Method for carrying out boron diffusion on monocrystalline silicon

Abstract

The invention provides a method for carrying out boron diffusion on monocrystalline silicon, which comprises the following steps: carrying out pretreatment on monocrystalline silicon, and growing a boron-loving thin film layer to obtain monocrystalline silicon of which the surface is a boron-loving thin film layer; reacting the monocrystalline silicon with the boron-loving thin film layer on the surface in the presence of oxygen and a boron source to obtain a B2O3 thin film layer covering the boron-loving thin film layer; the method comprises the following steps: carrying out a first boron diffusion reaction on monocrystalline silicon subjected to two times of film layer growth under an oxygen-free condition, carrying out cooling and film removal, carrying out a second boron diffusion reaction in the presence of oxygen, and carrying out a boron elimination reaction on the monocrystalline silicon under nitrogen and hydrogen conditions to obtain the boron-diffused monocrystalline silicon. According to the invention, the boron-loving thin film layer and the hydrogen-assisted propulsion technology are utilized, a deep PN junction and a high-sheet-resistance boron diffusion effect are realized under the condition that the temperature does not exceed 940 DEG C, the damage of high temperature to the silicon wafer body is effectively avoided, the conversion efficiency of the solar cell is improved, and convenience is provided for subsequent production of the solar cell with a complex structure.

Description

Technical Field

[0001] The present application belongs to the field of industrial chemistry, and in particular relates to a method for diffusing boron into single crystal silicon. Background Art

[0002] In the field of solar cell technology, with the growing global demand for renewable energy and the increasing awareness of environmental protection, how to improve the conversion efficiency of solar cells, reduce production costs and adapt to the design of more complex structures has become a hot topic of research. Solar cells, a device that can directly convert sunlight energy into electrical energy, are based on the artificially constructed PN junction structure to effectively separate photogenerated carriers (i.e., electrons and holes generated by light excitation), thereby forming a potential difference on both sides of the PN junction, thereby driving the generation of current.

[0003] In the production process of solar cells, the formation of PN junction is crucial, which directly affects the photoelectric conversion efficiency of the cell. At present, boron diffusion on the surface of N-type silicon is the mainstream method for forming high-quality PN junction. The boron diffusion process not only determines the depth of the PN junction, but also affects the doping concentration and sheet resistance of the single crystal silicon surface. These factors work together to affect the performance of solar cells.

[0004] Specifically, the junction depth of the PN junction is an important indicator for evaluating its quality. A deeper PN junction structure can effectively prevent the slurry from damaging the PN junction during the subsequent screen printing process, ensuring the stability and reliability of the battery. At the same time, a higher sheet resistance is also one of the key factors in improving the efficiency of solar cells. Sheet resistance is a physical quantity that measures the conductivity of the surface of single-crystal silicon, and its size is directly related to the recombination of the surface of single-crystal silicon. Generally speaking, lower surface concentrations and higher sheet resistance help reduce surface recombination, thereby improving photoelectric conversion efficiency. However, this also means that while pursuing high sheet resistance, it is necessary to ensure that the PN junction has a certain depth in order to achieve the best performance balance. Summary of the invention

[0005] In the prior art, long time and high temperature are often used to promote boron. The single crystal silicon formed by diffusion has low doping concentration, deep junction depth, and square resistance of 300Ω / □, which is a relatively ideal impurity distribution. However, as the promotion time and temperature decrease, the surface concentration will increase, the junction depth will become shallower, and the square resistance will become smaller, which will directly lead to a decrease in the conversion efficiency of the solar cell. In addition, long-term high-temperature promotion will cause certain damage to the silicon substrate itself. At the same time, high temperature can easily destroy structures such as tunnel oxide layers, so when designing and manufacturing batteries with more complex structures such as BC, the boron diffusion process must be completed first, which has great limitations.

[0006] In response to the above technical problems, the present application provides a method for diffusing boron into single crystal silicon.

