2000 mm.

[0077] In the present invention, the diameters of the previous crystal rod and the next crystal rod are independently preferably selected from 1 to 500 mm, more preferably 10 to 300 mm, and more preferably 50 to 100 mm.

[0078] The present invention then adds a crystal pulling growth process of a test crystal rod. The test crystal rod undergoes seeding and shouldering steps. After shouldering to the target diameter, the shoulder is turned to enter equal diameter growth. After the equal diameter length is controlled to a certain length, the crystal pulling is stopped, the crystal rod is taken out, and the equal diameter end time t2 of the test crystal rod is recorded. In the present invention, the test crystal rod is not the next crystal rod, but a crystal rod specially added for testing, and the amount of raw materials required for its growth can be ignored.

[0079] In the present invention, the certain length is preferably 5 to 10 mm, more preferably 6 to 9 mm, and even more preferably 7 to 8 mm.

[0080] The present invention then measures the resistance of the tail of the test crystal rod with equal diameter, calculates the concentration N2 of volatile doping elements in the silicon melt when the test crystal rod has equal diameter, and the total amount M2 of volatile doping elements in the silicon melt when the test crystal rod has equal diameter.

[0081] In the present invention, the tail resistivity is preferably the tail edge resistivity or the tail skin resistivity.

[0082] In the present invention, the length of the test crystal rod is preferably 10 to 1000 mm, more preferably 100 to 700 mm, and more preferably 200 to 400 mm.

[0083] In the present invention, the diameter of the test crystal rod is preferably 1 to 500 mm, more preferably 100 to 400 mm, and more preferably 200 to 300 mm.

[0084] In the present invention, the target diameter is preferably 250 to 350 mm, more preferably 270 to 330 mm, and even more preferably 290 to 310 mm.

[0085] In the present invention, the formula for calculating the concentration N2 of the volatile doping element in the silicon melt when the test crystal rod reaches the same diameter is preferably as shown in formula (1) and formula (2).

[0086] In the present invention, when the test crystal rod reaches the same diameter, the formula for the total amount of volatile doping elements M2 in the silicon melt is preferably as shown in formula (4):

[0087] M2=N2×(W1+W2) (4);

[0088] Wherein, N1 is preferably the concentration of volatile doping elements (atom / cm 3 ), W2 is preferably the volume of raw material re-added in step 2) (cm 3 ).

[0089] In the present invention, the concentration of volatile doping elements in the silicon melt is preferably N2, and the total amount of volatile doping elements in the silicon melt when the test crystal rod is equal in diameter is M 2。

[0090] The present invention further calculates the average loss rate V of the volatile doping elements from the end of the previous crystal rod pulling to the end of the test crystal rod pulling based on the total amount of volatile doping elements M1 in the silicon melt, the total amount of volatile doping elements M2 in the silicon melt, the end time t1 of the previous crystal rod pulling, and the end time t2 of the test crystal rod equal diameter.

[0091] In the present invention, the calculation formula of the average loss rate V of the volatile doping element is preferably as shown in formula (4):

[0092]

[0093] Finally, the present invention combines the average loss rate V obtained in the above steps to calculate the total amount of volatile doping elements that need to be supplemented at the beginning of the next crystal rod pulling, compensates the volatile doping elements in the system, completes the re-feeding, and performs the next crystal rod pulling.

[0094] In the present invention, the calculation formula for the total amount of volatile doping elements that need to be supplemented is preferably as shown in formula (5):

[0095] Δw=N×W+V×Δt-N1W1 (5).

[0096] Wherein, Δw is preferably the compensation amount of volatile doping elements in the re-injection stage; N is preferably the concentration of volatile doping elements in the silicon melt at the target resistivity; W is preferably the total volume (cm) of the silicon melt after re-injection. 3 ), V is preferably the average volatilization rate of the volatile elements from the end of the previous crystal ingot pulling to the end of the test crystal ingot shouldering; Δt is preferably the interval time (hours, h) from the end of the previous crystal ingot pulling to the start of the next crystal ingot seeding; N1 is preferably the concentration of volatile doping elements in the silicon melt at the end of the previous crystal ingot pulling; W1 is preferably the remaining silicon melt volume at the end of the previous crystal ingot pulling;

[0097] In the present invention, the re-investment stage is preferably a process from the end of the previous crystal ingot pulling to the beginning of the next crystal ingot seeding.

