Preparation method of silicon single crystal rod and silicon single crystal rod

Abstract

The invention discloses a preparation method of a silicon single crystal rod and the silicon single crystal rod. The preparation method comprises the steps that the preset position of a target single crystal silicon rod is selected, the first distance from the preset position to the head of the single crystal silicon rod is n times of the machining length of a wire cutting machine, the second distance from the preset position to the tail of the single crystal silicon rod is m times of the machining length of the wire cutting machine, and n and m are positive integers; determining the target resistivity of the preset position, calculating the doping amount of a dopant in the silicon solution according to the target resistivity, adding the dopant into the silicon solution according to the calculated doping amount of the dopant, and drawing a target single crystal silicon rod by adopting a Czochralski single crystal method; and the target single crystal silicon rod is cut at the preset position, a silicon rod section between the head of the target single crystal silicon rod and the preset position is used for preparing a first battery product, and a silicon rod section between the preset position and the tail of the target single crystal silicon rod is used for preparing a second battery product. According to the scheme, the yield of the produced single crystal silicon rods can be effectively improved, and the problem of cutting waste of the single crystal silicon rods is solved.

Description

Technical Field

[0001] The invention relates to a method for preparing a single crystal silicon rod and the single crystal silicon rod. Background Art

[0002] In the technology of pulling single crystal silicon rods using the Czochralski method (commonly known as the direct pulling single crystal method), the amount of dopant in the silicon solution affects the resistivity of the single crystal silicon rod. Based on this, the resistivity of the single crystal silicon rod head is mainly detected and the amount of dopant in the silicon solution is adjusted to achieve the purpose of adjusting the resistivity of the single crystal silicon rod.

[0003] However, due to the relatively high oxygen content at the head of the single crystal silicon rod, the detected resistivity of the single crystal silicon rod is low, which causes a relatively large deviation in the subsequent regulation of the doping amount of the silicon solution based on the detected resistivity, resulting in only a portion of the silicon rod segments in the pulled single crystal silicon rod having a resistivity that meets product requirements, a low yield rate of single crystal silicon rods, and a relatively large loss. In addition, at present, the cutting line of the silicon rod segment is determined based on the resistivity of the single crystal silicon rod, and the silicon rod segment cut based on the cutting line often needs to be further cut or multiple silicon rod segments are spliced ​​to meet the processing requirements of the cutting machine, resulting in low efficiency in cutting single crystal silicon rods. Summary of the invention

[0004] In view of this, the present invention provides a method for preparing a single crystal silicon rod and a single crystal silicon rod, which can effectively improve the yield rate of the produced single crystal silicon rods and avoid the problem of single crystal silicon rod cutting waste.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a single crystal silicon rod, comprising:

[0007] Step 1, selecting a preset position of a target single crystal silicon rod, wherein a first distance from the preset position to the head of the single crystal silicon rod is n times the processing length of the wire cutting machine, and a second distance from the preset position to the tail of the single crystal silicon rod is m times the processing length of the wire cutting machine, wherein n and m are positive integers;

[0008] Step 2, determining the target resistivity at the preset position, calculating the doping amount of the dopant in the silicon solution based on the target resistivity at the preset position, adding the dopant to the silicon solution with the calculated doping amount of the dopant, and then using the Czochralski method to pull the target single crystal silicon rod;

[0009] Step 3: cutting the target single crystal silicon rod at the preset position, wherein the silicon rod segment between the head of the target single crystal silicon rod and the preset position is used to prepare a first battery product, and the silicon rod segment between the preset position and the tail of the target single crystal silicon rod is used to prepare a second battery product.

[0010] In a second aspect, an embodiment of the present invention provides a single crystal silicon rod, which is prepared based on the method for preparing a single crystal silicon rod provided in the embodiment of the first aspect.

[0011] The technical solution of the first aspect of the above invention has the following advantages or beneficial effects:

[0012] The technical solution provided by the embodiment of the present invention selects a preset position of a target single crystal silicon rod, determines the target resistivity at the preset position, and calculates the doping amount of the dopant added to the silicon solution based on the target resistivity at the preset position. Compared with the prior art of detecting the resistivity of the head of the single crystal silicon rod and adjusting the doping amount of the dopant in the silicon solution based on the resistance of the head, the influence of the high oxygen content in the head of the single crystal silicon rod on the resistivity detection result can be reduced, the accuracy of the resistivity control of the pulled target single crystal silicon rod can be improved, and the yield rate of the produced single crystal silicon rods can be effectively improved.

