JPH0497523A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a pattern of polysilicon film having desired inclination angle with excellent reproducibility by utilizing a photoresist film and an oxide film provided backward the photoresist as a mask for etching of a polysilicon film. CONSTITUTION:A polysilicon film 12 is formed on an oxide film 11 as the base layer on a silicon substrate 10 and moreover an oxide film 13 is formed thereon as a mask. Next, after forming a photoresist film 14 on the film 13, the film 14 is patterned. Next, an oxide film 13A is formed as a second mask using the film 14 as the mask. Moreover, a pattern formation having an inclina tion angle (15 to 45 degrees) is made for the film 12 from the edge part of film 13A to the area just under the edge of the film 14 by executing the isotrop ic etching of the film 12 using the film 14 and film 13A as the mask. Next, the film 14 is removed, leaving a pattern formed by the film 12 and the film 13A. Thereby, a pattern of the polysilicon film having desired inclination angle can be obtained with good reproducibility.

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 etching a polysilicon film.

[Conventional technology]

Polysilicon films are used as electrodes and wiring in semiconductor devices, and the manufacturing method for slanting the polysilicon film in order to improve the coverage of interlayer films, etc., is as follows:
It was done as follows.

First, as shown in FIG. 3(a), a polysilicon film 12 is placed on a base oxide film 11 formed on a silicon substrate 10.
Form A. Next, as shown in FIG. 3(b), a photoresist film 14A is patterned on the polysilicon film 12A. Thereafter, as shown in FIG. 3(c), the polysilicon film 12 is removed using the photoresist film 14A as a mask.
The pattern A is formed by isotropic etching such as wet etching. Next, after etching the polysilicon film 12A, the photoresist Ill 4A is removed, and as shown in FIG.
) as shown in polysilicon! A pattern of 12A was formed on the base oxide film 11.

In addition to this, there is a resist retreat method as an etching method having an inclination angle. This will be explained below using FIG.

First, as shown in FIG. 4(a), a polysilicon film 12B is formed on the base oxide film 11, and then a photoresist film 12B is formed on the base oxide film 11.
A pattern is formed on 4B using photolithography technology.

At this time, the photoresist film 14B is previously tilted by a method such as heat treatment. Next, when patterning the polysilicon film 12B, etching is performed under conditions that are anisotropic and have a low selectivity with respect to the photoresist film 14B. By performing etching under the above conditions, the shape after etching is such that the inclination angle of the photoresist film 14B is transferred to the polysilicon film 12B, and by removing the photoresist film 14B, as shown in FIG. Fourth
As shown in Figure (C), a pattern of polysilicon film 12B with an inclined angle is formed on base oxide film 11.

[Problem to be solved by the invention]

In the conventional manufacturing method described above, the tilt angle is created by isotropic etching using a photoresist film patterned directly on the polysilicon film as a mask, so the tilt angle on the polysilicon film is approximately 45 degrees. However, there was a problem in that it was not possible to set an arbitrary angle of inclination.

Furthermore, when using the resist regression method, it is difficult to create a constant tilt angle on the photoresist film with good reproducibility.
Furthermore, there is a problem in that etching conditions that generally lower the selectivity between the polysilicon film and the photoresist film often also reduce the selectivity between the polysilicon film and the oxide film.

[Means to solve the problem]

A method of manufacturing a semiconductor device according to the present invention includes the steps of sequentially forming a polysilicon film, an oxide film, and a photoresist film on a base insulating film formed on a semiconductor substrate, and patterning the photoresist film to form a first mask. etching the oxide film using the first mask to form a second mask having a smaller area than the first mask; and etching the oxide film using the first and second masks. The method includes a step of etching a silicon film.

〔Example〕

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

FIGS. 1A to 1E are cross-sectional views of a semiconductor chip shown in the order of steps for explaining a first embodiment of the present invention.

First, as shown in FIG. 1(a), a polysilicon group 12 is formed on a base oxide film 11 on a silicon substrate 10, and then an oxide 1113 for a mask is formed to a thickness of 0.1 μm by thermal oxidation or CVD. Next, as shown in FIG. 1(b), a photoresist film 14 is formed on the oxide film 13, and then the photoresist film 14 is patterned using photolithography. Using the JI 114 as a mask, as shown in FIG. 1C, the oxide JI 113 is etched back from the photoresist film 14 by wet etching to form an oxide film 13A as a second mask.