[0098] In the present invention, the average loss rate of the volatile doping element is preferably the average loss rate of the volatile doping element in the re-investment stage.

[0099] In the present invention, at a set target resistivity ρ, based on equations (1) and (2), the concentration N of volatile doping elements in the silicon melt is calculated, W=W1+W2 is the total volume of the silicon melt after re-dosing, and the total amount M of volatile doping elements in the silicon melt is obtained.

[0100] The present invention provides a process for preparing a single crystal silicon rod as described in any one of the above technical solutions, wherein the head-to-tail resistance ratio of the single crystal silicon rod is less than or equal to 1.5.

[0101] The length of the single crystal silicon rod is greater than or equal to 3.5 m;

[0102] The number of single crystal silicon rods pulled from a single furnace is greater than or equal to 6;

[0103] The head resistance hit rate of single-furnace single-crystal silicon rods is greater than or equal to 95%.

[0104] The present invention is to complete and refine the overall technical solution, better ensure the structure and characteristics of the single crystal silicon rod prepared by the multiple-feeding and re-pulling method, and further improve the stability and continuity of the multiple-feeding and re-pulling method. The multiple-feeding and re-pulling method for preparing single crystal silicon with quantitative compensation of volatile doping elements in the re-feeding stage and the single crystal silicon rod prepared by the method can specifically include the following contents:

[0105] A method for measuring and calculating the remaining volatile doping elements in the silicon melt during the silicon material re-feeding stage in the process of preparing single crystal silicon by multiple feeding and re-pulling method. The method includes: after the re-feeding and chemical processing of silicon materials is completed, the test crystal rod is pulled through seeding and shouldering, and the tail resistivity of the test crystal rod is measured to determine the concentration of the remaining doping elements in the silicon melt.

[0106] The method for measuring and calculating the remaining volatile doping elements in the silicon melt during the silicon material re-investment stage is characterized in that the calculation formula is as follows:

[0107] ρ=6.242×10 18 / N1×10 Z’ (Formula 1)

[0108]

[0109] Where ρ is the resistivity (Ω·cm), N is the dopant concentration (cm -3 ), y=(log 10 N)-16, A'0=-3.0769; A'1=2.2108; A'2=-0.62272; A'3=0.057501; B'1=-0.68157; B'2=0.19833; B'3=-0.018376.

[0110] Specifically, volatile doping elements include antimony, gallium, and other elements with an evaporation coefficient in silicon melt greater than about 1×10 - 2 cm / s of volatile elements.

[0111] Specifically, the test crystal rod has a length of 10-1000 mm and a diameter of 1-500 mm.

[0112] A method for calculating the loss of volatile elements in the silicon material re-feeding stage, from the silicon material re-feeding to the seeding stage of the next root crystal rod in a process of preparing single crystal silicon by multiple feeding and re-pulling. The method includes recording the end time t1 after the previous crystal rod pulling is completed, measuring the resistivity of the tail of the crystal rod after the crystal rod is cooled and taken out, calculating the volatile doping element concentration N1 in the remaining silicon melt corresponding to time t1, and recording the remaining silicon melt volume W1. Re-feed silicon material to pull a test crystal rod, end the crystal pulling when the test crystal rod is equal to 5-10mm, record the end time t2 of the test crystal rod equalization, measure the resistivity of the edge skin of the test crystal rod tail and calculate the volatile dopant concentration N2 in the remaining silicon melt corresponding to time t2, and record the total volume W2 of the re-feed silicon material.

