Method for manufacturing diffusion film for semiconductor device

Abstract

The application discloses a manufacturing method of diffusion film for semiconductor devices, which realizes the simultaneous diffusion of P region and N region on the same surface of a silicon wafer in a diffusion process of semiconductor devices, and can form a diffusion impurity source with radial concentration gradient by the combination of thin films with different impurity concentrations, so as to realize the radial diffusion of semiconductor devices with different concentrations. The radial breakdown voltage deviation of PN junction caused by the radial resistivity difference of the silicon wafer substrate in the production of the silicon wafer by the Czochralski method is reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device manufacturing, and more specifically to a method for manufacturing a diffusion thin film for semiconductor devices. Background Technology

[0002] The semiconductor device industry is now entering the post-Moore era, with the main development trend being driven by four wheels: advanced process technology, advanced packaging, new materials, and architectural innovation. Breakthroughs are being made in both high performance and low cost, and global competition is characterized by high-end monopoly, mid-range competition, and a red ocean in the low-end market.

[0003] Diffusion technology plays a crucial role in semiconductor device doping processes, directly determining the performance and reliability of the device. Semiconductor diffusion refers to the process where impurity atoms from the surface of a silicon wafer diffuse into the wafer body under high temperature, forming a specific doping concentration and impurity gradient. The magnitude of this concentration and gradient directly determines the physical properties of the semiconductor device. Common impurity types used in silicon chip diffusion processes include phosphorus, boron, gallium, and aluminum, among others.

[0004] Existing diffusion processes, based on the impurity source, primarily categorize them as solid-state, liquid-state, and gaseous-state sources. Currently, selective doping in semiconductor device manufacturing requires the use of semiconductor photolithography and etching processes to create a barrier layer. As product standards become increasingly stringent, semiconductor devices often employ multiple photolithography and etching processes to achieve multi-layer, multi-region doping for higher performance. Each doping step necessitates an additional photolithography and etching step, leading to ever-increasing production costs. Furthermore, multiple photolithography and etching processes inevitably result in repeated chip exposure and high-temperature diffusion, directly increasing the risk of contamination and high-temperature stress on the semiconductor device, thus impacting production yield and reliability.

[0005] Liquid and gaseous sources adsorb impurity atoms onto the surface of a semiconductor silicon wafer via spin coating in an emulsion state or gas transport. These impurity atoms then diffuse into the silicon wafer at high temperatures. Therefore, to achieve selective diffusion, a barrier layer must be formed on the silicon wafer surface through high-temperature deposition or oxidation. The barrier layer in the areas requiring diffusion is then removed via photolithography and etching, while the barrier layer remains in other areas, thus achieving selective diffusion.

[0006] The solid-state diffusion market is dominated by paper-based diffusion, currently used primarily in vertically oriented power diodes. It typically diffuses across the entire silicon wafer, eliminating the need for a barrier layer. The manufacturing process usually employs a spray coating technique, directly adsorbing the desired impurity source onto the paper. However, the presence of the paper necessitates cutting it for selective diffusion. Cutting creates burrs that affect diffusion accuracy. Furthermore, to ensure stability, the paper is typically thick, requiring a certain weight to fix the diffusion position. This weight is usually applied to a thick silicon wafer, which can deform or even displace the small area of ​​the paper source after cutting, resulting in insufficient diffusion accuracy. Therefore, it can only achieve whole-surface diffusion, not selective diffusion. Additionally, the spray coating process results in relatively high surface roughness, leading to significant variations in diffusion concentration and gradient, which is detrimental to the performance and consistency of semiconductor devices.

[0007] Meanwhile, liquid and gaseous sources, due to their use of coating and gas transport, involve contact with the entire silicon wafer surface, thus preventing selective diffusion. Solid-state paper sources can be achieved through shearing, but since solid boron paper sources typically use B2O3 as the boron source, it is prone to moisture absorption. Storage, processing, and use all require strict control of the moisture content in the air. If the processing is prolonged, B2O3 can easily absorb moisture from the air, leading to substandard product quality. After spraying, the paper requires an additional shearing process, making it even more difficult to achieve selective diffusion. Therefore, there are currently no usable selective diffusion paper sources on the market.