[0013] In addition, compared with the prior art, in which the doping amount of dopants is regulated only according to the resistivity of the head of the single crystal silicon rod, resulting in an uncertain dividing line that meets the first battery product and the second battery product (this solution makes the length of the single crystal silicon rod after cutting not match the processing length of the cutting machine, which not only affects the processing efficiency of the wire cutting machine, but also easily causes waste of single crystal silicon), after the single crystal silicon rod is cut at the preset position, the silicon rod segment between the head of the target single crystal silicon rod and the preset position is used to prepare the first battery product, and the silicon rod segment between the preset position and the tail of the target single crystal silicon rod is used to prepare the second battery product. Not only can the resistivity of the target single crystal silicon rod meet the requirements of the two battery products, but also because the first distance from the preset position to the head of the single crystal silicon rod and the second distance from the preset position to the tail of the single crystal silicon rod both meet the processing length of the wire cutting machine, the dividing position of the single crystal silicon rod that meets the first battery product and the second battery product is exactly at the preset position, and the two sections of the single crystal silicon rod after cutting just meet the processing length of the cutting machine, which can reduce or even avoid the waste of single crystal silicon rods, improve the utilization rate of single crystal silicon rods, and improve the processing efficiency of the wire cutting machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the main process of the method for preparing a single crystal silicon rod according to an embodiment of the present invention;

[0015] Figure 2 is a schematic diagram of a cross-sectional structure of a single crystal silicon rod provided in an embodiment of the present invention;

[0016] Figure 3 It is a schematic diagram of the main process of the resistivity control method of a single crystal silicon rod according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] As described in the background technology, for the single crystal silicon rod pulled by the direct pulling single crystal method, the resistivity of the head of the single crystal silicon rod is generally detected and the doping amount of the silicon solution is adjusted, which will cause the resistivity of the single crystal silicon rod to be low. In addition, the resistivity of the single crystal silicon rod pulled by the direct pulling single crystal method has a certain trend in the axial distribution (that is, the resistivity decreases from the head to the tail of the single crystal silicon rod). The low resistivity is superimposed on the upward distribution trend of the resistivity carrier. Then, using the current conventional process (a single crystal silicon rod is only cut into one type of silicon wafer, which is used in one battery product) to cut the single crystal silicon rod, it is necessary to remove the silicon rod segment whose resistivity does not meet the product requirements, such as removing the head or tail of the single crystal silicon rod, resulting in waste of the single crystal silicon rod. For example, currently various types of batteries such as TOPCON batteries, BC batteries, HJT batteries, etc. have different requirements for the resistivity, oxygen content, minority carrier life, etc. of silicon wafers. For example, TOPCON cells are manufactured using a high-temperature process. The silicon wafers with high oxygen content are prone to forming concentric circles during the high-temperature process, which affects the efficiency of the cell. Therefore, TOPCON cells have significantly lower requirements for the resistivity and oxygen content of the silicon wafers. For normal TOPCON single crystal silicon rods, the high resistivity and high oxygen content parts of the head need to be directly cut off. The cut parts are treated as raw materials and re-fed to pull single crystals, resulting in waste of finished crystal pulling products and increasing the production cost of crystal pulling. For another example, for HJT cells, HJT cells are manufactured using a low-temperature process, which has relatively high requirements for the resistivity and oxygen content of silicon wafers. The high resistivity and high oxygen content parts of the head can better meet the needs of HJT cells, while the low resistivity and low oxygen content parts of the tail are difficult to meet the needs of HJT cells and need to be cut off.

[0018] Although there is currently a process for cutting a single crystal silicon rod into silicon rod segments that meet the needs of two battery products in order to improve the utilization rate of single crystal silicon rods, the doping amount of the dopant is controlled according to the resistivity of the single crystal silicon rod head, resulting in an uncertain dividing line between the first battery product and the second battery product (this solution makes the length of the single crystal silicon rod after cutting not match the processing length of the cutting machine, which not only affects the processing efficiency of the wire cutting machine, but also easily causes waste of single crystal silicon), resulting in low cutting efficiency and still unable to avoid the problem of waste of single crystal silicon rods.

[0019] In order to solve the above problems existing in the prior art, the embodiments of the present invention provide a method for preparing a single crystal silicon rod and a single crystal silicon rod. The method for preparing a single crystal silicon rod can pull a single crystal silicon rod that meets the requirements of two battery products at the same time, and the cut silicon rod segments meet the processing requirements of the two battery products, so as to solve the problems of low yield rate of the pulled single crystal silicon rod, cutting waste, low cutting efficiency and high crystal pulling production cost.

