Preparation method of monocrystalline silicon and monocrystalline silicon

Abstract

The invention relates to the technical field of semiconductor material preparation, in particular to a preparation method of monocrystalline silicon and the monocrystalline silicon. The preparation method of the monocrystalline silicon comprises the following steps: S1, melting: heating a silicon raw material to melt the silicon raw material to obtain a silicon melt, and adding a cerium source and / or a titanium source into the silicon melt; and S2, crystal growth: introducing a seed crystal, enabling the silicon melt to grow a crystal through a straight pulling process, then carrying out necking, shouldering, equal-diameter growth and ending, and cooling to obtain the crystal. The cerium and / or the titanium are / is added into the silicon melt, and the cerium can effectively inhibit the volatilization process of SiO, reduce the oxygen content in the monocrystalline silicon, promote the ordered arrangement of silicon atoms in a lattice structure and accelerate the growth rate of the monocrystalline silicon; the titanium can effectively absorb oxygen in a high-temperature environment to form a stable oxide, so that the contact and reaction between the oxygen and the monocrystalline silicon are reduced, and the oxygen content in the monocrystalline silicon is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor material preparation, and in particular to a method for preparing single crystal silicon and the single crystal silicon. Background Art

[0002] With the continuous development of the world economy, the demand for efficient energy in modernization construction is growing. Photovoltaic power generation, as a green energy and a major energy source for sustainable development of mankind, is increasingly valued and vigorously developed by countries around the world. Monocrystalline silicon wafers, as a basic material for photovoltaic power generation, have a wide market demand.

[0003] As the cornerstone material of the semiconductor industry, the quality and stability of single crystal silicon are directly related to the overall performance and reliability of electronic products. However, the traditional single crystal silicon preparation process has encountered many difficulties in the pursuit of high yield and high quality. In particular, the oxygen element is an unavoidable impurity in single crystal silicon, and its content control has become a key factor restricting the improvement of material performance. Oxygen impurities not only affect the electrical properties of single crystal silicon, but may also induce crystal defects, significantly reducing the yield and reliability of the product. Therefore, exploring an innovative method that can simultaneously increase the yield of single crystal silicon and reduce its internal oxygen content is of immeasurable value in promoting the continuous progress of the semiconductor industry.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The first object of the present invention is to provide a method for preparing single crystal silicon to solve the technical problem of high oxygen content in single crystals prepared by existing methods. The method of the present invention can significantly reduce the oxygen content in single crystal silicon by adding cerium source and / or titanium source to the silicon melt after melting the material.

[0006] The second object of the present invention is to provide a single crystal silicon produced by the single crystal silicon production method as described above.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] A method for preparing single crystal silicon comprises the following steps:

[0009] S1. Melt: heating a silicon raw material to melt it to obtain a silicon melt, and adding a cerium source and / or a titanium source to the silicon melt;

[0010] S2. Crystal growth: Introduce seed crystals and grow crystals from the silicon melt through a Czochralski process, followed by necking, shouldering, equal-diameter growth and tailing, and obtain the crystals after cooling.

[0011] Preferably, the cerium source includes cerium oxide and / or cerium hydroxide.

[0012] Preferably, the added amount of the cerium source accounts for 0.01wt%-0.1wt% of the mass of the silicon raw material.

[0013] Preferably, the titanium source includes Ti-6Al-4V alloy and / or Ti-1100 alloy.

[0014] Preferably, the added amount of the titanium source accounts for 0.01wt%-1wt% of the mass of the silicon raw material.

[0015] Preferably, in step S1, the crucible in the melting process rotates at 0.5-1.5 rpm.

[0016] Preferably, in step S1, the power of the main heater in the melting process is 80-90 kW, the power of the bottom heater is 90-100 kW, and the temperature of the melt is 1450-1470°C.

[0017] Preferably, in step S1, the argon flow rate of the melting process is 70-120 slpm.

[0018] Preferably, in step S2, the heating power of the crystal growth process is 40-80 kW.

[0019] Preferably, in step S2, the crystal pulling speed in the crystal growth process is 70-120 mm / hr.

[0020] Preferably, in step S2, the crucible speed during the crystal growth process is 4-15 rpm, and the crystal speed is 4-11 rpm.