[0008] Therefore, in the diffusion process of semiconductor devices, how to perform selective diffusion doping to reduce the number of photolithography and etching processes in the semiconductor device manufacturing process, thereby reducing production costs and improving semiconductor device performance is an urgent problem to be solved. Summary of the Invention

[0009] The first aspect of the present invention provides a method for preparing a diffusion thin film for semiconductor devices, comprising: stirring a phosphorus source and / or a boron source and a modifier, and then forming a film by casting, wherein the modifier includes at least one of polyvinyl alcohol, polyethylene glycol, silicon dioxide, and aluminum oxide.

[0010] In some embodiments, the phosphorus source includes phosphorus oxides.

[0011] In some embodiments, the phosphorus source includes at least one of aluminum metaphosphate, silicon pyrophosphate, and other oxides of phosphorus.

[0012] In some embodiments, the boron source includes at least one of boron nitride and boron oxide.

[0013] In some embodiments, the diffusion film for semiconductor devices includes at least one of a phosphorus source diffusion film and a boron source diffusion film.

[0014] In some embodiments, the preparation method further includes slitting the film after it has been formed.

[0015] In some embodiments, the raw material of the phosphorus source diffusion film includes aluminum metaphosphate at a mass ratio of 45-85%.

[0016] In some embodiments, the raw material of the phosphorus source diffusion film includes 20-30% silicon pyrophosphate by mass.

[0017] In some embodiments, the raw material of the phosphorus source diffusion film includes silicon dioxide at a mass ratio of 8-20%.

[0018] In some embodiments, the raw material of the phosphorus source diffusion film includes 5-10% polyvinyl alcohol by mass. In some embodiments, the raw material of the phosphorus source diffusion film includes 5-10% polyethylene glycol by mass.

[0019] In some embodiments, the raw material of the boron source diffusion film includes 80-90% by mass of nano-boron nitride sheets.

[0020] In some embodiments, the raw material of the boron source diffusion film contains 5-10% alumina by mass.

[0021] In some embodiments, the raw material of the boron source diffusion film includes 5-10% polyvinyl alcohol by mass.

[0022] In some embodiments, the raw material of the boron source diffusion film includes 5-10% polyethylene glycol by mass.

[0023] In some embodiments, the stirring time in the mixing tank is 0.5-12 hours; and / or, the gap between the scrapers of the casting is 30-1500 μm; and / or, the casting speed is 0.3-1.0 m / min.

[0024] In some embodiments, the preparation method further includes compositing the slit semiconductor device with a diffusion thin film.

[0025] In some embodiments, after the composite is formed, a phosphorus source diffusion film and a boron source diffusion film are simultaneously present on a composite film.

[0026] In some embodiments, different concentrations of phosphorus sources are present simultaneously on a composite membrane after the composite is formed.

[0027] In some embodiments, different concentrations of boron sources are present simultaneously on a composite membrane after the composite is formed.

[0028] A second aspect of the present invention provides a method for fabricating a PN junction diode, comprising preparing a diffusion film for semiconductor devices according to the aforementioned preparation method, and then diffusion of the diffusion film for semiconductor devices onto a silicon wafer.

[0029] In some embodiments, the diffusion film for semiconductor devices is a composite film containing both a phosphorus source diffusion film and a boron source diffusion film, which are diffused on the silicon wafer to form P-regions and N-regions, respectively.

[0030] In some embodiments, the diffusion film for the semiconductor device is a composite film containing different concentrations of phosphorus or boron sources, which is diffused on the silicon wafer to form a P-region or N-region with a radial gradient.

[0031] The production process implemented by this invention is as follows: Figure 1 Since traditional B2O3 is prone to moisture absorption and unstable during processing, this invention uses nano-boron nitride sheets as the boron doping source.