[0007] The specific technical solutions of this application are as follows:

[0008] A method for diffusing boron into single crystal silicon, comprising:

[0009] The single crystal silicon is subjected to pretreatment and the boron-philic thin film layer is grown to obtain the single crystal silicon with the boron-philic thin film layer on the surface;

[0010] The single crystal silicon with a boron-philic thin film layer on the surface is reacted in the presence of oxygen and a boron source to obtain a B2O3 thin film layer covering the boron-philic thin film layer;

[0011] The single crystal silicon that has undergone two thin film layer growths undergoes a first boron diffusion reaction in an oxygen-free condition, is cooled, and after the film is removed, undergoes a second boron diffusion reaction in the presence of oxygen. The single crystal silicon then undergoes a boron elimination reaction in the presence of nitrogen and hydrogen to obtain a boron-diffused single crystal silicon.

[0012] Furthermore, the pretreatment is double-sided texturing or double-sided polishing.

[0013] Furthermore, the growth of the boron-philic thin film layer includes: the single crystal silicon reacts in the presence of SiH4, B2H6, Ar and H2 to form a first boron-philic thin film layer on the surface of the single crystal silicon; the single crystal silicon with the first boron-philic thin film layer on the surface reacts in the presence of SiH4, B2H6, Ar and N2O at a reaction temperature of 300 to 400°C to obtain a second boron-philic thin film layer covering the first boron-philic thin film layer.

[0014] Furthermore, the thickness of the first boron-philic thin film layer is 5-10 nm, and the thickness of the second boron-philic thin film layer is 5-10 nm.

[0015] Furthermore, the single crystal silicon with a boron-philic thin film layer on the surface is reacted in the presence of oxygen and a boron source, the reaction temperature is 800-830° C., and the reaction pressure is 90Pa-150Pa.

[0016] Furthermore, the thickness of the B2O3 thin film layer is 5 to 10 nm.

[0017] Furthermore, the reaction temperature of the first boron diffusion reaction is 900-960° C., and the reaction time is 10-30 min.

[0018] Furthermore, the film removal is a wet process film removal.

[0019] Furthermore, the reaction temperature of the second boron diffusion reaction is 900-940° C., and the reaction time is 20-40 min.

[0020] Furthermore, the reaction temperature of the boron elimination reaction is 900-940° C., and the reaction time is 10-20 min.

[0021] Furthermore, after the boron elimination reaction is performed, the method further includes a step of etching the boron diffused single crystal silicon using HF.

[0022] Furthermore, the present application also provides a boron-diffused single crystal silicon obtained according to the above-mentioned method of diffusing boron into single crystal silicon.

[0023] Effects of the Invention

[0024] The present application uses a boron-philic thin film layer to assist in the first boron diffusion reaction. Compared with the traditional method of directly depositing B2O3 on the surface of single crystal silicon, more boron can be doped into the surface of single crystal silicon during the first step of deposition and oxygen-free advancement. The high-concentration boron in this area is used as the boron source for the second step of advancement, and a deeper PN junction can be prepared under low-temperature advancement conditions. And the second boron diffusion uses hydrogen as an auxiliary gas. Taking advantage of the fast diffusion rate of boron impurities in a hydrogen atmosphere, the precipitation of high-concentration boron on the outermost surface of SiO2 and single crystal silicon is accelerated. The reduction of the boron content in the SiO2 film layer can increase the protectiveness of the SiO2 film layer and increase the debugging window of subsequent wet processes; the reduction of the boron concentration on the surface of single crystal silicon can effectively increase the square resistance and improve the passivation effect of the boron diffusion process. At the same time, the low surface boron concentration is also conducive to processes such as laser mold opening. DETAILED DESCRIPTION

[0025] The present application is further described below in conjunction with examples. It should be understood that the examples are only used to further describe and illustrate the present application and are not used to limit the present application.

[0026] Unless otherwise defined, the technical and scientific terms in this specification have the same meaning as those generally understood by those skilled in the art. Although similar or identical methods and materials as described herein may be used in experiments or practical applications, materials and methods are described herein below. In the event of a conflict, the present specification including the definitions therein shall prevail. In addition, materials, methods and examples are provided for illustration only and are not restrictive. The present application is further described below in conjunction with specific embodiments, but is not intended to limit the scope of the present application.

