Drawing method of silicon single crystal rod

Abstract

The embodiment of the invention relates to the photovoltaic field, and provides a single crystal silicon rod drawing method which comprises the following steps: acquiring a first curve which is a relation curve between the equal diameter length and the resistivity of a single crystal silicon rod with a first dopant; acquiring a first preset length based on the first curve; the method comprises the following steps: adding a silicon material and a first doping agent into a crucible, sequentially carrying out a melting process, a seeding process and a shouldering process, and then entering an equal-diameter growth process; in the equal-diameter growth procedure, after the equal-diameter length of an initial crystal bar formed through equal-diameter growth reaches a first preset length, a second doping agent is added into the crucible, the equal-diameter growth procedure continues to be carried out till the equal-diameter length of the initial crystal bar reaches a second preset length, and then an ending procedure is carried out, a segregation coefficient of the first dopant is less than a segregation coefficient of the second dopant. The drawing method of the silicon single crystal rod provided by the embodiment of the invention at least can improve the uniformity of the resistivity of the drawn silicon single crystal rod.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of single crystal silicon production, and in particular to a method for drawing a single crystal silicon rod. Background Art

[0002] Monocrystalline silicon rods are important raw materials for the manufacture of photovoltaic panels and semiconductor devices. In recent years, with the rapid expansion of the photovoltaic market and technological progress, the production capacity and quality of monocrystalline silicon rods have been significantly improved. The maturity of technologies such as Czochralski (CZ method) and floating zone melting (FZ method) ensures the purity and crystal quality of monocrystalline silicon rods, thereby improving the conversion efficiency of solar cells and the performance of semiconductor devices.

[0003] In the process of preparing solar-grade or semiconductor-grade single-crystal silicon rods, dopants are usually added to the silicon melt in the crucible of the single-crystal furnace, and then pulled into single-crystal silicon rods through the single-crystal furnace. Due to the unstable operation of the production line in the current preparation process of single-crystal silicon rods, and the difference in the concentration of dopants in each layer of silicon melt in the crucible, the resistance uniformity of the prepared single-crystal silicon rods is difficult to meet the standards, which in turn affects the quality of the single-crystal silicon rods. Summary of the invention

[0004] The embodiment of the present application provides a method for drawing a single crystal silicon rod, which is at least beneficial to improving the uniformity of the axial resistivity of the single crystal silicon rod.

[0005] According to some embodiments of the present application, the embodiments of the present application provide a method for pulling a single crystal silicon rod, including: obtaining a first curve, the first curve being a relationship curve between the equal-diameter length and the resistivity of a single crystal silicon rod having a first dopant; based on the first curve, obtaining the equal-diameter length corresponding to the resistivity of the single crystal silicon rod when the resistivity is a preset resistivity, and using it as the first preset length; adding silicon material and the first dopant into a crucible, and sequentially performing a melting process, a seeding process, and a shoulder release process, and then entering an equal-diameter growth process; in the equal-diameter growth process, after the equal-diameter length of the initial crystal rod formed by the equal-diameter growth reaches the first preset length, adding a second dopant into the crucible, and continuing the equal-diameter growth process until the equal-diameter length of the initial crystal rod reaches the second preset length, and then entering a finishing process, wherein the segregation coefficient of the first dopant is less than the segregation coefficient of the second dopant.

[0006] In some embodiments, the first dopant is a simple substance or a compound containing an antimony doping element; and the second dopant is a simple substance or a compound containing a phosphorus doping element.

[0007] In some embodiments, the process steps of adding the second dopant into the crucible include: performing the first step, adding a first sub-weight of the second dopant; taking the equal-diameter length of the initial crystal rod when the second dopant is added for the first time as the initial length, performing the second step, the second step is to obtain the equal-diameter length of the initial crystal rod as the first length in real time; when the difference between the first length and the initial length is a first preset value, performing the third step, the third step is to add a second sub-weight of the second dopant; repeating the second step; when the difference between the first length and the initial length is a second preset value, performing the fourth step, the fourth step is to add a third sub-weight of the second dopant; repeating the second step, the third step, the second step and the fourth step in sequence until the equal-diameter length of the initial crystal rod reaches the second preset length.

[0008] In some embodiments, the first sub-weight, the second sub-weight and the third sub-weight are equal; and / or the first preset value is equal to the second preset value.