[0032] The reaction principle of boron nitride as a dopant source is as follows:

[0033] Because boron nitride has good stability, does not absorb moisture, and is easy to process, this invention uses boron nitride instead of boron oxide to achieve easier processing. When using it, customers can generate boron oxide simply by introducing oxygen, thus avoiding the difficulties of processing the original diffusion film.

[0034] The further reaction of this doping reaction is as follows:

[0035] The generated boron can diffuse into silicon at high temperatures, thus achieving the doping function of the semiconductor.

[0036] The diffusion process is usually carried out at high temperatures, generally above 1200°C, and even up to 1350°C in the laboratory (e.g., 1200~1350°C). Therefore, the two reactions can be carried out simultaneously without increasing the cost. It must be pointed out that since this invention adds boron nitride as a boron source, the chemical reaction process requires the conversion of boron nitride to boron oxide. Ordinary boron nitride is prone to agglomeration due to its large particle size, which leads to a decrease in the rate of chemical reaction (1) and a weakening of uniformity, thus affecting the reaction results. This invention uses nanosheet boron nitride as the material, which has high surface energy, good dispersion effect, high rate of chemical reaction (1), good uniformity, and better diffusion effect.

[0037] The diffusion film production process described in this invention is as follows: Figure 1 The specific description is as follows: Determine the impurity source required by the customer. If it is boron, use nano boron nitride sheets. If it is another source, mix it directly with the additives into the stirring process. Specific impurity sources can be phosphorus or boron. The specific formula is as follows: Phosphorus source diffusion film formulation mass ratio: Aluminum metaphosphate: 45-60%, Silicon pyrophosphate: 20-25%, Silicon dioxide: 8-15%, Polyvinyl alcohol: 3-8%, Polyethylene glycol: 3-8%; Boron source diffusion thin film formulation mass ratio: Nano boron nitride sheets: 75-85%, Alumina: 5-10%, Polyvinyl alcohol: 3-8%, Polyethylene glycol: 3-7%.

[0038] Add the above proportions to the mixing tank and stir for 0.5-12 hours. Then it can be taken out for the next process of casting.

[0039] The casting process mainly involves forming a film from the prepared slurry. The specific casting process parameters are as follows: Casting temperature: 30-200℃ Scraper gap: 30-1500μm Casting speed: 0.3-1.0 m / min.

[0040] The cast film can then be sent to the next process for slitting.

[0041] The slitting process can be customized according to customer needs, with different areas being cut off. Customers can then directly apply the cut film to the silicon wafer to achieve selective diffusion. Alternatively, different films can be cut off and then laminated to achieve simultaneous diffusion of two or more impurities or diffusion of different concentrations on the same surface.

[0042] Effects and advantages of this invention This invention achieves selective diffusion by manufacturing a diffusion film. Different patterns of diffusion sources can be achieved through different slicing, thus realizing diffusion in different regions. This feature directly eliminates the need for photolithography, oxidation, etching and other processes in traditional semiconductor device manufacturing processes, greatly reducing the number of processes in semiconductor chip production and lowering costs.

[0043] To achieve stable production of the boron diffusion source, this invention uses boron nitride instead of traditional boron oxide, avoiding the production difficulties caused by the hygroscopic properties of boron oxide. Since ordinary boron nitride powder is prone to agglomeration, the nano-boron nitride sheets used in this invention avoid the incomplete chemical reaction (1) caused by the agglomeration of traditional boron nitride powder. This achieves uniform diffusion in the semiconductor device.