[0021] Preferably, in step S2, the argon gas flow rate during the crystal growth process is 70-120 slpm.

[0022] A single crystal silicon is prepared by the method for preparing single crystal silicon described in any one of the aforementioned embodiments.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention adds cerium and / or titanium to the silicon melt. The addition of cerium can regulate the chemical environment in the single crystal furnace and effectively inhibit the volatilization process of SiO, thereby greatly reducing the oxygen content in the single crystal silicon. The addition of cerium also promotes the orderly arrangement of silicon atoms in the lattice structure, accelerates the growth rate of the single crystal silicon, and achieves a double leap in output and quality. In a high temperature environment, titanium can effectively absorb oxygen and combine it with other substances in the furnace to form a stable oxide, thereby reducing the contact and reaction between oxygen and single crystal silicon and reducing the oxygen content in the single crystal silicon.

[0025] (2) In the conventional method, dopants are usually loaded into the crucible together with silicon raw materials, which is not conducive to the uniform dispersion of dopants. At the same time, the power of the melting process is relatively high, and the dopants are easy to volatilize, making it difficult to play a good role. However, in the present invention, cerium and / or titanium are added after the silicon raw materials are melted and before seeding. Cerium and / or titanium are added while the crucible is rotating, which is conducive to the uniform distribution of cerium and / or titanium in the silicon melt. At the same time, its volatilization can be avoided or reduced, thereby improving the effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 A schematic diagram of the position of the single crystal silicon oxygen content test surface provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present invention. If specific conditions are not indicated in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0029] A first aspect of the present invention provides a method for preparing single crystal silicon, comprising the following steps:

[0030] S1. Melt: heating a silicon raw material to melt it to obtain a silicon melt, and adding a cerium source and / or a titanium source to the silicon melt;

[0031] S2. Crystal growth: Introduce seed crystals and use the CZ process to grow crystals from the silicon melt, followed by necking, shouldering, equal-diameter growth and tailing, and the crystals are obtained after cooling.

[0032] The present invention introduces cerium and / or titanium into silicon melt to optimize the chemical environment of the single crystal silicon growth process, and can significantly reduce the oxygen content in the single crystal silicon. In the process of single crystal silicon growth, oxygen often exists in the silicon melt in the form of SiO. The introduction of cerium can inhibit the volatilization of SiO to a certain extent, thereby reducing the residual amount of oxygen in the single crystal silicon. The cerium element can also promote the orderly arrangement of silicon atoms in the lattice structure. The orderly crystal structure helps to reduce oxygen impurities caused by defects or non-uniform distribution, further reducing the oxygen content. The addition of cerium also accelerates the growth rate of single crystal silicon, increases the crystal pulling speed, and achieves a double leap in output and quality. Titanium can react with oxygen at high temperature, effectively adsorb and fix oxygen impurities in the single crystal growth environment, thereby reducing the oxygen content in the single crystal silicon.

[0033] Reducing the oxygen content helps to improve the electrical properties, mechanical properties and thermal stability of single crystal silicon, and improve the overall quality of single crystal silicon; the method of the present invention does not require complicated equipment modification and process adjustment, and is simple to operate and easy to implement; the cost of the dopant used is relatively low, and it can significantly reduce the scrap rate of single crystal silicon caused by excessively high oxygen content, thereby reducing production costs.

[0034] According to the present invention, cerium and / or titanium are added after the silicon raw material is melted and before seeding. The cerium and / or titanium are added when the crucible is rotating, which is beneficial for the uniform distribution of cerium and / or titanium in the silicon melt. At the same time, it can also avoid or reduce its volatilization in the high-temperature melting process, thereby improving the effect.

[0035] In some specific embodiments of the present invention, the cerium source used includes cerium oxide and / or cerium hydroxide.

