JPH05335195A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enhance a resist in focal depth so as to obtain a desired resist pattern equally formed for both the higher part and the lower part of a step even in a region with large level difference. CONSTITUTION:A photoresist film 4 is applied onto a semiconductor substrate 1 and exposed to light through the intermediary of a mask 5, whereby only the surface of the film 4 is removed by developing. Then, dyeing liquid is applied onto the surface of the photoresist film 4 and heated, whereby a dyeing layer 8 is formed on the surface of the photoresist film 4. Then, a developing process is carried out, and the exposed part 7 is removed together with the dye layer 8. In succession, all the surface of the substrate 1 is exposed using the unexposed dye layer 8 as a mask and then developed, whereby a fine photoresist pattern 4A is obtained. In result, the pattern image of a mask 5 transferred onto the photoresist film 4 is determined by a first light exposure, and it is good enough that the pattern image is printed on only the surface of the photoresist film 4 as an optical contrast in a first light exposure process, so that a photoresist is enhanced in focal depth and a pattern image can be formed high enough in resolution both on a higher part and a lower part in a region large in level difference at the same time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming a fine pattern with a resist film.

[0002]

2. Description of the Related Art A conventional method of forming a fine pattern in a semiconductor device manufacturing process will be described with reference to FIGS.

First, as shown in FIG. 3A, an oxide film 2 and an Al film 3 are formed on a semiconductor substrate 1, and then a photoresist film 4 is applied on the front surface. For example, i-line wavelength (36
5 nm) through the mask 5,
Expose.

Next, as shown in FIG. 3B, the semiconductor substrate 1 is heated in order to improve the pattern shape after development.

Next, as shown in FIG. 3C, when development is performed using an alkaline developing solution, only the exposed portion is dissolved,
A positive type fine photoresist pattern 4A is formed.

Thereafter, the Al film 3 is etched by dry etching using the photoresist pattern 4A as a mask to form an Al wiring.

[0007]

As described above, since various steps due to the oxide film 2 and the like exist on the semiconductor substrate,
If a photoresist film is applied on this, the influence of the step on the semiconductor substrate is directly received. As a result,
The focus position of the photoresist film above the step is different from the focus position where the photoresist film below the step is resolved, and the tolerance range (focal depth) of the focus of the photoresist film is increased above and below a large step. Since it cannot be resolved with high accuracy at the top and bottom of the step at the same time, it becomes difficult to form a fine pattern. Further, since the resist film thickness greatly changes at the position where the step moves from the upper part to the lower part of the step, the resolution with respect to the change of the resist film thickness is different due to the influence of the standing wave, which makes it difficult to separate and resolve with high accuracy. Become. Therefore, there is a problem that the reliability and the degree of integration of the semiconductor device cannot be improved.

[0008]

According to the method of manufacturing a semiconductor device of the first invention, a step of forming a resist film on one main surface of a semiconductor substrate and a step of removing only the surface of the resist film through a mask are possible. First exposure with a different exposure amount, a step of mixing a dye on the exposed surface of the resist film and then developing to remove the exposed portion, and a mask of the resist film with a part of the surface removed. And a step of performing a second exposure.

In the method for manufacturing a semiconductor device of the second invention, a step of forming a resist film on one main surface of a semiconductor substrate, and a step of mixing a dye on the surface of the resist film and then only a surface of the resist film through a mask The first exposure step is performed with an exposure amount that can be removed by development, and the second exposure step is performed after the resist film is developed to remove only the exposed portion of the surface.

[0010]

The present invention will be described below with reference to the drawings. 1A to 1D are cross-sectional views of semiconductor chips for explaining a first embodiment of the present invention.

First, as shown in FIG. 1A, a photoresist film 4 is applied onto a semiconductor substrate 1 having an oxide film 2 and an Al film 3 and having a step. Next, using the exposure amount such that only the surface of the photoresist film is removed by the development, for example, the exposure amount 0.7 times the resolution of the photoresist film 4 is used, the ultraviolet light 6 is passed through the mask 5. For example, the first exposure is performed at the wavelength of i-line (365 nm) to form the exposed portion 7.

Next, as shown in FIG. 1 (b), a dye in which an organic solvent such as ether or alcohol is dissolved is applied to the surface of the photoresist film 4 and heated on a hot plate to apply the dye to the photoresist film. The dye layer 8 is formed by mixing the dye layer 8 on the surface. Examples of the dye that absorbs i-rays include azobenzene-based 4-nitroazobenzene (Nitroazo).
Benzene), a diphenyl polyene (Diphenyl polyene: n = 1 to 1)
4), benzazole-based 2- (4-methoxycarbonylstyryl) benzazole [2- (4-Methox
ycarbonylstyryl) benzozo
le] and the like can be used.

Next, as shown in FIG. 1C, development is performed to remove only the exposed portion 7 on the surface of the photoresist film.
Next, a second exposure (overall exposure) is performed with broadband (wide wavelength width) light 9 or light in a direction perpendicular to the substrate.

Next, as shown in FIG. 1D, development is performed to form a fine photoresist pattern 4A. Next, the Al film 3 is etched using the photoresist pattern 4A as a mask to form an Al wiring 3A.

In FIG. 1B, instead of the hot plate, infrared rays or far infrared rays may be used to heat only the surface of the photoresist film to mix the dye into the surface of the photoresist film 4. In this case, the amount of dye mixed on the surface of the photoresist film can be easily controlled.

