A method for manufacturing a boron film for reducing the thickness of a silicon wafer diffused borosilicate glass layer

Abstract

The present invention belongs to the technical field of silicon wafer diffusion films, and specifically relates to a method for manufacturing a boron film for reducing the thickness of a silicon wafer diffusion borosilicate glass layer, comprising the following steps: step 1: preparing a liquid boron diffusion source; step 2: precipitating the liquid boron diffusion source to form a solid boron diffusion film; step 3: post-processing, during which the solid boron diffusion film is dried at low temperature; step 4: cutting and forming the dried solid boron diffusion film; and step 5: sorting. Compared with the prior art, (1) after the silicon wafer is diffused using the boron diffusion film prepared by the present invention, only a very thin (not more than 50 nanometers) borosilicate glass layer is left on the surface of the silicon wafer, and no mechanical treatment is required; the mechanical stress of the silicon wafer will not be increased; (2) the product characteristics of the silicon wafer after diffusion treatment are improved; and (3) the yield of the final product chip is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon wafer diffusion films, and in particular relates to a method for manufacturing a boron film for reducing the thickness of a silicon wafer diffused borosilicate glass layer. Background Art

[0002] In the prior art, a boron diffusion source is used to perform silicon wafer diffusion treatment, and a thick borosilicate glass layer (thickness of more than 300 nanometers) is formed on the surface of the silicon wafer after diffusion. The thick borosilicate glass layer needs to be removed mechanically (sand blowing or grinding), which not only increases the complexity of the silicon wafer diffusion process, but also increases the mechanical stress of the silicon wafer due to sand blowing or grinding, and also easily causes damage and scrapping of the silicon wafer due to the sand blowing or grinding process. Summary of the invention

[0003] In view of the problem that a thick borosilicate glass layer exists on the surface of the silicon wafer after boron diffusion treatment and needs to be sandblasted or ground, the present invention provides a boron film manufacturing method for reducing the thickness of the silicon wafer diffused borosilicate glass layer.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is: a method for manufacturing a boron film for reducing the thickness of a borosilicate glass layer diffused on a silicon wafer, comprising the following steps:

[0005] Step 1: Preparation of liquid boron diffusion source: adding boron-containing raw materials, adhesives, separation agents and absorbents into a batching tank according to a certain proportion and mixing them to obtain a liquid boron diffusion source;

[0006] Step 2: Liquid boron diffusion source is precipitated to form a solid boron diffusion film;

[0007] Step 3: post-processing, during which the solid boron diffusion film is dried at low temperature;

[0008] Step 4: cutting and shaping the dried solid boron diffusion membrane;

[0009] Step 5: Sorting.

[0010] Preferably, the separating agent is aluminum oxide powder; the absorbent is aluminum hydroxide powder; and the weight ratio of the aluminum oxide powder to the aluminum hydroxide powder is 3:1 to 6:1.

[0011] Preferably, the boron-containing raw material includes one or more of methyl borate, ethyl borate, boron oxide, boron nitrate and boric acid.

[0012] Preferably, the adhesive is cellulose gum.

[0013] Preferably, in step 2, a liquid boron diffusion source is coated on the surface of the metal plate to form a solid boron diffusion film.

[0014] Preferably, in step three, the solid boron diffusion film is dried by infrared irradiation at a drying temperature lower than 100°C.

[0015] A method for reducing the thickness of the borosilicate glass layer on the surface of a silicon wafer after boron diffusion treatment, comprising laminating the surface-treated silicon wafer and the above-mentioned sorted solid boron diffusion film, wherein the solid boron diffusion film adheres to the surface of the silicon wafer to be diffused with boron; and then placing the laminate into a quartz boat for diffusion treatment.

[0016] Compared with the prior art, the advantages and positive effects of the present invention are:

[0017] Compared with the prior art, after the boron diffusion film prepared by the present invention is used to diffuse the silicon wafer, (1) only a very thin (less than 50 nanometers) borosilicate glass layer is left on the surface of the silicon wafer after the boron diffusion treatment, and no mechanical treatment (sandblasting or grinding) is required. The layer can be removed by acid immersion treatment, and the mechanical stress of the silicon wafer will not be increased.

[0018] (2) Improve the product characteristics after silicon wafer diffusion treatment: Because the process of mechanically removing the borosilicate glass layer is reduced, the factors affecting the characteristic control of the final product - the chip are reduced, which is more conducive to chip characteristic control;

[0019] (3) It is beneficial to the yield control of the final product chip: because mechanical processing is reduced during the production process, it is beneficial to reduce fragmentation and damage, which is beneficial to improving the chip manufacturing yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the following briefly introduces the drawings required for describing the embodiment. Figure 1 Flow chart of the method for manufacturing a boron film to reduce the thickness of the borosilicate glass layer diffused on a silicon wafer. DETAILED DESCRIPTION

[0021] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described below with reference to the accompanying drawings and embodiments.

[0022] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments of the following disclosure.