[0044] Another advantage of this invention is that, since it does not use a traditional spraying process, it avoids the problem of excessive thickness in the composite product caused by the presence of paper, which would render it unusable. Furthermore, the spraying process, due to the high surface roughness of paper, cannot achieve low-concentration slurry spraying, thus making it impossible to realize diffusion sources with different concentration gradients on a single sheet of paper. Using a casting process, multiple thin films can be composited, achieving different concentrations on a single diffusion film. This avoids the PN junction differences caused by the radial resistivity variation of Czochralski-grown single-crystal silicon wafers during semiconductor power diode production, ensuring consistent breakdown voltage. The specific principle is explained in Implementation Example Two. Attached Figure Description

[0045] Figure 1 This is a production flow diagram of the diffusion film of the present invention.

[0046] Figure 2 This is a comparison between Example 1 and the traditional method of using the diffusion film of the present invention. The left side is the traditional method and the right side is the method used in the example.

[0047] Figure 3 This is a comparison of the diffusion film of the present invention in Example 2 with the conventional method. The left side is the conventional method, and the right side is the method used in the example. Detailed Implementation

[0048] To better understand the above-mentioned objectives, features, and advantages of this application, the application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. Many specific details are set forth in the following description to provide a thorough understanding of this application; the described embodiments are merely a part of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The term "and / or" as used herein includes all and any combination of one or more of the associated listed items.

[0050] This application provides a method for manufacturing a diffusion thin film for semiconductor devices.

[0051] The manufacturing method of this diffusion film is as follows: Figure 1 Firstly, this invention has two doping sources: the boron source uses nano boron nitride sheets, and the phosphorus source uses aluminum metaphosphate and silicon pyrophosphate.

[0052] Example 1 Phosphorus source diffusion film: The proportions of each substance are as follows: Aluminum metaphosphate: 45%, Silicon pyrophosphate: 25%, Silicon dioxide: 15%, Polyvinyl alcohol: 7.5%, Polyethylene glycol: 7.5%; The specific production process is as follows: Silicon pyrophosphate, lithium metaphosphate, and SiO2 are weighed according to the proportions after passing through a 200-300 mesh sieve and then poured into a ball mill jar for dry ball milling for 30-60 minutes.

[0053] Lithium metaphosphate powder: deionized water = 1 : 10 mass ratio. Heat the water to 85-90℃, pour it into a mixing tank and stir for 60-90 minutes until it is completely transparent and free of particles. Let it cool naturally to 40-50℃.

[0054] The solid and polyvinyl alcohol powder liquid after ball milling are poured into a mixing tank and stirred in two stages, with the specific stirring parameters as follows: Low-speed stirring: 80-100 r / min for 20 minutes, then increase the speed to 450-550 r / min for 60 minutes.

[0055] After stirring, let it stand for 10 minutes, then vacuum degas for 20 minutes. Transfer to casting process.

[0056] The mixed slurry is transferred to a casting machine. The substrate is a PET film containing silicone oil. The casting parameters are as follows: Conveyor belt speed: 0.8 m / min, using stainless steel scrapers with a scraper gap of 40μm, using a four-temperature zone for gradually increasing temperature baking, with the four temperatures being 80℃ for 4 minutes, 115℃ for 4 minutes, 155℃ for 4 minutes, and 175℃ for 4 minutes.

[0057] After baking, the film can be transferred and cut according to the customer's actual size and application.

[0058] Boron-source diffused thin films: The proportions of each substance are as follows: Nano boron nitride sheets: 75%, Alumina: 10%, Polyvinyl alcohol: 7.5%, Polyethylene glycol: 7.5%.

[0059] The specific production process is as follows: Nano boron nitride sheets and alumina are weighed according to the ratio after passing through a 200-300 mesh sieve, and then poured into a ball mill jar for dry ball milling for 35-65 minutes.

[0060] Polyvinyl alcohol powder: deionized water = 1 : 10 (mass ratio). When the water temperature is raised to 85-90℃, pour it into a mixing tank and stir for 60-90 minutes until it is completely transparent and free of particles. Let it cool naturally to 40-50℃.

[0061] After ball milling, the boron nitride, alumina solid, and polyvinyl alcohol powder liquid are poured into a mixing tank and stirred in two stages. The specific stirring parameters are as follows: Low-speed stirring: 80-100 r / min for 20 minutes, then increase the speed to 450-550 r / min for 60 minutes.