[0036] In some specific embodiments of the present invention, the amount of cerium source added is 0.01wt%-0.1wt% of the mass of the silicon raw material, for example, it can be any point value among 0.01wt%, 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, and 0.1wt%, or a range value consisting of any two point values; this ratio range can not only give full play to the positive role of cerium element, but also avoid the adverse effects that may be caused by excessive doping; too little cerium source is difficult to achieve a good oxygen reduction effect; too much cerium source may cause the cerium content in the single crystal to be too high, thereby affecting the electrical and mechanical properties of the single crystal, such as resistivity, thermal conductivity, etc.; secondly, too much cerium source may form deposits on the surface of the single crystal, affecting the uniformity of the thermal field and the heat transfer efficiency, and then affecting the single crystal growth process; in addition, too much cerium source may also increase the corrosion and wear of the crystal pulling equipment, requiring more maintenance and replacement of parts.

[0037] In some specific embodiments of the present invention, the titanium source used includes Ti-6Al-4V alloy and / or Ti-1100 alloy; Ti-6Al-4V alloy has good high temperature performance and corrosion resistance, which helps to reduce the oxygen content in the furnace and improve the quality and purity of single crystal silicon; Ti-1100 alloy has good fatigue resistance and high temperature performance, can remain stable at high temperatures, and helps to reduce the oxygen content in the furnace. Adding an appropriate amount of titanium source can combine with the oxygen element in the single crystal to form a stable compound, thereby reducing the oxygen content in the single crystal; at the same time, the titanium source can also promote the growth of the single crystal and improve the crystallization quality, which helps to improve the quality and performance of the single crystal.

[0038] In some specific embodiments of the present invention, the amount of the titanium source added is 0.01wt%-1wt% of the mass of the silicon raw material, for example, it can be any point value among 0.01wt%, 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.5wt%, 0.6wt%, 0.8wt%, 1wt% or a range value composed of any two point values; if the amount of the titanium source added is too much, the titanium content in the single crystal will be too high, thereby affecting the electrical and mechanical properties of the single crystal, such as resistivity, thermal conductivity, etc.; at the same time, too much titanium source may also form deposits on the surface of the single crystal, affecting the uniformity of the thermal field and the heat transfer efficiency, thereby affecting the single crystal growth process; in addition, too much titanium source may also lead to increased corrosion and wear of the crystal pulling equipment, requiring more maintenance and replacement of parts; on the contrary, if the amount of the titanium source added is too little, the effect of reducing the oxygen content in the single crystal silicon may not be achieved.

[0039] In some specific embodiments of the present invention, before melting the material, the following steps are also included: the single crystal furnace is thoroughly cleaned and evacuated to ensure that there is no interference from impurities in the furnace.

[0040] In some specific embodiments of the present invention, in step S1, the crucible of the melting process is rotated to 0.5-1.5 rpm, for example, it can be any point value among 0.5 rpm, 0.7 rpm, 0.9 rpm, 1 rpm, 1.2 rpm, 1.4 rpm, 1.5 rpm or a range value consisting of any two point values.

[0041] In some specific embodiments of the present invention, in step S1, the power of the main heater in the melting process is 80-90kW, for example, it can be any point value among 80kW, 82kW, 84kW, 85kW, 86kW, 88kW, and 90kW, or a range value consisting of any two point values; the power of the bottom heater is 90-100kW, for example, it can be any point value among 90kW, 92kW, 94kW, 95kW, 96kW, 98kW, and 100kW, or a range value consisting of any two point values; the temperature of the melt is 1450-1470℃, for example, it can be any point value among 1450℃, 1455℃, 1458℃, 1460℃, 1462℃, 1465℃, and 1470℃, or a range value consisting of any two point values.

[0042] In some specific embodiments of the present invention, in step S1, the argon flow rate of the melting process is 70-120 slpm, for example, it can be any point value among 70 slpm, 80 slpm, 90 slpm, 100 slpm, 110 slpm, 120 slpm or a range value consisting of any two point values.

[0043] In some specific embodiments of the present invention, in step S2, the heating power of the crystal growth process is 40-80 kW, and the heating power refers to the main heater power. The crystal growth process only uses the main heater for heating. For example, the heating power can be any point value among 40 kW, 48 kW, 50 kW, 60 kW, 62 kW, 70 kW, and 80 kW, or a range value consisting of any two point values.

[0044] In some specific embodiments of the present invention, in step S2, the crystal pulling speed in the crystal growth process is 70-120 mm / hr, for example, it can be any point value among 70 mm / hr, 80 mm / hr, 90 mm / hr, 100 mm / hr, 110 mm / hr, 120 mm / hr or a range value consisting of any two point values.