[0009] In some embodiments, the first sub-weight, the second sub-weight, and the third sub-weight present a gradually decreasing trend; and / or the first preset value and the second preset value present an increasing trend.

[0010] In some embodiments, the first sub-weight, the second sub-weight, and the third sub-weight present a gradually increasing trend; and / or the first preset value and the second preset value present a decreasing trend.

[0011] In some embodiments, the process steps of adding the second dopant into the crucible include: real-time detection of the resistivity of the initial crystal rod; performing a fifth step, wherein when the resistivity rises to a third preset value, a fourth sub-weight of the second dopant is added; and repeating the fifth step; until the equal-diameter length of the initial crystal rod reaches the second preset length.

[0012] In some embodiments, the third preset value in the fifth step is equal or unequal each time; and / or the fourth subweight in the fifth step is equal or unequal each time.

[0013] In some embodiments, a first preset environment is used to perform the melting process on the silicon material and the first dopant; the process parameters of the first preset environment include: the rotation speed of the crucible is 1rpm~2rpm, the power of the main heater is 95kw~110kw, the power of the bottom heater is 80kw~90kw, the rotation speed of the stretching rod is 1rpm~2rpm; the gas flow rate of the protective gas is 100slpm~120slpm.

[0014] In some embodiments, after adding the second dopant, the equal-diameter growth process is continued using a second preset environment; the process parameters of the second preset environment include: the crucible rotation speed is 3.5rpm~7rpm, the main heater power is 45kw~65kw, the bottom heater power is 0kw, the speed of the stretching rod is 7rpm~9rpm; the gas flow rate of the protective gas is 85slpm~100slpm.

[0015] The technical solution provided by the embodiments of the present application has at least the following advantages:

[0016] The method for pulling a single crystal silicon rod provided in the embodiment of the present application adds a first dopant and a second dopant, wherein the segregation coefficient of the first dopant is less than the segregation coefficient of the second dopant; in this way, the first dopant mainly plays a role in the early stage, and the second dopant plays a role in the later stage, so that the resistivity of the head and tail of the crystalline silicon can be made closer, thereby improving the uniformity of the axial resistivity and the radial resistivity, and the resistivity uniformity in the corresponding silicon wafer is also improved. Secondly, the first dopant is added when the silicon material is added, and the second dopant is added when the initial silicon rod is at a preset resistivity, that is, the two dopants are not added at the same time, which can avoid the difference in local strain of the single crystal silicon rod caused by the different atomic radii of the two dopants, which may lead to the formation of oxidation-induced stacking faults, and increase the leakage current of the PN junction of the semiconductor or solar cell formed based on the silicon rod. The two dopants are not added at the same time, which also avoids the formation of a recombination center between the first dopant and the second dopant, so that the impurities in the single crystal furnace form an oxygen precipitation layer with this recombination center, and then physical defects and other problems occur. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] One or more embodiments are exemplarily illustrated by the figures in the corresponding drawings. These exemplified descriptions do not constitute a limitation on the embodiments. Unless otherwise specified, the figures in the drawings do not constitute a scale limitation. In order to more clearly illustrate the embodiments of the present application or the technical solutions in the traditional technology, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A flow chart of a method for pulling a single crystal silicon rod provided in one embodiment of the present application;

[0019] Figure 2 A schematic diagram of the structure of a single crystal furnace in a method for pulling a single crystal silicon rod provided in an embodiment of the present application;

[0020] Figure 3A graph of a first curve in a method for pulling a single crystal silicon rod provided in an embodiment of the present application;

[0021] Figure 4 A curve diagram of equal diameter length and resistivity of a single crystal silicon rod prepared by a single crystal silicon rod pulling method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0022] As can be seen from the background technology, the resistivity of single crystal silicon rods prepared by the current single crystal silicon rod pulling method is non-uniform.

[0023] The embodiment of the present application provides a method for pulling a single crystal silicon rod, which reduces the mutual reaction between the two dopants and the misalignment problem caused by the difference in atomic radius between the dopants and the silicon material by controlling the timing of adding two dopants; and controls the difference in resistivity between the head and tail of the single crystal silicon rod by using the two dopants, thereby improving the uniformity of the axial resistivity of the single crystal silicon rod.