[0027] The present application provides a method for diffusing boron into single crystal silicon, which comprises:

[0028] The single crystal silicon is subjected to pretreatment and the boron-philic thin film layer is grown to obtain the single crystal silicon with the boron-philic thin film layer on the surface;

[0029] The single crystal silicon with a boron-philic thin film layer on the surface is reacted in the presence of oxygen and a boron source to obtain a B2O3 thin film layer covering the boron-philic thin film layer;

[0030] The single crystal silicon that has undergone two thin film layer growths undergoes a first boron diffusion reaction in an oxygen-free condition, is cooled, and after the film is removed, undergoes a second boron diffusion reaction in the presence of oxygen. The single crystal silicon then undergoes a boron elimination reaction in the presence of nitrogen and hydrogen to obtain a boron-diffused single crystal silicon.

[0031] In a specific embodiment, the pretreatment is double-sided texturing or double-sided polishing. Double-sided texturing can increase the roughness of the surface of monocrystalline silicon, thereby more effectively capturing and absorbing sunlight and improving the conversion efficiency of radio and television. It can also enhance the adhesion between the surface of monocrystalline silicon and subsequent coatings, ensure the stability and durability of the coatings, and help the monocrystalline silicon to better dissipate heat during subsequent work, reducing the impact of temperature on battery performance. Double-sided polishing can ensure the consistency of the quality of the two surfaces of the material, avoiding the differences that may occur after single-sided polishing. At the same time, double-sided polishing can also reduce the curvature of monocrystalline silicon and improve the optical properties of monocrystalline silicon.

[0032] In a specific embodiment, the boron-philic thin film layer is grown by reacting the single crystal silicon in the presence of SiH4, B2H6, Ar and H2 to form a first boron-philic thin film layer on the surface of the single crystal silicon; the single crystal silicon with the first boron-philic thin film layer on the surface reacts in the presence of SiH4, B2H6, Ar and N2O to obtain a second boron-philic thin film layer covering the first boron-philic thin film layer, and the reaction temperature is 300-400°C, for example, 300°C, 305°C, 310°C, 315°C, 320°C, 325°C, 330°C, 335°C, 340°C, 345°C, 350°C, 355°C, 360°C, 365°C, 370°C, 375°C, 380°C, 385°C, 390°C, 395°C, 400°C. The movement rate of boron atoms in the boron-philic thin film layer is faster than that of directly diffusing on the surface of single crystal silicon, so that boron atoms can enter the interior of single crystal silicon more easily and quickly, thereby improving the efficiency of boron diffusion. Due to the presence of the boron-philic thin film layer, boron atoms can penetrate deeper into the interior of single crystal silicon when diffusing, which helps to form a deeper PN junction, and further ensures that the slurry will not destroy the structure of the PN junction in subsequent processes such as screen printing, thereby ensuring the stability and conversion efficiency of solar cells. By growing a boron-philic thin film layer on the surface of single crystal silicon, a better boron diffusion effect can be achieved at a lower temperature (about 900°C), thereby avoiding damage to single crystal silicon caused by high temperature and reducing production costs. And with the assistance of the boron-philic thin film layer, a deeper PN junction and high square resistance can be achieved at low temperatures, thereby improving the photoelectric conversion efficiency of solar cells.

[0033] In a specific embodiment, the thickness of the first boron-philic thin film layer is 5 to 10 nm, for example, 5 nm, 5.3 nm, 5.5 nm, 5.8 nm, 6 nm, 6.3 nm, 6.5 nm, 6.8 nm, 7 nm, 7.3 nm, 7.5 nm, 7.8 nm, 8 nm, 8.3 nm, 8.5 nm, 8.8 nm, 9 nm, 9.3 nm, 9.5 nm, 9.8 nm, and 10 nm. The thickness of the second boron-philic thin film layer is 5 to 10 nm, for example, 5 nm, 5.3 nm, 5.5 nm, 5.8 nm, 6 nm, 6.3 nm, 6.5 nm, 6.8 nm, 7 nm, 7.3 nm, 7.5 nm, 7.8 nm, 8 nm, 8.3 nm, 8.5 nm, 8.8 nm, 9 nm, 9.3 nm, 9.5 nm, 9.8 nm, 10 nm. When the thickness of the boron-philic thin film layer is within the range of 5 to 10 nm, it can more effectively promote the diffusion of boron atoms on the surface of single crystal silicon. It not only provides a good diffusion path for the boron element, but also maintains sufficient film stability, avoiding the obstruction of the diffusion of the boron element due to excessive thickness or the inability of the boron element to be effectively retained on the surface of single crystal silicon due to excessive thinness. At the same time, after completing its function of assisting diffusion, the boron-philic thin film layer can be easily removed by a wet process. A thinner film layer can reduce the time of wet processing and the consumption of chemical reagents, thereby reducing production costs.