[0045] In some specific embodiments of the present invention, in step S2, the crucible speed of the crystal growth process is 4-15rpm, for example, it can be any point value among 4rpm, 6rpm, 8rpm, 10rpm, 12rpm, 14rpm, and 15rpm, or a range value consisting of any two point values. If the crucible speed is too low, the temperature gradient of the silicon melt will be large, resulting in crystal rod dislocation, and the crucible speed is too fast, which will accelerate the reaction between the crucible and the silicon melt and affect the quality of single crystal silicon; the crucible speed is 4-11rpm, for example, it can be any point value among 4rpm, 6rpm, 8rpm, 10rpm, and 11rpm, or a range value consisting of any two point values. If the crystal rod speed is too low, the temperature gradient in the silicon melt will increase, resulting in crystal rod dislocation, and if the crystal rod speed is too fast, the crystal rod will be twisted, increasing the defective rate.

[0046] In some specific embodiments of the present invention, in step S2, the argon gas flow rate during the crystal growth process is 70-120 slpm, for example, it can be any point value among 70 slpm, 80 slpm, 90 slpm, 100 slpm, 110 slpm, 120 slpm, or a range value consisting of any two point values.

[0047] In some specific embodiments of the present invention, step S2 is followed by cutting and polishing steps to obtain a single crystal silicon wafer.

[0048] The second aspect of the present invention provides a single crystal silicon, which is prepared by the single crystal silicon preparation method described in any one of the above embodiments. The single crystal silicon provided by the present invention has low oxygen content and few crystal defects.

[0049] The embodiments of the present invention will be described in detail below in conjunction with specific examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If specific conditions are not specified in the examples, they are carried out under normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially. In the following examples and comparative examples, the main heater and the bottom heater are turned on during the melt process, and only the main heater is turned on during the crystal growth process.

[0050] Example 1

[0051] S1. Fill the high-purity silicon raw material (99.999%), hoist a full crucible of 980kg into the single crystal furnace, start the single crystal furnace and start melting the material according to the process settings, set the power of the main heater to 85kw, the power of the bottom heater to 95kw, the pot to 1rpm, the argon flow rate to 120slpm, adjust the furnace temperature to 1458-1460℃, and when the silicon raw materials in the furnace are melted, put the prepared cerium oxide into the single crystal furnace through the doping device at the neck cavity of the single crystal furnace, and the amount is 0.05wt% of the mass of the silicon raw materials;

[0052] S2. Introduce seed crystals and pull single crystal silicon through the direct pulling process, wherein the seeding power is 62kw, the equal-diameter power is 48kw, the crystal pulling speed is 90mm / hr, the crucible rotation is 4-6-5rpm (the crucible rotation starts at 4rpm, and when the equal-diameter length is 300mm, the crucible rotation is adjusted to 6rpm, and when the equal-diameter length is 2500mm, the crucible rotation is adjusted to 5rpm), the crystal rotation is 8rpm, and the argon flow rate is 100slpm. After the single crystal silicon growth is completed, post-processing steps such as cooling, cutting, and polishing are carried out to obtain single crystal silicon wafers.

[0053] Example 2

[0054] The only difference between Example 2 and Example 1 is that the cerium source and the silicon material are added at the same time, and the other conditions are the same as those of Example 1. The specific steps are as follows:

[0055] S1. Fill the crucible with high-purity silicon raw material (99.999%), 980kg of the material, and add cerium oxide in an amount of 0.05wt% of the mass of the silicon raw material, and hoist it into the single crystal furnace. Start the single crystal furnace and start melting the material according to the process settings. The power of the main heater is set to 85kw, the power of the bottom heater is set to 95kw, the pot is turned to 1rpm, the argon flow rate is 120slpm, and the furnace temperature is adjusted to 1458-1460℃ to completely melt the silicon raw material in the single crystal furnace;

[0056] S2. Introduce seed crystals and pull single crystal silicon through the direct pulling process, wherein the seeding power is 62kw, the equal-diameter power is 48kw, the crystal pulling speed is 90mm / hr, the crucible rotation is 4-6-5rpm (the crucible rotation starts at 4rpm, and when the equal-diameter length is 300mm, the crucible rotation is adjusted to 6rpm, and when the equal-diameter length is 2500mm, the crucible rotation is adjusted to 5rpm), the crystal rotation is 8rpm, and the argon flow rate is 100slpm. After the single crystal silicon growth is completed, post-processing steps such as cooling, cutting, and polishing are carried out to obtain single crystal silicon wafers.

