JPH04302419A - Manufacture of diffusion wafer - Google Patents

Abstract

PURPOSE:To provide a manufacture method of a diffusion wafer having less number of processes and less troubles regarding safety, sanitation and pollution. CONSTITUTION:Dopant particle 10 which is formed by attaching a dopant source 12 to a surface of powder particle 11 as release agent is interposed between laminated silicon wafers 20, 20 and diffusion heat treatment is carried out which is equivalent to forced diffusion. A dopant substance is diffused deeply and directly to a surface of the silicon wafer 20 by the use of dopant vapor which is generated from the dopant source 12 of the dopant particle 10. A process of deposition for diffusing dopant substance in advance to a surface layer of the silicon wafer 20 and a process of cleaning following it are omitted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor wafer in which dopant substances such as phosphorus and boron are diffused.

0002

[Prior Art] Diffusion wafers are usually manufactured by deposition,
It is manufactured through the following steps: cleaning, powder application, and intrusion diffusion. This manufacturing method will be explained based on FIG. 3.

Deposition is a process in which a dopant material is diffused into a shallow layer of the wafer 1. In this process,
For example, wafers 1 having a dopant source 2 such as POCl3 containing a dopant material deposited on their surfaces are arranged on a boat and heated. 1a represents a diffusion layer of dopant material.

After the deposition, the dopant source 2 remaining on the surface of the wafer 1 is washed away by a cleaning solution in the cleaning process, and powder made of quartz (SiO2) or silicon as a release agent is applied to the surface in the powdering process. Particles 3 are deposited. Then, by rearranging the wafers 1 in a polymerized state and performing a diffusion heat treatment, the diffusion layer 1a spreads to a deep layer. The process of overlapping the wafers 1 and diffusing the dopant material to a deep layer is called intrusion diffusion.

[0005]

[Means for Solving the Problems] In this method of manufacturing a diffusion wafer, it is necessary to line up a large number of wafers 1 on a boat during deposition. Moreover,
The wafers had to be rearranged during indentation diffusion, which was extremely unreasonable. In addition, the deposition process itself requires a relatively long processing time of about 5 to 6 hours, and when POCl3 is used as a dopant source, exhaust equipment with anti-pollution measures is required due to its toxicity. do. Furthermore, the cleaning process that follows the deposition also requires complete gas exhaust equipment and anti-pollution equipment, since the cleaning liquid contains harmful substances. Therefore, both processes require large installation costs and are also a factor in increasing the number of man-hours.

[0006] An object of the present invention is to provide a method for manufacturing diffusion wafers that can manufacture high-quality diffusion wafers with a small number of man-hours and has relatively few problems in terms of safety, hygiene, and pollution.

[0007]

[Means for Solving the Problems] The method for manufacturing a diffusion wafer of the present invention involves interposing dopant particles whose surfaces are coated with a dopant source on the surfaces of powder particles serving as a release agent between stacked wafers, and performing diffusion heat treatment. It is characterized by doing.

[0008]

[Operation] When stacked wafers are subjected to diffusion heat treatment, dopant vapor is generated from the surface coating dopant source of dopant particles interposed between the wafers, and is trapped between the wafers. Therefore, even if the dopant material is not deposited on the wafer surface, deep diffusion is performed on the wafer at a depth equivalent to or greater than the intrusion diffusion of the deposited wafer. Therefore, the deposition step and subsequent cleaning step are omitted.

[0009]

EXAMPLES The method of the present invention will be explained in detail below based on examples. FIG. 1 is a schematic diagram showing an example of a wafer manufacturing process according to the method of the present invention.

The method uses dopant particles 10 in a diffusion heat treatment of a silicon wafer 20. Dopant particles 1
No. 0 is one in which a solid dopant source 12 is coated on the surface of powder particles 11 as a release agent. The dopant particles 10 are manufactured, for example, by adding the powder particles 11 to a solution of the dopant source 12, evaporating the solvent while stirring, and then drying the solution. The manufactured dopant particles 10 are stored in a dry desiccator.

[0011] The powder particles 11 are made of quartz, silicon, or the like, and their particle size is usually 50 to 150 μm. As the dopant source 12, harmless P2 O5 or the like is desirable. The coating amount of the dopant source 12 is preferably 10 to 40% in terms of weight ratio to the powder particles 11. A low coverage of dopant source 12 reduces the diffusion surface concentration of silicon wafer 20 and increases its surface resistance. On the other hand, if the amount is too high, the diffusion surface concentration of the silicon wafer 20 will become excessive, resulting in insufficient surface resistance. Furthermore, the wafer surface may exhibit an abnormal appearance. Solid dopant source 1
In order to prevent the particles 2 from peeling off from the powder particles 11, it is desirable to use a silica-based binder such as Silanol (trade name). The silica binder is desirably added in an amount of about 2 to 10% in terms of weight ratio to the powder particles 11, and fixes the dopant source 12 on the surface of the powder particles 11.

