JPS62137831A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a hole, which has sufficiently tapered wall so that a metal wiring is not broken, in an insulating film only by anisotropic etching, by using a multilayer positive photoresist film, in which upper layers have higher optical sensitivity than that of the lower layers, as a mask for etching when the hole is formed in the insulating film. CONSTITUTION:A PSG film 2 is formed on one main surface of a semiconductor substrate 1. A three-layer photoresist film, in which the sensitivity of the upper layer film is higher than that of the lower layer film, is formed on the surface of the PSG film 2. Then, exposure and development are performed with a specified mask pattern, and a hole is formed at a specified region in the photoresist film. Because of the difference in the optical sensitivity in the photoresist films, the opening parts of the photoresist films 3, 4 and 5 become large in this order. When these parts are adequately baked, the side surface of the holes in the multilayer photoresist films becomes considerably smooth. With the tapered multilayer photoresist films 3, 4 and 5 as masks, reactive ions 7 are projected from the upper part of the substrate using an RIE method, and the PSG film 2 is etched away. The tapered part is slowly retreated, and the tapered part is formed in the hole in the PSG film.

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 openings in an insulating film.

[Conventional technology]

Conventionally, in order to form an opening in an insulating film formed on a semiconductor substrate, for example, as shown in FIG. A positive type photoresist 6 is applied on the surface, exposed and developed in a predetermined mask pattern to form an opening in the photoresist film 7, and then baked to a temperature of 491 to form a photoresist 6 on the side surface of the opening (see Fig. 2). (a)). Next, using a reactive ion etching (hereinafter referred to as RIE) method, reactive ions 7 are irradiated from above the substrate to perform anisotropic etching to form openings in the PSG film 2 that is not covered with the photoresist 6 ( Figure 2(b)). By the way, the taper formed on the side surface of the opening in the photoresist 6 is slight even when baked, and the shape of the photoresist 8 before etching is small.
The amount of retreat of the photoresist during etching is also small compared to the previous one.

Therefore, as shown in Figure 2 (bl Therefore, as shown in Fig. 3, following the step shown in Fig. 2(a), first an appropriate amount of the entire upper part of the pores of the PSG film is isotropically etched using a hydrofluoric acid buffer. Next, the remaining portion is anisotropically etched using the R, IE method to form an opening, and the upper corner of the opening is rounded.

[Problem that the invention seeks to solve]

In the above-mentioned conventional method of combining isotropic etching and anisotropic etching, especially when a PSG film is used as an insulating film, the etching rate of the PSG film with a hydrofluoric acid buffer is extremely high, so the openings are extremely wide. grow bigger,
This is disadvantageous for miniaturization of elements. Further, there is a major drawback in that dirt in the hydrofluoric acid buffer adheres to the wafer surface, causing defects in the openings. It is an object of the present invention to provide a method for eliminating the above-mentioned drawbacks and forming an opening in an insulating film with a sufficient taper to prevent metal wiring from breaking by using only anisotropic etching.

[Failure to solve the problem]

The method for manufacturing a semiconductor device of the present invention includes a semi-conductor having an insulating film.
forming a multilayer photoresist film by laminating two or more types of positive photoresists having different stress sensitivities on the entire surface of the T-body substrate so that the upper layer has higher sensitivity than the lower layer; A step of exposing and developing the multilayer photoresist film with a predetermined mask pattern to form an opening whose side surface is open toward the outside of the film, and a multilayer photoresist film having the opening? The method is characterized in that an opening is formed in the insulating film using an anisotropic etching method as a mask, and the side surface of the insulating film above the opening is sloped.

〔Example〕

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

FIGS. 1(a) to 1(Fd) are vertical cross-sectional views of step J of an embodiment of the present invention.

First, as shown in FIG. 1(a), a first positive photoresist film 3 is applied to the surface of P2O[2 formed on the entire surface of the semiconductor substrate 1. Furthermore, a second positive type photoresist 4 having higher photosensitivity is coated on the photoresist film 3. Furthermore, on the photoresist film 4,
A third positive type photoresist film 5 having even higher photosensitivity is applied to form a three-layer photoresist film in which the upper layer has higher sensitivity than the lower layer.

Next, as shown in FIG. 1B, exposure and development are performed using a predetermined mask pattern to form openings in predetermined areas of the photoresist film. At this time, due to the difference in photosensitivity of the photoresist films, the openings in each of the photoresist films become larger in the order of 7 photoresist films 3 and 4.5.

Next, as shown in FIG. 1(C), when this is properly baked, the side surfaces of the openings in the multilayer photoresist film are quite smooth and have a sufficiently large taper compared to the single layer 7 photoresist film. An aperture having an outwardly open shape is formed.

Next, as shown in FIG. 1(d), reactive ions 7 are injected from above the substrate using the RIE method as a tapered poly/i17 otres) [3,4,5'i mask.
The PSG film 2 is removed by etching. The multilayer photoresist shape 8' before etching has a more gradual slope with the opening side surfaces of the photoresist opening outward compared to the -1-photoresist shape 8. ) A portion of the taper of the openings M3, 4, and 5 is etched more than in the case of the photoresist and gradually recedes, forming a corresponding taper in the opening of the PEG film.

Usually, reactive ion etching of PSGg is performed using CF47H.
It is carried out using 2-based or CHF3102-based gas. At that time, the etching selectivity ratio of psog to 7 photoresist a is about 2.5 to 5.0, but by changing the gas flow rate ratio, the etching selectivity ratio can be changed, and the required amount of photoresist regression can be adjusted. Can be controlled.

Further, in this embodiment, a three-layer 7 photoresist film has been described, but by using a multilayer photoresist film, a smooth taper can be formed by the photoresist openings.

In addition, by selecting the number of photoresist layers, photosensitivity, and exposure conditions, RI
Using only the E method, it is possible to form holes in an insulating film having various extents and angles of inclination.

〔Effect of the invention〕

As explained above, the present invention uses a multilayer positive photoresist film in which a film with higher photosensitivity is placed in the upper layer as an etching mask when forming holes in an insulating film. Since the side surface of the opening in the insulating film can be tapered using only the anisotropic etching method, it is very advantageous for miniaturizing the device. Furthermore, unlike the wet etching method, there is less dust adhesion, which is highly effective in improving the manufacturing yield of semiconductor devices.

[Brief explanation of drawings]

FIGS. 1(a) to (d) are vertical cross-sectional views in the order of steps of an embodiment of the present invention, FIGS. 2(a) to (b) are longitudinal cross-sectional views in the order of steps showing the prior art, and FIG. FIG. 1... Semiconductor substrate, 2... Phosphorsilicate glass (PSC)) IO13, 4, 5, 6... Positive photoresist film, 7... reactive ions,
8.8'...Photoresist shape before etching. Agent Patent attorney Hi Uchihara, 1 Kaya 1
Figure $ 2 Figure $ 3 Figure

Claims (1)

[Claims] forming a multilayer photoresist film by laminating two or more types of positive photoresist films with different photosensitivity on one main surface of a semiconductor substrate having an insulating film so that the upper layer film has higher sensitivity than the lower layer film; , exposing and developing the multilayer photoresist film with a predetermined mask pattern to form apertures with side surfaces opening toward the outside of the film; and using the multilayer photoresist film having the apertures as a mask, anisotropic A method of manufacturing a semiconductor device, comprising forming an opening in the insulating film by an etching method, and making a side surface of the insulating film above the opening slope.