[0057] Example 3

[0058] The only difference between Example 3 and Example 1 is that the amount of cerium source added is 0.01wt% of the mass of the silicon raw material. The other conditions are the same as those of Example 1. The specific steps are as follows:

[0059] S1. Fill the high-purity silicon raw material (99.999%), hoist a full crucible of 980kg into the single crystal furnace, start the single crystal furnace and start melting the material according to the process settings, set the power of the main heater to 85kw, the power of the bottom heater to 95kw, the pot to 1rpm, the argon flow rate to 120slpm, adjust the furnace temperature to 1458-1460℃, and when the silicon raw materials in the furnace are melted, put the prepared cerium oxide into the single crystal furnace through the doping device at the neck cavity of the single crystal furnace, and the amount is 0.01wt% of the mass of the silicon raw materials;

[0060] S2. Introduce seed crystals and pull single crystal silicon through the direct pulling process, wherein the seeding power is 62kw, the equal-diameter power is 48kw, the crystal pulling speed is 90mm / hr, the crucible rotation is 4-6-5rpm (the crucible rotation starts at 4rpm, and when the equal-diameter length is 300mm, the crucible rotation is adjusted to 6rpm, and when the equal-diameter length is 2500mm, the crucible rotation is adjusted to 5rpm), the crystal rotation is 8rpm, and the argon flow rate is 100slpm. After the single crystal silicon growth is completed, post-processing steps such as cooling, cutting, and polishing are carried out to obtain single crystal silicon wafers.

[0061] Example 4

[0062] The only difference between Example 4 and Example 1 is that the amount of cerium source added is 0.1wt% of the mass of the silicon raw material, and the other conditions are the same as those of Example 1. The specific steps are as follows:

[0063] S1. Fill the high-purity silicon raw material (99.999%), hoist a full crucible of 980kg into the single crystal furnace, start the single crystal furnace and start melting the material according to the process settings, set the main heater power to 85kw, the bottom heater power to 95kw, the pot speed to 1rpm, the argon flow rate to 120slpm, adjust the furnace temperature to 1458-1460℃, and when the silicon raw material in the furnace is melted, put the prepared cerium oxide into the single crystal furnace through the doping device at the neck cavity of the single crystal furnace, and the amount is 0.1wt% of the mass of the silicon raw material;

[0064] S2. Introduce seed crystals and pull single crystal silicon through the direct pulling process, wherein the seeding power is 62kw, the equal-diameter power is 48kw, the crystal pulling speed is 90mm / hr, the crucible rotation is 4-6-5rpm (the crucible rotation starts at 4rpm, and when the equal-diameter length is 300mm, the crucible rotation is adjusted to 6rpm, and when the equal-diameter length is 2500mm, the crucible rotation is adjusted to 5rpm), the crystal rotation is 8rpm, and the argon flow rate is 100slpm. After the single crystal silicon growth is completed, post-processing steps such as cooling, cutting, and polishing are carried out to obtain single crystal silicon wafers.

[0065] Example 5

[0066] S1. In this embodiment, Ti-6Al-4V alloy is selected as the titanium alloy additive, and the titanium alloy raw material is crushed into a powder with a particle size of 10-50 μm; high-purity silicon raw material (99.999%) is filled, and a full crucible of 980 kg is hoisted into the single crystal furnace, and the single crystal furnace is started to melt the material according to the process settings. The power of the main heater is set to 85 kW, the power of the bottom heater is set to 95 kW, the pot is turned to 1 rpm, the argon flow rate is 120 slpm, and the temperature in the furnace is adjusted to 1458-1460 ° C. When the silicon raw material in the furnace is melted, the prepared titanium alloy powder is put into the single crystal furnace through the doping device at the neck cavity of the single crystal furnace. The addition amount of titanium alloy accounts for 0.5wt% of the mass of the silicon raw material, which is 4.9 kg;