[0034] In a specific embodiment, a single crystal silicon with a boron-philic thin film layer on the surface is reacted in the presence of oxygen and a boron source, and the reaction temperature is 800-830°C, for example, 800°C, 802°C, 804°C, 806°C, 808°C, 810°C, 812°C, 814°C, 816°C, 818°C, 820°C, 822°C, 824°C, 826°C, 828°C, 830°C. The boron element diffuses rapidly through the boron-philic thin film layer and reacts with oxygen to form a B2O3 thin film layer, which not only stably fixes the boron element, but also further ensures the uniformity of the distribution of the boron element on the surface of the single crystal silicon. By diffusing boron on the boron-philic thin film layer, effective boron diffusion can be achieved at a lower temperature, which helps to reduce the damage to the single crystal silicon body caused by high temperature and protect the integrity and performance of the single crystal silicon.

[0035] In a specific embodiment, a single crystal silicon with a boron-philic film layer on the surface is reacted in the presence of oxygen and a boron source to obtain a B2O3 film layer covering the boron-philic film layer. The B2O3 film layer is the main carrier of the boron source. By covering it on the boron-philic film layer, it can be ensured that the boron source can effectively diffuse into the interior of the single crystal silicon through the boron-philic film layer during the subsequent heat treatment process, and the B2O3 film layer serves as a storage and transmission layer for the boron source. The boron-philic film layer accelerates the movement rate of boron atoms. The two work together to significantly improve the efficiency and depth of boron diffusion. At the same time, the B2O3 film layer has a certain protective effect on the boron-philic film layer, which can prevent the boron-philic film layer from receiving unnecessary damage or destruction during the subsequent heat treatment.

[0036] In a specific embodiment, the thickness of the B2O3 film layer is 5 to 10 nm, for example, 5 nm, 5.3 nm, 5.5 nm, 5.8 nm, 6 nm, 6.3 nm, 6.5 nm, 6.8 nm, 7 nm, 7.3 nm, 7.5 nm, 7.8 nm, 8 nm, 8.3 nm, 8.5 nm, 8.8 nm, 9 nm, 9.3 nm, 9.5 nm, 9.8 nm, 10 nm. A thinner B2O3 layer helps to ensure the uniformity of boron diffusion. An overly thick B2O3 layer may increase the resistance to the diffusion of boron atoms, resulting in uneven diffusion and affecting the quality of the PN junction. This thickness can well balance the diffusion speed and uniformity, and can be more easily completely removed in the subsequent wet process to remove the film, reducing the surface stress and damage of the single crystal silicon that may be caused by an overly thick film layer.

[0037] In a specific embodiment, the reaction temperature of the first boron diffusion reaction is 900-960°C. For example, it may be 900°C, 903°C, 905°C, 908°C, 910°C, 913°C, 915°C, 918°C, 920°C, 923°C, 925°C, 928°C, 930°C, 933°C, 935°C, 938°C, 940°C, 943°C, 945°C, 948°C, 950°C, 953°C, 955°C, 958°C, and 960°C. Compared with the high temperature of more than 1000℃ required for traditional boron diffusion, setting the temperature at 900-960℃ can significantly reduce the thermal stress that single-crystalline silicon is subjected to during the diffusion process, thereby reducing damage to the single-crystalline silicon body. The low temperature environment helps to protect other structures in the single-crystalline silicon and avoid damage caused by high temperature. This is especially important for the subsequent production of solar cells with complex structures. At the same time, excessively high temperatures may increase the boron diffusion rate at the edge of the single-crystalline silicon, resulting in excessively high doping concentrations in the edge area. The reaction time is 10 to 30 min, for example, 10 min, 10.5 min, 11.5 min, 12 min, 12.5 min, 13 min, 13.5 min, 14 min, 14.5 min, 15 min, 15.5 min, 16 min, 16.5 min, 17 min, 17.5 min, 18 min, 18.5 min, 19 min, 19.5 min, 20 min, 20.5 min, 21 min, 21.5 min, 22 min, 22.5 min, 23 min, 23.5 min, 24 min, 24.5 min, 25 min, 25.5 min, 26 min, 26.5 min, 27 min, 27.5 min, 28 min, 28.5 min, 29 min, 29.5 min, and 30 min. A time that is too short may not allow boron to diffuse fully. Although a reaction time that is too long can increase the depth of diffusion, it will also increase production costs and equipment occupancy time. In addition, the boron concentration on the surface of single crystal silicon can be controlled within the reaction time to avoid excessive surface concentration that may cause difficulties in subsequent processing or affect battery performance.

