JPH03259528A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent dimensional spread at lower side, and form an excellent pattern on an Si3N4 film and an Si substrate, by stacking the Si3N4 film and a resist mask on the Si substrate, performing heat treatment after the surface is modified by exposure to plasma gas, and turning the resist aperture section into a curve type. CONSTITUTION:On a semi-insulative GaAs substrate 1, an Si3N4 film 2 and a photoresist mask 3 are stacked by a plasma CVD method. By plasma etching using CF4, an aperture is formed in the Si3N4 film 2, and the resist 3 (PMMA) is modified; the aperture section of the resist 3 is worked into a curve type by heat treatment at 170 deg.C in N2 for about 30 minutes; by wet etching, the GaAs substrate 1 in the aperture part of the resist 3 and the Si3N4 film 2 is scrapped off and covered with Ti 4. Since the mutual adhesion of the substrate 1, the Si3N4, and the PMMA resist is excellent, the permeation of etching liquid into the interface can be prevented, and accurate wet etching completely equal to an upper pattern can be realized.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for manufacturing a semiconductor device.

BACKGROUND ART As a method for forming an upper layer film partially connected to a semiconductor substrate on a semiconductor substrate, the steps shown in the step-by-step cross-sectional views of FIGS. 2(a) to 2(C) are conventionally known. .

As shown in FIG. 2(a), a photoresist pattern 6 having an opening that partially penetrates the substrate is formed on a semiconductor substrate 5, and the upper layer is formed at the end of the opening of the photoresist 6. To prevent it from breaking, as shown in Figure 2 (b),
The cross-sectional shape of the opening of the photoresist 6 is processed into a curved shape, and in some cases, the semiconductor substrate exposed under the opening is
After surface treatment by etching, as shown in FIG.
There is something called forming.

Problem to be Solved by the Invention However, conventionally, when the cross-sectional shape of the opening of the seven photoresist patterns 6 is processed by heat treatment or the like as shown in FIG. 2(b), the close contact between the semiconductor substrate 5 and the photoresist 6 is Because of the poor properties, there is a problem in that the dimension of the opening on the substrate side after processing becomes wider than the dimension A before processing. Similarly, due to the poor adhesion between the semiconductor substrate 5 and the photoresist pattern 6, if the semiconductor substrate 5 is subjected to wet etching using the photoresist pattern 6 as a mask before forming the upper layer film 7, the etching may occur from the opening. semiconductor substrate 5
There was a problem in that the etching solution penetrated into the interface between the photoresist 6 and the photoresist 6, making it impossible to perform normal pattern processing.

Means for Solving the Problems In order to solve the above problems, in the manufacturing method of the present invention,
First, a silicon nitride film is deposited on a semiconductor substrate, and a photoresist pattern having partial openings is formed on the silicon nitride film. Next, the semiconductor substrate on which this photoresist has been formed is exposed to plasma gas and then heat-treated to process the cross-sectional shape of the photoresist opening into a curved shape. A dielectric film or a conductive film is formed along the line.

Effect When the above manufacturing method is used, the adhesion between the photoresist pattern and the lower layer (silicon nitride film) and between the semiconductor substrate and the upper layer (silicon nitride film) is better than when the photoresist pattern is formed directly on the semiconductor substrate. Due to the synergistic effect that the surface of the photoresist is modified by exposing it to plasma gas before heat treatment, the cross section of the photoresist opening accompanying the subsequent heat treatment is This prevents the bottom dimension from expanding. Similarly, since the silicon nitride film, photoresist, and semiconductor substrate have good adhesion, the underlying silicon nitride film and semiconductor substrate were etched using the photoresist pattern as a mask. In this case, the etching solution is prevented from penetrating into the interfaces of each layer, and good pattern processing can be achieved.

Embodiment FIGS. 1(a) to 1(e) are cross-sectional views showing an embodiment of the present invention in the order of steps. The process of forming the conductive film will be described in detail. First, as shown in FIG. 1(a), BLAZ 7CVD
(Chemical Vapor
A silicon nitride film 2 is deposited to a thickness of 800 Å using the on method. Next, as shown in FIG. 1(b), pattern processing is performed using an electron beam drawing photoresist PMMA3. Next, RI E (Reactive Ion Etchi)
ng) method, the exposed portion of the silicon nitride film 2 is etched with plasma using CF4 gas, and the PM
The MA resist 3 is modified at the same time. Furthermore, by performing heat treatment at 170°C for 30 minutes in a nitrogen atmosphere,
As shown in FIG. 1(C), the cross-sectional shape of the opening of the PMMA resist 3 is processed into a curved shape. Next, as shown in FIG. 1(d), the semi-insulating GaA exposed in the openings of the resist 3 and silicon nitride film 2 is etched by wet etching.
The surface of the s-substrate 1 is scraped. Next, as shown in FIG. 1(e), the silicon nitride film 2 and PM
A metal titanium layer 4 is formed on the semi-insulating GaAs substrate 1 on which the MA resist 3 is formed.

In this example, the substrate is a semi-insulating GaAs substrate, and the underlying dielectric film of the photoresist is plasma CVD.
Although a silicon nitride film formed by the D method is used, the substrate is not limited to this, and the thickness of the silicon nitride film and the deposition method are also not limited to this.

Further, the photoresist to be shaped is not limited to the electron beam direct writing PMMA of this embodiment. In this example, surface modification for shape processing of photoresist,
RIE partially etches the underlying silicon nitride film.
The etching method and etching gas are not limited to this, and both may be performed separately.

In this example, the heat treatment for shaping the photoresist was performed at 170°C for 30 minutes in a nitrogen atmosphere, but the atmosphere is not limited to this, and the processing temperature and time may vary depending on the type of resist and the desired curve shape. Varies depending on In this example,
Although the silicon nitride film under the opening and the semiconductor substrate further below it were etched, the surface treatment under the photoresist opening is not limited to this. In this example, a metallic titanium film is used as the upper layer, but other conductive or dielectric materials may be used, and the material is not limited to the material used in this example.

Effects of the Invention As described above, the present invention first deposits a silicon nitride film as a base on a semiconductor substrate, forms a photoresist pattern with partial openings on this dielectric film, and By exposing the resist pattern to plasma gas to modify its surface and then applying heat treatment, it is possible to process the cross-sectional shape of the photoresist opening into a curved shape without increasing the dimension below the opening, and it is possible to process the cross-sectional shape of the photoresist opening into a curved shape. Because of the good adhesion between the nitride film, photoresist, and semiconductor substrate, it prevents the etching solution from penetrating the interface during wet etching, allowing normal wet etching to follow the upper pattern. The effects are significant.

[Brief explanation of drawings]

FIG. 1 is a step-by-step sectional view for explaining a method of manufacturing a semiconductor device according to the present invention, and FIG. 2 is a step-by-step sectional view for explaining a conventional manufacturing method. 1... Semi-insulating GaAs substrate, 2...
Silicon nitride film, 3... Photoresist (PM
MA), 41. . ...Titanium, 5...Semiconductor substrate, 6...
...Photoresist, 7...Dielectric film or conductive film.

Claims (1)

[Claims] Depositing a dielectric film on a semiconductor substrate, forming a photoresist pattern partially having openings on the dielectric film, exposing the photoresist pattern to plasma gas, and then Manufacturing a semiconductor device comprising the steps of performing heat treatment to process the cross-sectional shape of the photoresist opening into a curved shape, and forming a conductor or dielectric material along the processed shape of the photoresist. Method.