Method and apparatus for selecting a surface material for an internal water-cooled tube of a single crystal silicon growth furnace

Abstract

The application discloses a method and device for selecting the surface material of a water-cooled jacket in a single crystal silicon growth furnace, and belongs to the technical field of photovoltaics. The method comprises the following steps: setting a thermal field boundary condition; determining a carbon-oxygen boundary condition, including determining a carbon-oxygen impurity source, a carbon-oxygen impurity control equation and a boundary condition of the carbon-oxygen impurity in different transport processes or regions; determining the emissivity of the water-cooled jacket; performing a single crystal silicon growth test; analyzing the test results to select the surface material of the water-cooled jacket; the higher the emissivity of the surface material of the water-cooled jacket, the stronger the heat dissipation of the crystal surface, the higher the solid-liquid interface deflection, the higher the dissolved oxygen impurity content in the melt, and the higher the turbulent viscosity and oxygen diffusion rate in the central region of the melt; the lower the emissivity of the surface material of the water-cooled jacket, the lower the thermal stress in the crystal. The application can analyze the influence of the emissivity of the surface material of the water-cooled jacket on the thermal field in crystal growth and the oxygen impurity distribution in the melt, thereby providing guidance for the selection of the surface material of the water-cooled jacket.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of photovoltaic, and particularly relates to a method and device for selecting surface material of an internal water-cooled sleeve of a single crystal silicon growth furnace. BACKGROUND

[0002] One of the materials for photovoltaic devices, single crystal silicon, is mainly produced by the Czochralski method. The thermal field of the growth furnace has a serious impact on the oxygen of crystal growth. In the interior of the Czochralski single crystal silicon crystal, oxygen atoms exist in the silicon single crystal in the form of interstitial atoms, and the concentration is basically maintained between 5-20 (ppma), and when the oxygen concentration is too high, oxygen precipitates and oxygen clusters are generated. The existence of oxygen atoms has advantages and disadvantages. When oxygen atoms exist, the hardness of the silicon wafer can be improved, which is beneficial to mechanical processing; oxygen atoms can combine with vacancies in silicon to form groups, attract surrounding oxygen atoms to form oxygen precipitates, and low-concentration oxygen precipitates can act as gettering centers to adsorb other impurity defects, thereby improving the electrical properties of the silicon wafer. However, when the oxygen precipitates are too much, the minority carrier lifetime in the silicon wafer cell is reduced, and the leakage current is increased. At the same time, oxygen precipitates can cause bulk microdefects, affecting the performance of photovoltaic cells, and oxygen precipitates can be oxidized at high-temperature heat treatment, generating oxidation-induced stacking faults, resulting in "black heart circles" in the crystal bar, affecting the performance of the silicon wafer. At the same time, the existence of oxygen atoms can cause the resistivity of P-type single crystal silicon to rise and the resistivity of N-type single crystal silicon to decrease, affecting the conversion efficiency of the silicon wafer cell. Therefore, in the current general saturation of oxygen impurities in single crystal silicon, the disadvantages outweigh the advantages, which can have a very adverse effect on the battery assembly, so it is necessary to control the content of oxygen impurities during the pulling process.

[0003] Water-cooled jacket as one of the most important components affecting the thermal field is widely studied. For example, Liu Lijun et al. studied the influence of the height of the water-cooled jacket on the thermal field of the crystal growth furnace, and found that the longer the length of the water-cooled jacket, the stronger the cooling capacity of the crystal. Hye Jun Jeon et al. studied the influence of double-cooled water jacket and length on the thermal field of crystal growth. Li Yourong et al. studied the relationship between the distance between the water-cooled jacket and the crystal and the crystal growth interface shape and the internal stress of the crystal. Zhao et al. studied that after adding the water-cooled jacket, the heat transfer capacity of the crystal is greatly increased, which is beneficial to improve the growth rate of the crystal. Japanese researchers studied the influence of the emissivity of the water-cooled jacket on the critical speed V, so as to obtain a perfect crystal with completely combined vacancies and gaps. Qi Xiaofang studied the influence of the water-cooled jacket on the thermal field of crystal growth and the oxygen content of the melt, and found that after increasing the water-cooled jacket, the cooling capacity of the crystal becomes stronger, but also increases the oxygen content in the crystal. Although many scholars optimize the position and structure of the water-cooled jacket, few people study the influence of different materials of the water-cooled jacket on the thermal field of crystal growth and the oxygen content in the melt. The material of the water-cooled jacket is generally a material with high thermal conductivity, which can take away the radiant heat absorbed by the surface of the material through the circulating cooling water inside, so the most important thing of the water-cooled jacket is to improve the ability of the water-cooled jacket to absorb radiant heat. Based on this, it is necessary to study the influence of the emissivity of the water-cooled jacket on the thermal field of crystal growth and the oxygen field of the melt. SUMMARY

[0004] The present application aims to at least partially solve one of the above-mentioned technical problems in the related art.