[0038] In a specific embodiment, the film removal is a wet process, which removes the boron-philic film layer and B2O3 layer on the surface of the single crystal silicon. These film layers play an auxiliary role in the boron diffusion process, but if not removed, they may become impurities that affect the performance of solar cells.

[0039] In a specific embodiment, the wet process for removing the film is to use HF or a mixed solution thereof to dissolve the boron-philic film layer and the B2O3 layer.

[0040] In a specific embodiment, before the second boron diffusion reaction is performed, the process further includes reacting the removed single crystal silicon in the presence of BCl3 and O2, so that a layer of B2O3 film with a thickness of 5nm to 10nm is grown on the single crystal silicon. The B2O3 film serves as a boron source for supplementing boron during the subsequent second boron diffusion reaction, thereby preventing the boron that has diffused into the single crystal silicon from being reversely diffused to the outside of the single crystal silicon during the subsequent second boron diffusion reaction, thereby resulting in insufficient boron concentration in the single crystal silicon.

[0041] In a specific embodiment, the reaction temperature of the second boron diffusion reaction is 900-940° C., for example, 900° C., 903° C., 905° C., 908° C., 910° C., 913° C., 915° C., 918° C., 920° C., 923° C., 925° C., 928° C., 930° C., 933° C., 935° C., 938° C., 940° C. The diffusion rate of boron atoms in single crystal silicon is still relatively fast within this temperature range, and the boron atoms can be effectively pushed into the interior of the single crystal silicon to form a deeper PN junction, while maintaining a relatively high diffusion efficiency. The low temperature range of 900-940° C. significantly reduces the thermal damage to the single crystal silicon body, protects the integrity of the single crystal silicon, makes the process more gentle, and is conducive to the production of high-quality solar cells. The reaction time is 20 to 40 min, for example, 20 min, 20.5 min, 21 min, 21.5 min, 22 min, 22.5 min, 23 min, 23.5 min, 24 min, 24.5 min, 25 min, 25.5 min, 26 min, 26.5 min, 27 min, 27.5 min, 28 min, 28.5 min, 29 min, 29.5 min, 30 min, 30.5 min, 31 min, 31.5 min, 32 min, 32.5 min, 33 min, 33.5 min, 34 min, 34.5 min, 35 min, 35.5 min, 36 min, 36.5 min, 37 min, 37.5 min, 38 min, 38.5 min, 39 min, 39.5 min, and 40 min. During this period of time, boron atoms have enough time to diffuse inside the single crystal silicon, ensuring that the depth of the PN junction meets the requirements while maintaining a uniform distribution of boron concentration within the single crystal silicon, which is beneficial to improving the photoelectric conversion efficiency of solar cells. In addition, the low-temperature diffusion process optimizes the diffusion time to avoid thermal damage to the single crystal silicon body caused by excessive diffusion time, thereby protecting the integrity of the single crystal silicon.

[0042] In a specific embodiment, in the second boron diffusion reaction, by controlling the amount of oxygen introduced and the temperature, a SiO2 film layer can be formed on the surface of the single crystal silicon. The SiO2 film layer has good insulation and stability and can protect the boron-doped region of the single crystal silicon. In an oxygen environment, a portion of the high-concentration boron in the surface area of ​​the single crystal silicon will continue to diffuse into the interior of the single crystal silicon, and a portion of it will also enter the newly formed SiO2 film layer. This diffusion effect further deepens the penetration depth of boron in the silicon wafer, which is helpful for the quality of the PN junction, and makes the distribution of boron atoms in the single crystal silicon and the SiO2 film layer more reasonable, forming an ideal impurity concentration distribution with a low surface boron concentration and a gradually increasing concentration towards the inside.

