JPS6340341A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To operate the title semiconductor device at a high speed by reducing the capacitance between wirings by a method wherein the prescribed etching is performed respectively on the first and the second insulating films and the second and the third insulating films which can be etched mutually selectively. CONSTITUTION:An SiO2 film 2 is formed on a substrate 1, and a polycrystalline Si film 3A is formed thereon. An SiO2 film 6 is formed on the film 3A. Then, the film 6 is selectively removed, the film 3A is processed into a polycrystalline Si gate film 3 using the film 6 as a mask, and a pattern is formed by selectively removing the film 2 in the same manner as above. Then, an SiO2 4 is formed by thermally oxidizing the substrate 1, and a silicon nitride film 7 and an SiO2 8 are formed on the film 4. Subsequently, the film 8 is removed by performing an anisotropic etching. As a result, the film 8 is left on the sidewall part only of the film 3 in a self-alignment manner. Then, the films 4 and 7 are removed. Subsequently, a damageless SiO2 film 9 is formed by thermally oxidizing the substrate 1. Then, a polycrystalline Si gate film 5 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming an interlayer insulating film between multilayer interconnections.

[Conventional technology]

FIG. 2 is a process sectional view showing a conventional technique of this type.

In FIG. 2, 1 is a silicon substrate, 2 is a first-layer silicon oxide film, 3 is a first-layer polycrystalline silicon gate film, 4A is a second-layer silicon oxide film on a silicon substrate, and 4B is a silicon oxide film formed by thermal oxidation. A silicon oxide film 5 is a second layer polycrystalline silicon gate film as an interlayer insulating film on the first layer polycrystalline silicon gate film 3 formed at the same time as the second layer silicon oxide film 4A. Further, t□z1 is the thickness of the second silicon oxide film, and tox2 is the thickness of the interlayer insulating film 4B.

Also, s1ox3 is the first layer polycrystalline silicon gate film 3
This is the thickness of the silicon oxide film formed on the sidewalls of .

Next, a method for forming such a structure will be explained.@First, a first layer silicon oxide film 2 is formed on the entire surface of a silicon substrate 1, and then a polycrystalline silicon oxide film 2, which will become a first layer polycrystalline silicon gate film 3, is formed by CVD. A crystalline silicon film is also formed over the entire surface. Thereafter, using photolithography and etching techniques, the polycrystalline silicon film is selectively etched into a desired pattern to form a first layer polycrystalline silicon gate film 3. Subsequently, using this first layer silicon gate film 3 as a mask, the exposed first layer silicon oxide film 2 is removed (
Figure 2(a)). Note that instead of the first layer silicon oxide film 2, a silicon nitride film or a multilayer structure film of a silicon oxide film and a silicon nitride film may be used.

Subsequently, the entire wafer is heat-treated in an oxidizing atmosphere to form a second layer silicon oxide film 4A, which is a thermally oxidized film, on the silicon substrate 1. At this time, the first polycrystalline silicon gate film 3 is also oxidized, and a silicon oxide film 4B is formed on its upper and side walls (FIG. 2(b)). After this, the polycrystalline silicon film that will become the second layer wiring material is
It is formed by VD to form the second layer polycrystalline silicon gate film 5 (FIG. 2(C)).

As described above, in the conventional semiconductor device, the silicon substrate 1
Since the four upper second layer silicon oxide films and the silicon oxide film 4B on the first layer polycrystalline silicon gate film 3 are formed simultaneously by oxidation, no matter what oxidation method is used, Even if polycrystalline silicon doped with impurities is used as the first layer polycrystalline silicon gate film 3, the oxide film thickness tOXl on the silicon substrate 1 shown in FIG. The relationship between the thickness of the oxide film toxz*tOX3 formed on the top surface and sidewalls of 3 is as follows.

2 toxl (toxz≦5tox1...
・ (1) 2 taxi (tOx3≦3tox1
(2) [Problems to be Solved by the Invention] Generally, in a semiconductor device, in order to increase the signal transmission speed of the wiring in each layer, it is desired to reduce the capacitance between the wiring as much as possible. For this purpose, the silicon oxide film thickness tox2 on the upper surface of the first layer polycrystalline silicon gate film 3 in FIG.
It is desired that the silicon oxide film thickness tox3 on the sides and sides be as large as possible. On the other hand, as the degree of integration of semiconductor devices increases, the thickness tOXI of the silicon oxide film 4A on the silicon substrate 1 forming transistors and the like inevitably becomes smaller. However, as mentioned above, as long as the conventional method is used, the relationship (1) and (21) hold between the two, so if toxl is decreased, tox2
Similarly, tox3 is also small, resulting in an increase in the capacitance between the wirings.

The present invention has been made to solve the above-mentioned problems, and aims to provide a semiconductor device having low inter-wiring capacitance, capable of high-speed operation, and having a high degree of integration.

[Ninth way to solve the problem]

In the method for manufacturing a semiconductor device according to the present invention, a first insulating film covering a first conductive layer is formed, and then second and third insulating films are formed to cover them.

At this time, the first and second . The second and third isolation films are not capable of being selectively etched with respect to each other. Then the third
The insulating film is subjected to anisotropic etching to remove the first conductive layer, leaving only the side wall portion.