[0005] To this end, the present application aims to provide a method and device for selecting the surface material of the water-cooled jacket tube in a single crystal silicon growth furnace, which can analyze the influence of the emissivity of the surface material of the water-cooled jacket on the thermal field in crystal growth and the distribution of oxygen impurities in the melt, and provide guidance for the selection of the surface material of the water-cooled jacket tube.

[0006] In order to solve the above technical problems, the present application is implemented as follows:

[0007] The embodiment of the present application provides a method for selecting the surface material of the water-cooled jacket tube in a single crystal silicon growth furnace, and the method comprises the following steps:

[0008] Setting the thermal field boundary condition;

[0009] Determining the carbon-oxygen boundary condition, including determining the carbon-oxygen impurity source, the carbon-oxygen impurity control equation and the boundary condition of the carbon-oxygen impurity in different transport processes or regions;

[0010] Determining the emissivity of the water-cooled jacket;

[0011] Performing a single crystal silicon growth test;

[0012] Analyzing the test results and selecting the surface material of the water-cooled jacket tube according to the analysis results.

[0013] The higher the emissivity of the water-cooled jacket surface material, the stronger the heat dissipation of the crystal surface, the higher the solid-liquid interface deflection, the higher the oxygen impurity content dissolved in the melt, the higher the turbulent viscosity and oxygen diffusion rate in the center region of the melt, and the higher the oxygen impurity concentration at the crystal growth interface position.

[0014] The lower the emissivity of the water-cooled jacket surface material, the lower the thermal stress in the crystal, and the lower the oxygen concentration at the crystal growth interface position.

[0015] In addition, the method for selecting the water-cooled jacket surface material inside the single crystal silicon growth furnace according to the present application can also have the following additional technical features:

[0016] In some embodiments, the boundary conditions of the regional oxygen impurities include the boundary conditions of the wall surface of the carbon-oxygen impurity transport process of the crystal growth furnace and other wall surface boundary conditions required for solving the oxygen concentration control equation.

[0017] In some embodiments, the emissivity of the water-cooled jacket is 0.2, 0.4, 0.6, or 0.8.

[0018] In some embodiments, the content of setting the thermal field boundary conditions includes that the crystal rotation speed is 9.5 rpm, the crucible rotation speed is set to -6.5 rpm, - represents the opposite direction to the crystal rotation direction, and the crystal pulling speed is 1.2 mm / min.

[0019] In some embodiments, the carbon-oxygen impurity transport process inside the crystal growth furnace includes:

[0020] The quartz crucible and the melt interface: quartz dissolves into the melt;

[0021] The argon and the melt interface: oxygen atoms evaporate in the form of silicon monoxide, and carbon monoxide dissolves into the silicon melt;

[0022] The high-temperature graphite heater wall surface: high-temperature graphite reacts with silicon monoxide to generate carbon monoxide;

[0023] The crystal crystallization interface front: oxygen atoms and carbon atoms solidify into the crystal interior.

[0024] In some embodiments, the self-defined scalar function in the Fluent software is used as the oxygen atom control equation in the thermal field; the control equation in the argon is:

[0025]

[0026] where ω SiO is the mass fraction of silicon monoxide in argon, SC t is the turbulent Schmidt number in argon, and u ArD is the velocity of argon gas, p SiO D is the diffusion coefficient of silicon monoxide in argon gas, p Ar D is the density of argon gas;

[0027]

[0028] The control equation of oxygen in the melt is:

[0029]

[0030] Where, ω o D is the mass fraction of oxygen in the melt, SC t D is the Schmidt number of turbulent flow in the melt, u m D is the velocity of the melt, D o D is the diffusion coefficient of oxygen atoms in the melt.

[0031] In some embodiments, the quantitative boundary condition of oxygen atom concentration at the interface between quartz and the melt is:

[0032]

[0033] Where, T represents temperature, C o D represents the molar concentration of oxygen atoms;

[0034] At the interface between argon gas and the melt, two reaction equilibrium equations and two reaction atom conservation equations are included, respectively:

[0035] Silicon monoxide reaction equilibrium equation:

[0036]

[0037] Carbon monoxide reaction equilibrium equation:

[0038]

[0039] Oxygen atom conservation equation:

[0040]

[0041] Carbon atom conservation equation:

[0042]

[0043] Where: C Ar D represents the molar concentration of argon gas, C SiO D represents the molar concentration of silicon monoxide, and R is the natural gas constant;

[0044] At the surface of the high-temperature graphite heater, the reaction equilibrium equation and the atom conservation equation are included, respectively:

[0045] Silicon monoxide and carbon monoxide reaction equilibrium equation:

[0046]

[0047] where G is Gibbs free energy;

[0048] Carbon atom conservation equation:

[0049]

[0050] In front of the crystal crystallization interface, including:

[0051] Oxygen atom conservation equation:

[0052]

[0053] Carbon atom conservation equation:

[0054]

[0055] where D c(m) is the diffusion coefficient of carbon in the melt, v pull is the crystal pulling speed, k c is the carbon segregation coefficient, k o is the oxygen segregation coefficient.