[0062] After stirring, let it stand for 10 minutes, then vacuum degas for 20 minutes. Transfer to casting process.

[0063] The mixed slurry is transferred to a casting machine. The substrate is a PET film containing silicone oil. The casting parameters are as follows: Conveyor belt speed: 0.8 m / min, using stainless steel scrapers with a scraper gap of 40μm, using a four-temperature zone for gradually increasing temperature baking, with the four temperatures being 80℃ for 4 minutes, 115℃ for 4 minutes, 155℃ for 4 minutes, and 175℃ for 4 minutes.

[0064] After baking, the film can be transferred and cut according to the customer's actual size and application.

[0065] Figure 2 This is a comparative introduction to the production of diffusion films using the method of Example 1 and conventional methods.

[0066] Traditional methods require the following process to produce silicon wafers: After the wafers are prepared, a barrier oxidation is first performed. The silicon wafers are placed in a high-temperature furnace and oxygen is introduced to form an oxide layer on their surface (1) to form a subsequent diffusion barrier layer. After the oxide barrier layer is completed, a portion of the surface oxide layer is removed by photolithography (the oxide layer on the left side is removed in the figure). Then, surface doping is performed using a gaseous or latex liquid source, usually boron diffusion, i.e., using a boron source. Due to the presence of the barrier layer, the impurities on the right are blocked by the oxide layer, and the impurities on the left diffuse to form a P-region (2).

[0067] After completing the P-region diffusion, a barrier layer oxidation is repeated. After the oxide layer is formed, photolithography diffusion is performed. The photolithography area is changed to the right side, that is, the barrier layer on the right side will be removed, while the barrier layer on the left side is retained. Then, doping is performed through a gaseous or latex liquid source. Usually, a phosphorus source is used for phosphorus diffusion. Due to the presence of the barrier layer, the impurities on the left side are blocked by the oxide layer, and the impurities on the right side diffuse to form the N region (3).

[0068] After completion, the barrier layer is removed, and metal is evaporated or chemically plated on the P region (2) and N region (3) to complete the fabrication of the entire PN junction diode chip.

[0069] The method of the present invention is as follows Figure 2 The prepared silicon wafer is directly attached to the left and right sides by the slit phosphorus diffusion film (5) and boron diffusion film (4), and then placed in a high-temperature furnace to directly complete the diffusion of impurity atoms to form P region (6) and N region (7). After completion, metal is evaporated or chemically plated on P region (6) and N region (7) to complete the manufacturing of the entire PN junction diode chip.

[0070] As can be seen in Example 1, the diffusion film manufactured by the present invention can be directly diffused in different regions without the need for cumbersome barrier layer oxidation and photolithography processes. This reduces manufacturing steps, lowers the contamination and stress of these processes, and enables low-cost and high-reliability lateral diode chip production.

[0071] Example 2 Low-concentration boron source diffusion film formulation: The proportions of each substance are as follows: Nano boron nitride sheets: 75%, Alumina: 10%, Polyvinyl alcohol: 7.5%, Polyethylene glycol: 7.5%.

[0072] Medium-concentration boron source diffusion film formulation: The proportions of each substance are as follows: Nano boron nitride sheets: 80%, Alumina: 5%, Polyvinyl alcohol: 7.5%, Polyethylene glycol: 7.5%.

[0073] High-concentration boron source diffusion film formulation: The proportions of each substance are as follows: Nano boron nitride sheets: 85%, Alumina: 5%, Polyvinyl alcohol: 5%, Polyethylene glycol: 5%.

[0074] Based on the above three formulas, the following production process is adopted: Nano boron nitride sheets and alumina are weighed according to the ratio after passing through a 200-300 mesh sieve, and then poured into a ball mill jar for dry ball milling for 35-65 minutes.