[0113] Specifically, the calculation method of volatile doping element loss during the silicon material re-investment stage, from the silicon material re-investment stage to the secondary root crystal ingot seeding stage, is characterized in that the calculation method of volatile doping element loss is as follows:

[0114]

[0115] Where t1 is the time when the previous crystal rod pulling ends; t2 is the time when the test crystal rod equal diameter ends; N1 is the concentration of volatile doping elements in the silicon melt corresponding to time t1; N2 is the concentration of volatile dopants in the silicon melt corresponding to time t2. The calculation methods of N1 and N2 are shown in Formula 1 and Formula 2.

[0116] Specifically, in the silicon material re-injection stage, from the silicon material re-injection to the second root crystal ingot seeding stage, the calculation method of volatile element loss is that the length of the first root crystal ingot is 10 to 10000 mm, the diameter is 1 to 500 mm, and the doping elements contain antimony, gallium and other elements with an evaporation coefficient greater than 1×10 in the silicon melt. -2 cm / s of volatile elements.

[0117] Specifically, the doping elements include antimony, gallium, and other elements whose evaporation coefficient in silicon melt is greater than about 1×10 -2 cm / s of volatile elements.

[0118] Specifically, the calculation method of the compensation amount of the volatile dopant is as follows:

[0119] Δw=N×W+V×Δt-N1W1 (Formula 5)

[0120] Among them, Δw is the compensation amount of volatile dopants in the re-investment stage, N is the concentration of volatile dopants in the silicon melt at the target resistivity, W is the total volume of the silicon melt after re-investment, V is the average volatilization rate of volatile elements from the start of feeding to seeding in the re-investment stage, Δt is the duration of the re-investment stage from the start of feeding to seeding, N1 is the concentration of volatile dopants in the remaining silicon melt after the previous crystal rod is pulled, and W1 is the total volume of the remaining silicon melt after the previous crystal rod is pulled. The calculation method of N and N1 is formula 1 and 2.

[0121] Specifically, the number of times of silicon material re-injection is 2 to 15 times. In the re-injection stage, the seeding power is 20 to 80 kW, the shouldering power is 20 to 80 kW, the equal diameter power is 20 to 80 kW, the crystal rod length is 10 to 10000 mm, and the crystal rod diameter is 10 to 500 mm.

[0122] The single crystal silicon rod prepared by the present invention is doped with antimony, gallium and other elements whose evaporation coefficient in silicon melt is greater than about 1×10 -2 cm / s of volatile elements. The length of the crystal rod is 10 to 10000 mm, and the diameter of the crystal rod is 10 to 500 mm.

[0123] Specifically, the hit rate of the head resistance of the crystal rod is greater than 95%, and the head resistivity difference between the crystal rods is within 20%.

[0124] Further:

[0125] A process for preparing single crystal silicon by a multiple-feeding repulling method with quantitative compensation of volatile doping elements in the re-feeding stage, including silicon material charging, material melting, seeding, shoulder release, shoulder resistivity measurement, calculation of volatile dopant concentration in the remaining melt, quantitative compensation of volatile dopant, establishment of data model, and completion of the re-feeding process. The specific operation steps are as follows:

[0126] Step 1: After the previous crystal ingot pulling is completed, the cooled crystal ingot is taken out from the single crystal furnace, the tail resistivity is measured, and the end time t1 of the ingot pulling is recorded. According to the tail resistivity, the concentration of volatile dopants in the remaining silicon melt is calculated.

[0127] The calculation method is shown in Formula 1 and Formula 2:

[0128] ρ=6.242×10 18 / N1×10 Z’ (Formula 1)

[0129]

[0130] Where ρ is the resistivity (Ω·cm), N is the dopant concentration (cm -3 ), y=(log 10 N)-16, A'0=-3.0769; A'1=2.2108; A'2=-0.62272; A'3=0.057501; B'1=-0.68157; B'2=0.19833; B'3=-0.018376.

[0131] According to the concentration of volatile dopants in the silicon melt, the total amount of volatile dopants M1 in the silicon melt is calculated. The calculation method is shown in Formula 3:

[0132] M1=N1×W1 (Formula 3);

[0133] Wherein, N1 is the concentration of volatile dopants in the silicon melt at the end of the previous crystal ingot pulling, and W1 is the volume of the remaining silicon melt at the end of the previous crystal ingot pulling.