[0056] In some embodiments, the Gibbs free energy satisfies the following conditions:

[0057] ΔG = -81300 + 3.02T J / mol, T < 1640K

[0058] ΔG = -22100 - 33.1T J / mol, 1640K < T < 1687K

[0059] ΔG = -72100 - 3.44T J / mol, T > 1687K.

[0060] In some embodiments, other wall boundary conditions required to solve the oxygen concentration control equation include:

[0061] In the inlet wall, the quantitative boundary conditions of silicon monoxide and carbon monoxide are both 0;

[0062] In the outlet wall, the concentration gradient is set to 0.

[0063] The embodiment of the application also provides a single crystal silicon growth furnace internal water-cooled sleeve surface material selection device, comprising a processor and a memory, the memory has a software program stored thereon, characterized in that the processor can realize the content of the single crystal silicon growth furnace internal water-cooled sleeve surface material selection method as claimed in any one of the above when running the software program on the memory.

[0064] Compared with the prior art, the present application has at least the following advantages:

[0065] In the embodiment of the present application, the provided method for selecting the surface material of the water-cooled sleeve inside the single crystal silicon growth furnace has strong secondary development, compared with professional crystal simulation software, Fluent can set the related physical property parameters of the internal components of the furnace more freely, and the UDF compiled by C language can realize the desired function;

[0066] In the embodiment of the present application, the provided method for selecting the surface material of the water-cooled sleeve inside the single crystal silicon growth furnace has strong economy, through simulation experiment, the influence of the modified physical property parameters of the water-cooled sleeve surface material on the crystal bar growth quality can be judged and evaluated, avoiding the waste of manpower, material resources and financial resources in experiments;

[0067] In the embodiment of the present application, the provided method for selecting the surface material of the water-cooled sleeve inside the single crystal silicon growth furnace has very high safety, the single crystal silicon growth process is an extremely high temperature environment, Fluent simulation can simulate these dangerous scenes in a safe computer environment, avoiding potential safety accidents;

[0068] In the embodiment of the present application, the provided method for selecting the surface material of the water-cooled sleeve inside the single crystal silicon growth furnace can accurately control the temperature gradient: it is helpful for silicon atoms to arrange in order according to a specific direction when solidifying, thereby forming a uniform and defect-free single crystal structure, improving the quality and performance of the crystal, and making it more suitable for high-end semiconductors and photovoltaics and other fields with strict requirements on the quality of the crystal;

[0069] In the embodiment of the present application, the provided method for selecting the surface material of the water-cooled sleeve inside the single crystal silicon growth furnace can improve the heat exchange efficiency: it can absorb the heat on the surface of the single crystal silicon rod faster, release the stress in the silicon rod in time, and then improve the growth speed of the single crystal, thereby improving the production capacity of the single crystal furnace, producing more high-quality single crystal silicon rods in the same time, reducing production cost, and improving production efficiency;

[0070] In the embodiment of the present application, the provided method for selecting the surface material of the water-cooled sleeve inside the single crystal silicon growth furnace can reduce thermal stress and crystal defects: it can reduce the density of dislocations and twinning defects in the crystal caused by thermal stress, improve the integrity and consistency of the crystal, reduce the performance instability problems in the subsequent processing and use process, and improve the yield of the product;

[0071] The material selected by the method for selecting the surface material of the water-cooled jacket inside the single crystal silicon growth furnace can enhance corrosion resistance and oxidation resistance, prolong the service life of the water-cooled jacket, reduce downtime and cost increase caused by equipment component replacement and maintenance, ensure stability and continuity of the crystal growth process, and improve production efficiency and economic benefits.

[0072] The material selected by the method for selecting the surface material of the water-cooled jacket inside the single crystal silicon growth furnace can improve thermal radiation characteristics: when it is necessary to reduce the heat absorption of the water-cooled jacket, a material with good thermal reflection performance can be selected to reduce the problem of low crystal pulling temperature caused by too fast heat dissipation; and when the temperature in the furnace is too high, a material capable of absorbing radiant heat can be used to accelerate heat absorption, so as to quickly adjust the temperature and keep the temperature in the furnace within a suitable range, thereby ensuring the quality of crystal pulling.

[0073] The material selected by the method for selecting the surface material of the water-cooled jacket inside the single crystal silicon growth furnace can reduce impurity pollution, which is helpful to improve the purity of single crystal silicon. For the semiconductor industry, high-purity single crystal silicon is the basis for manufacturing high-performance chips and other devices, and can effectively improve the performance and reliability of semiconductor devices.