[0075] Polyvinyl alcohol powder: deionized water = 1 : 10 (mass ratio). When the water temperature is raised to 85-90℃, pour it into a mixing tank and stir for 60-90 minutes until it is completely transparent and free of particles. Let it cool naturally to 40-50℃.

[0076] After ball milling, the boron nitride, alumina solid, and polyvinyl alcohol powder liquid are poured into a mixing tank and stirred in two stages. The specific stirring parameters are as follows: Low-speed stirring: 80-100 r / min for 20 minutes, then increase the speed to 450-550 r / min for 60 minutes.

[0077] After stirring, let it stand for 10 minutes, then vacuum degas for 20 minutes. Transfer to casting process.

[0078] The mixed slurry is transferred to a casting machine. The substrate is a PET film containing silicone oil. The casting parameters are as follows: Conveyor belt speed: 0.8 m / min, using stainless steel scrapers with a scraper gap of 40μm, using a four-temperature zone for gradually increasing temperature baking, with the four temperatures being 80℃ for 4 minutes, 115℃ for 4 minutes, 155℃ for 4 minutes, and 175℃ for 4 minutes.

[0079] After baking, three types of boron diffusion films with high, medium, and low concentrations are obtained.

[0080] The high-concentration boron diffusion film was cut into 4-inch diameter (100mm) diffusion films using a mold, and then a 67mm cavity was cut out inside to form a ring with an outer diameter of 100mm and an inner diameter of 67mm.

[0081] Take out the medium-concentration boron diffusion film and cut it into a diameter of 70 mm using a mold. Then cut out a 34 mm hole inside it to form a ring with an outer diameter of 70 mm and an inner diameter of 34 mm.

[0082] Take out the low-concentration boron diffusion film and cut it into a circular diffusion film with a diameter of 40 mm using a mold.

[0083] The high, medium, and low concentration boron diffusion films are aligned with each other, double-sided adhesive is applied to the surface, and a rolling process is used to stack them into a 100mm diffusion film. This film is the boron diffusion film with a low concentration in the middle and a high concentration in the outer ring.

[0084] Reference Figure 3 This is a comparison of the boron diffusion film produced by the method in Example 2 with that produced by conventional methods.

[0085] Currently, most of the single-crystal silicon used in semiconductor devices is produced by the Czochralski process. As the number of impurity atoms in the crucible decreases with each step of the Czochralski process, and due to the temperature gradient that occurs during the process, there will inevitably be a difference in impurity concentration along the diameter of the silicon wafer, which is commonly referred to as radial resistivity. like Figure 3 In the diagram, the dashed lines representing the silicon wafer preparation indicate the radial concentration difference of N-type Czochralski single crystal silicon. It can be seen that due to the Czochralski single crystal process, the N-type silicon wafer has a high concentration in the center and a low concentration at the edges. In traditional diffusion methods, since the concentration of the diffusion source (8) is the same, the concentration of the P-region (9) formed by diffusion is also consistent radially, causing the PN junction to bend, and the corresponding space charge region to also bend. This results in the entire silicon wafer having a higher breakdown voltage at the edges than at the center, which can lead to downgrading or substandard breakdown voltage in diode chip production, affecting product yield.

[0086] The method of the present invention is as follows Figure 3 Impurity films (10) can be stacked in different layers to achieve different concentrations in different layers. After diffusion process, radial gradient is achieved. Specifically, a P region (11) with a certain impurity concentration gradient in the diameter direction is formed, which realizes that both the P region and the N region are curved to ensure consistent distance and consistent length of space charge region in each region.

[0087] The formulas for the breakdown voltage, maximum electric field strength, and depletion layer width of a diode are as follows:

[0088] Among them, VB: reverse breakdown voltage, which is the reverse voltage when the diode PN junction undergoes avalanche breakdown. It is the withstand voltage of the device and a core indicator for diffusion process control. Emax: Maximum electric field strength in the depletion layer. It refers to the maximum electric field strength in the depletion layer of the PN junction. When this value reaches the critical breakdown electric field of silicon, the device will undergo avalanche breakdown. Wd: Space charge region width, refers to the total width of the space charge region in the semiconductor when the PN junction is reverse biased.

