JPH02140914A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a method for manufacturing a semiconductor device for flattening steps located on the surface of a photoresist by changing the transmission rate of X rays according to the thickness of a mask material. CONSTITUTION:A mask 10 consists of a mask substrate 1 and mask materials 2a, 2b, and 2c. When X rays are directed onto the mask 10, they cannot pass through the thick mask material 2a, a small amount of X rays passes through the medium-thick mask material 2b and a large amount of X rays pass through the thin mask 2c. Also, nearly all X rays can pass through an area without any mask materials, thus allowing a photoresist to be strongly sensitized. Thus, by changing the thickness of the mask materials 2a, 2b, and 2c, the amount of X rays projected to a photoresist 5 can be changed and the amount to be eliminated is changed according to the difference of sensitization. As a result a photoresist film pattern 6 with a flat surface can be obtained as a photoresist after development treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and more particularly to an improvement in a method for manufacturing a semiconductor device using an X-ray exposure mask.

[Conventional technology]

FIG. 3 is a cross-sectional view showing a conventional method for manufacturing a semiconductor device. In the figure, 1 is a mask substrate, 2 is an X-ray mask material, 3 is a semiconductor substrate, 4 is a film to be processed formed on the semiconductor substrate 3, and 5 is a photoresist film formed on the film to be processed 4. . Further, the arrow in the figure indicates the direction of incidence of the X-ray light.

Next, a manufacturing flow of a semiconductor device using a conventional method will be explained. A film 4 to be processed is formed on the semiconductor substrate 3 by various methods, and a photoresist la is applied on the film 4 to be processed 1.
Apply 5. By exposing a part of the photoresist 5 to light using ordinary X-ray masks 1 and 2 and developing it, the area exposed to the X-ray light becomes sensitized. The photoresist film 5 is removed, and the X-ray mask pattern 8 is transferred to the photoresist film 5 (FIG. 3b)) If it is a resist, the unexposed areas will disappear during the development process and a pattern will be formed). This food resist pattern 6
A pattern is formed on the film to be processed 4 by etching using the mask as an etching-resistant mask (FIG. 3C).
).

[Problem to be solved by the invention]

Conventional fog light using X-ray light does not have a photoresist with good sensitivity to X-rays, so it is not possible to produce strong contrast, and it is difficult to obtain a good photoresist pattern profile when forming fine patterns. This has been a drawback of X-ray exposure technology.

This invention takes advantage of the weaknesses of X-ray exposure as described above, and
The thickness of the mask material of the radiation exposure mask is changed, and the photoresist surface is exposed to X-ray light using such a mask.
It is an object of the present invention to provide a method for manufacturing a semiconductor device that can flatten steps on the surface of a photoresist through a subsequent development process.

[Means to solve the problem]

In the method for manufacturing a semiconductor device according to the present invention, the thickness of the mask material of the X-ray exposure mask is changed so that the transmittance of X-rays is changed depending on the thickness of the mask material. In this method, only the concave portions are irradiated with weak X-ray light, which also takes into account the poor contrast characteristics of the photoresist itself, and makes it possible to flatten the photoresist surface after development.

[Effect]

The planarization of the photoresist surface according to the present invention can be used in place of the lower resist layer that conventionally requires a thick resist cladding film thickness in a multilayer resist process, and the lower resist layer can be made thinner and planar. Therefore, subsequent pattern formation of the lower resist layer can be easily and accurately performed.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a method for manufacturing a semiconductor device according to an embodiment of the present invention, in which 1 is a mask substrate, 2a is a thick X-ray mask material, and 2b is a medium-thick X-ray mask material. ,
2C is a thin X-ray mask material, 3 is a semiconductor substrate, and 5 is a photoresist film. Further, in the figure, arrows indicate the direction of incidence of X-rays.

Next, the present manufacturing method will be explained.

First, a 7-photoresist film 5 is placed on a semiconductor substrate 3 with an underlying step.
When the photoresist film S is coated, the photoresist film S reflects the underlying level difference and is coated thickly on the concave portions of the step and thinly on the convex portions of the step as shown in the figure. The thickness of the photoresist film 5 in the recessed portions also differs depending on the density of the underlying step pattern, with the film thickness being thicker in the denser portions of the pattern (and thinner in the coarser portions).

When planarizing the photoresist film 5 as shown in FIG. 1a), a mask 10 shown in the figure is prepared.

This mask 10 includes a mask substrate 1 and an X mask material 2at.
2 bs 2 C, and when X-rays are incident on this, the thick mask material 2a does not allow the X-rays to pass through, and the medium-thick mask material 2b allows a small amount of X-ray light to pass through. A considerable amount of X-ray light can pass through the thin mask 2c. Furthermore, in areas where there is no mask material, most of the X-ray light can pass through, and the photoresist can be strongly exposed. Therefore, a masking material 2a is not formed in areas where a thick portion of the resist 5 is to be removed by the development process, and a thick masking material 2a is formed in areas where almost no resist 5 is to be removed. X irradiated onto the photoresist 5 by changing the thickness of c
By changing the amount of light and changing the amount removed depending on the degree of exposure, it is possible to obtain a photoresist film pattern 6 with a flat surface as shown in FIG. 1b) as a photoresist after development. can.

In this way, since the photoresist surface can be flattened in this example, it can be used in place of the lower resist layer that required a thick resist cladding film thickness in conventional multilayer resist processes, and the lower resist layer can be made thin and flat. The subsequent pattern formation of the lower resist layer can be performed accurately and easily.

In the above embodiment, the thickness of the mask material is shown in three stages, but the thickness of the mask material is not limited to this, and can be changed in multiple stages.

Further, in the above embodiment, the X-ray masks 1, 2a to 2C having different thicknesses in multiple stages were used as the mask material.
As in another embodiment of the present invention shown in the figure, replicas 22a to 22c formed using five steps of photoresist are formed on the mask substrate 1 instead of an X-ray mask, and these are used as an exposure mask. However, the same effect as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the thickness of the X-ray mask material is changed in multiple stages and the exposure is performed using this mask. This method has the advantage that a resist film with a flat surface can be formed even on a semiconductor substrate with a certain surface, and this can be applied to the formation of a lower resist layer in a multilayer resist process.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a method for manufacturing a semiconductor device according to an embodiment of the present invention, FIG. 2 is a diagram showing a method for manufacturing a semiconductor device according to another embodiment of the invention, and FIG. 3 is a diagram showing a method for manufacturing a semiconductor device according to another embodiment of the invention. FIG. i-' mask substrate, 2, 2a to 2C122a to 22c
= X-ray mask material, 3... semiconductor substrate, 4... film to be etched, 5... coated photoresist film before planarization, 6... photoresist film subjected to planarization treatment. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1) A method for manufacturing a semiconductor device, including a step of applying a photoresist on a substrate having a step on the surface, and an X-ray exposure mask having a thickness corresponding to the resist step formed on the resist surface. a patterned mask,
Alternatively, a photoresist film having a flat surface is formed by exposing the photoresist to X-ray light using a mask having a replica at a position corresponding to the resist step, and then developing the photoresist. A method for manufacturing a semiconductor device, characterized in that: