Boron diffusion method for monocrystalline silicon wafer
By cleaning and forming a hydrophilic alumina film with pretreatment solution, combined with annealing and surface treatment technology, the problem of uneven boron concentration during boron diffusion in single crystal silicon wafers is solved, and more efficient boron diffusion and the stability and hydrophilicity of the alumina film are achieved.
Patent Information
- Application Number
- CN202411828566.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-12
- Publication Date
- 2025-04-11
AI Technical Summary
During the boron diffusion process of existing single crystal silicon wafers, due to the formation of silicon oxide and the density of alumina film, the concentration of boron on the surface of the silicon is uneven, hindering the further diffusion of boron.
The silicon wafer is cleaned by pretreatment solution to form a hydrophilic alumina film, and annealing and surface treatment is performed using an annealing furnace and plasma surface treatment instrument to enhance the stability and hydrophilicity of the alumina film and promote the diffusion of boron.
It slows down the uneven concentration of boron on the silicon surface area, improves the diffusion concentration and depth of boron, and enhances the stability and hydrophilicity of the alumina film, achieving deeper cleaning and modification.
Smart Images
Figure CN119811988A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of boron diffusion of single crystal silicon slices, and specifically relates to a method for boron diffusion of single crystal silicon slices. Background Art
[0002] Boron diffusion of single crystal silicon wafers is an important semiconductor manufacturing technology, mainly used to change the conductivity of silicon wafers. Its principle is based on the chemical reaction between boron and silicon. Through high-temperature treatment, the boron material interacts with the surface of the silicon wafer, forming a boron-doped layer on the surface of the silicon wafer, thereby changing the conductivity of the silicon wafer.
[0003] In the existing boron diffusion process of single crystal silicon wafers, due to the formation of silicon oxide, the solid solubility of boron in silicon oxide is greater, which easily causes the segregation and enrichment of boron at the interface of silicon oxide and silicon, and prevents the further diffusion of boron to the silicon substrate; at the same time, some hydrophilic aluminum oxides used form a metal oxide film on the surface of single crystal silicon wafers, but aluminum oxide is a material with high hardness, high melting point and high chemical stability. After the film is formed on the surface of single crystal silicon, it may form a dense protective layer, which makes it difficult for the reducing agent to penetrate into the film and react with the aluminum oxide. Even if part of the aluminum oxide on the surface is reduced, the inside may still remain in an unreduced state and penetrate into the deep layer of the material.
[0004] Therefore, a method for boron diffusion in single crystal silicon wafers is proposed to address the above problems. Summary of the invention
[0005] The purpose of the present invention is to alleviate the phenomenon of uneven boron concentration in the silicon surface area, increase the diffusion concentration and depth of boron, enhance the stability and hydrophilicity of the aluminum oxide film, reduce the oxide on its surface, and penetrate into the deep layer of the material to achieve deeper cleaning and modification. The present application provides a method for boron diffusion in single crystal silicon wafers.