[0134] Step 2: Complete the target re-dosing amount of the next silicon rod, chemical processing, and temperature stabilization.

[0135] Step 3: Test the crystal rod seeding and shoulder placement.

[0136] Step 4: Put the test crystal rod shoulder to the target diameter, turn the shoulder to enter the equal diameter, control the equal diameter length between 5 and 10 mm, stop pulling the crystal, take out the crystal rod, and record the end time t2 of the test crystal rod equal diameter.

[0137] Step 5: Measure the edge resistance of the test crystal rod at the end of the equal diameter, calculate the volatile dopant concentration in the silicon melt when the test crystal rod is equal in diameter according to Formula 1 and Formula 2, and calculate the total amount of volatile dopant M2 in the silicon melt when the test crystal rod is equal in diameter according to Formula 3.

[0138] Step 6: According to Formula 4, calculate the average loss rate V of the volatile dopant from the end of the previous crystal ingot pulling to the end of the test crystal ingot shouldering.

[0139]

[0140] Step 7: According to Formula 5, calculate the total amount of volatile dopant that needs to be added when the next crystal rod is initially pulled.

[0141] Δw=N×W+V×Δt-N1W1 (Formula 5)

[0142] Among them, Δw is the compensation amount of volatile dopants in the re-investment stage, N is the concentration of volatile dopants in the silicon melt at the target resistivity, W is the total volume of the silicon melt after re-investment, V is the average volatilization rate of volatile elements from the end of the previous crystal ingot pulling to the end of the test crystal ingot shouldering, Δt is the interval time from the end of the previous crystal ingot pulling to the start of this round of crystal ingot seeding, N1 is the concentration of volatile dopants in the remaining silicon melt after the previous crystal ingot pulling, and W1 is the total volume of the remaining silicon melt after the previous crystal ingot pulling. The calculation methods of N and N1 are shown in formulas 1 and 2.

[0143] Step 8: Compensate for volatile doping elements and complete reinvestment.

[0144] See also Figure 1 , Figure 1 The present invention provides a schematic diagram of the process flow of preparing single crystal silicon rods by the multiple feeding and pulling method.

[0145] The above content of the present invention provides a process for preparing single crystal silicon by a multiple-feeding and re-pulling method with quantitative compensation of volatile doping elements in the re-feeding stage, and a single crystal silicon rod prepared therefrom. The process for preparing single crystal silicon rods by a multiple-feeding and re-pulling method provided by the present invention is a method for measuring and calculating the concentration of volatile dopants in the remaining silicon melt in the re-feeding stage of the multiple-feeding and re-pulling method, thereby achieving the purpose of accurately compensating the concentration of volatile dopants and ensuring the consistency of quality between crystal rods. After the silicon material is re-fed, the present invention takes samples from the silicon melt for detection, calculates the concentration of volatile doping elements remaining in the silicon melt, thereby achieving accurate quantitative supplementation of volatile dopants in the re-feeding link, and effectively solves the problem of difficulty in accurate quantitative supplementation in the re-feeding stage of preparing single crystal silicon rods by the direct pulling method due to the strong volatility of the doping elements.

[0146] The Czochralski single crystal re-throwing process for quantitatively supplementing volatile doping elements provided by the present invention can accurately measure the concentration of volatile dopants in the remaining silicon melt in the re-throwing stage without making any changes to the crystal pulling furnace; it can also accurately obtain the compensation amount of volatile dopants in the re-throwing stage to ensure the stability of the crystal rod quality; at the same time, no auxiliary equipment is required, the cost is low, the economy is good, it is suitable for a variety of volatile dopants, the scope of use is wide, and it is suitable for the existing multi-time feeding re-throwing method for preparing single crystal silicon, without changing the process, and the production efficiency is high.