[0020] Specifically, Figure 1 As shown, the method for preparing a single crystal silicon rod provided in an embodiment of the present invention may include the following steps:

[0021] Step S101: selecting a preset position of a target single crystal silicon rod, wherein a first distance from the preset position to the head of the single crystal silicon rod is n times the processing length of the wire cutting machine, and a second distance from the preset position to the tail of the single crystal silicon rod is m times the processing length of the wire cutting machine, wherein n and m are positive integers;

[0022] Among them, the target single crystal silicon rod generally refers to the silicon rod segment from the starting position to the end position of the single crystal silicon rod with equal diameter growth, which is generally used to cut into two silicon rod segments that meet the needs of two battery products respectively.

[0023] like Figure 2 The single crystal silicon rod shown in the figure, wherein the head H of the single crystal silicon rod generally refers to the starting position of the single crystal silicon rod equal diameter growth; the tail T of the single crystal silicon rod generally refers to the ending position of the single crystal silicon rod equal diameter growth, that is, the diameter of the head H of the single crystal silicon rod is generally equal to or similar to the diameter of the tail T of the single crystal silicon rod. The target single crystal silicon rod is between the head H of the single crystal silicon rod and the tail T of the single crystal silicon rod.

[0024] Among them, the preset position of the target single crystal silicon rod refers to the position of the cutting line used to cut the single crystal silicon rod into two sections. In the axial direction of the target single crystal silicon rod, the first distance from the preset position of the target single crystal silicon rod to the head of the single crystal silicon rod is n times the processing length of the wire cutting machine, and the first distance is generally a fixed value; in the axial direction of the target single crystal silicon rod, the second distance from the preset position of the target single crystal silicon rod to the tail of the single crystal silicon rod is m times the processing length of the wire cutting machine, and the second distance is generally also a fixed value, wherein n and m are positive integers, n can be equal to m, and n may not be equal to m. In other words, relative to the head and / or tail of the single crystal silicon rod, the circumference of the preset position is relatively fixed. The first distance and the second distance can meet the requirements of the size of the battery product, and the utilization rate of the single crystal silicon rod can be further improved during the processing of the single crystal silicon rod, and the waste of the single crystal silicon rod can be reduced.

[0025] by Figure 2 Taking the target single crystal silicon rod shown in FIG. 1 as an example, the preset position of this step can be as follows: Figure 2 Any one or more positions on the circumference corresponding to the identified P1 may also be any one or more positions on the circumference corresponding to the identified P2. However, after being selected in step S101, the preset position becomes a fixed position. Figure 2 If any one or more positions on the circumference corresponding to the marked P1 are preset positions, the first distance is Figure 2 The second distance of x1 is Figure 2 Identified y1; for Figure 2 If any one or more positions on the circumference corresponding to the marked P2 are preset positions, the first distance is Figure 2 The second distance is x2, which is marked as Figure 2 Marked y2.

[0026] In addition, for the above-mentioned preset position, in addition to satisfying that the above-mentioned first distance and the second distance both satisfy the processing length of the wire cutting machine (that is, the first distance from the preset position to the head of the single crystal silicon rod is n times the processing length of the wire cutting machine, and the second distance from the preset position to the tail of the single crystal silicon rod is m times the processing length of the wire cutting machine, where n and m are positive integers), preferably, the above-mentioned step S101 selects the preset position can also be further selected based on at least one of the following two conditions:

[0027] Condition 1: The oxygen content of the target single crystal silicon rod at the preset position is less than or equal to 5.5×10 17 atoms / cm 3 ;

[0028] Condition 2: When pulling the target single crystal silicon rod, the pulling speed at the preset position is greater than or equal to 1.5 mm / min.

[0029] More preferably, the first distance from the preset position to the head of the single crystal silicon rod is n times the processing length of the wire cutting machine, and the second distance from the preset position to the tail of the single crystal silicon rod is m times the processing length of the wire cutting machine. The preset position also satisfies the above two conditions at the same time.

[0030] Through research, it was found that the oxygen content at the detection position will affect the accuracy of the detection results. Specifically, the current resistivity detection depends on the doping concentration or doping amount of the metal doping element, that is, the resistivity is affected by the doping concentration or doping amount of the metal doping element. As a donor, one oxygen atom can provide 2 electrons, and electrons can affect the actual doping concentration or actual doping amount of the metal doping element, thereby affecting the accuracy of the detection. The higher the oxygen content, the greater the impact on the detection (specifically, the resistivity of the detected P-type single crystal silicon rod can be higher, and the resistivity of the detected N-type single crystal silicon rod can be lower). In the axial direction of the single crystal silicon rod, from the head of the single crystal silicon rod to the tail of the single crystal silicon rod, the oxygen content shows a decreasing trend, and after the oxygen content is reduced to a certain level, the oxygen content no longer shows an obvious change trend. Through further research, it was found that when the oxygen content is less than or equal to 5.5×10 17 atoms / cm 3 Therefore, in the process of selecting the preset position in step S101, the first distance from the preset position to the head of the single crystal silicon rod is n times the processing length of the wire cutting machine, and the second distance from the preset position to the tail of the single crystal silicon rod is m times the processing length of the wire cutting machine. 17 atoms / cm 3 location.