[0006] The technical solution adopted by the present invention is as follows: A method for boron diffusion in a single crystal silicon wafer comprises the following steps: Step 1: Prepare pretreatment solution 1, mix NaOH solution with ammonium hydroxide to form a solution of a certain concentration, immerse the silicon wafer in the solution, the solution temperature is usually controlled at 70℃-90℃, and the immersion time is 5-20 minutes to achieve alkaline polishing of the silicon wafer, and completely clean the silicon wafer to remove residual chemicals and pollutants; Step 2: Prepare pretreatment solution 2, mix deionized water, ammonia and hydrogen peroxide to form an alkaline environment, immerse the silicon wafer in the solution, maintain the temperature at 70-80°C for 5-10 minutes to remove particles and organic matter; Step 3: Prepare pretreatment solution 3, mix ionized water, hydrogen peroxide and hydrochloric acid to form acidic conditions, transfer the silicon wafer into the solution, and soak it at 70-80°C for 5-10 minutes to remove metal ions; Step 4: Prepare pretreatment solution 4, which is a diluted hydrofluoric acid solution. Immerse the silicon wafer in the diluted hydrofluoric acid for 5-10 minutes to remove the natural oxide layer on the surface of the silicon wafer and inhibit its re-formation. After each chemical treatment, rinse with a large amount of deionized water to completely remove the residual chemicals and prepare for the subsequent diffusion process. Step 5: Select hydrophilic and chemically stable aluminum oxide, use electron beam evaporation vapor deposition technology, use an electron beam heating source to evaporate the metal oxide material, and deposit it on the silicon wafer, so as to form a uniform and dense metal oxide film on the cleaned silicon wafer; Step 6: Annealing the aluminum oxide film in an annealing furnace, and using an inert gas as a protective atmosphere can prevent the aluminum oxide film from being oxidized or contaminated during the heat treatment process, so as to generate negative charges in the aluminum oxide, achieve a better passivation effect, and help enhance the stability and hydrophilicity of the aluminum oxide film; Step 7: Use a plasma surface treatment device to treat the aluminum oxide film, which can reduce the oxide on its surface and penetrate into the deep layer of the material to achieve deeper cleaning and modification; Step 8: Then spin-coat a liquid boron source on the hydrophilic metal oxide substrate and dry it on a hot stage. Place the silicon wafer coated with the liquid boron source in a high-temperature environment for heat treatment. At high temperatures, the boron material will chemically react with the surface of the silicon wafer to form a boron-doped layer, thereby changing the conductive properties of the silicon wafer.
[0007] Furthermore, the mixing ratio of deionized water, ammonia water and hydrogen peroxide in the second pretreatment solution is about 1:1:5 to 1:2:7.
[0008] Furthermore, the mixing ratio of the ionized water, hydrogen peroxide and hydrochloric acid in the pretreatment solution is about 1:1:6 to 1:1:7.
[0009] Furthermore, the inert gas is any one of argon or nitrogen.
[0010] Furthermore, the annealing temperature of the annealing furnace is set to 500° C., and the annealing time is 2 hours.
[0011] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. In the present invention, a layer of hydrophilic metal oxide is deposited on the cleaned N-type single crystal silicon wafer, which can block oxygen from entering the silicon substrate during the boron diffusion process, avoid the formation of silicon dioxide on the substrate surface, slow down the phenomenon of uneven boron concentration in the silicon surface area, and increase the diffusion concentration and depth of boron.
[0012] 2. In the present invention, an annealing furnace is used to anneal the aluminum oxide film, and an inert gas is used as a protective atmosphere to prevent the aluminum oxide film from being oxidized or contaminated during the heat treatment process, so as to generate negative charges in the aluminum oxide and achieve a better passivation effect, which helps to enhance the stability and hydrophilicity of the aluminum oxide film. The aluminum oxide film is treated with a sub-surface treatment instrument to reduce the oxide on its surface and penetrate into the deep layer of the material to achieve deeper cleaning and modification.