[0089] The value of Emax is generally related to the material; for silicon, it is approximately 3 × 10⁻⁶. 5 V / cm.

[0090] Therefore, it can be concluded that the breakdown voltage is proportional to the width of the space charge region. In Example 2 of this invention, the Wd of the lateral region can be made consistent, while the traditional method results in a wider edge and a narrower middle. That is, the breakdown voltage of the N-substrate product is higher at the edge than in the middle using the traditional method. Because the width is consistent, the breakdown voltage in the middle and at the edge is consistent, thus achieving a consistent breakdown voltage of the diode chip.

Claims

1. A method for preparing a diffusion thin film for semiconductor devices, characterized in that, include: A phosphorus source and / or boron source and a modifier are stirred together, and then a film is formed by casting. The modifier includes at least one of polyvinyl alcohol, polyethylene glycol, silica, and alumina. Optionally, the phosphorus source includes phosphorus oxides; Optionally, the phosphorus source includes at least one of aluminum metaphosphate, silicon pyrophosphate, and other oxides of phosphorus; Optionally, the boron source includes at least one of boron nitride and boron oxide.

2. The preparation method according to claim 1, characterized in that, The diffusion film for semiconductor devices includes at least one of phosphorus-source diffusion films and boron-source diffusion films.

3. The preparation method according to claim 2, characterized in that, The preparation method also includes slitting the film after it is formed.

4. The preparation method according to claim 2, characterized in that, The raw material of the phosphorus source diffusion film includes aluminum metaphosphate at a mass ratio of 45-85%. Optionally, the raw material of the phosphorus source diffusion film includes silicon pyrophosphate at a mass ratio of 20-30%. Optionally, the raw material of the phosphorus source diffusion film includes silicon dioxide at a mass ratio of 8-20%; Optionally, the raw material of the phosphorus source diffusion film includes 5-10% polyvinyl alcohol by mass. Optionally, the raw material of the phosphorus source diffusion film includes 5-10% polyethylene glycol by mass.

5. The preparation method according to claim 1, characterized in that, The raw material of the boron source diffusion film includes 80-90% by mass of nano-boron nitride sheets; Optionally, the raw material of the boron source diffusion film contains 5-10% alumina by mass. Optionally, the raw material of the boron source diffusion film includes 5-10% polyvinyl alcohol by mass. Optionally, the raw material of the boron source diffusion film includes 5-10% polyethylene glycol by mass.

6. The preparation method according to claim 1, characterized in that, The stirring time in the mixing tank is 0.5-12 hours; and / or the gap between the scrapers of the casting is 30-1500 μm; and / or the casting speed is 0.3-1.0 m / min.

7. The preparation method according to claim 1, characterized in that, The preparation method further includes compositing the slit semiconductor device with a diffusion film; Optionally, after the composite, a phosphorus source diffusion film and a boron source diffusion film coexist on a single composite film; Optionally, different concentrations of phosphorus sources may coexist on a single composite membrane after the composite process. Optionally, different concentrations of boron sources may be present simultaneously on a composite membrane after the composite process.

8. A method for fabricating a PN junction diode, characterized in that, The method includes preparing a diffusion film for semiconductor devices according to any one of claims 1 to 7, and then using the diffusion film for semiconductor devices to diffuse on a silicon wafer.

9. The preparation method according to claim 8, characterized in that, The diffusion film for semiconductor devices is a composite film containing both phosphorus-source diffusion films and boron-source diffusion films, which are diffused on the silicon wafer to form P-regions and N-regions, respectively.

10. The preparation method according to claim 8, characterized in that, The diffusion film for the semiconductor device is a composite film containing different concentrations of phosphorus or boron sources, which is diffused on the silicon wafer to form a P-region or N-region with a radial gradient.

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