[0043] In a specific embodiment, the reaction temperature of the boron elimination reaction is 900-940°C, for example, 900°C, 903°C, 905°C, 908°C, 910°C, 913°C, 915°C, 918°C, 920°C, 923°C, 925°C, 928°C, 930°C, 933°C, 935°C, 938°C, 940°C. By reducing the boron concentration on the surface of the single crystal silicon, the number of surface recombination centers can be reduced, thereby improving the passivation effect of the single crystal silicon, reducing the energy loss of the solar cell during operation, and improving the photoelectric conversion efficiency. In addition, within this temperature range, the diffusion rate of boron impurities in the SiO2 film layer will be accelerated. In the presence of hydrogen, the boron impurities can be more effectively volatilized from the SiO2 film layer and the surface of the single crystal silicon to the external air, which helps to reduce the boron concentration on the surface of the single crystal silicon and in the SiO2 film layer, thereby achieving a higher sheet resistance. The reaction time is 10 to 20 minutes, for example, 10 minutes, 10.5 minutes, 11.5 minutes, 12 minutes, 12.5 minutes, 13 minutes, 13.5 minutes, 14 minutes, 14.5 minutes, 15 minutes, 15.5 minutes, 16 minutes, 16.5 minutes, 17 minutes, 17.5 minutes, 18 minutes, 18.5 minutes, 19 minutes, 19.5 minutes, and 20 minutes. The reaction time allows the boron impurities to diffuse effectively in the hydrogen atmosphere and accelerates the precipitation of high-concentration boron on the outermost surface of SiO2 and the silicon wafer, and the diffusion rate of the boron impurities reaches a high level, which can effectively promote the volatilization of boron to the outside, thereby reducing the boron concentration on the silicon wafer surface and the SiO2 film layer.

[0044] In one embodiment, the boron elimination reaction can be carried out in

[0045] In a specific embodiment, after the deboration reaction, the step of etching the boron-diffused single crystal silicon with HF is also included. In the deboration reaction, most of the boron impurities have been volatilized through the oxygen-free propulsion process of nitrogen and hydrogen, but the SiO2 film layer still remains on the surface of the single crystal silicon, and the film layer needs to be removed to expose the treated single crystal silicon surface for subsequent processes. HF can effectively etch away the SiO2 film layer, and the damage to the single crystal silicon itself is small, and the boron doping distribution on the surface of the single crystal silicon can be further adjusted by HF etching.

[0046] The present application uses a boron-philic thin film layer to assist in the first boron diffusion reaction. Compared with the traditional method of directly depositing B2O3 on the surface of single crystal silicon, more boron can be doped into the surface of single crystal silicon during the first step of deposition and oxygen-free advancement. The high-concentration boron in this area is used as the boron source for the second step of advancement, and a deeper PN junction can be prepared under low-temperature advancement conditions. And the second boron diffusion uses hydrogen as an auxiliary gas. Taking advantage of the fast diffusion rate of boron impurities in a hydrogen atmosphere, the precipitation of high-concentration boron on the outermost surface of SiO2 and single crystal silicon is accelerated. The reduction of the boron content in the SiO2 film layer can increase the protectiveness of the SiO2 film layer and increase the debugging window of subsequent wet processes; the reduction of the boron concentration on the surface of single crystal silicon can effectively increase the square resistance and improve the passivation effect of the boron diffusion process. At the same time, the low surface boron concentration is also conducive to processes such as laser mold opening.

[0047] Example

[0048] The following is a detailed description of the implementation methods of the present application through specific examples, but the following content should not be construed as limiting the present application in any way. The substances used in the examples are all commercially available products unless otherwise specified.

[0049] Example

[0050] Prepare silicon wafers: Select N-type original silicon wafers with a resistivity of 12Ω·cm and a thickness of 130μm, perform double-sided polishing to ensure that the surface of the silicon wafer is flat and free of impurities, and use deionized water and a mixture of dilute hydrofluoric acid and nitric acid to thoroughly clean the silicon wafer to remove surface stains and oxides.

[0051] Boron-philic thin film growth: Put the double-sided polished silicon wafer into the boron diffusion equipment, and introduce SiH4, B2H6, Ar and H2 at 200℃, RF power 15W, RF frequency 13.56MHz to grow a 5nm thick boron-philic thin film layer containing boron hydride amorphous silicon on both sides of the silicon wafer. Then increase the temperature to 300℃, introduce SiH4, B2H6, Ar and N2O, and cover it with a 5-10nm thick BSG layer. Cool to room temperature and take out.