[0074] The selection device for the surface material of the water-cooled jacket inside the single crystal silicon growth furnace comprises the method for selecting the surface material of the water-cooled jacket inside the single crystal silicon growth furnace, and thus has all the features and advantages of the method for selecting the surface material of the water-cooled jacket inside the single crystal silicon growth furnace. Additional aspects and advantages of the present application will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0075] Figure 1 A single crystal silicon growth furnace structure diagram disclosed for an embodiment of the present application;

[0076] Figure 2 A water-cooled jacket emissivity and heater power, crystal axial temperature gradient relationship diagram disclosed for an embodiment of the present application;

[0077] Figure 3 A water-cooled jacket surface material emissivity and water-cooled jacket heat dissipation rate, crystal net radiation heat dissipation rate relationship diagram disclosed for an embodiment of the present application;

[0078] Figure 4 A crystal growth interface deflection diagram under different water-cooled jacket emissivity disclosed for an embodiment of the present application;

[0079] Figure 5A graph of thermal stress in the crystal under different emissivities of the water-cooled jacket is disclosed for an embodiment of the present application;

[0080] Figure 6 A graph of oxygen concentration near the solid-liquid interface under different emissivities of the water-cooled jacket is disclosed for an embodiment of the present application;

[0081] Figure 7 A graph of temperature distribution in the melt when the emissivity of the surface material of the water-cooled jacket is different is disclosed for an embodiment of the present application;

[0082] Figure 8 A graph of turbulent viscosity distribution in the melt under different emissivities of the water-cooled jacket is disclosed for an embodiment of the present application.

[0083] Explanation of reference numerals:

[0084] 1 - furnace side wall; 2 - argon zone; 3 - pulling rod; 4 - first heat insulating material; 5 - second heat insulating material; 6 - graphite; 7 - water-cooled jacket; 8 - silicon crystal; 9 - graphite heater; 10 - silicon melt; 11 - quartz crucible; 12 - graphite crucible; 13 - support table; 14 - third heat insulating material. DETAILED DESCRIPTION

[0085] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0086] The embodiments of the present application will be described in detail below with reference to the drawings and specific embodiments and application scenarios thereof.

[0087] Please refer to Figure 1 In some embodiments of the present application, a method for selecting the surface material of the water-cooled jacket in a single crystal silicon growth furnace is provided, and the contents thereof will be described in detail below.

[0088] 1. Determine the thermal field boundary conditions: in the crystal growth furnace, the crystal rotation speed is set to 9.5 rpm, the rotation speed of the crucible 4 is set to -6.5 rpm, and the crystal pulling speed is set to 1.2 mm / min. The control equations and boundary conditions of other related thermal fields can refer to the prior art.

[0089] 2. Determine the carbon-oxygen boundary conditions: in the crystal growth furnace, carbon-oxygen impurities will be generated in the crystal melt during the crystal growth process. The sources of carbon-oxygen impurities in the crystal, the carbon-oxygen impurity control equation, and the boundary conditions of oxygen impurities in different transport processes or regions will be introduced in turn below.

[0090] Source of carbon and oxygen impurities: In the Czochralski monocrystalline silicon crystal, oxygen and carbon are the most important impurity elements in the monocrystalline silicon. The source of oxygen mainly includes two parts, the first part is the oxygen impurities existing in the polycrystalline silicon material itself, and the second part is that the quartz crucible will react with the high-temperature melt, so that oxygen enters the melt, and finally crystallizes at the solid-liquid interface into the crystal. The carbon and oxygen impurities transport of the crystal growth furnace mainly includes the following four processes:

[0091] The first process: quartz, melt interface, quartz dissolves into the melt:

[0092]

[0093] The second process: on the surface of argon and melt, oxygen atoms evaporate in the form of silicon monoxide, and carbon monoxide dissolves into the silicon melt:

[0094]

[0095] The third process: on the surface of high-temperature graphite heater, high-temperature graphite reacts with silicon monoxide to generate carbon monoxide:

[0096]

[0097] The fourth process: at the front of the crystal crystallization interface, oxygen atoms and carbon atoms solidify into the crystal interior:

[0098] O(m)→O(s) (5)

[0099] C(m)→C(s) (6)

[0100] Wherein, (s) represents solid, (m) represents melt, and (g) represents gas.

[0101] Oxygen atom control equation: Since the content of oxygen atoms in the melt and argon is very small, the influence of the content of oxygen atoms on the flow field, thermal field, etc. of argon and melt can be ignored, and only the convection and diffusion equation of oxygen atoms in argon and melt needs to be solved. The user-defined scalar function (User-defined Scalar UDS) in the Fluent software can meet the equation, so the UDS is considered to solve the oxygen atom control equation in the thermal field. The control equation of oxygen atoms in argon is as follows:

[0102]

[0103] Where: ω SiO represents the mass fraction of silicon monoxide in argon, SC t is the Schmidt number of turbulent flow in argon, taking 0.7, u Ar represents the velocity of argon / ms -1, D SiO Diffusion coefficient of argon in silicon / m 2 s -1 , p Ar Densities of argon atmosphere, m t Represent turbulent viscosity; In physics, it is a vector differential operator (Hamiltonian operator), which can be used to calculate the gradient of a scalar field in vector analysis. Represent the partial derivative with respect to time, The physical quantities inside are all scalars, whose values satisfy the following formula:

[0104]

[0105] In the melt:

[0106]

[0107] In the formula, ω O Mass fraction of oxygen atoms in the melt, SC t Schmidt number of turbulence in the melt, take 0.7, u m Velocity of the melt, D o Diffusion coefficient of oxygen atoms in the melt / m 2 s -1 , whose value is 5.0 x 10 -8 m 2 s -1 , p m Density of silicon melt.