[0031] Generally speaking, the temperature of the solution decreases as the pulling speed increases, and the decrease in the temperature of the solution represents a decrease in the oxygen content. During the pulling process of single crystal silicon rods, in the equal diameter stage, the initial pulling speed is initially increased from 1.0~1.3mm / min. For the position after the length reaches 300mm, the 100-centimeter pulling speed (the average pulling speed from this position to the first 100mm) can reach 1.5mm / min or above 1.5mm / min. Combined with on-site measurements, it was found that after the 100-centimeter pulling speed was greater than or equal to 1.5mm / min, the accuracy of the resistivity test results was improved. Based on this, on the basis of making the first distance from the preset position to the head of the single crystal silicon rod n times the processing length of the wire cutting machine, and the second distance from the preset position to the tail of the single crystal silicon rod m times the processing length of the wire cutting machine, the position with a pulling speed greater than or equal to 1.5mm / min is preferentially selected as the above-mentioned preset position.

[0032] Furthermore, the target resistivity of the preset position satisfies: the resistivity of the silicon rod segment from the preset position to the head of the single crystal silicon rod satisfies the first battery product, and the resistivity of the silicon rod segment from the preset position to the tail of the single crystal silicon rod satisfies the second battery product.

[0033] For the target single crystal silicon rod of this step, the silicon solution used in the pulling process may contain only one dopant or multiple dopant. The doping elements contained in one dopant or multiple dopant are generally the same, for example, they may be N-type dopants (such as dopants containing phosphorus) or P-type dopants (such as dopants containing boron).

[0034] Step S102: determining a target resistivity at a preset position, calculating a doping amount of a dopant in a silicon solution based on the target resistivity at the preset position, adding a dopant to the silicon solution based on the calculated doping amount of the dopant, and then pulling a target single crystal silicon rod using a Czochralski method;

[0035] The target resistivity of the preset position can generally be determined according to the requirements of the two battery products. The target resistivity can be a preset range, which can allow a certain control error in pulling the target single crystal silicon rod, reduce the control difficulty, and ensure the yield rate of the pulled target single crystal silicon rod. The specific implementation process of this step will be described in detail below and will not be repeated here.

[0036] Step S103: cutting the target single crystal silicon rod at a preset position, wherein the silicon rod segment between the head of the target single crystal silicon rod and the preset position is used to prepare the first battery product, and the silicon rod segment between the preset position and the tail of the target single crystal silicon rod is used to prepare the second battery product.

[0037] Generally speaking, there is also an overlapping interval between the first resistivity control range of the silicon wafer required for the first battery product and the third resistivity control range of the silicon wafer required for the second battery product, and the target resistivity of the preset position of the target single crystal silicon rod is within the overlapping interval. By limiting the target resistivity of the preset position to the overlapping interval between the first resistivity control range and the third resistivity control range, the preset position can be selected within a range, ensuring that the preset position has a certain degree of selection flexibility, and the resistivity of the drawn single crystal silicon rod can fluctuate within the resistivity control range, reducing the process accuracy of the single crystal silicon rod drawing process, improving the yield rate of the single crystal silicon rod, and being able to use the preset position as a cutting line to cut the single crystal silicon rod, while satisfying the first battery product and the second battery product, and there will be no single crystal silicon area that does not meet the battery product, effectively improving the utilization rate of the single crystal silicon rod.

[0038] It is worth noting that the selection of the first battery product and the second battery product of the embodiment of the present invention is based on experience, market demand, process requirements, etc., and it is only necessary to ensure that there is an overlapping range between the first resistivity control range of the silicon wafer required by the first battery product and the third resistivity control range of the silicon wafer required by the second battery product, so as to ensure the utilization rate of the single crystal silicon rod. Accordingly, after the first battery product and the second battery product are determined, if the resistivity of the target single crystal silicon rod does not meet the requirements, the resistivity of the target single crystal silicon rod can be adjusted based on the above step S102.