[0067] S2. Introduce seed crystals and pull single crystal silicon through the direct pulling process, wherein the seeding power is 62kw, the equal-diameter power is 48kw, the crystal pulling speed is 90mm / hr, the crucible rotation is 4-6-5rpm (the crucible rotation starts at 4rpm, and when the equal-diameter length is 300mm, the crucible rotation is adjusted to 6rpm, and when the equal-diameter length is 2500mm, the crucible rotation is adjusted to 5rpm), the crystal rotation is 8rpm, and the argon flow rate is 100slpm. After the single crystal silicon growth is completed, post-processing steps such as cooling, cutting, and polishing are carried out to obtain single crystal silicon wafers.

[0068] Example 6

[0069] The only difference between Example 6 and Example 5 is that the addition amount of Ti-6Al-4V alloy powder is 0.01wt% of the mass of silicon raw material, and the other conditions are the same as those of Example 5. The specific steps are as follows:

[0070] S1. In this embodiment, Ti-6Al-4V alloy is selected as the titanium alloy additive, and the titanium alloy raw material is crushed into a powder with a particle size of 10-50 μm; high-purity silicon raw material (99.999%) is filled, and a full crucible of 980 kg is hoisted into the single crystal furnace, and the single crystal furnace is started to melt the material according to the process settings. The power of the main heater is set to 85 kW, the power of the bottom heater is set to 95 kW, the pot is turned to 1 rpm, the argon flow rate is 120 slpm, and the temperature in the furnace is adjusted to 1458-1460 ° C. When the silicon raw material in the furnace is melted, the prepared titanium alloy powder is put into the single crystal furnace through the doping device at the neck cavity of the single crystal furnace, and the addition amount of titanium alloy accounts for 0.01 wt% of the mass of the silicon raw material;

[0071] S2. Introduce seed crystals and pull single crystal silicon through the direct pulling process, wherein the seeding power is 62kw, the equal-diameter power is 48kw, the crystal pulling speed is 90mm / hr, the crucible rotation is 4-6-5rpm (the crucible rotation starts at 4rpm, and when the equal-diameter length is 300mm, the crucible rotation is adjusted to 6rpm, and when the equal-diameter length is 2500mm, the crucible rotation is adjusted to 5rpm), the crystal rotation is 8rpm, and the argon flow rate is 100slpm. After the single crystal silicon growth is completed, post-processing steps such as cooling, cutting, and polishing are carried out to obtain single crystal silicon wafers.

[0072] Example 7

[0073] The difference between Example 7 and Example 5 is that the addition amount of Ti-6Al-4V alloy powder is 1wt% of the mass of silicon raw material, and the other conditions are the same as those of Example 5. The specific steps are as follows:

[0074] S1. In this embodiment, Ti-6Al-4V alloy is selected as the titanium alloy additive, and the titanium alloy raw material is crushed into a powder with a particle size of 10-50 μm; high-purity silicon raw material (99.999%) is filled, and a full crucible of 980 kg is hoisted into the single crystal furnace, and the single crystal furnace is started to melt the material according to the process settings. The power of the main heater is set to 85 kW, the power of the bottom heater is set to 95 kW, the pot is turned to 1 rpm, the argon flow rate is 120 slpm, and the temperature in the furnace is adjusted to 1458-1460 ° C. When the silicon raw material in the furnace is melted, the prepared titanium alloy powder is put into the single crystal furnace through the doping device at the neck cavity of the single crystal furnace, and the addition amount of titanium alloy accounts for 1wt% of the mass of the silicon raw material;

[0075] S2. Introduce seed crystals and pull single crystal silicon through the direct pulling process, wherein the seeding power is 62kw, the equal-diameter power is 48kw, the crystal pulling speed is 90mm / hr, the crucible rotation is 4-6-5rpm (the crucible rotation starts at 4rpm, and when the equal-diameter length is 300mm, the crucible rotation is adjusted to 6rpm, and when the equal-diameter length is 2500mm, the crucible rotation is adjusted to 5rpm), the crystal rotation is 8rpm, and the argon flow rate is 100slpm. After the single crystal silicon growth is completed, post-processing steps such as cooling, cutting, and polishing are carried out to obtain single crystal silicon wafers.

