JPH01283818A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To see that the diffusion layer does not deepen more than necessary by changing the thickness of the first film so as to control the concentration inside a silicon substrate of impurity contained in the second film and the depth of a diffusion layer. CONSTITUTION:Two-layer films 2 and 4 containing different impurities are formed on the surface of a silicon substrate 1. Next, by applying heat treatment, impurity contained in the first film 2 directly diffuses into the silicon substrate 1 and a first impurity diffused layer 3 is formed. And at the same time impurity contained in the second film 4 diffuses into the silicon substrate 1 passing through the first film 2, and a second impurity diffused layer 5 is formed. Hereby, it becomes possible to control the concentration in silicon substrate of impurity to be diffused later and the depth of its diffusion by the thickness of the film formed in the first place, and since only one heat treatment is enough, the depth of impurity diffusion does not deepen more than necessary.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device in which two different impurity diffusion layers are formed in a silicon substrate. [Prior Art] FIG. 1 is a cross-sectional view showing a method for forming an impurity diffusion layer of a semiconductor device; in the figure, (1) is a silicon substrate; (1) is a silicon substrate;
2) is a film containing impurities, (8) is a diffusion layer of impurities contained in film (2), (4) is a film containing impurities different from film (2), and (6) is a film in (4). This is a diffusion layer of impurities contained in the .

Next, the effect will be explained.

Film containing impurities on the surface of silicon substrate (1) (2)
form. Next, impurities are diffused into the silicon substrate (1) by heat treatment to form an impurity diffusion layer (
8) [Fig. 2(a)]. Next, after removing the film (2), a film (4) containing different impurities is formed on the silicon substrate (1) [FIG. 2(b)]. Next, heat treatment is performed to form an impurity diffusion layer (5) [FIG. 2(C)].

[Problem to be solved by the invention]

In such a conventional method for forming an impurity diffusion layer, the concentration and diffusion depth of impurities to be diffused later in the silicon substrate can only be controlled by the conditions of heat treatment. Further, since it is necessary to perform the heat treatment twice, there is a problem that the diffusion depth of the impurity to be diffused first becomes deep.

This invention was made to solve the above-mentioned problems, and it is possible to control the concentration and diffusion depth of impurities to be diffused later in the silicon substrate by controlling the thickness of the initially formed film, and also to control the diffusion depth of impurities that are to be diffused later. The purpose of this is to prevent the impurity diffusion depth from becoming deeper than necessary because it only needs to be done once.

[Means to solve the problem]

The method for forming an impurity diffusion layer according to the present invention involves forming two layers of first and second layers containing different impurities on a silicon substrate, and then performing heat treatment to form two types of first and second layers in the silicon substrate. Two impurity diffusion layers are formed simultaneously.

[Effect]

The method for forming an impurity diffusion layer in the present invention controls the impurity concentration in the silicon substrate of the impurity contained in the second film and the depth of the diffusion layer by changing the thickness of the first film.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (1) is a silicon substrate, (2) is a first film containing impurities, (8) is a first impurity diffusion layer contained in the first film (2), and (4) is a first film containing impurities. A second film containing impurities different from the first film (2), (5) is the second film (4)
This is the second impurity diffusion layer contained therein.

Next, the effect will be explained.

First, 2 rfl films (2) and (4) containing different impurities are formed on the surface of a silicon substrate (1). Then, by performing heat treatment, the impurities contained in the first film (2) are directly diffused into the silicon substrate (1), forming a first impurity diffusion layer (8). At the same time, the second film (
The impurities contained in 4) pass through the first film (2) and diffuse into the silicon substrate (1) to form the second impurity diffusion layer (5).
) is formed.

〔Effect of the invention〕

As described above, according to the present invention, the concentration of impurities contained in the second film in the silicon substrate and the depth of the diffusion layer can be controlled by changing the thickness of the first film, and the heat treatment Since only one step is required, the diffusion layer does not become deeper than necessary.

[Brief explanation of the drawing]

FIG. 1 (al+1)l is a cross-sectional view of each step of a silicon substrate showing a method for forming an impurity diffusion layer of a semiconductor device according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view of each step of the silicon substrate shown in FIG. (
6) is the second impurity diffusion layer. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A method for manufacturing a semiconductor device in which an impurity layer is formed in a silicon substrate, the method comprising diffusing impurities into the silicon substrate from two layers of films containing different impurities formed on the silicon substrate. .