[0108] Boundary conditions of oxygen atoms: The carbon and oxygen impurity transport in the crystal growth furnace is mainly divided into the following four processes. The boundary conditions of the wall surface where these four processes occur and other wall surface boundary conditions required to solve the oxygen concentration control equation are introduced below.

[0109] The first process: at the interface between quartz and melt

[0110] The quartz crucible will be melted at high temperature, and mass transfer to other areas of the melt through convection and diffusion of the melt. At the interface between the melt and the crucible, the oxygen atom concentration satisfies the quantitative boundary condition.

[0111]

[0112] Where T represents temperature / K, Co represents the volume concentration of oxygen atoms / atom cm -3 .

[0113] The second process: the interface between the melt and argon

[0114] Two chemical reactions, evaporation of silicon monoxide gas and dissolution of carbon monoxide gas, occur at the interface between the melt and argon gas, i.e. the free interface. These two chemical reactions involve four atoms or molecules, i.e. oxygen atom, carbon atom, silicon monoxide molecule and carbon monoxide molecule. Therefore, four balance equations are needed to model the process, including two reaction balance equations and two reaction atom conservation equations (also called material conservation equations).

[0115] The reaction balance equations are as follows:

[0116] The reaction balance equation of silicon monoxide is:

[0117]

[0118] The reaction balance equation of carbon monoxide is:

[0119]

[0120] The material conservation equations are as follows:

[0121] The oxygen atom conservation equation is:

[0122]

[0123] The carbon atom conservation equation is:

[0124]

[0125] In the above equations: C Ar represents the molar concentration of argon gas / mol m -3 , C SiO represents the molar concentration of silicon monoxide / mol m -3 , R is the natural gas constant, which is 8.314, C SiO is the molar concentration of SiO in argon gas, C o is the molar concentration of oxygen in the silicon melt, C Si is the molar concentration of Si in the silicon melt, which is generally taken as 1, C co is the molar concentration of CO in argon gas, C c is the concentration of C in the melt, D SiO / D co are the diffusion coefficients of SiO and CO in argon gas, respectively, Do / D c are the diffusion coefficients of oxygen and carbon in the melt, respectively; and T is the temperature.

[0126] Third process: high-temperature graphite wall surface

[0127] On the high temperature graphite wall, silicon monoxide reacts with high temperature graphite to generate silicon carbide and carbon monoxide, so that the wall exists two molecules, carbon monoxide and silicon monoxide. Similarly, two equations are needed to solve the concentration of two kinds of molecules. That is, the reaction equilibrium equation, the atomic conservation equation.

[0128] Silicon monoxide and carbon monoxide reaction equilibrium equation:

[0129]

[0130] Wherein, G is Gibbs free energy, which satisfies the following formula:

[0131] ΔG = -81300 + 3.02T J / mol, T < 1640K (16)

[0132] ΔG = -22100 - 33.1T J / mol, 1640K < T < 1687K (17)

[0133] ΔG = -72100 - 3.44T J / mol, T > 1687K (18)

[0134] Carbon atomic conservation equation:

[0135]

[0136] Fourth process: solid-liquid interface

[0137] Because of the different solubility of oxygen atoms in the crystal and melt, segregation effect will occur at the solid-liquid interface, that is, at the crystallization front of the melt and the crystal, due to the small solubility of oxygen atoms in the crystal, the excess oxygen atoms in the crystal will be precipitated at the interface front during the crystallization process. The main unknown quantity is the concentration of oxygen atoms, so only one reaction equilibrium equation is needed to solve the concentration of oxygen atoms, and the carbon atoms are the same.

[0138] Oxygen atom conservation equation,

[0139]

[0140] Carbon atomic conservation equation,

[0141]

[0142] Wherein, D c(m) is the diffusion coefficient of carbon in the melt, which is 5.0 x 10 -8 m 2 s -1 v pull is the crystal pulling speed, taking 1.0 mm / min, k c is the carbon segregation coefficient, taking 0.07, and the same reason, ko The oxygen segregation coefficient is 0.85.

[0143] Fifth process: import and export wall surface and other wall surface

[0144] In the import wall surface, the quantitative boundary condition of silicon monoxide and carbon monoxide is taken, and it is considered that the import is all argon gas and no other gas exists, therefore, the value of silicon monoxide and carbon monoxide is 0, and the quantitative boundary condition is taken. The export is considered to be fully developed, that is, the concentration almost does not change, so the concentration gradient is 0, and the zero gradient boundary condition is set for other wall surfaces.

[0145] In some embodiments of the present application, the user-defined scalar function UDS (User defined scalar) in the Fluent software is used to solve the melt carbon and silicon, carbon monoxide and silicon monoxide in argon gas. Because the content of each is very small, the influence on the temperature and flow field can be ignored, therefore, only the convection diffusion equation of the user-defined scalar function needs to be calculated, and the related impurity concentration content can be solved.

[0146] The present application defines four groups of different water cooling jacket emissivity (divided into 0.2, 0.4, 0.6, 0.8 according to size), and studies the influence of water cooling jacket emissivity on the thermal field and oxygen field of the crystal growth furnace. As shown in Figure 2 The relationship between the heater 3 power and the crystal axial temperature gradient under different water cooling jacket emissivity is shown. It can be found that when the emissivity of the water cooling jacket surface is increased, the heater power in the crystal growth furnace is also increased, and at the same time, the axial temperature gradient of the crystal is also increased with the increase of the emissivity of the water cooling jacket.

[0147] Figure 3For different emissivity of the water-cooled jacket surface material, the net heat loss rate from the water-cooled jacket surface is Q1, and the radiation flux from the crystal surface to the environment is Q2. When the emissivity of the water-cooled jacket surface material increases, the heat conduction from the water-cooled jacket surface Q1 increases, and the net radiation Q2 from the crystal surface to the environment also increases accordingly. Therefore, to maintain the crystal growth, more heat needs to be conducted from the melt and the crucible to maintain the melting point temperature of the triple point, so the power of the heater inside the crystal growth furnace increases. At the same time, due to the increase of the heat Q2 radiated from the crystal to the environment, i.e. the increase of the heat dissipation of the crystal, the temperature inside the crystal above the crystal also decreases accordingly, and for the crystal growth interface, the temperature basically remains around 1685K, so the axial temperature gradient of the crystal increases with the increase of the heat dissipation capacity of the crystal. The reason for this situation is that the model is based on the quasi-steady state assumption, when the calculation converges, the temperature of all the walls inside the furnace no longer changes. All the radiation walls in the model are diffuse gray walls, which satisfy the Kirchhoff law. For opaque material surfaces, the emissivity of the material surface is equal to the absorptivity, so when the water-cooled jacket surface material has a higher emissivity, the ability of the water-cooled jacket surface material to absorb radiation heat also increases, and the water-cooled jacket can absorb the radiation heat from the crystal and the heat shield environment and conduct it away through the cooling water, so the temperature above the crystal is relatively low, and the required heater power also increases accordingly.

[0148] Figure 4 The relationship between the emissivity of the water-cooled jacket surface material and the shape of the solid-liquid interface. It can be found that when the emissivity of the water-cooled jacket surface material increases, the heat dissipated by the crystal can be more efficiently absorbed, and the cooling capacity of the crystal becomes stronger, but the deflection of the solid-liquid interface increases. The reason for this situation is that due to the increase of the emissivity of the water-cooled jacket surface material, the ability of the water-cooled jacket to absorb heat through radiation increases rapidly, so the radiation and convection heat dissipation capacity near the triple point of the silicon crystal surface increases significantly. When the heat dissipation capacity of the silicon crystal sidewall near the triple point increases significantly, the melt inside needs to transmit higher heat to maintain the temperature of the triple point, and the temperature difference inside the melt increases, which is manifested as a higher temperature of the crucible sidewall. However, near the central axis of the solid-liquid interface, the melt also transmits too much heat, i.e. the triple point has strong heat dissipation, and the melt transmits more heat to the solid-liquid interface, but due to the low thermal conductivity of the crystal and the high thermal conductivity of the melt, the heat transmitted by the melt increases near the central axis of the crystal crystallization interface, so the interface at this place moves upward, which is manifested as that the higher the emissivity of the water-cooled jacket surface material, the stronger the heat dissipation of the crystal surface, but the higher the deflection of the solid-liquid interface.

[0149] The Von Mises equivalent thermal stress in the crystal under different emissivity of the water-cooled jacket is as follows: Figure 5It can be found that the maximum stress of the crystal side wall increases with the increase of the emissivity of the water-cooled jacket surface material. When the emissivity of the water-cooled jacket surface material increases from 0.2 to 0.6 and 0.8, the maximum thermal stress in the crystal is transferred from the side wall of the crystal to the solid-liquid interface of the crystal. The reason for this is that when the emissivity of the water-cooled jacket surface material is low, the heat absorption capacity of the water-cooled jacket is weak, the heat dissipation capacity of the crystal side wall is equivalent to the heat dissipation capacity of the crystal axial direction, at this time, the solid-liquid interface is the flattest, and therefore the maximum thermal stress occurs at the side wall of the crystal. When the emissivity of the water-cooled jacket increases, the heat dissipation capacity of the crystal surface is significantly enhanced, and therefore the radial temperature gradient of the crystal in the direction of the side wall close to the solid-liquid interface is significantly increased, and therefore the thermal stress of the crystal side wall is significantly increased. At the same time, near the solid-liquid interface, due to the large difference between the cooling capacity of the crystal side wall and the cooling capacity near the rotating shaft of the crystal, the temperature change of the crystal near the rotating shaft of the solid-liquid interface is also very large, and due to the weak heat dissipation, the interface is convex to the crystal, and therefore the stress at the solid-liquid interface is significantly increased, and even greater than the maximum thermal stress near the side wall of the crystal.