[0039] In addition, the first battery product may be determined first, so that the head of the target single crystal silicon rod satisfies the first battery product, and the second battery product may be selected according to the distribution of the doping concentration in the axial direction of the target single crystal silicon rod. That is to say, the embodiment of the present invention may also select the second battery product based on the first battery product and the distribution of the resistivity of the target single crystal silicon rod whose head satisfies the first battery product in the axial direction, and after the first battery product and the second battery product are determined, the resistivity of the target single crystal silicon rod is controlled by controlling the doping amount of the target single crystal silicon rod based on the above steps S101 to S102, and the silicon rod segments required for the first battery product and the silicon rod segments required for the second battery product are prepared through the above step S103 to ensure the utilization rate of the single crystal silicon rod.

[0040] The first battery product and the second battery product involved in the technical solution provided in the embodiment of the present invention are not simply freely or arbitrarily selected by the user according to the needs, but are combined with the resistivity of the target single crystal silicon rod or the distribution of the doping concentration in the axial direction, so that the selected battery product is more in line with the target single crystal silicon rod, further reducing the waste of cutting the single crystal silicon rod. And based on the first battery product and the distribution of the doping concentration in the axial direction of the target single crystal silicon rod, the second battery product is determined, and a better crystal growth process can be adapted for the growth of the target single crystal silicon rod, thereby improving the crystallization rate of the single crystal growth, increasing the unit yield, and further increasing the unit yield and reducing the production cost.

[0041] Therefore, by detecting the resistivity of a preset position and subsequently adjusting the doping amount of the dopant in the silicon solution based on the detected resistivity of the preset position, compared with the prior art of detecting the resistivity of the head of the single crystal silicon rod and adjusting the doping amount of the dopant in the silicon solution based on the resistance of the head, the influence of the high oxygen content in the head of the single crystal silicon rod on the resistivity detection results can be reduced, the accuracy of the resistivity control of the pulled target single crystal silicon rod can be improved, and the yield rate of the produced single crystal silicon rods can be effectively improved.

[0042] In addition, compared with the prior art, in which the doping amount of dopants is regulated only according to the resistivity of the head of the single crystal silicon rod, resulting in an uncertain dividing line that meets the first battery product and the second battery product (this solution makes the length of the single crystal silicon rod after cutting not match the processing length of the cutting machine, which not only affects the processing efficiency of the wire cutting machine, but also easily causes waste of single crystal silicon), after the single crystal silicon rod is cut at the preset position, the silicon rod segment between the head of the target single crystal silicon rod and the preset position is used to prepare the first battery product, and the silicon rod segment between the preset position and the tail of the target single crystal silicon rod is used to prepare the second battery product. Not only can the resistivity of the target single crystal silicon rod meet the requirements of the two battery products, but also because the first distance from the preset position to the head of the single crystal silicon rod and the second distance from the preset position to the tail of the single crystal silicon rod both meet the processing length of the wire cutting machine, the dividing position of the single crystal silicon rod that meets the first battery product and the second battery product is exactly at the preset position, and the two sections of the single crystal silicon rod after cutting just meet the processing length of the cutting machine, which can reduce or even avoid the waste of single crystal silicon rods, improve the utilization rate of single crystal silicon rods, and improve the processing efficiency of the wire cutting machine.

[0043] For the above step S102, it generally directly uses the target resistivity of the preset position to adjust the doping amount of the dopant in the silicon solution. Specifically, the specific implementation method of adjusting the doping amount of the dopant in the silicon solution is: using the target resistivity of the preset position to calculate the doping concentration of the head of the target single crystal silicon rod; and according to the calculated doping concentration of the head of the target single crystal silicon rod, calculate the doping amount of the dopant in the silicon solution, so that the head of the target single crystal silicon rod drawn from the adjusted silicon solution meets the first battery product.

[0044] Compared with the existing direct detection of the resistivity of the head of the single crystal silicon rod, the embodiment of the present invention provides a method of calculating the doping concentration of the head of the target single crystal silicon rod based on the target resistivity at a preset position, which can reduce or even avoid the influence of oxygen on the detection result, so that the calculated doping concentration of the head of the target single crystal silicon rod can be more accurate. Furthermore, since the resistivity and doping concentration of the head of the single crystal silicon rod have a relatively strong correlation with the initial doping amount of the dopant in the silicon solution, the technical solution calculates the doping amount of the dopant in the silicon solution according to the doping concentration of the head of the target single crystal silicon rod, and can more accurately control the doping amount of the dopant in the silicon solution.

