JPH06163450A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a semiconductor device, wherein impurity doping processes can be lessened in number. CONSTITUTION:When a diffusion layer non-uniform in impurity concentration is formed on the surface of a semiconductor substrate 1, an insulating layer is formed on the surface of the semiconductor substrate first, then the insulating layer formed on a region where a diffusion layer of comparatively high impurity concentration is to be formed is partially removed, another insulating layer 5 is formed on the insulating layer-removed region and the residual insulating layer, a resist film is formed on the insulating layer 5 excluding a region where a diffusion layer is formed, the insulating layer 5 is subjected to an etching process, and then impurities 19 are diffused for doping for the formation of a diffusion layer.

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 device, and more particularly to a method for manufacturing a semiconductor device including a step of forming diffusion layers having different impurity concentrations on a semiconductor substrate.

[0002]

2. Description of the Related Art When forming a diffusion layer having different impurity concentrations on the surface of a semiconductor substrate, first, an insulating layer is formed on the surface of the semiconductor substrate, and then the insulating layer on the portion where one diffusion layer is formed is removed. After doping with impurities, cover this part with an insulating layer and repeat the same process for the part where another diffusion layer is formed, or the part where a diffusion layer with high impurity concentration is formed It was common to remove the upper insulating layer and dope impurities sequentially.

[0003]

However, the above method has a drawback in that the impurity doping step is required as many times as the number of diffusion layers having different impurity concentrations. In view of the above-mentioned problems, the present invention has the following problems.
It is an object of the present invention to provide a method for manufacturing a semiconductor device that can reduce the number of impurity doping steps.

[0004]

In order to solve the above-mentioned problems, a method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device, wherein diffusion layers having different impurity concentrations are formed on a surface of a semiconductor substrate. After forming the insulating layer on the surface of the semiconductor substrate, the insulating layer on the portion for forming the diffusion layer having a relatively high impurity concentration is partially removed, and the insulating layer is further formed on the removed portion and the remaining insulating layer portion. After the formation, a resist film is formed on the insulating layer while leaving a portion for forming the diffusion layer, and the insulating layer is etched, and then impurity doping for forming the diffusion layer is performed. It is characterized by.

In the method of manufacturing a semiconductor device of the present invention, the etching process is usually performed until the insulating layer on the portion for forming the diffusion layer having a high impurity concentration is completely removed.
Of course, at the stage of finishing the etching process, the insulating layer on the portion for forming the diffusion layer having a relatively low impurity concentration is not completely removed and is still left. However, the etching process may be stopped until the insulating layer on the portion for forming the diffusion layer having a high impurity concentration is completely removed. Even in this state, there is a difference in the thickness of the insulating film between the insulating layer remaining on the portion forming the diffusion layer having a high impurity concentration and the insulating layer remaining on the portion forming the diffusion layer having a low impurity concentration. Is.

[0006]

According to the present invention, when impurities are doped, a thin insulating layer is left on the semiconductor substrate at least in the portion where the diffusion layer having a relatively low impurity concentration is formed. The impurity injection amount (dose amount) is controlled. Therefore, even if the implantation is performed at the same time, a difference in the impurity concentration according to the difference in the remaining thickness of the insulating layer is generated between the diffusion portions. By adjusting the thickness of the insulating layer left on the semiconductor substrate, it is possible to control the impurity concentration in the diffusion layer having a relatively low concentration to be a desired concentration.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. Of course, the present invention is not limited to the following embodiments. First, as shown in FIG. 2, a first insulating layer 2 of silicon oxide or the like is formed on the surface of a semiconductor substrate 1 of silicon or the like, and a resist film 3 is formed thereon by using a photolithography technique. To do. Then, by performing the etching process and the resist film removing process, as shown in FIG. 3, the opening 4 is formed in the insulating layer 2 where a diffusion layer having a relatively high impurity concentration is formed.
After forming, the entire surface of the semiconductor substrate 1 is oxidized.

Then, as shown in FIG. 4, the insulating layer 5 on the surface of the semiconductor substrate 1 is thin in the portion 5a covering the opening 4 and thick in the other portions 5b. Next, as shown in FIG. 5, the resist film 6 is formed on the portion other than the portion where the diffusion layer is formed.
Then, as shown in FIG. 1, an etching process is performed until the thin portion 5a of the insulating layer 5 is removed and the opening portion 7 reappears, and then impurities are implanted.
At this time, the relatively thin insulating layer 8 remains on the semiconductor substrate 1 in the portion other than the opening 4 for forming the diffusion layer having a relatively low impurity concentration. Impurity 19 is
As shown by the broken line in FIG. 1, not only the opening 7 but also the portion where the thin insulating layer 8 remains is implanted. However, FIG.
As shown in FIG.
Since the impurity is implanted through the diffusion layer 10, the dose amount of the obtained diffusion layer 10 becomes smaller than the dose amount of the diffusion layer 9 in the opening portion 7. In this way, the formation of the diffusion layers 9 and 10 having different impurity concentrations can be realized in one impurity doping step.

[0009]

According to the manufacturing method of the present invention, as described above, the insulating layer is left in the portion where the diffusion layer is formed, and the impurity concentration is controlled by the thickness of the insulating layer. It has become possible to form a plurality of different diffusion layers by a small number of impurity doping steps.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an insulating layer etching / impurity implantation process in an example.

FIG. 2 is a cross-sectional view showing a resist film forming process in an example.

FIG. 3 is a cross-sectional view showing an opening forming process in an example.

FIG. 4 is a sectional view showing an oxidation treatment step in the example.

FIG. 5 is a cross-sectional view showing a resist film forming process in an example.

FIG. 6 is a sectional view showing a diffusion layer formed in an example.

[Explanation of symbols]

 1 Semiconductor Substrate 2,5,8 Insulation Layer 3,6 Resist Film 9,10 Diffusion Layer 19 Impurity

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor device, wherein a diffusion layer having different impurity concentrations is formed on a surface of a semiconductor substrate, for forming a diffusion layer having a relatively high impurity concentration after forming an insulating layer on the surface of the semiconductor substrate. Part of the insulating layer is removed, and an insulating layer is further formed on the removed part and the remaining insulating layer part, and then the resist film is formed on the insulating layer leaving a part to form a diffusion layer. A method for manufacturing a semiconductor device, which comprises forming and etching the insulating layer, and then performing impurity doping for forming a diffusion layer. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the etching process is performed until the insulating layer on the portion for forming the diffusion layer having a high impurity concentration is completely removed.