[0150] The relationship between the emissivity of the water-cooled jacket and the stress of the crystal side wall and the thermal stress of the solid-liquid interface. When the emissivity of the water-cooled jacket increases, the thermal stress in the crystal is also increased. Therefore, for the selection of the water-cooled jacket material, a material with low emissivity is selected as the water-cooled jacket surface material as much as possible, and when the emissivity of the material at this position is low, the heat dissipation of the crystal surface is equivalent to the heat dissipation capacity of the crystal, at this time, the solid-liquid interface is relatively flat, and the thermal stress in the crystal is relatively small, which is beneficial to improve the growth quality and growth efficiency of the crystal.

[0151] The emissivity of the water-cooled jacket surface material will affect the temperature distribution in the melt, and therefore will also affect the oxygen near the melt and the solid-liquid interface. Figure 6 The oxygen concentration distribution of the solid-liquid interface under different emissivities of the water-cooled jacket. Obviously, when the emissivity is 0.2, the oxygen concentration of the solid-liquid interface is the lowest. Since the heat shield angle in the present application is 0 degrees and the pulling speed is uniform, the oxygen concentration can be analyzed from two aspects of the source of oxygen and the diffusion of oxygen.

[0152] Firstly, the source of oxygen. When the temperature of the side wall of the crucible is relatively high, the dissolved oxygen impurities entering the melt will increase, and the dissolution rate of the quartz crucible will increase. Figure 7 The temperature distribution in the melt under different emissivities of the water-cooled jacket. Obviously, when the emissivity of the water-cooled jacket is 0.8, the temperature of the side wall of the melt is the highest, and obviously, when the emissivity of the water-cooled jacket is 0.8, the content of the dissolved oxygen impurities in the melt is the highest.

[0153] Secondly, the diffusion rate of the oxygen impurities. Figure 8 The turbulent viscosity of the melt under different emissivities of the water-cooled jacket. The turbulent viscosity will affect the diffusion rate of the oxygen impurities in the melt. From the above analysis, it can be found that the turbulent viscosity of the melt is the lowest when the emissivity of the water-cooled jacket is 0.2, and the turbulent viscosity of the melt is the highest when the emissivity of the water-cooled jacket is 0.8. Therefore, the turbulent viscosity of the melt is inversely proportional to the diffusion rate of the oxygen impurities in the melt. Figure 8It can be found that when the emissivity of the water-cooled jacket increases, the turbulent viscosity of the center region of the melt also increases significantly. Therefore, when the emissivity of the water-cooled jacket surface material increases, the temperature of the melt side wall becomes high, and more 0 atoms are precipitated into the melt. At the same time, the turbulent viscosity inside the melt also increases significantly, so the transport rate of oxygen in the melt also increases significantly, and under the joint action of the two, the impurity content of oxygen near the solid-liquid interface also increases.

[0154] In the present application, the influence of the emissivity of the water-cooled jacket surface material on the thermal field in crystal growth and the oxygen impurity distribution in the melt is studied. In terms of the thermal field, the higher the emissivity of the water-cooled jacket surface material, the stronger the cooling ability of the water-cooled jacket to the inside of the furnace body, although the axial temperature gradient in the crystal is improved, the thermal stress in the crystal is also significantly improved, and at the same time, the solid-liquid interface moves towards the crystal direction, therefore, for the water-cooled jacket surface material, the emissivity of its surface should not be too high, and the thermal field under a more suitable water-cooled jacket emissivity is more conducive to the growth of the crystal. At the same time, when the heat dissipation ability of the crystal is improved, the heater power required to maintain the crystal growth also increases, and the temperature gradient in the melt is also larger, which is manifested as a higher crucible side wall temperature. In terms of the oxygen impurity in the melt, due to the increase of the emissivity of the water-cooled jacket surface material, the cooling ability of the crystal is improved, so the temperature of the interface between the melt and the crucible side wall also increases to compensate for the heat loss caused by the cooling of the crystal to ensure the stability of the three-phase point, but when the crucible side wall temperature increases, more oxygen impurities will be precipitated from the quartz crucible into the melt. At the same time, due to the increase of the turbulent viscosity in the melt, the diffusion rate of oxygen in the melt is accelerated, and the oxygen impurity near the solid-liquid interface is increased, and the emissivity of the water-cooled jacket surface material is too high, which will increase the oxygen content near the solid-liquid interface.

[0155] The parts of the present application not described in detail can refer to the prior art or be known to those skilled in the art, and the present application will not be described in detail.

[0156] The embodiments of the present application are described above in combination with the drawings, but the present application is not limited to the above specific embodiments, and the above specific embodiments are only illustrative and not limiting, and those skilled in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, which all belong to the protection of the present application.