As described above, in the first embodiment, after exposing only the surface portion of the photoresist film 4 by the first exposure,
Dye is mixed into the surface of the photoresist film 4 to remove the exposed portion by the first exposure by development, and second exposure (overall exposure) is performed using the dye layer 8 in the unexposed portion as a mask for development. Thus, the pattern image of the mask transferred to the photoresist film 4 is determined by the first exposure. Then, since a fine photoresist pattern is formed by the second exposure, it suffices that the light contrast be obtained only in the surface portion of the photoresist film in the first exposure. In the conventional technique, light contrast is required for the entire photoresist film in order to obtain a photoresist pattern, whereas in the present embodiment, only the surface of the photoresist film has light contrast in the first exposure. Therefore, when the pattern width is 0.5 μm, the depth of focus in the first exposure is 1.5 μm to 3.0 μm.
Since it is improved by about 2 times, it is possible to resolve at the same time even at the top and bottom of a large step.

As the second exposure method, by using only the exposure light in the direction perpendicular to the semiconductor substrate, the pattern size obtained by the first exposure and development can be directly transferred to the bottom. Further, by using a light source with a wide wavelength width, the standing wave effect inside the photoresist can be suppressed.

2 (a) to 2 (c) are sectional views of a semiconductor chip for explaining the second embodiment of the present invention.

First, as shown in FIG. 2, a photoresist film 4 is applied on the Al film 3 on the semiconductor substrate 1 as in the first embodiment. Next, on the surface of the photoresist film 3,
A dye dissolved in a solvent is applied, and only the surface of the photoresist 4 is heated using far infrared rays 10 to mix the dye into the resist surface to form a dye layer 8A.

Next, as shown in FIG. 2 (b), the UV light 6 is passed through the mask 5 using an exposure amount that can almost remove the dye-containing depth portion of the photoresist film surface.
For example, the first exposure is performed with the wavelength of i-line.

Then, as shown in FIG. 2C, development is performed to remove only the photoresist surface portion of the exposed portion. Next, the entire surface is exposed by using broad band light 9 having a wide wavelength width and is developed to form a fine photoresist pattern 4A. Thereafter, the Al film 3 is etched using the photoresist pattern 4A as a mask to form an Al wiring.

Also in the second embodiment, as in the first embodiment, fine Al wiring can be formed with high precision.

In the above embodiment, the first exposure light is i
Although the case of using ultraviolet rays such as rays has been described, the present invention is not limited to this, and far infrared rays, electron rays, X rays, and excimer laser beams may be used. Further, far ultraviolet rays and excimer laser beams can be used in addition to ultraviolet rays for the second exposure.

[0024]

As described above, according to the present invention, a mask made of a dye layer mixed with a dye is formed on the surface portion of a resist film having a step, and the remaining resist film is exposed using this mask. It is possible to form a fine pattern of resist with good resolution. Therefore, fine wiring and the like can be accurately formed even in a stepped portion, so that there is an effect that the reliability and the degree of integration of the semiconductor device can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a semiconductor chip for explaining a first embodiment of the present invention.

FIG. 2 is a sectional view of a semiconductor chip for explaining a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of a semiconductor chip for explaining a conventional method of manufacturing a semiconductor device.

[Explanation of symbols]

 1 Semiconductor substrate 2 Oxide film 3,3A Al film 4 Photoresist film 4A Photoresist pattern 5 Mask 6 UV light 7 Exposure part 8 Dye layer 9 Broadband light 10 Far infrared

Claims (9)

[Claims] 1. A step of forming a resist film on one main surface of a semiconductor substrate, a step of performing a first exposure with an exposure amount capable of removing only the surface of the resist film by a development through a mask, and the step of exposing It is characterized by including the steps of mixing the dye on the surface of the resist film and then developing it to remove the exposed portion, and performing the second exposure using the resist film from which a part of the surface has been removed as a mask. Method of manufacturing semiconductor device. 2. A step of forming a resist film on one main surface of a semiconductor substrate, and a step of exposing the surface of the resist film with a dye and then exposing the surface of the resist film only through a mask with an exposure amount capable of being removed by development. 1. A method of manufacturing a semiconductor device, comprising: the step of performing the first exposure; and the step of developing the resist film to remove only the exposed portion on the surface and then performing the second exposure. 3. The method of manufacturing a semiconductor device according to claim 1, wherein a dye having an absorption for the light of the wavelength for performing the second exposure is mixed into the surface of the resist film. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the dye is mixed on the surface of the resist film using a solvent containing the dye. 5. The method of manufacturing a semiconductor device according to claim 1, wherein the dye is applied to the surface of the resist film and then heated to mix the dye. 6. The method for manufacturing a semiconductor device according to claim 5, wherein heating is performed using infrared light or far infrared light. 7. The method of manufacturing a semiconductor device according to claim 1, wherein the second exposure is performed using light in a direction perpendicular to the semiconductor substrate. 8. The method of manufacturing a semiconductor device according to claim 1, wherein the second exposure is performed using light having a wide wavelength width. 9. The method of manufacturing a semiconductor device according to claim 1, wherein any one of ultraviolet rays, far infrared rays, and excimer laser beams is used as the second exposure light.