[0024] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0025] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0026] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0027] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0028] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0029] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0030] In the accompanying drawings corresponding to the embodiments of the present application, the thickness and area of ​​the layer are magnified for better understanding and ease of description. When describing a component (such as a layer, film, region or substrate) on another component or on the surface of another component, the component can be "directly" located on the surface of another component, or there can be a third component between the two components. On the contrary, when describing a component on the surface of another component or when another component is formed or provided on the surface of a component, it means that there is no third component between the two components. In addition, when describing a component as "substantially" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a partial edge of the entire surface.

[0031] In the description of the embodiments of the present application, when a component "includes" another component, unless otherwise specified, other components are not excluded, and other components may be further included. In addition, when a component such as a layer, film, region, or plate is referred to as being "on / located on" another component, it may be "directly on" the other component (i.e., located on the surface of the other component with no other components between them), or another component may exist in between. In addition, when a component such as a layer, film, region, or plate is "directly located on" another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it means that no other components are located in between.

[0032] The terms used in the description of the various embodiments described herein are only used to describe specific embodiments and are not intended to be limiting. As used in the description of the various embodiments described and in the appended claims, "the part" is also intended to include the plural form unless the context clearly indicates otherwise. Among them, a component includes a layer, a film, a region, or a plate.

[0033] The following will describe the various embodiments of the present application in detail with reference to the accompanying drawings. However, it will be appreciated by those skilled in the art that in the various embodiments of the present application, many technical details are provided in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solution claimed in the present application can be implemented.

[0034] Figure 1 A flow chart of a method for pulling a single crystal silicon rod provided in one embodiment of the present application.

[0035] refer to Figure 1 The present application provides a method for pulling a single crystal silicon rod, comprising the following steps:

[0036] S1. Obtain a first curve, which is a relationship curve between the equal diameter length and resistivity of a single crystal silicon rod having a first dopant; based on the first curve, obtain the equal diameter length corresponding to the single crystal silicon rod when the resistivity is a preset resistivity, and use it as the first preset length.

[0037] S2, adding silicon material and a first dopant into a crucible, and sequentially performing a melting process, a seeding process, and a shoulder release process, and then entering an equal diameter growth process.

[0038] S3. In the equal-diameter growth process, after the equal-diameter length of the initial crystal rod formed by the equal-diameter growth reaches a first preset length, a second dopant is added into the crucible, and the equal-diameter growth process is continued until the equal-diameter length of the initial crystal rod reaches a second preset length, and then a finishing process is entered, wherein the segregation coefficient of the first dopant is smaller than the segregation coefficient of the second dopant.

[0039] The method for pulling a single crystal silicon rod provided in the embodiment of the present application adds a first dopant and a second dopant, wherein the segregation coefficient of the first dopant is less than the segregation coefficient of the second dopant; in this way, the first dopant mainly plays a role in the early stage, and the second dopant plays a role in the later stage, so that the resistivity of the head and tail of the crystalline silicon can be made closer, thereby improving the uniformity of the axial resistivity and the radial resistivity, and the resistivity uniformity in the corresponding silicon wafer is also improved. Secondly, the first dopant is added when the silicon material is added, and the second dopant is added when the initial silicon rod is at a preset resistivity, that is, the two dopants are not added at the same time, which can avoid the difference in local strain of the single crystal silicon rod caused by the different atomic radii of the two dopants, which may lead to the formation of oxidation-induced stacking faults, and increase the leakage current of the PN junction of the semiconductor or solar cell formed based on the silicon rod. The two dopants are not added at the same time, which also avoids the formation of a recombination center between the first dopant and the second dopant, so that the impurities in the single crystal furnace form an oxygen precipitation layer with this recombination center, and then physical defects and other problems occur.

[0040] The method for preparing a single crystal silicon rod will be described in detail below with reference to the accompanying drawings.

[0041] Figure 2 A schematic structural diagram of a single crystal furnace in a method for pulling a single crystal silicon rod provided in one embodiment of the present application.

[0042] The method for pulling a single crystal silicon rod provided in the embodiment of the present application is a Czochralski method, in which a single crystal silicon rod is pulled by a single crystal furnace. Figure 2 The single crystal furnace 1 at least includes: a single crystal furnace body 11, a crucible 12, the crucible 12 is located in the single crystal furnace body 11, and the crucible 12 is used to contain and melt silicon materials. The single crystal furnace 1 also includes a doping device 2, which runs through the single crystal furnace body 11 and is located above the crucible 12. The second dopant is added through the doping device 2 instead of adding the dopant at the top, so that the molten liquid 200 caused by the addition of the dopant can be reduced. The physical defects may affect the quality and resistivity of the prepared single crystal silicon rod.