Claims

1. A method for selecting the surface material of the water-cooled jacket inside a single-crystal silicon growth furnace, characterized in that, The method includes: Set thermal field boundary conditions; Determine the carbon-oxygen boundary conditions, including determining the sources of carbon-oxygen impurities, the governing equations for carbon-oxygen impurities, and the boundary conditions for carbon-oxygen impurities in different transport processes or regions. Determine the emissivity of the water-cooled jacket; Single-crystal silicon growth simulation experiments were conducted using Fluent software. The effects of the emissivity of the water-cooling jacket surface material on heat dissipation of the crystal surface, solid-liquid interface deflection, oxygen impurity content dissolved in the melt, turbulent viscosity in the central region of the melt, oxygen diffusion rate, oxygen impurity concentration at the crystal growth interface, and thermal stress inside the crystal were analyzed to select the surface material of the water-cooling jacket.

2. The method for selecting the surface material of the water-cooled jacket inside the single-crystal silicon growth furnace according to claim 1, characterized in that, Boundary conditions for regional oxygen impurities include boundary conditions of the walls of the crystal growth furnace for the transport of carbon and oxygen impurities, as well as other wall boundary conditions required to solve the oxygen concentration control equation.

3. The method for selecting the surface material of the water-cooled jacket inside the single-crystal silicon growth furnace according to claim 1, characterized in that, The emissivity of the water-cooled jacket is 0.2, 0.4, 0.6 or 0.

8.

4. The method for selecting the surface material of the water-cooled jacket inside the single-crystal silicon growth furnace according to claim 1, characterized in that, The thermal boundary conditions are set as follows: the crystal rotation speed is 9.5 rpm, the crucible rotation speed is set to -6.5 rpm (- represents the opposite direction of crystal rotation), and the crystal pulling speed is 1.2 mm / min.

5. The method for selecting the surface material of the water-cooled jacket inside the single-crystal silicon growth furnace according to claim 2, characterized in that, The carbon and oxygen impurity transport process within the crystal growth furnace includes: The interface between the quartz crucible and the melt: the quartz melts and enters the melt; Argon-melt interface: Oxygen atoms evaporate in the form of silicon monoxide, and carbon monoxide dissolves into the silicon melt; High-temperature graphite heater wall surface: High-temperature graphite reacts with silicon monoxide to produce carbon monoxide; At the crystallization interface front: oxygen atoms and carbon atoms solidify and enter the interior of the crystal.

6. The method for selecting the surface material of the water-cooled jacket inside the single-crystal silicon growth furnace according to claim 1, characterized in that, A custom scalar function from Fluent software is used as the governing equation for oxygen atoms in the thermal field; its governing equation in argon is as follows: ， in, This represents the mass fraction of silicon monoxide in argon gas. The turbulent Schmidt number in argon gas. The velocity of argon gas, Let be the diffusion coefficient of silicon monoxide in argon gas. The density of argon gas; ， Its governing equation in the melt is: ， in, This represents the mass fraction of oxygen in the melt. The Schmitt number for turbulent flow within the melt. For the velocity of the melt, is the diffusion coefficient of oxygen atoms in the melt.

7. The method for selecting the surface material of the water-cooled jacket inside the single-crystal silicon growth furnace according to claim 5, characterized in that, At the interface between quartz and melt, the quantitative boundary condition for oxygen atom concentration is: ， in, T Represents temperature. Represents the molar concentration of oxygen atoms; At the interface between argon gas and the melt, there are two reaction equilibrium equations and two reaction atom conservation equations, which are as follows: The equilibrium equation for the reaction of silicon monoxide is as follows: ， The equilibrium equation for the carbon monoxide reaction is as follows: ， The oxygen atom conservation equation: ， Carbon atom conservation equation: ， in: Represents the molar concentration of argon gas. Represents the molar concentration of silicon monoxide. R It is the natural gas constant; On the wall of the high-temperature graphite heater, the reaction equilibrium equation and the atom conservation equation are as follows: The equilibrium equation for the reaction between silicon monoxide and carbon monoxide is as follows: ， in, G For Gibbs free energy; Carbon atom conservation equation: ， At the crystallization interface front, including: The oxygen atom conservation equation: ， Carbon atom conservation equation: ， in, The diffusion coefficient of carbon in the melt. For crystal pulling speed, The carbon segregation coefficient, The oxygen condensation coefficient.

8. The method for selecting the surface material of the water-cooled jacket inside the single-crystal silicon growth furnace according to claim 7, characterized in that, Gibbs free energy satisfies the following condition: ， ， 。 9. The method for selecting the surface material of the water-cooled jacket inside the single-crystal silicon growth furnace according to claim 2, characterized in that, Other wall boundary conditions required to solve the oxygen concentration governing equation include: At the inlet wall, the quantitative boundary conditions for both silicon monoxide and carbon monoxide are 0; At the outlet wall, the concentration gradient is set to 0.

10. A device for selecting the surface material of a water-cooled jacket inside a single-crystal silicon growth furnace, comprising a processor and a memory, wherein the memory stores a software program, characterized in that... When the processor runs the software program on the memory, it can implement the method for selecting the surface material of the water-cooled sleeve inside the single-crystal silicon growth furnace as described in any one of claims 1 to 9.

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