[0023] Example 1

[0024] The following is combined with Figure 1 The present invention is further described in the following Figure 1 A method for manufacturing a boron film for reducing the thickness of a silicon wafer diffused borosilicate glass layer is shown, comprising the following steps:

[0025] Step 1: Preparation of liquid boron diffusion source: adding boron-containing raw materials, adhesives, separation agents and absorbents into a batching tank according to a certain proportion and mixing them to obtain a liquid boron diffusion source;

[0026] Step 2: Liquid boron diffusion source is precipitated to form a solid boron diffusion film;

[0027] Step 3: post-treatment, during which the solid boron diffusion film is dried at low temperature (to prevent decomposition of the absorbent);

[0028] Step 4: cutting and shaping the dried solid boron diffusion membrane;

[0029] Step 5: Sorting.

[0030] The separating agent is aluminum oxide powder; the absorbing agent is aluminum hydroxide powder; and the weight ratio of the aluminum oxide powder to the aluminum hydroxide powder is 3:1.

[0031] The boron-containing raw material is methyl borate; the adhesive is cellulose gum.

[0032] The weight ratios of the boron-containing raw material (methyl borate), adhesive, separating agent and absorbent are 5%, 20%, 56.25% and 18.75% respectively.

[0033] In step 2, a liquid boron diffusion source is coated on the surface of the metal plate to precipitate and form a solid boron diffusion film.

[0034] In step 3, the solid boron diffusion film is dried by infrared irradiation and the drying temperature is lower than 100° C. (target 50° C.).

[0035] A method for reducing the thickness of the borosilicate glass layer on the surface of a silicon wafer after boron diffusion treatment, wherein the surface treated silicon wafer and the sorted solid boron diffusion film are stacked (the two have equal areas), the solid boron diffusion film is attached to the surface of the silicon wafer to be diffused with boron; and then the stack is loaded into a quartz boat for diffusion treatment.

[0036] During the diffusion process, aluminum hydroxide is heated at about 200°C to decompose into active alumina (γ-Al2O3) to absorb the "boron source" in the solid boron diffusion film (because active alumina has porosity, high dispersion and large specific surface area). In the subsequent diffusion process, the active alumina will slowly release the absorbed boron source. In this way, high concentrations of boron will not accumulate on the surface of the silicon wafer all at once, thereby reducing the thickness of the borosilicate glass layer on the surface of the silicon wafer.

[0037] Example 2

[0038] The difference between this embodiment and embodiment 1 is that the weight ratio of aluminum oxide powder to aluminum hydroxide powder is 6:1.

[0039] The boron-containing raw material is ethyl borate.

[0040] The weight ratios of the boron-containing raw material (ethyl borate), adhesive, separator and absorbent are 20%, 40%, 34.29% and 5.71% respectively.

[0041] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes for application in other fields. However, any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for reducing the thickness of the borosilicate glass layer on the surface of a silicon wafer after boron diffusion treatment, characterized in that: The surface treated silicon wafer and the prepared solid boron diffusion film are stacked, and the solid boron diffusion film is attached to the surface of the silicon wafer to be diffused with boron; then the stacked wafer is loaded into a quartz boat for diffusion treatment; The preparation of the solid boron diffusion film comprises the following steps: Step 1: Preparation of liquid boron diffusion source: adding boron-containing raw material, adhesive, separating agent and absorbent into a batching tank according to a certain proportion and mixing them evenly to obtain a liquid boron diffusion source; the separating agent is aluminum oxide powder; the absorbent is aluminum hydroxide powder; Step 2: Liquid boron diffusion source is precipitated to form a solid boron diffusion film; Step 3: post-processing, during which the solid boron diffusion film is dried at low temperature; Step 4: cutting and shaping the dried solid boron diffusion membrane; Step 5: sorting; During the diffusion treatment process, the absorbent aluminum hydroxide powder is heated and decomposes into active alumina γ-Al2O3 within the active alumina conversion temperature range. The active alumina absorbs the boron source in the solid boron diffusion film. In the subsequent diffusion treatment process, the active alumina will slowly release the absorbed boron source.

2. The method for reducing the thickness of the borosilicate glass layer on the surface of a silicon wafer after boron diffusion treatment according to claim 1, characterized in that: The weight ratio of the aluminum oxide powder to the aluminum hydroxide powder is 3:1 to 6:

1.

3. The method for reducing the thickness of the borosilicate glass layer on the surface of a silicon wafer after boron diffusion treatment according to claim 2, characterized in that: The boron-containing raw material includes one or more of methyl borate, ethyl borate, boron oxide, boron nitrate and boric acid.

4. The method for reducing the thickness of the borosilicate glass layer on the surface of a silicon wafer after boron diffusion treatment according to claim 3, characterized in that: The adhesive is cellulose gum.

5. The method for reducing the thickness of the borosilicate glass layer on the surface of a silicon wafer after boron diffusion treatment according to claim 4, characterized in that: In the step 2, a liquid boron diffusion source is coated on the surface of the metal plate to form a solid boron diffusion film.

6. The method for reducing the thickness of the borosilicate glass layer on the surface of a silicon wafer after boron diffusion treatment according to claim 5, characterized in that: In the step three, the solid boron diffusion film is dried by infrared irradiation and the drying temperature is lower than 100°C.

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