[0045] The specific implementation method of calculating the doping concentration of the target single crystal silicon rod head is as follows:

[0046] The target doping concentration at the preset position is calculated using the conversion relationship between resistivity and doping concentration and the target resistivity; different conversion relationships are used for different doping elements. The following uses phosphorus and boron as doping elements to explain the conversion relationship in detail.

[0047] For example, when the doping element is phosphorus, the corresponding conversion relationship is shown in the following calculation formula group (A).

[0048] (A)

[0049] in, Indicates that the doping element is a target doping concentration of phosphorus; Indicates the target resistivity;

[0050] ; ; ; ; ; ; .

[0051] For example, when the doping element is boron, the corresponding conversion relationship is shown in the following calculation formula group (1).

[0052] (1)

[0053] in, Indicates that the doping element is a target doping concentration of boron element; Indicates the target resistivity.

[0054] After the target doping concentration is calculated, the doping concentration of the head of the target single crystal silicon rod can be calculated by using the target doping concentration, the solidification rate of the silicon solution corresponding to the preset position, and the segregation coefficient of the dopant. The specific implementation method can be:

[0055] The doping concentration of the head of the single crystal silicon rod is calculated using the following calculation formula (2);

[0056] (2)

[0057] in, represents the calculated doping concentration of the head of the target single crystal silicon rod; Indicates the calculated target doping concentration of a preset position of a target single crystal silicon rod; Indicates the solidification rate of the silicon solution corresponding to the preset position; Indicates the dopant segregation coefficient; wherein, the solidification rate of the silicon solution corresponding to the preset position generally refers to the proportion of the crystallized silicon solution to the total solution before pulling after the single crystal silicon rod is pulled to the preset position. In addition, the dopant segregation coefficient is determined by the dopant itself, and is a fixed value when the dopant is determined.

[0058] Furthermore, the above-mentioned specific implementation of calculating the doping amount of the dopant in the silicon solution is as follows: using the following calculation formula (3) to calculate the initial doping concentration of the silicon solution used to pull the target single crystal silicon rod;

[0059] (3)

[0060] in, represents the initial doping concentration of the silicon solution used to pull the target single crystal silicon rod; Indicates the doping concentration of the head of the target single crystal silicon rod; Represents the segregation coefficient of the dopant; wherein the initial doping concentration of the silicon solution used to pull the target single crystal silicon rod refers to the doping concentration that the silicon solution needs to reach before pulling the target single crystal silicon rod.

[0061] On the basis of calculating the initial doping concentration of the silicon solution used to pull the target single crystal silicon rod, the doping amount of the dopant in the silicon solution is calculated using the calculated initial doping concentration of the silicon solution and the volume of the silicon solution. Specifically, the doping amount of the dopant can be directly obtained by multiplying the initial doping concentration by the volume of the silicon solution, that is, the doping amount of the dopant is directly related to the volume of the silicon solution.

[0062] In addition, for the target single crystal silicon rod, other indicators such as oxygen content, minority carrier lifetime, carbon content, etc. can be controlled on the basis of resistivity by adjusting the environmental conditions of direct pulling, such as pressure, temperature, direct pulling rate, original purity, purity of auxiliary materials, etc., so that while the resistivity meets the requirements of the first battery product and the second battery product, these other indicators can also meet the requirements of the first battery product and the second battery product.

[0063] Furthermore, after the above-mentioned step S103, the cut single crystal silicon rod segments can also be divided into two battery product lines, so as to be processed into square rods by squaring, grinding and polishing. In this process, since the single crystal silicon rod segments can meet the needs of their corresponding battery products, the use of the single crystal silicon rod segments can be maximized without cutting off and removing the parts that do not meet the needs of the battery products, thereby ensuring the utilization rate of the single crystal silicon rods.

[0064] Furthermore, an embodiment of the present invention also provides a method for controlling the resistivity of a single crystal silicon rod. Figure 3 As shown, the resistivity control method of the single crystal silicon rod may include the following steps:

[0065] Step S301: selecting a preset position of a target single crystal silicon rod, wherein a first distance from the preset position to the head of the single crystal silicon rod is n times the processing length of the wire cutting machine, and a second distance from the preset position to the tail of the single crystal silicon rod is m times the processing length of the wire cutting machine, wherein n and m are positive integers;

[0066] Among them, the target single crystal silicon rod generally refers to the silicon rod segment from the starting position to the end position of the single crystal silicon rod with equal diameter growth, which is generally used to cut into two silicon rod segments that meet the needs of two battery products respectively.