[0013] 3. In the present invention, the liquid boron source can be spin-coated more evenly on the hydrophilic metal oxide surface, which helps to improve the phenomenon of uneven resistance after diffusion on the silicon surface. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION
[0015] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example
[0016] Reference Figure 1A method for boron diffusion of a single crystal silicon wafer comprises: preparing a pretreatment solution 1, mixing a NaOH solution with ammonium hydroxide to form a solution of a certain concentration, immersing the silicon wafer in the solution, wherein the solution temperature is usually controlled at 70°C-90°C, and the immersion time is 5-20 minutes, so as to achieve alkaline polishing of the silicon wafer and completely clean the silicon wafer to remove residual chemicals and pollutants; preparing a pretreatment solution 2, mixing deionized water, ammonia water and hydrogen peroxide to form an alkaline environment, immersing the silicon wafer in the solution, maintaining the temperature at 70-80°C for 5-10 minutes to remove particles and organic matter; preparing a pretreatment solution 1, mixing a NaOH solution with ammonium hydroxide to form a solution of a certain concentration, immersing the silicon wafer in the solution, maintaining the temperature at 70-80°C for 5-10 minutes to remove particles and organic matter; Solution three, mix ionized water, hydrogen peroxide and hydrochloric acid to form acidic conditions, transfer the silicon wafer to the solution, and soak it at 70-80°C for 5-10 minutes to remove metal ions; prepare pretreatment solution four, treatment solution four is a diluted hydrofluoric acid solution, immerse the silicon wafer in the diluted hydrofluoric acid, usually for 5-10 minutes, to remove the natural oxide layer on the surface of the silicon wafer and inhibit its re-formation. After each chemical treatment, rinse with a large amount of deionized water to thoroughly remove residual chemicals and remove impurities and oxides on the surface of the silicon wafer, which can prepare for the subsequent diffusion process.
[0017] Reference Figure 1 , hydrophilic and chemically stable aluminum oxide is selected, and electron beam evaporation vapor deposition technology is used to evaporate the metal oxide material using an electron beam heating source, and deposit it on the silicon wafer, so as to form a uniform and dense metal oxide film on the cleaned silicon wafer; specifically, a layer of hydrophilic metal oxide is deposited on the cleaned N-type single crystal silicon wafer, which can block oxygen from entering the silicon substrate during the boron diffusion process, avoid the formation of silicon dioxide on the substrate surface, slow down the uneven concentration of boron in the silicon surface area, and increase the diffusion concentration and depth of boron.
[0018] Reference Figure 1 Using an annealing furnace to anneal the aluminum oxide film and using inert gas as a protective atmosphere can prevent the aluminum oxide film from being oxidized or contaminated during the heat treatment process, so as to generate negative charges in the aluminum oxide and achieve a better passivation effect, which helps to enhance the stability and hydrophilicity of the aluminum oxide film. Using a plasma surface treatment instrument to treat the aluminum oxide film can reduce the oxide on its surface and penetrate into the deep layer of the material to achieve deeper cleaning and modification.
[0019] Reference Figure 1 , and then spin-coat a liquid boron source on the hydrophilic metal oxide substrate and dry it on a hot stage. The silicon wafer coated with the liquid boron source is placed in a high-temperature environment for heat treatment. At high temperatures, the boron material will chemically react with the surface of the silicon wafer to form a boron-doped layer, thereby changing the conductive properties of the silicon wafer; specifically, the liquid boron source can be spin-coated more evenly on the hydrophilic metal oxide surface, which helps to improve the uneven resistance after diffusion on the silicon surface.
[0020] The implementation principle of the embodiment of the method for boron diffusion of a single crystal silicon wafer of the present application is as follows: The PVP film on the outermost side of the building decorative board is made of PVP resin, which has excellent waterproof performance and weather resistance. It can effectively prevent moisture penetration and protect the building decorative board from moisture and pollution. When the PVP film is damaged, the water molecules in the moisture may contact the plate-like water-absorbing resin from the damaged position, and the plate-like water-absorbing resin has a certain osmotic pressure, so that the water molecules can overcome the surface tension and enter the resin. Once the water molecules enter the water-absorbing resin, they will diffuse between the polymer chains of the resin and form hydrogen bonds with the hydrophilic groups, causing the volume of the water-absorbing resin to expand rapidly to form a gel-like substance. Several deformation holes can provide deformation space for the expansion of the water-absorbing resin, thereby further protecting the decorative board from moisture, thereby improving the moisture-proof effect of the building decorative board after film pasting.