[0043] Figure 3 This is a graph of a first curve in a method for pulling a single crystal silicon rod provided in an embodiment of the present application.

[0044] It should be noted that Figure 3 The corresponding relationship between the resistivity and the equal diameter length of the single crystal silicon rod doped with antimony element, wherein the horizontal axis is the equal diameter length, in cm, and the vertical axis is the resistivity, in Ω·cm.

[0045] In step S1, in some embodiments, the process steps for obtaining the first curve include: performing a melting process, a seeding process, a shouldering process, and a diameter equalization process on silicon material and a first dopant to form a single crystal silicon rod with the first dopant; measuring the diameter equalization length of the single crystal silicon rod and the resistivity corresponding to each diameter equalization length, and plotting the first curve. For example Figure 3 The first curve shown, from Figure 3 It can be seen that as the equal diameter length increases, the resistivity of the single crystal silicon rod continues to increase until the dopant is consumed.

[0046] In some embodiments, the first curve is obtained through a simulation process.

[0047] In the process of lower temperature and in the early stage of molten silicon material, liquid silicon will react with the crucible at high temperature to form oxygen atoms. The oxygen atoms exist in the form of interstitial oxygen. The interstitial oxygen in silicon is an impurity with a relatively fast diffusion rate. When oxygen-containing silicon undergoes high-temperature heat treatment, the oxygen in the body will diffuse, resulting in the aggregation of oxygen atoms, which may then produce oxygen precipitation and may induce secondary defects such as dislocations and stacking faults.

[0048] In some embodiments, the first dopant is a dopant that inhibits oxygen precipitation, such as antimony or arsenic. Among them, compared with phosphorus, antimony and arsenic have higher electron concentrations in antimony-doped single crystal silicon rods and arsenic-doped single crystal silicon rods at the same temperature, and thus the concentration of charged vacancies is higher. Due to the Coulomb force, the ionized donor Sb+ / As+ and the charged vacancies are easily combined to form "Sb-V pairs (Sb-Vpairs)" / "As-V pairs (As-Vpairs)", and the interstitial oxygen will form Sb-VO / As-VO complexes with "Sb-V pairs" / "As-V pairs", thereby forming oxygen precipitation. However, since the recombination time of the complex is too long, it is not easy to form a complex, so the defects of the single crystal silicon rod are smaller and the resistivity is higher.

[0049] In some embodiments, the first dopant is a single substance or compound containing an antimony doping element. The segregation coefficient of the antimony doping element is 0.023, and the antimony doping element has a large volatilization. The volatility of antimony refers to the ability of antimony atoms to escape from the silicon melt and become gaseous under high temperature conditions. This property is of great significance for controlling the impurity content and oxygen content in the silicon rod. During the growth of single crystal silicon, the volatilization of antimony can promote the volatilization of oxygen on the surface of the melt, thereby inhibiting the oxygen in the silicon melt from entering the silicon crystal, reducing the oxygen content of the silicon rod, and thus increasing the minority carrier lifetime.

[0050] In some embodiments, the second dopant is a single substance or compound containing a phosphorus doping element. In this way, the solid solubility of phosphorus in crystalline silicon is relatively high, thereby forming a highly doped single crystal silicon rod. Secondly, the covalent radius of phosphorus atoms is 1.06, the covalent radius of silicon atoms is 1.11, the covalent radius of arsenic atoms is 1.2, and the covalent radius of antimony atoms is 1.4. The addition of high concentrations of phosphorus into silicon single crystals alone will cause lattice contraction, and the lattice constant of heavily doped phosphorus silicon single crystals will decrease relative to undoped silicon single crystals. Lattice defects may exist in heavily doped phosphorus silicon single crystals, leading to problems such as leakage current. By using the first dopant and the second dopant, the covalent radius of phosphorus atoms is smaller than that of silicon atoms, and the covalent radius of arsenic or antimony is larger than that of silicon atoms. Arsenic or antimony is used to compensate for the volume effect of phosphorus (when the two elements are co-doped), so that the change in the lattice constant of the highly doped N-type heavily doped CZ silicon single crystal relative to the lattice constant of the antimony-doped single crystal silicon rod is reduced to an allowable value, and dislocation line defects caused by lattice mismatch can be eliminated or significantly reduced.