[0067] Among them, the preset position of the target single crystal silicon rod refers to the position of the cutting line used to cut the single crystal silicon rod into two sections. In the axial direction of the target single crystal silicon rod, the first distance from the preset position of the target single crystal silicon rod to the head of the single crystal silicon rod is n times the processing length of the wire cutting machine, and the first distance is generally a fixed value; in the axial direction of the target single crystal silicon rod, the second distance from the preset position of the target single crystal silicon rod to the tail of the single crystal silicon rod is m times the processing length of the wire cutting machine, and the second distance is generally also a fixed value, wherein n and m are positive integers. In other words, relative to the head and / or tail of the single crystal silicon rod, the circumference of the preset position is relatively fixed. The first distance and the second distance can meet the requirements of the size of the battery product, and the utilization rate of the single crystal silicon rod can be further improved during the processing of the single crystal silicon rod, and the waste of the single crystal silicon rod can be reduced.

[0068] In addition, for the above-mentioned preset position, in addition to satisfying that the above-mentioned first distance and the second distance both satisfy the processing length of the wire cutting machine (that is, the first distance from the preset position to the head of the single crystal silicon rod is n times the processing length of the wire cutting machine, and the second distance from the preset position to the tail of the single crystal silicon rod is m times the processing length of the wire cutting machine, where n and m are positive integers), preferably, the above-mentioned step S101 selects the preset position can also be further selected based on at least one of the following two conditions:

[0069] Condition 1: The oxygen content of the target single crystal silicon rod at the preset position is less than or equal to ;

[0070] Condition 2: When pulling the target single crystal silicon rod, the pulling speed at the preset position is greater than or equal to .

[0071] More preferably, the first distance from the preset position to the head of the single crystal silicon rod is n times the processing length of the wire cutting machine, and the second distance from the preset position to the tail of the single crystal silicon rod is m times the processing length of the wire cutting machine. The preset position also satisfies the above two conditions at the same time.

[0072] Step S302: determine the target resistivity at the preset position, calculate the doping amount of the dopant in the silicon solution based on the target resistivity at the preset position, add the dopant to the silicon solution with the calculated doping amount of the dopant, and then use the direct pulling method to pull the target single crystal silicon rod.

[0073] Among them, the target resistivity of the preset position can generally be determined according to the requirements of the two battery products. The target resistivity can be a preset range, which can allow a certain control error in pulling the target single crystal silicon rod, reduce the control difficulty, and ensure the yield rate of the pulled target single crystal silicon rod.

[0074] Specifically, for the above step S302, the target resistivity of the preset position is generally used directly to adjust the doping amount of the dopant in the silicon solution. Specifically, the specific implementation method of adjusting the doping amount of the dopant in the silicon solution is: the doping concentration of the head of the target single crystal silicon rod is calculated according to the target resistivity of the preset position; and the doping amount of the dopant in the silicon solution is calculated according to the calculated doping concentration of the head of the target single crystal silicon rod, so that the head of the target single crystal silicon rod drawn by the adjusted silicon solution meets the first battery product. Compared with the existing direct detection of the resistivity of the head of the single crystal silicon rod, the embodiment of the present invention provides a method of calculating the doping concentration of the head of the target single crystal silicon rod according to the target resistivity of the preset position, which can reduce or even avoid the influence of oxygen on the detection result, so that the calculated doping concentration of the head of the target single crystal silicon rod can be more accurate. Furthermore, since the resistivity and doping concentration of the head of the single crystal silicon rod have a relatively strong correlation with the initial doping amount of the dopant in the silicon solution, the technical solution calculates the doping amount of the dopant in the silicon solution according to the doping concentration of the head of the target single crystal silicon rod, which can more accurately adjust the doping amount of the dopant in the silicon solution.

[0075] The specific implementation method of calculating the doping concentration of the target single crystal silicon rod head is as follows:

[0076] The target doping concentration at the preset position is calculated using the conversion relationship between resistivity and doping concentration and the target resistivity; and the doping concentration at the head of the target single crystal silicon rod is calculated using the target doping concentration, the solidification rate of the silicon solution corresponding to the preset position, and the segregation coefficient of the dopant. The conversion relationship between resistivity and doping concentration and the calculation formula for calculating the doping concentration at the head of the target single crystal silicon rod have been described in detail in the above embodiment and will not be repeated here.

[0077] Furthermore, the specific implementation of the above calculation of the doping amount of the dopant in the silicon solution is: using the above calculation formula (3), the initial doping concentration of the silicon solution used to pull the target single crystal silicon rod is calculated. The calculation formula (3) has been described in detail in the above embodiment and will not be repeated here.