[0147] In order to further illustrate the present invention, a process for preparing single crystal silicon rods by a multiple feeding and pulling method and the single crystal silicon rods prepared therefrom are described in detail below in combination with embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are given only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention, and the protection scope of the present invention is not limited to the embodiments described below.

[0148] Example

[0149] A process for preparing single crystal silicon by a multiple-feeding repulling method with quantitative compensation of volatile doping elements in the re-feeding stage, including silicon material charging, material melting, seeding, shoulder release, shoulder resistivity measurement, calculation of volatile dopant concentration in the remaining melt, quantitative compensation of volatile dopant, establishment of data model, and completion of the re-feeding process. The specific operation steps are as follows:

[0150] Step 1: After the previous crystal ingot pulling is completed, the cooled crystal ingot is taken out from the single crystal furnace, the tail resistivity is measured, and the end time t1 of the ingot pulling is recorded. According to the tail resistivity, the concentration of volatile dopants in the remaining silicon melt is calculated.

[0151] The calculation method is shown in Formula 1 and Formula 2:

[0152] ρ=6.242×10 18 / N1×10 Z’ (Formula 1)

[0153]

[0154] Where ρ is the resistivity (Ω·cm), N is the dopant concentration (cm -3 ), y=(log 10 N)-16, A'0=-3.0769; A'1=2.2108; A'2=-0.62272; A'3=0.057501; B'1=-0.68157; B'2=0.19833; B'3=-0.018376.

[0155] Where ρ is the resistivity (Ω·cm), N is the dopant concentration (cm -3 ), y=(log 10 N)-16, A'0=-3.0769; A'1=2.2108; A'2=-0.62272; A'3=0.057501; B'1=-0.68157; B'2=0.19833; B'3=-0.018376.

[0156] According to the concentration of volatile dopants in the silicon melt, the total amount of volatile dopants M1 in the silicon melt is calculated. The calculation method is shown in Formula 3:

[0157] M1=N1×W1 (Formula 3);

[0158] Wherein, N1 is the concentration of volatile dopants in the silicon melt at the end of the previous crystal ingot pulling, and W1 is the volume of the remaining silicon melt at the end of the previous crystal ingot pulling.

[0159] Step 2: Complete the target re-dosing amount of the next silicon rod, chemical processing, and temperature stabilization.

[0160] Step 3: Test the crystal rod seeding and shoulder placement.

[0161] Step 4: Put the test crystal rod shoulder to the target diameter, turn the shoulder to enter the equal diameter, control the equal diameter length between 5 and 10 mm, stop pulling the crystal, take out the crystal rod, and record the end time t2 of the test crystal rod equal diameter.

[0162] Step 5: Measure the edge resistance of the test crystal rod at the end of the equal diameter, calculate the volatile dopant concentration in the silicon melt when the test crystal rod is equal in diameter according to Formula 1 and Formula 2, and calculate the total amount of volatile dopant M2 in the silicon melt when the test crystal rod is equal in diameter according to Formula 3.

[0163] Step 6: According to Formula 4, calculate the average loss rate V of the volatile dopant from the end of the previous crystal ingot pulling to the end of the test crystal ingot shouldering.

[0164]

[0165] Step 7: According to Formula 5, calculate the total amount of volatile dopant that needs to be added when the next crystal rod is initially pulled.

[0166] Δw=N×W+V×Δt-N1W1 (Formula 5)

[0167] Among them, Δw is the compensation amount of volatile dopants in the re-investment stage, N is the concentration of volatile dopants in the silicon melt at the target resistivity, W is the total volume of the silicon melt after re-investment, V is the average volatilization rate of volatile elements from the end of the previous crystal ingot pulling to the end of the test crystal ingot shouldering, Δt is the interval time from the end of the previous crystal ingot pulling to the start of this round of crystal ingot seeding, N1 is the concentration of volatile dopants in the remaining silicon melt after the previous crystal ingot pulling, and W1 is the total volume of the remaining silicon melt after the previous crystal ingot pulling. The calculation methods of N and N1 are shown in formulas 1 and 2.

[0168] Step 8: Compensate for volatile doping elements and complete reinvestment.

