JPS5935421A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain an epitaxial layer with no defect by a method wherein the surface of an impurity diffused layer is lapped into the mirror face, a predetermined thickness is removed, and then epitaxial growth is performed. CONSTITUTION:A P diffused layer is selectively formed on an N type Si substrate using a normal technique. The exposed surface of the diffused layer is mechanically and chemically lapped into the mirror face using silicic acid powder, whereby the surface is removed in depth of ca. 5mum. An Si epitaxial layer is formed thereon, so that the epitaxial layer with no defect can be obtained. By so doing, it becomes possible to manufacture SCRs for large power from the epitaxial wafers and to improve the yield even in other bipolar elements.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for manufacturing a semiconductor device,
In particular, the present invention relates to a manufacturing method suitable for high-power thyristors and the like.

[Technical background of the invention]

Epitaxial wafers are generally used as semiconductor wafers for bipolar devices, but with the current epitaxial technology it is possible to form an epitaxial layer completely defect-free, so an epitaxial wafer with no defects can be obtained after the epitaxial process. Yield is extremely low. Therefore, in manufacturing bipolar ICs, etc., in which a single semiconductor chip is divided into multiple semiconductor chips,
If only defective chips are removed, the yield will not be extremely low even if epitaxial wafers are used, but
In the production of high-power silices in which a single sheet of wafer is used as individual elements, the yield will be extremely poor if an epitaxial wafer is used. For this reason,
Conventionally, high-power thyristors, in which a single semiconductor wafer constitutes one element, could not be manufactured using epitaxial wafers.

[Problems with background technology]

Below, an overview of the method for manufacturing epitaxial wafers used for manufacturing bipolar ICs, low-power transistors, etc., and the problems that exist therein will be explained.

Conventionally, evitaxial ueno has been manufactured by the following method. First, a semiconductor wafer of a predetermined conductivity type is manufactured by the C2 method or the FZ method, and a predetermined portion of the semiconductor wafer is doped with an acceptor impurity or a donor impurity by a thermal diffusion method to form an impurity diffusion layer. Next, after cleaning the surface of this impurity diffusion layer with sulfuric acid, hydrogen peroxide, hydrochloric acid, etc., the surface of the wafer is scrubbed with a clean cloth while dropping pure water to clean the wafer surface. After this cleaning treatment, a single crystal epitaxial layer is grown on the surface of the impurity diffusion layer by epitaxial growth.

However, in the conventional method as described above, no matter how carefully the surface scrubbing is performed, a small amount of residue remains on the wafer surface after the cleaning process, and this residue causes defects such as mounds in the next epimexical process. This causes defects to occur in the epitaxial layer, so it has been almost impossible to produce epitaxial wafers with no defects using conventional methods.

Therefore, since epitaxial wafers manufactured by conventional methods always have defects, epitaxial wafers cannot be used in high-power thyristors that use one wafer as one element; Cyrisk was manufactured exclusively by the total diffusion method or the diffusion alloy method.

[Purpose of the invention]

An object of the present invention is to solve the problems in the conventional method, obtain a defect-free epitaxial wafer, and provide an improved semiconductor device manufacturing method using the same. An object of the present invention is to provide a method for manufacturing a semiconductor device that can manufacture a high-power thyristor using an epitaxial process.

[Summary of the invention]

The present inventors made various attempts to obtain an epitaxial layer having a defect-free epitaxial layer, and as a result, after the formation of impurity diffusion p, the surface of the diffusion layer was subjected to mechanical force).
The inventors have found that a defect-free epitaxial layer can be obtained by epitaxially growing the layer after 5 μm thickness is removed by chemical mirror polishing, thereby confirming that the problems of the prior art can be completely solved.

[Embodiments of the invention]

A whole N-type silicon wafer with a Miller index (111) and a resistivity of 150 to 200 ΩCM was washed with a mixture of pure water, hydrochloric acid, and hydrogen peroxide, and then oxidized for 30 minutes in dry oxygen at 1100°C to form a surface. A SiO2 film with a thickness of 950 A was formed.

Next, phosphorus was ion-implanted into the wafer at a dose of 7 x 1014/rd through this oxide film at an accelerating voltage of 140 keV, and then the wafer was cleaned again with the mixed solution, and the wafer after cleaning was heated at 1100°C for about 7 hours. It is oxidized by a steam oxidation method to form an oxide film with a thickness of about 1.5 μm. After this oxide film is formed, the sea urchin... is treated with the above mixed solution in 1. Washing...
After cleaning, the sea urchin was placed in a mixed gas of nitrogen and oxygen at 1260° C. for about 50 hours to diffuse phosphorus into the wafer. The diffusion depth of this phosphorus is 55 μm±4 μm.

After phosphorus diffusion, the oxide film on the wafer surface was etched with hydrofluoric acid to expose the phosphorus diffusion layer, and the wafer was further cleaned with the cleaning solution.

Next, the surface of the wafer with the phosphorus diffusion layer exposed as described above is mechanically and chemically mirror polished using silicate powder to remove 5 μm of the surface of the phosphorus diffusion layer, and the surface of the wafer after mirror polishing is 40μm thick by epitaxial growth
An N-type single crystal epitaxial layer with a specific resistance of 0.1Ω (7) was formed.

100 epitaxial wafers were manufactured by the method of the present invention as described above, and the same number of epitaxial wafers were manufactured using the same silicon wafer by the conventional method (i.e., the method of scrubbing the surface with a clean cloth after cleaning). The incidence of mounds was investigated for two types of epitaxial wafers.

The attached drawings compare the mound occurrence rate (the number of mounds generated per wafer) of epitaxial wafers manufactured by the method of the present invention with those of epitaxial wafers manufactured by the conventional method. In the figure, the bar graph on the left side is the result of the conventional method, and the bar graph on the right side is the result of the method according to the present invention. 80 out of 100 wafers have one mound, and only 15 wafers have one mound.
Only one wafer using the conventional method has no mounds, and 4 of the wafers have 5 mounds.
It has even reached 0%.

The above epitaxial wafer is subjected to base diffusion using a conventional method.
When a thyristor element was fabricated by emitter diffusion and then electrode formation, no good thyristor element was obtained using the epitaxial wafer using the conventional method, but with the epitaxial wafer of the present invention, the thyristor manufacturing process yielded a good product rate of about 50%. The proposed method was found to be extremely effective.

〔Effect of the invention〕

From the above results, according to the method of the present invention, it is possible to manufacture defect-free epitaxial wafers, and therefore, it is possible to manufacture high-power silica-free epitaxial wafers, and at the same time, it is possible to manufacture epitaxial wafers with no defects. It is also clear that an improvement in yield is achieved.

[Brief explanation of the drawing]

The accompanying drawing is a graph comparing the number of mounds generated per epitaxial wafer 1 manufactured by the method of the present invention and the number of mounds generated per epitaxial wafer 1 manufactured by the conventional method. =95= 7?7-Do appeasement L Maki-shi

Claims (1)

[Claims] 1. After forming an impurity diffusion layer on the surface of a semiconductor substrate, the surface of the impurity diffusion layer is mechanically and chemically mirror-polished to remove only the required thickness, and an epitaxial layer is formed on the mirror-polished impurity diffusion layer. 1. A method of manufacturing a semiconductor device, comprising the step of forming an epitaxial layer of a predetermined thickness by a method.