[0078] Subsequently, the doping amount of the dopant in the silicon solution is calculated using the calculated initial doping concentration of the silicon solution and the volume of the silicon solution. In this step, the doping amount of the dopant can be directly obtained by multiplying the initial doping concentration by the volume of the silicon solution, that is, the doping amount of the dopant is directly related to the volume of the silicon solution.

[0079] Compared with the existing method of detecting the resistivity of the head of the single crystal silicon rod, the technical solution provided by the embodiment of the present invention can reduce the influence of high oxygen content on the resistivity detection results by detecting the target resistivity at a preset position, and can effectively improve the accuracy of the detected resistivity. Subsequently, based on the detected target resistivity at the preset position, the doping amount of the dopant in the silicon solution is adjusted, which can improve the accuracy of the resistivity control of the pulled target single crystal silicon rod.

[0080] Furthermore, an embodiment of the present invention also provides a single crystal silicon rod, which is prepared based on the method for preparing the single crystal silicon rod provided in the above embodiment.

[0081] The single crystal silicon rod can meet the needs of two battery products, that is, the single crystal silicon rod can be cut from a preset position, and the two cut single crystal silicon rod segments respectively meet the needs of different battery products, so that the single crystal silicon rod can be used in an optimal way and the waste of single crystal silicon rod can be reduced.

[0082] The introduction provided in the above steps is only used to help understand the method, structure and core idea of ​​the present invention. For ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also belong to the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a single crystal silicon rod, characterized in that: include: Step 1, selecting a preset position of a target single crystal silicon rod, wherein a first distance from the preset position to the head of the single crystal silicon rod is n times the processing length of the wire cutting machine, and a second distance from the preset position to the tail of the single crystal silicon rod is m times the processing length of the wire cutting machine, wherein n and m are positive integers; Step 2, determining the target resistivity at the preset position, calculating the doping amount of the dopant in the silicon solution based on the target resistivity at the preset position, adding the dopant to the silicon solution with the calculated doping amount of the dopant, and then using the Czochralski method to pull the target single crystal silicon rod; Step 3: cutting the target single crystal silicon rod at the preset position, wherein the silicon rod segment between the head of the target single crystal silicon rod and the preset position is used to prepare a first battery product, and the silicon rod segment between the preset position and the tail of the target single crystal silicon rod is used to prepare a second battery product.

2. The method for preparing a single crystal silicon rod according to claim 1, characterized in that: Calculating the doping amount of the dopant in the silicon solution based on the target resistivity of the preset position includes: Calculating the doping concentration of the head of the target single crystal silicon rod based on the target resistivity at the preset position; The doping amount of the dopant in the silicon solution is calculated according to the calculated doping concentration of the head of the target single crystal silicon rod.

3. The method for preparing a single crystal silicon rod according to claim 2, characterized in that: Calculating the doping concentration of the head of the target single crystal silicon rod based on the target resistivity at the preset position includes: Calculating the target doping concentration at the preset position by using the conversion relationship between resistivity and doping concentration and the target resistivity; The doping concentration of the head of the target single crystal silicon rod is calculated using the target doping concentration, the solidification rate of the silicon solution corresponding to the preset position, and the segregation coefficient of the dopant.

4. The method for preparing a single crystal silicon rod according to any one of claims 1 to 3, characterized in that: The oxygen content of the target single crystal silicon rod at the preset position is less than or equal to .

5. The method for preparing a single crystal silicon rod according to any one of claims 1 to 3, characterized in that: When pulling the target single crystal silicon rod, the pulling speed at the preset position is greater than or equal to .

6. The method for preparing a single crystal silicon rod according to any one of claims 1 to 3, characterized in that: The target resistivity of the preset position satisfies: the resistivity of the silicon rod segment from the preset position to the head of the single crystal silicon rod satisfies the first battery product, and the resistivity of the silicon rod segment from the preset position to the tail of the single crystal silicon rod satisfies the second battery product.

7. The method for preparing a single crystal silicon rod according to claim 6, characterized in that: There is an overlapping range between the first resistivity control range of the silicon wafer required for the first battery product and the third resistivity control range of the silicon wafer required for the second battery product. The target resistivity of the preset position of the target single crystal silicon rod is within the overlapping range.

8. The method for preparing a single crystal silicon rod according to claim 1, characterized in that: The head of the target single crystal silicon rod and the tail of the single crystal silicon rod are the starting position and the ending position of the equal diameter stage.

9. A single crystal silicon rod, characterized in that: The single crystal silicon rod is prepared according to the method for preparing a single crystal silicon rod according to any one of claims 1 to 8.

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