In the diffusion heat treatment, dopant particles 10 are first sprinkled onto the surfaces of a plurality of silicon wafers 20 . This is done in the same way as powder application during conventional indentation diffusion. The amount of dopant particles 10 sprinkled is 1 to 10 mg expressed as a ratio to the wafer surface area.
/cm2 is desirable. If the amount of dopant particles 10 attached is small, the surface resistivity ρs' will vary widely within the surface of the silicon wafer 20, and the wafers will stick together. On the other hand, if the amount is too high, the diffusion surface concentration becomes too high, causing an abnormal appearance on the wafer surface.

After sprinkling of the dopant particles 10 is completed, the silicon wafers 20 are stacked and arranged in parallel, and a diffusion heat treatment corresponding to indentation diffusion is performed. This heat treatment generates dopant vapor from the dopant source 12 of the dopant particles 10. The dopant vapor is sealed between adjacent wafers 20 , 20 and diffuses the dopant material deep into the surface of wafer 20 . Therefore, even if the dopant material is not deposited on the surface of the wafer 20 in advance, a diffusion layer 21 equivalent to the diffusion layer 21 which is equivalent to pushing and diffusing the deposited wafer is formed on the wafer surface. The powder particles 11 prevent the wafers 20, 20 from sticking together. Also, since the dopant source 12 of the dopant particles 10 is a solid, it is possible to use harmless substances such as P2O5. As a result, POCl, a powerful drug,
3 (liquid), the problem of remaining unreacted POCl3 and generating Cl is eliminated. Therefore, safety and health problems and pollution problems are reduced, and ancillary equipment such as exhaust gas equipment is also simplified.

Next, the results of implementing this method will be explained. Particle size is 1
For 100 wt% of powder particles made of 00 μm quartz,
20w each of P2 O5 and silanol (trade name)
Binder particles coated with a ratio of t% and 5wt% were produced. This was applied to the surface of a silicon wafer with a diameter of 100 mm and a thickness of 500 μm at a rate of 0.2 g and 0.5 g per wafer.
After sprinkling at a ratio of 1.5 g, silicon wafers were arranged and subjected to diffusion heat treatment in the same manner as indentation diffusion. The heat treatment conditions were 1280°C x 150hr. The diffusion layer thickness xjc of the manufactured N type 40 to 50 Ωcm diffusion wafer,
The surface specific resistance ρs' was measured. For comparison, similar measurements were also performed on diffusion wafers manufactured by performing deposition, cleaning, powder application, and forced diffusion on the same silicon wafer. The measurement results are shown in Table 1. Further, FIG. 2 shows the surface resistivity distribution for each wafer in the diffusion wafer manufactured by this method.

Although the diffusion wafer manufactured by this method eliminates the deposition and cleaning steps, it has a diffusion quality equal to or higher than that of the diffusion wafer manufactured by the conventional method in which these steps are carried out.

[0016]

[Table 1]

[0017]

As is clear from the above description, the method for manufacturing a diffusion wafer of the present invention can omit both the deposition and cleaning steps, which are indispensable for manufacturing a diffusion wafer. Therefore, the number of man-hours for manufacturing the diffusion wafer is significantly reduced. Furthermore, since a safe dopant source can be used and harmful cleaning liquids are no longer necessary, safety and health problems and pollution problems are reduced, and gas exhaust equipment and pollution control equipment can be simplified.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of a diffusion wafer manufacturing process in the method of the present invention.

FIG. 2 is a chart showing the quality of diffusion wafers manufactured by the method of the present invention.

FIG. 3 is a schematic diagram showing a diffusion wafer manufacturing process in a conventional method.

[Explanation of symbols]

10 Dopant particles 11 Powder particles as release agent 12 Dopant source 20 Silicon wafer 21 Diffusion layer

Claims (2)

[Claims] 1. A method for manufacturing a diffusion wafer, which comprises performing diffusion heat treatment by interposing dopant particles, the surfaces of which are coated with a dopant source, as a release agent between stacked wafers. 2. The method of manufacturing a diffusion wafer according to claim 1, wherein the powder particles as the release agent are quartz or silicon.