JPS6278853A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To leave the silicon oxide film having a film thickness enough for dielectric isolation on the side surface of the polysilicon film by a method wherein the etching to be performed on the silicon oxide film in the region other than the prescribed region is carried out in two stages, anisotropic etching and isotropic etching. CONSTITUTION:A three layer film consisting of a phosphorus-doped polysilicon film 3, a silicon oxide film 4 formed by thermal-oxidizing the film 3 and a silicon nitride film 5 is provided on one main surface of a silicon substrate 1 having a two layer insulating film. A silicon oxide film 11 is deposited on the whole surface by a vapor-phase growth method. The whole surface if thermal-oxidized to eliminate the acute angle part at the same time as the film thickness of the oxide film 11 on the side surface of the silicon film 3 is increased. Most of the oxide film 11 is removed by an anisotropic plasma etching method. The residual is removed with anisotropic wet etching liquid. The nitride film 5 and a silicon nitride film 10, both exposed on the surface, and a silicon oxide film 2 are etched way in order. A silicon oxide film 8 and a polysilicon film 9 are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of forming an insulating film between conductive layers.

[Conventional technology]

Conventionally, in order to form an insulating film between conductors, the underlying conductor
dlLI - chemical vapor deposition on the surface
An insulating film is formed by an apor deposition (hereinafter referred to as CVD) method, and an upper conductive layer is formed thereon.

[Problem that the invention seeks to solve]

The conventional method for forming an insulating film described above depends on the film thickness and film quality.
Although it is superior in that it can form a uniform insulating film, the edges and corners of the lower conductive layer that have been processed into a predetermined shape remain as they were when they were formed, with no roundness and sharp angles. The electric field concentrates in that area, and the insulating film is likely to be destroyed. Furthermore, since an insulating film is interposed not only between the lower and upper conductive layers, but also between the underlying insulating film and the upper conductive layer, for example, in a semiconductor memory device using two-layer polycrystalline silicon, the upper conductive layer When used as the gate electrode of an insulated gate field effect transistor, it is necessary to remove a portion of the insulating film by photolithography, which complicates the process and requires margin for alignment, making the device There are drawbacks that make it unsuitable for miniaturization.

[Means for solving problems]

A method for manufacturing a semiconductor device according to the present invention includes a step of forming a three-layer film including a first conductive film, a first oxide film, and an oxidation prevention film in a predetermined region of the whole surface of a semiconductor substrate having an insulating film;
a step of forming a second oxide film on the entire surface; and a step of forming a third oxide film made of the oxide film of the first conductive film at the interface between the #c1 conductive film and the second oxide film. , leaving the 8g2 oxide film only on the side surfaces of the first oxide film and the third oxide film by an anisotropic etching method;
The method is characterized by including a step of forming a second conductive film that is electrically insulated from the first conductive film through an oxide film and a third oxide film.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

1 to 6 are vertical cross-sectional views in the order of steps of an embodiment of the present invention. A phosphorus-doped polysilicon film 3, a silicon oxide film 4 and a silicon nitride film 5 formed by thermal oxidation of the silicon substrate 1 have a two-layer insulating film in which silicon nitride M10 is laminated on a silicon oxide film 2. A three-layer film is provided, and this three-layer film is processed into a predetermined shape. Next, a silicon oxide film 11 is formed on the entire surface by vapor phase growth.
(FIG. 1), the entire surface is thermally oxidized to increase the thickness of the silicon oxide film on the side surfaces of the polysilicon film 3 and to eliminate the sharp corners (FIG. 2). At this time, the silicon substrate surface portion without the polysilicon M3 and the upper surface of the polysilicon film 3 are not oxidized because they are covered with the silicon nitride film IO. Next, most of the silicon oxide film 11 is removed by an anisotropic plasma etching method (FIG. 3), and then the remaining residue is removed by an isotropic wet etching solution (FIG. 4). Next, the silicon nitride film 5.10 and the silicon oxide film 2 exposed on the surface are sequentially removed by etching (FIG. 5). After that, a silicon oxide film 8 and a polysilicon film 9 are formed (
Figure 6).

In this example, a silicon oxide film 11 formed by a vapor phase growth method is used.
By performing two steps of anisotropic etching and isotropic etching to remove the silicon oxide film 11 in areas other than a predetermined area, the polysilicon film 3 is thermally oxidized to a moderate degree after the silicon oxide film 11 is deposited. Even if this is not done, silicon oxide 11 can be left on the side surface of the polysilicon film 3 in an amount sufficient for insulation isolation.

〔Effect of the invention〕

As explained above, the present invention forms an insulating film that is in contact with the side surface of the lower conductive film pattern and covers the entire surface of the substrate, and forms a thin oxide film of the lower conductive film at the interface where the side surface of the lower conductive film pattern contacts the insulating film. Then, an upper conductive film is formed which is electrically insulated from the lower conductive film via this oxide film and the thick insulating film left by anisotropic etching. This makes it possible to form an insulating film that has excellent insulation properties and is suitable for planarization and miniaturization of elements.

[Brief explanation of drawings]

1 to 6 are vertical cross-sectional views in the order of steps of an embodiment of the present invention. 1... Silicon substrate, 2, 4, 8.11...
... silicon oxide film, 3.9 ... polysilicon film, 5.10 ... silicon nitride film. !・ ν ・ Agent Patent attorney Yo Uchihara (:(-1)

Claims (1)

[Claims] A step of forming a three-layer film consisting of a first conductive film, a first oxide film, and an oxidation prevention film in a predetermined region of one main surface of a semiconductor substrate having an insulating film, and forming a second oxide film on the entire surface. forming a third oxide film made of an oxide film of the first conductive film at the interface between the first conductive film and the second oxide film; a step of leaving the No. 2 oxide film only on the side surfaces of the first oxide film and the third oxide film; A method for manufacturing a semiconductor device, comprising the step of forming an insulating second conductive film.