[0052] B2O3 film growth: BCl3 and O2 are introduced into the boron diffusion equipment at 90Pa and 800℃ to grow a 5nm thick B2O3 film on the boron-philic film layer.

[0053] Oxygen-free advancement: Continue oxygen-free advancement at 900°C for 10-30 minutes to allow boron to enter the surface area of ​​the silicon wafer through the boron-philic layer.

[0054] Removing the film layer: After cooling to room temperature, use 1% hydrochloric acid and 5% hydrofluoric acid to remove the B2O3 and BSG on the surface, then use a low-concentration NaOH solution with a concentration of 0.1% for alkaline washing, and then use ozone and hydrofluoric acid to treat the surface to remove the surface polysilicon film layer.

[0055] Aerobic advancement: Place the silicon wafer in a high-temperature furnace tube, first introduce BCl3 and O2 at 90Pa, 800℃, grow a 5nm thick B2O3 film on it, raise the temperature to 900℃ and introduce a large amount of oxygen, keep the temperature constant for 20 minutes, generate a SiO2 film layer and promote further diffusion of boron.

[0056] Anaerobic advancement and boron elimination: After extracting oxygen, nitrogen and hydrogen are introduced, and the temperature is kept constant at 900°C for 10 minutes to promote the volatilization of boron impurities and reduce the surface boron concentration.

[0057] Etching the SiO2 film layer: Use a 5% HF hydrofluoric acid solution to etch away the SiO2 film layer on the surface to obtain the required low-temperature boron diffusion sample.

[0058] Example 1

[0059] The difference between this embodiment and embodiment 1 is that the reaction temperature for growing the first boron-philic thin film layer is 250°C.

[0060] Example 2

[0061] The only difference between this embodiment and embodiment 1 is that the reaction temperature for growing the first boron-philic thin film layer is 300°C.

[0062] Example 3

[0063] The difference between this embodiment and embodiment 1 is that the reaction temperature for growing the second boron-philic thin film layer is 350°C.

[0064] Example 4

[0065] The only difference between this embodiment and embodiment 1 is that the reaction temperature for growing the second boron-philic thin film layer is 400°C.

[0066] Example 5

[0067] The only difference between this embodiment and embodiment 1 is that the reaction temperature for growing the B2O3 thin film layer is 815°C.

[0068] Example 6

[0069] The only difference between this embodiment and embodiment 1 is that the reaction temperature for growing the B2O3 thin film layer is 830°C.

[0070] Example 7

[0071] The only difference between this embodiment and embodiment 1 is that the reaction temperature of the first boron diffusion reaction is 930°C.

[0072] Example 8

[0073] The only difference between this embodiment and embodiment 1 is that the reaction temperature of the first boron diffusion reaction is 960°C.

[0074] Example 9

[0075] The only difference between this embodiment and embodiment 1 is that the reaction temperature of the second boron diffusion reaction is 920°C.

[0076] Example 10

[0077] The only difference between this embodiment and embodiment 1 is that the reaction temperature of the second boron diffusion reaction is 940°C.

[0078] Embodiment 11

[0079] The difference between this embodiment and embodiment 1 is that the reaction temperature of the boron elimination reaction is 920°C.

[0080] Example 12

[0081] The only difference between this embodiment and embodiment 1 is that the reaction temperature of the boron elimination reaction is 940°C.

[0082] Comparative Example 1

[0083] The only difference between this comparative example and Example 1 is that the reaction temperature for growing the first boron-philic thin film layer is 100°C.

[0084] Comparative Example 2

[0085] The only difference between this comparative example and Example 1 is that the reaction temperature for growing the first boron-philic thin film layer is 400°C.

[0086] Comparative Example 3

[0087] The only difference between this comparative example and Example 1 is that the reaction temperature for growing the second boron-philic thin film layer is 200°C.

[0088] Comparative Example 4

[0089] The only difference between this comparative example and Example 1 is that the reaction temperature for growing the second boron-philic thin film layer is 500°C.

[0090] Comparative Example 5

[0091] The only difference between this comparative example and Example 1 is that the reaction temperature for growing the B2O3 thin film layer is 700°C.