[0051] In some embodiments, the first dopant is set to antimony and the second dopant is set to phosphorus, so as to improve the uniformity of the resistivity of the single crystal silicon rod. The specific principle is: during the doping process, in the early stage, the antimony element can react with the oxygen element, thereby reducing the oxygen concentration, making the resistivity of the single crystal silicon rod in the early stage more uniform; in the middle stage, that is, when the second dopant is doped, due to the difference in evaporation rate of antimony and phosphorus during the doping process, the two dopants have the same influence on the resistivity of the silicon ingot; as time goes by, the contribution of antimony becomes smaller and smaller. When the antimony evaporates, that is, in the later stage of crystal pulling, only a single phosphorus dopant is in effect, so that the resistivity of the head and tail of the crystal rod is closer, thereby improving the uniformity of the axial resistivity, and the resistivity uniformity in the corresponding silicon wafer is also improved.

[0052] Among them, when the doping amount of the doping element is small, calculation errors are prone to occur. The error can be reduced by forming a compound containing antimony doping elements or phosphorus doping elements for equivalent amplification. The compound can be a master alloy. The master alloy refers to a binary alloy composed of a dopant and Si (or other semiconductor materials), such as P-Si, B-Si, etc. It should be noted that the total number of dopants in the master alloy and in the melt remains unchanged, that is: (M alloy / d alloy) · Cm = (W + M alloy) · C0 / d alloy, where Cm is the concentration of the dopant in the master alloy, M alloy is the weight of the master alloy, d alloy is the weight of the dopant, W is the weight of the silicon material, and C0 is the concentration of the dopant in the single crystal silicon rod.

[0053] For example, the compound containing antimony doping element may be a silicon-antimony alloy. The compound containing phosphorus doping element may be a silicon-phosphorus alloy.

[0054] In S2, the weight of the silicon material input and the weight of the first dopant can be calculated according to the needs. Take an example of antimony-doped single crystal silicon doping: the diameter of the crystal to be grown is required to be 70 mm, the length is 10 meters (896.2 kg), and the doping concentration is to calculate the required amount of antimony alloy. First, calculate the required doping amount (approximately 40 g) based on the charge amount and the doping concentration, then select the doping alloy, and then calculate the required amount of alloy. If Si-Sb is selected as the doping alloy, the amount of Si-Sb alloy is 242 g. According to experience, 20% of Sb will evaporate during crystal pulling, so about 303 g of Si-Sb alloy is required to pull a crystal of the above size. If the diameter of the Si-Sb alloy is also 70 mm, its length should be about 33 mm. If Ag-Sb alloy is used, the required alloy amount can be similarly calculated to be 201g based on the crystal size, doping concentration and Ag:Sb ratio. Adding the 20% that will evaporate, 250g of Ag-Sb alloy is actually needed. If the alloy diameter is also 70mm, its length should be 6.3mm. The same doping effect can be obtained by using Au-Sb or Sn-Sb alloy.

[0055] Similarly, the amount of the second dopant is calculated in the same way. The required doping amount of the second dopant is calculated, and the required doping amount is calculated based on the charge amount and the doping concentration. Then, the doping alloy is selected and the required alloy amount is calculated.

[0056] In some embodiments, a first preset environment is used to perform a melting process on silicon material and a first dopant; the process parameters of the first preset environment include: a crucible rotation speed of 1rpm to 2rpm, a main heater power of 95kw to 110kw, a bottom heater power of 80kw to 90kw, a stretch rod rotation speed of 1rpm to 2rpm; and a gas flow rate of the protective gas of 100slpm to 120slpm.

[0057] The crucible has a rotation speed of 1 rpm or 2 rpm. The main heater power can be 95 kW, 100 kW, 105 kW or 110 kW. The bottom heater power can be 80 kW, 82 kW, 84 kW, 86 kW, 88 kW or 100 kW. The rotation speed of the stretching rod can be 1 rpm or 2 rpm. The gas flow rate of the shielding gas can be 100 slpm, 103 slpm, 105 slpm, 108 slpm or 120 slpm. The shielding gas can be argon or other inert gases.

[0058] It should be noted that the end of the stretching rod is connected to a seeding rod, and the stretching rod is used to pull a single crystal silicon rod.

[0059] In some embodiments, silicon material and the first dopant can be added to the crucible at the same time, and then the single crystal furnace is closed and evacuated, and the heater is started to start the melting operation, and the rotation speed of the crucible is turned on, for example, 1 rpm to 3 rpm, and the melting time can be 10 hours to 24 hours to completely melt the silicon material and the first dopant.