[0021] The decorative panels produced by the above film pasting method have good protection, decoration and durability enhancement functions, and are also very economical and practical; the degree of adhesion is high, and the viscosity and expansion properties of the water-absorbing resin can make the film fit tightly with the building decorative panels to form a waterproof, dust-proof and anti-slip surface layer; the durability is good, the water-absorbing resin has good durability and stability, and can maintain the integrity and beauty of the film for a long time, and extend the service life of the decorative panels; the corrosion resistance is strong, the water-absorbing resin has a certain corrosion resistance, and can prevent the erosion of acid, alkali and other chemical substances, and protect the decorative panels from damage; it is economical and affordable, the price of the water-absorbing resin film is relatively low, which can effectively protect the investment in building decorative panels, and also reduce maintenance costs.
[0022] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.
[0023] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for boron diffusion in a single crystal silicon wafer, characterized in that: The steps include: Step 1: Prepare pretreatment solution 1, mix NaOH solution with ammonium hydroxide to form a solution of a certain concentration, immerse the silicon wafer in the solution, the solution temperature is usually controlled at 70℃-90℃, and the immersion time is 5-20 minutes to achieve alkaline polishing of the silicon wafer, and completely clean the silicon wafer to remove residual chemicals and pollutants; Step 2: Prepare pretreatment solution 2, mix deionized water, ammonia and hydrogen peroxide to form an alkaline environment, immerse the silicon wafer in the solution, maintain the temperature at 70-80°C for 5-10 minutes to remove particles and organic matter; Step 3: Prepare pretreatment solution 3, mix ionized water, hydrogen peroxide and hydrochloric acid to form acidic conditions, transfer the silicon wafer into the solution, and soak it at 70-80°C for 5-10 minutes to remove metal ions; Step 4: Prepare pretreatment solution 4, which is a diluted hydrofluoric acid solution. Immerse the silicon wafer in the diluted hydrofluoric acid for 5-10 minutes to remove the natural oxide layer on the surface of the silicon wafer and inhibit its re-formation. After each chemical treatment, rinse with a large amount of deionized water to completely remove the residual chemicals and prepare for the subsequent diffusion process. Step 5: Select hydrophilic and chemically stable aluminum oxide, use electron beam evaporation vapor deposition technology, use an electron beam heating source to evaporate the metal oxide material, and deposit it on the silicon wafer, so as to form a uniform and dense metal oxide film on the cleaned silicon wafer; Step 6: Annealing the aluminum oxide film in an annealing furnace, and using an inert gas as a protective atmosphere can prevent the aluminum oxide film from being oxidized or contaminated during the heat treatment process, so as to generate negative charges in the aluminum oxide, achieve a better passivation effect, and help enhance the stability and hydrophilicity of the aluminum oxide film; Step 7: Use a plasma surface treatment device to treat the aluminum oxide film, which can reduce the oxide on its surface and penetrate into the deep layer of the material to achieve deeper cleaning and modification; Step 8: Then spin-coat a liquid boron source on the hydrophilic metal oxide substrate and dry it on a hot stage. Place the silicon wafer coated with the liquid boron source in a high-temperature environment for heat treatment. At high temperatures, the boron material will chemically react with the surface of the silicon wafer to form a boron-doped layer, thereby changing the conductive properties of the silicon wafer.
2. The method for boron diffusion of a single crystal silicon wafer according to claim 1, characterized in that: The mixing ratio of deionized water, ammonia water and hydrogen peroxide in the second pretreatment solution is about 1:1:5 to 1:2:
7.
3. The method for boron diffusion of a single crystal silicon wafer according to claim 1, characterized in that: The mixing ratio of the ionized water, hydrogen peroxide and hydrochloric acid in the pretreatment solution is about 1:1:6 to 1:1:
7.
4. The method for boron diffusion of a single crystal silicon wafer according to claim 1, characterized in that: The inert gas is any one of argon or nitrogen.
5. A method for boron diffusion of a single crystal silicon wafer as claimed in claim 4, characterized in that: The annealing temperature of the annealing furnace is set to 500° C., and the annealing time is 2 h.