[0076] Comparative Example 1

[0077] Comparative Example 1 is similar to Example 1, except that no cerium source is added, and the other conditions are the same as those of Example 1. The specific steps are as follows:

[0078] S1. Fill the high-purity silicon raw material (99.999%) with 980kg of full crucible material and hoist it into the single crystal furnace. Start the single crystal furnace and start melting the material according to the process settings. Set the power of the main heater to 85kw, the power of the bottom heater to 95kw, the pot to 1rpm, the argon flow rate to 120slpm, and adjust the furnace temperature to 1458-1460℃ to completely melt the silicon raw material.

[0079] S2. Introduce seed crystals and pull single crystal silicon through the direct pulling process, wherein the seeding power is 62kw, the equal-diameter power is 48kw, the crystal pulling speed is 90mm / hr, the crucible rotation is 4-6-5rpm (the crucible rotation starts at 4rpm, and when the equal-diameter length is 300mm, the crucible rotation is adjusted to 6rpm, and when the equal-diameter length is 2500mm, the crucible rotation is adjusted to 5rpm), the crystal rotation is 8rpm, and the argon flow rate is 100slpm. After the single crystal silicon growth is completed, post-processing steps such as cooling, cutting, and polishing are carried out to obtain single crystal silicon wafers.

[0080] Test example

[0081] The single crystal silicon wafers prepared in each embodiment and comparative example were respectively taken, and the oxygen content of different surfaces of the single crystal silicon was detected by infrared spectrometer. The position of the test surface of the oxygen content in the single crystal silicon is as follows: Figure 1 The test results are shown in Table 1, and the unit of oxygen content is ppma.

[0082] Table 1

[0083]

[0084]

[0085] It can be seen from the data in Table 1 that the oxygen content of the single crystal silicon in the examples is lower than that in the comparison example 1, indicating that the addition of cerium source and titanium source can reduce the oxygen content in the single crystal silicon. Compared with the comparison example 1, the oxygen content in the example 1 is reduced by about 10%.

[0086] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing single crystal silicon, characterized in that: The following steps are involved: S1. Melt: heating a silicon raw material to melt it to obtain a silicon melt, and adding a cerium source and / or a titanium source to the silicon melt; S2. Crystal growth: Introduce seed crystals and grow crystals from the silicon melt through a Czochralski process, followed by necking, shouldering, equal-diameter growth and tailing, and obtain the crystals after cooling.

2. The method for preparing single crystal silicon according to claim 1, characterized in that: The cerium source includes cerium oxide and / or cerium hydroxide.

3. The method for preparing single crystal silicon according to claim 1, characterized in that: The added amount of the cerium source accounts for 0.01wt%-0.1wt% of the mass of the silicon raw material.

4. The method for preparing single crystal silicon according to claim 1, characterized in that: The titanium source includes Ti-6Al-4V alloy and / or Ti-1100 alloy.

5. The method for preparing single crystal silicon according to claim 1, characterized in that: The amount of the titanium source added is 0.01wt%-1wt% of the mass of the silicon raw material.

6. The method for preparing single crystal silicon according to claim 1, characterized in that: In step S1, at least one of the following characteristics is met: (1) The crucible speed of the melting process is 0.5-1.5 rpm; (2) The power of the main heater in the melting process is 80-90 kW, the power of the bottom heater is 90-100 kW, and the temperature of the melt is 1450-1470° C.; (3) In step S1, the argon gas flow rate of the melting process is 70-120 slpm.

7. The method for preparing single crystal silicon according to claim 1, characterized in that: In step S2, the heating power of the crystal growth process is 40-80 kW.

8. The method for preparing single crystal silicon according to claim 1, characterized in that: In step S2, the crystal pulling speed during the crystal growth process is 70-120 mm / hr; And / or, in step S2, the crucible speed during the crystal growth process is 4-15 rpm, and the crystal speed is 4-11 rpm.

9. The method for preparing single crystal silicon according to claim 1, characterized in that: In step S2, the argon gas flow rate during the crystal growth process is 70-120 slpm.

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

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