[0169] According to the conventional process, an N-type single crystal silicon rod is pulled, the dopant is pure antimony, the diameter of the crystal rod and the amount of the crystal rod are shown in Table 1, and the volatilization rate of the volatile dopant is measured as above, and the dopant is supplemented so that the resistivity of the head of each crystal rod is 1.0Ω·cm. Table 1 is the relevant data in the embodiment of the present invention.

[0170] Table 1

[0171]

[0172]

[0173] In Table 1, a is the diameter of the crystal rod / mm, b is the feed amount / kg, c is the resistivity of the target crystal rod head / Ω·cm, d is the length of the test crystal rod / mm, e is the resistivity of the end of the previous crystal rod / Ω·cm, f is the weight of the remaining silicon melt at the end of the previous crystal rod preparation / kg, g is the remaining amount of dopant in the silicon melt at the end of the previous crystal rod preparation / (atom), h is the resistivity of the end of the test crystal rod / Ω·cm, i is the remaining amount of dopant in the silicon melt at the end of the test crystal rod preparation / (atom), j is t2-t1 / h, k is the volatilization rate of the dopant dosage / (atom / h), and l is the dopant supplementation amount / g.

[0174] Note: When the mass units in Table 1 are calculated in the formula, the conversion between mass and volume can be realized by density. The density of single crystal silicon (silicon material) is 2.33g / cm 3 The density of the melted silicon is 2.54 g / cm 3 .

[0175] Statistics of the crystal rods prepared in the embodiments of the present invention are shown in Table 2. Table 2 shows the parameters of the crystal rods prepared in the embodiments of the present invention.

[0176] Table 2

[0177]

[0178] The above is a detailed introduction to a process for preparing single crystal silicon by a multiple-feeding and re-pulling method with quantitative compensation of volatile doping elements in the re-feeding stage provided by the present invention, and the single crystal silicon rod prepared by the process. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and its core ideas of the present invention, including the best mode, and also enables any technician in the field to practice the present invention, including the manufacture and use of any device or system, and the implementation of any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in several ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims, and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A process for preparing single crystal silicon rods by multiple feeding and pulling method, characterized in that: The following steps are involved: 1) After the previous crystal ingot is pulled, the tail resistivity of the previous crystal ingot is measured, and the pulling end time t1 of the previous crystal ingot is obtained; Based on the tail resistivity, the concentration of the volatile doping element in the remaining silicon melt is calculated, and then based on the concentration N1 of the volatile doping element in the remaining silicon melt, the total amount M1 of the volatile doping element in the silicon melt is calculated again; 2) Based on the consumption of the previous crystal ingot pulling, complete the target re-injection of silicon material for the next crystal ingot, material processing and temperature stabilization operations; 3) Add a crystal pulling growth process for the test crystal rod. The test crystal rod undergoes the seeding and shouldering processes. After the shouldering reaches the target diameter, the shoulder is turned to enter the equal diameter growth. After the equal diameter length is controlled to a certain length, the crystal pulling is stopped, the crystal rod is taken out, and the equal diameter end time t2 of the test crystal rod is recorded; 4) measuring the resistance of the tail of the test crystal rod with equal diameter, calculating the concentration N2 of the volatile doping element in the silicon melt when the test crystal rod has equal diameter, and the total amount M2 of the volatile doping element in the silicon melt when the test crystal rod has equal diameter; 5) Based on the total amount of volatile doping elements M1 and M2 in the silicon melt obtained in the above steps, as well as the end time t1 of the previous crystal ingot pulling and the end time t2 of the test crystal ingot equalization, the average loss rate V of the volatile doping elements from the end of the previous crystal ingot pulling to the end of the test crystal ingot pulling is calculated; 6) Based on the average loss rate V obtained in the above steps, calculate the total amount of volatile doping elements that need to be replenished at the beginning of the next crystal rod pulling, compensate the volatile doping elements in the system, complete the re-injection, and carry out the next crystal rod pulling.