[0060] In some embodiments, the silicon material and the first dopant may be added to the crucible in multiple times, for example, a first preset weight of polysilicon material is added the first time, a second preset weight of polysilicon material is added the second time, and finally the remaining polysilicon material is completely added to the crucible the last time.

[0061] The first dopant may be dispersed with the silicon material and added to the crucible multiple times. In other embodiments, the first dopant may be added to the crucible after the last addition of the polysilicon material, thereby reducing the volatilization loss of the first dopant.

[0062] In some embodiments, after adding the second dopant, the equal-diameter growth process is continued using a second preset environment. The process parameters of the second preset environment include: the crucible rotation speed is 3.5rpm~7rpm, the main heater power is 45kw~65kw, the bottom heater power is 0kw, the stretching rod rotation speed is 7rpm~9rpm; the gas flow rate of the protective gas is 85slpm~100slpm.

[0063] Wherein, the rotation speed of the crucible can be 3.5rpm, 4.5rpm, 5.5rpm, 6.5rpm or 7rpm. The power of the main heater can be 45kw, 50kw, 55kw, 60kw or 65kw. The rotation speed of the stretching rod can be 7rpm, 8rpm or 9rpm. The gas flow rate of the protective gas can be 85slpm, 86slpm, 88slpm, 90slpm, 92slpm, 94slpm, 96slpm, 98slpm or 100slpm. The protective gas can be argon or other inert gases.

[0064] In some embodiments, the second dopant has a resistivity of 0.003 Ω·cm to 0.005 Ω·cm.

[0065] The resistivity of the second dopant is 0.003Ω·cm, 0.0035Ω·cm, 0.004Ω·cm, 0.0045Ω·cm or 0.005Ω·cm.

[0066] In a specific example, refer to Figure 3 , the preset resistivity may be 1.000Ω·cm, and the first preset length is 190cm.

[0067] It should be noted that the second dopant can be added into the crucible through the doping device 2. In this way, there is no need to perform steps such as vacuuming, and the impact on the environment in the single crystal furnace is small, so that the physical defects of the prepared single crystal silicon rod are smaller, thereby having a lower leakage current and a higher yield.

[0068] In some embodiments, a second dopant is placed in a delivery chamber of a doping device. Before the second dopant is added to the crucible, the doping device is in a retracted state. At this time, at least a portion of the delivery chamber is located in the delivery port or the mounting hole, that is, the length of the delivery chamber extending into the single crystal furnace body is relatively short, thereby preventing the second dopant in the delivery chamber from being melted or evaporated due to excessive temperature in the furnace. When it is necessary to add the second dopant to the crucible, the inner substrate located in the retracted position is pushed to the extended position. At this time, the doping device in the retracted state is converted to a delivery state, and the delivery chamber moves to the top of the crucible, thereby adding the second dopant in the delivery chamber to the crucible. The single crystal furnace can effectively deliver the second dopant into the crucible through the doping device, which can better reduce the loss of the second dopant due to its own physical properties, thereby ensuring that the change trend of the head and tail resistivity of the single crystal silicon can be effectively regulated during the crystal pulling process, and the doping device is cleverly combined with the single crystal furnace body, and no longer occupies the space of the weight and tungsten wire rope of the single crystal furnace.

[0069] In some embodiments, the process steps of adding the second dopant into the crucible include: performing the first step, adding the second dopant of the first sub-weight; taking the equal diameter length of the initial crystal rod when the second dopant is added for the first time as the initial length, performing the second step, the second step is to obtain the equal diameter length of the initial crystal rod as the first length in real time; when the difference between the first length and the initial length is the first preset value, performing the third step, the third step is to add the second dopant of the second sub-weight; repeating the second step; when the difference between the first length and the initial length is the second preset value, performing the fourth step, the fourth step is to add the second dopant of the third sub-weight; repeating the second step, the third step, the second step and the fourth step in sequence until the equal diameter length of the initial crystal rod reaches the second preset length. The second dopant is added in multiple times to avoid the problem of large terminal resistivity caused by the volatilization of the dopant.

[0070] In some embodiments, the first subweight, the second subweight, and the third subweight are equal.

[0071] In some embodiments, the first preset value is equal to the second preset value.

[0072] In some embodiments, the first sub-weight, the second sub-weight, and the third sub-weight present a gradually decreasing trend.