[0092] Comparative Example 6

[0093] The only difference between this comparative example and Example 1 is that the reaction temperature for growing the B2O3 thin film layer is 900°C.

[0094] Comparative Example 7

[0095] The only difference between this comparative example and Example 1 is that the reaction temperature of the first boron diffusion reaction is 800°C.

[0096] Comparative Example 8

[0097] The only difference between this comparative example and Example 1 is that the reaction temperature of the first boron diffusion reaction is 1000°C.

[0098] Comparative Example 9

[0099] The only difference between this comparative example and Example 1 is that the reaction temperature of the second boron diffusion reaction is 800°C.

[0100] Comparative Example 9

[0101] The only difference between this comparative example and Example 1 is that the reaction temperature of the second boron diffusion reaction is 1000°C.

[0102] Comparative Example 11

[0103] The difference between this comparative example and Example 1 is that the reaction temperature of the boron elimination reaction is 900°C.

[0104] Comparative Example 12

[0105] The difference between this comparative example and Example 1 is that the reaction temperature of the boron elimination reaction is 940°C.

[0106] Comparative Example 13

[0107] The difference between this comparative example and Example 1 is that the growth of the boron-philic thin film layer is not performed.

[0108] Comparative Example 14

[0109] The only difference between this comparative example and Example 1 is that the growth of the B2O3 thin film layer is not performed.

[0110]

[0111]

[0112] The above is only the preferred experimental example of the present application, and does not limit the present application in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent experimental example with equivalent changes. However, any simple modification, equivalent change and modification made to the above experimental examples based on the technical essence of the present application without departing from the content of the technical solution of the present application still falls within the protection scope of the technical solution of the present application.

Claims

1. A method for diffusing boron into single crystal silicon, wherein: include: The single crystal silicon is subjected to pretreatment and the boron-philic thin film layer is grown to obtain the single crystal silicon with the boron-philic thin film layer on the surface; The single crystal silicon with a boron-philic thin film layer on the surface is reacted in the presence of oxygen and a boron source to obtain a B2O3 thin film layer covering the boron-philic thin film layer; The single crystal silicon that has undergone two thin film layer growths undergoes a first boron diffusion reaction in an oxygen-free condition, is cooled, and after the film is removed, undergoes a second boron diffusion reaction in the presence of oxygen. The single crystal silicon then undergoes a boron elimination reaction in the presence of nitrogen and hydrogen to obtain a boron-diffused single crystal silicon.

2. The method according to claim 1, wherein: The pretreatment is double-sided texturing or double-sided polishing.

3. The method according to claim 1, wherein: The boron-philic thin film layer growth comprises: The single crystal silicon reacts in the presence of SiH4, B2H6, Ar and H2 at a reaction temperature of 200 to 300° C. to form a first boron-philic thin film layer on the surface of the single crystal silicon; The single crystal silicon with the first boron-philic film layer on the surface reacts in the presence of SiH4, B2H6, Ar and N2O at a reaction temperature of 300-400° C. to obtain a second boron-philic film layer covering the first boron-philic film layer.

4. The method according to claim 3, wherein: The thickness of the first boron-philic thin film layer is 5-10 nm, and the thickness of the second boron-philic thin film layer is 5-10 nm.

5. The method according to claim 1, wherein: The single crystal silicon with a boron-philic thin film layer on the surface is reacted in the presence of oxygen and a boron source, the reaction temperature is 800-830° C., and the reaction pressure is 90Pa-150Pa.

6. The method according to claim 5, wherein: The thickness of the B2O3 thin film layer is 5 to 10 nm.

7. The method according to claim 1, wherein: The reaction temperature of the first boron diffusion reaction is 900-960° C., and the reaction time is 10-30 minutes.

8. The method according to claim 1, wherein: The film removal is a wet process film removal.

9. The method according to claim 1, wherein: The reaction temperature of the second boron diffusion reaction is 900-940° C., and the reaction time is 20-40 minutes.

10. The method according to claim 1, wherein: The reaction temperature of the boron elimination reaction is 900-940° C., and the reaction time is 10-20 minutes.

11. The method according to claim 1, wherein: After the boron elimination reaction is performed, the method further includes etching the boron diffused single crystal silicon using HF. 12 . A boron-diffused single crystal silicon obtained by the method for diffusing boron into single crystal silicon according to claim 1 .

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