2. The process according to claim 1, characterized in that The volatile doping element comprises a volatile element having an evaporation coefficient in the silicon melt greater than or equal to about 1×10 -2 cm / s of volatile elements; In the step 1), the formula for calculating the concentration of the volatile doping element in the remaining silicon melt is as shown in formula (1) and formula (2): p=6.242×10 18 / N1×10 Z’ (1); Where ρ is the tail resistivity (Ω·cm), N1 is the atomic concentration of the volatile doping element in the remaining silicon melt (atom / cm 3 ), y=(log 10 N1)-16; Among them, A'0=-3.0769, A'1=2.2108, A'2=-0.62272, A'3=0.057501, B'1=-0.68157, B'2=0.19833, B'3=-0.018376.

3. The process according to claim 2, characterized in that The volatile doping element includes antimony and / or gallium; In the step 1), the formula for recalculating the total amount of volatile doping elements M1 in the silicon melt is shown in formula (3): M1=N1×W1 (3); Where N1 is the concentration of volatile doping elements in the silicon melt at the end of the previous ingot pulling (atom / cm 3 ), W1 is the remaining silicon melt volume at the end of the previous crystal ingot pulling (cm 3 ).

4. The process according to claim 1, characterized in that The lengths of the previous crystal rod and the next crystal rod are independently selected from 10 to 10000 mm; The diameters of the previous crystal rod and the next crystal rod are independently selected from 1 to 500 mm; The certain length is specifically 5 to 10 mm; The tail resistivity is specifically the tail edge resistivity or the tail skin resistivity.

5. The process according to claim 1, characterized in that The length of the test crystal rod is 10 to 1000 mm; The diameter of the test crystal rod is 1 to 500 mm; The target diameter is 250-350 mm.

6. The process according to claim 2, characterized in that The formula for calculating the concentration N2 of the volatile doping element in the silicon melt when the test crystal rod reaches the same diameter is shown in formula (1) and formula (2).

7. The process according to claim 6, characterized in that When the diameter of the test crystal rod is equal, the total amount of volatile doping elements M2 in the silicon melt is as shown in formula (4): M2=N2×(W1+W2) (4); Where N1 is the concentration of volatile doping elements in the silicon melt when the test ingot is equal in diameter (atom / cm 3 ), W2 is the volume of raw material added in step 2) (cm 3 ). The concentration of volatile doping elements in the silicon melt N2, and the total amount of volatile doping elements in the silicon melt when the test crystal rod is equal in diameter, M 2。 8. The process according to claim 7, characterized in that The calculation formula of the average loss rate V of the volatile doping element is shown in formula (4):

9. The process according to claim 7, characterized in that The calculation formula for the total amount of volatile doping elements that need to be supplemented is shown in formula (5): Δw=N×W+V×Δt-N1W1 (5); Wherein, Δw is the compensation amount of volatile doping elements in the re-injection stage; N is the concentration of volatile doping elements in the silicon melt at the target resistivity; W is the total volume of the silicon melt after re-injection (cm 3 ), V is the average volatilization rate of volatile elements from the end of the previous crystal ingot pulling to the end of the test crystal ingot shouldering; Δt is the interval time (hours) from the end of the previous crystal ingot pulling to the start of the next crystal ingot seeding; N1 is the concentration of volatile doping elements in the silicon melt at the end of the previous crystal ingot pulling; W1 is the volume of the remaining silicon melt at the end of the previous crystal ingot pulling (cm 3 ); The re-investment stage specifically refers to the process from the end of the previous crystal ingot pulling to the next crystal ingot seeding; The average loss rate of the volatile doping element is the average loss rate of the volatile doping element in the reinvestment stage.

10. A process for preparing a single crystal silicon rod according to any one of claims 1 to 9, characterized in that: The head-to-tail resistance ratio of the single crystal silicon rod is less than or equal to 1.5; The length of the single crystal silicon rod is greater than or equal to 3.5 m; The number of single crystal silicon rods pulled from a single furnace is greater than or equal to 6; The head resistance hit rate of single-furnace single-crystal silicon rods is greater than or equal to 95%.

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