Further, the second insulating film that is not covered with the third insulating film is removed by etching, and a fourth insulating film is formed on the surface of the semiconductor substrate exposed in the portion where the first conductive layer is not formed.

[Effect]

The first insulating film on the first conductive layer and the fourth insulating film on the portion of the semiconductor substrate where the first conductive layer is not formed are formed completely independently, for example, only the first insulating film is formed by CVD. It is also possible to form it thickly by a method. Furthermore, if the third insulating film is left on the side wall portion of the first conductive layer using anisotropic etching, the thickness of the interlayer insulating film in this portion also increases.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
On the right side of the figure, the silicon substrate 1 is placed on top of the silicon substrate 1.
A first layer of silicon oxide M2 is formed by thermal oxidation, and three first layer polycrystalline silicon films are formed thereon (see FIG. 1(a)).
)).

Subsequently, a silicon oxide film 6 is formed on the first layer polycrystalline silicon film 3A by the CVD method (FIG. 1(b)).
.

Next, using photolithography and etching techniques, the silicon oxide film 6 is selectively removed, and then, using the silicon oxide H1X6 as a mask, the three first layer polycrystalline silicon films are formed into a first layer polycrystalline silicon gate. Similarly, the first layer silicon oxide film 2 is successively and selectively removed to form a desired pattern (FIG. 1(C)).

Next, the silicon substrate 1 is thermally oxidized to form a second layer silicon oxide film 4, and then a silicon nitride film 7 is formed over the entire surface of the second layer silicon oxide film 4 by a CVD method or a heat treatment method in an Ns atmosphere. (Fig. 1(d)).

Furthermore, a silicon oxide film 8 is formed using the CVD method (FIG. 1(C)). After that, RIE (React
The silicon oxide film 8 is removed by the ive ion etching method. At this time, silicon nitride film 7
Etching is stopped at the interface with (FIG. 1(f)). By selecting appropriate etching conditions, the etching selectivity between silicon oxide wX8 and silicon nitride film 7 can be made sufficiently large, and silicon nitride film 7 can be easily etched.
Etching can be stopped at the interface. By using RIE using anisotropic etching, the silicon oxide film 8 can be left in a self-aligned manner only on the sidewalls of the first layer polycrystalline silicon gate film 3 without using a mask or the like. can.

Next, the silicon nitride film 7 is removed using an etching technique (FIG. 1 (2)), and the second layer silicon oxide film 4 on the silicon substrate 1 is also removed (FIG. 1 Φ)). after that,
The silicon substrate 1 is thermally oxidized again to form a silicon oxide film 9. This is because the quality of the silicon oxide film on the silicon substrate 1 has a great influence on the characteristics of the device, so the silicon oxide film 4 that has been damaged in the previous process is removed and the silicon oxide film is oxidized without damage. This was replaced with membrane 9. Next, a second layer polycrystalline silicon gate film 5 is formed using the CVD method (FIG. 1(i)).

Based on the embodiment described above, the second layer silicon oxide film 4
may be formed using a deposition method such as a CVD method instead of a thermal oxidation method.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to form a thick glabella insulating film including the side wall portion of the first conductive layer without using an extra mask by using anisotropic etching. Since the insulating film on the semiconductor substrate without the first conductive layer can be formed thinly independently of the interlayer insulating film, the inter-wiring capacitance is low, high-speed operation is possible, and a semiconductor device with a high degree of integration can be obtained. It has the effect of

[Brief explanation of drawings]

FIG. 1 is a process sectional view showing an embodiment of the present invention, and FIG. 2 is a process sectional view showing a conventional example. 1... Silicon substrate, 3... First layer polycrystalline silicon gate film, 4, 6, 8, 9... Silicon oxide film, 5... Second layer polycrystalline silicon case. ) Jl, 7・
m-・Silicon nitride film.

Claims (4)

[Claims] (1) A step of selectively forming a first conductive layer on the surface of a semiconductor substrate, a step of forming a first insulating film covering this first conductive layer, and a step of forming a first conductive layer and a first conductive layer. A second insulating film that can be selectively etched with respect to the first insulating film and a third insulating film that can be selectively etched with respect to the second insulating film are sequentially formed to cover the insulating film. a step of performing anisotropic etching on the third insulating film and removing the third insulating film leaving only the side wall portion of the first conductive layer; a step of removing the second insulating film by etching and exposing the surface of the semiconductor substrate in a portion where the first conductive layer is not formed; a step of forming a fourth insulating film on the exposed surface of the semiconductor substrate; 1. A method of manufacturing a semiconductor device, comprising the step of forming a conductive layer. (2) The first and third insulating films are silicon oxide films,
2. The method of manufacturing a semiconductor device according to claim 1, wherein the first insulating film and the third insulating film on at least the first conductive layer are each formed by a CVD method. (3) The method of manufacturing a semiconductor device according to claim 2, wherein the second insulating film is a silicon nitride film and is formed by a CVD method. (4) The semiconductor device according to claim 2, wherein the second insulating film is a silicon nitride film, and the silicon oxide film constituting the first insulating film is formed by nitriding. Production method.