Furthermore, as shown in FIG. 1(d), the photoresist film 1
4 and oxide film 13A as a mask, polysilicon M1 is
By performing isotropic etching in step 2, a pattern with an inclined angle (15 degrees to 45 degrees) extending from the edge of the oxide film 13A to just below the edge of the photoresist film 14 is formed on the polysilicon film 12. The photoresist film 14 is removed by a method commonly used in zero order, leaving a pattern formed of polysilicon group 12 and oxidized M13A as shown in FIG. 1(e). At this time, the oxide film 13A remaining on the polysilicon film 12 is used as it is as an interlayer insulating film.

In this embodiment, when forming an inclination angle of 45 degrees or more on the polysilicon group, first, when etching the oxide film 13 as shown in FIG. 0 For example, when forming an inclination angle of 60 degrees on the polysilicon film 12 with a thickness of 0.3 μm, the oxide film 1
3 is retracted by about 0.2 μmtIi to form the second mask 6
Next, in the etching of the polysilicon film 12 shown in FIG. Attach.

Next, a mechanism for creating an inclination angle according to the present invention will be explained.

As shown in Figure 1(C), the shape before etching is
An oxide film 13A as a second mask and a photoresist film 14 are formed on the polysilicon film 12 on the base oxide film 11, and the photoresist film 14 is formed between the polysilicon film 12 and the photoresist film 14. Oxidation as a second mask! A gap 15 equal to the film thickness of 13A is opened. By performing isotropic etching, the gap 15
A chemical solution or reactive gas enters the etching layer, and the polysilicon film 12 hidden under the photoresist film 14 is also etched. The etching speed of the polysilicon film 12 in the gap 15 is slower than that in the exposed part of the polysilicon film 12 outside the edge of the photoresist film 14 because the amount of chemical solution or reactive gas supplied is smaller. ing.

Therefore, as shown in FIG. 1(d), the polysilicon film 1
The shape of 2 is the oxide film 1 from just below the edge of the photoresist M14.
It has a slope that reaches the end of 3A. That is, the inclination angle (θ) applied to the polysilicon film 12 is a function of the thickness (1) of the polysilicon film 12 and the amount (1) of retreat of the oxide film 13A as the second mask from the photoresist film 14. Cage, θ
=jan-Jt/ρ).

Next, a second embodiment of the present invention will be described with reference to the drawings. FIGS. 2(a) to 2(c) are cross-sectional views of a semiconductor chip shown in the order of steps for explaining a second embodiment of the present invention.

As shown in FIG. 2 (a), polysilicon 1!12 is formed on the base nitride M21 on the silicon substrate 10, and then oxide M13 for a mask is formed on the polysilicon film 12.Photoresist The steps from film pattern formation to formation of the oxide film 13B as a second mask, etching of the polysilicon film 12, and removal of the photoresist film are the first steps.
Perform the same operation as in the example.

FIG. 2(b) is a cross-sectional view of the semiconductor chip after removing the photoresist film serving as the first mask. In this state, the polysilicon film 12 with an inclined angle is patterned on the base nitride film 21, and the polysilicon film 12
The 0th order oxide film 13 on which the oxide film 13B is formed
B is selectively etched using, for example, buffered hydrofluoric acid, leaving only the base nitride film 21 and the polysilicon M12, as shown in FIG. 2(c).

In this embodiment, since a nitride film different from the oxide film for the mask is used as the base, there is an advantage that only this oxide film can be selectively removed after patterning the polysilicon film.

〔Effect of the invention〕

As explained above, the present invention uses a photoresist film and an oxide film that is set back from the photoresist as a mask for etching a polysilicon film. A gap will be created depending on the Since the chemical solution or reactive gas used when etching the polysilicon film enters this gap, the polysilicon film is etched at an inclination angle ( θ
) can be added. That is, by controlling the amount of recession of the oxide film as a mask, it is possible to obtain a polysilicon film pattern having a desired tilt angle with good reproducibility.

[Brief explanation of drawings]

1 and 2 are sectional views of a semiconductor chip for explaining the first and second embodiments of the present invention, and FIGS. 3 and 4 are sectional views of a semiconductor chip for explaining the prior art. It is. 10... Silicon substrate, 11... Base oxide film, 12
゜12A, 12B...Polysilicon film, 13.13A
...Oxide film, 14.14A, 14B... Photoresist film, 21... Base nitride film.

Claims (1)

[Claims] 1. A step of sequentially forming a polysilicon film, an oxide film, and a photoresist film on a base insulating film formed on a semiconductor substrate, and patterning the photoresist film to form a first mask. etching the oxide film using the first mask to form a second mask having a smaller area than the first mask; and etching the polysilicon film using the first and second masks. A method for manufacturing a semiconductor device, comprising the step of etching. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the underlying insulating film is an oxide film or a nitride film.