[0073] In some embodiments, the first preset value and the second preset value present an increasing trend.

[0074] In some embodiments, the first sub-weight, the second sub-weight, and the third sub-weight present a gradually increasing trend; and / or, the first preset value and the second preset value present a decreasing trend.

[0075] In some embodiments, the first sub-weight, the second sub-weight, and the third sub-weight present a gradually increasing trend; and / or the first preset value and the second preset value present a decreasing trend.

[0076] In some embodiments, the first preset value ranges from 2 cm to 100 cm; the first sub-weight ranges from 0.001 kg to 0.1 kg.

[0077] The first preset value may be 2 cm, 10 cm, 20 cm, 30 cm, 40 cm, 50 cm, 60 cm, 70 cm, 80 cm, 90 cm or 100 cm. The first sub-weight may range from 0.001 kg, 0.005 kg, 0.01 kg, 0.03 kg, 0.05 kg, 0.07 kg or 0.1 kg.

[0078] In some embodiments, the process step of adding the second dopant into the crucible includes: detecting the resistivity of the second crystal in real time; performing the fifth step, which is to add a fourth weight of the second dopant when the resistivity rises to a third preset value; repeating the fifth step; until the equal diameter length of the initial crystal rod reaches a second preset length. The resistivity is controlled in real time, thereby improving the uniformity of the resistivity of the single crystal silicon rod.

[0079] In some embodiments, the third preset value in each fifth step is equal or unequal; and / or the fourth subweight in each fifth step is equal or unequal.

[0080] Figure 4 A curve diagram of equal diameter length and resistivity of a single crystal silicon rod prepared by a single crystal silicon rod pulling method provided in an embodiment of the present application. Figure 4 A graph of equal diameter length and resistivity of single crystal silicon rods prepared by a method for pulling single crystal silicon rods of first sub-weight, second sub-weight and third sub-weight in which the second dopant is added multiple times and the first preset value is equal to the second preset value.

[0081] refer to Figure 4 The head and tail resistivity of the single crystal silicon rod prepared by the single crystal silicon rod pulling method provided in the embodiment of the present application is controlled within the range of 0.900Ω·cm to 1.100Ω·cm, indicating that the axial resistivity of the single crystal silicon rod is relatively uniform.

[0082] In some embodiments, the first preset length, the second preset length, the first subweight, the second subweight, the third subweight, the first preset value, and the range of the second preset value can be controlled by controlling the range of the resistivity. For example, a first curve and a second curve after adding a certain weight of the second dopant are obtained, and the first preset length, the second preset length, the first subweight, the second subweight, the third subweight, the first preset value, and the range of the second preset value are obtained by simulating and integrating the first curve and the second curve, and corresponding adjustments are made.

[0083] In a specific example, if the change in resistivity is large, the time for adding the second dopant twice is shortened, that is, the first preset value and the second preset value are shortened or the weight of the second dopant added each time is reduced.

[0084] The method for pulling a single crystal silicon rod provided in the embodiment of the present application adds a first dopant and a second dopant, wherein the segregation coefficient of the first dopant is less than the segregation coefficient of the second dopant; in this way, the first dopant mainly plays a role in the early stage, and the second dopant plays a role in the later stage, so that the resistivity of the head and tail of the crystalline silicon can be made closer, thereby improving the uniformity of the axial resistivity and the radial resistivity, and the resistivity uniformity in the corresponding silicon wafer is also improved. Secondly, the first dopant is added when the silicon material is added, and the second dopant is added when the initial silicon rod is at a preset resistivity, that is, the two dopants are not added at the same time, which can avoid the difference in local strain of the single crystal silicon rod caused by the different atomic radii of the two dopants, which may lead to the formation of oxidation-induced stacking faults, and increase the leakage current of the PN junction of the semiconductor or solar cell formed based on the silicon rod. The two dopants are not added at the same time, which also avoids the formation of a recombination center between the first dopant and the second dopant, so that the impurities in the single crystal furnace form an oxygen precipitation layer with this recombination center, and then physical defects and other problems occur.

[0085] Correspondingly, another embodiment of the present application further provides a single crystal furnace, which can be used to execute the single crystal silicon rod pulling method provided in the above embodiment. The technical features that are the same or corresponding to the above embodiment will not be described in detail here.

[0086] The single crystal furnace includes: a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other through the communication bus; the memory is used to store computer programs; the processor is used to implement the steps of the pulling method described in any of the above embodiments when executing the program stored in the memory.

[0087] Correspondingly, another embodiment of the present application further provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the steps of the drawing method described in any of the above embodiments are implemented.

[0088] It should be noted that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it may include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. The non-relational database may include a distributed database based on blockchain, etc., but is not limited thereto.

[0089] The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, etc., but is not limited thereto.

[0090] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0091] Those skilled in the art can understand that the above-mentioned embodiments are specific examples for implementing the present application, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of the present application. Any person skilled in the art can make their own changes and modifications without departing from the spirit and scope of the present application, so the scope of protection of the present application shall be based on the scope defined in the claims.

Claims

1. A method for pulling a single crystal silicon rod, characterized in that: The following steps are involved: Obtaining a first curve, which is a curve of the relationship between the equal diameter length and the resistivity of a single crystal silicon rod having a first dopant; based on the first curve, obtaining the equal diameter length corresponding to the single crystal silicon rod when the resistivity is a preset resistivity, and using it as a first preset length; Adding silicon material and the first dopant into a crucible, and sequentially performing a melting process, a seeding process, and a shoulder release process, and then entering an isodiameter growth process; In the isodiametric growth process, after the isodiametric length of the initial crystal rod formed by the isodiametric growth reaches the first preset length, the second dopant is added into the crucible, and the isodiametric growth process is continued until the isodiametric length of the initial crystal rod reaches the second preset length, and then the finishing process is entered, wherein the segregation coefficient of the first dopant is smaller than the segregation coefficient of the second dopant.

2. The drawing method according to claim 1, characterized in that: The first dopant is a simple substance or a compound containing an antimony doping element; the second dopant is a simple substance or a compound containing a phosphorus doping element.

3. The drawing method according to claim 1, characterized in that: The process step of adding the second dopant into the crucible comprises: Performing a first step of adding a first sub-weight of the second dopant; Taking the equal diameter length of the initial crystal rod when the second dopant is added for the first time as the initial length, performing the second step, wherein the second step is to obtain the equal diameter length of the initial crystal rod as the first length in real time; When the difference between the first length and the initial length is a first preset value, performing a third step, wherein the third step is adding a second sub-weight of the second dopant; Repeat the second step; When the difference between the first length and the initial length is a second preset value, the fourth step is performed, wherein the fourth step is to add a third sub-weight of the second dopant; the second step, the third step, the second step and the fourth step are repeated in sequence until the equal diameter length of the initial crystal rod reaches the second preset length.

4. The drawing method according to claim 3, characterized in that: The first subweight, the second subweight and the third subweight are equal; and / or the first preset value is equal to the second preset value.

5. The drawing method according to claim 3, characterized in that: The first sub-weight, the second sub-weight and the third sub-weight present a gradually decreasing trend; and / or the first preset value and the second preset value present an increasing trend.

6. The drawing method according to claim 3, characterized in that: The first sub-weight, the second sub-weight and the third sub-weight present a gradually increasing trend; and / or the first preset value and the second preset value present a decreasing trend.

7. The drawing method according to claim 1, characterized in that: The process step of adding the second dopant into the crucible includes: detecting the resistivity of the initial crystal rod in real time; performing a fifth step, wherein when the resistivity rises to a third preset value, adding a fourth sub-weight of the second dopant; and repeating the fifth step; Until the equal diameter length of the initial crystal rod reaches the second preset length.

8. The drawing method according to claim 7, characterized in that: The third preset value in the fifth step is equal or unequal each time; and / or the fourth subweight in the fifth step is equal or unequal each time.

9. The drawing method according to claim 1, characterized in that: The melting process is performed on the silicon material and the first dopant in a first preset environment; the process parameters of the first preset environment include: the rotation speed of the crucible is 1rpm~2rpm, the power of the main heater is 95kw~110kw, the power of the bottom heater is 80kw~90kw, the rotation speed of the stretching rod is 1rpm~2rpm; the gas flow rate of the protective gas is 100slpm~120slpm.

10. The drawing method according to claim 1, characterized in that: After adding the second dopant, the equal-diameter growth process is continued using the second preset environment; the process parameters of the second preset environment include: the crucible rotation speed is 3.5rpm~7rpm, the main heater power is 45kw~65kw, the bottom heater power is 0kw, the speed of the stretching rod is 7rpm~9rpm; the gas flow rate of the protective gas is 85slpm~100slpm.

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