JPS6233428A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a fine pattern by PCM process using ordinary ultraviolet ray resist only without using a far ultraviolet ray resist as photoresist by a method wherein a light absorbing film mainly comprising polyimide is formed between two layers of photoresist films. CONSTITUTION:A silicon substrate 1 formed of a step difference around 0.5mum thick and a polycrystalline silicon layer 2 is coated with a positive type photoresist material 1.8mum thick to form the first photoresist film 3. Later the whole body is heated on a hotplate at 100 deg.C for 60sec. Next the first photoresist 3 is coated with photoabsorbent mainly comprising polyimide 2,000Angstrom thick to be heated on the hotplate at 100 deg.C for 60sec forming a light absorbing film 4. Finally the light absorbing film 4 is coated with photoresist 1.0mum thick to be heated on the hotplate at 100 deg.C for 40sec forming the second photoresist film 5 which is exposed using a specified mask.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a semiconductor device including a method for forming a fine pattern on a semiconductor substrate.

[Conventional technology]

Conventionally, P is a method of forming fine patterns on a semiconductor substrate having steps using a coating agent such as a resist.
CM (Fortable Comformable
A method called the Mas k ) method has been proposed.

In this method, as shown in FIG. 2(a), first, a positive deep ultraviolet resist film 6 such as polymethyl metagelate, which is mainly sensitive to 200 to 250 nm, is formed on the surface of the semiconductor substrate 1. , then 350-450 nm
A photoresist film 7 made of a normal phenol novolak resin having a photosensitive area is formed. Next, as shown in FIG. 2(h), a photoresist pattern 7a is formed only on the upper photoresist film 7 using an exposure device using an ultraviolet light source of 300 nm to 450 nm. At this time, the lower deep ultraviolet resist film 6 is not exposed to light because its sensitivity range is different.

Next, as shown in Figure 2 (C), the wavelength is 200 to 300n.
The entire surface of the semiconductor substrate is irradiated with parallel far ultraviolet rays of about m.

In the areas where the upper layer photoresist #7 remains, it absorbs far ultraviolet rays and serves as a mask for the lower layer resist film, so the lower layer far ultraviolet resist film 6, which has been reduced in molecular weight by irradiation with an appropriate solvent, is developed. By removing it, a fine deep ultraviolet resist pattern 6a is obtained. During development, the upper layer photoresist pattern 7a may or may not be dissolved.

[Problem that the invention seeks to solve]

The conventional pattern forming method using the PCM method described above has three main drawbacks as shown below.

First of all, when the upper and lower resist materials are applied in two layers, the two types of resist materials mix or react at the interface between these two layers, resulting in a resist material that has different properties from those resist materials. Metamorphic layers are formed. The presence of this metamorphosed layer makes it difficult to develop the deep ultraviolet resist film 6 below.

Second, the lower layer positive deep UV resist material generally has relatively low sensitivity and requires longer exposure times than the upper layer photoresist material, reducing productivity.

Third, positive deep UV resists generally have poor resistance to parallel plate reactive ion etching, that is, dry etching resistance, so when a fine pattern formed by a resist material is transferred to a semiconductor substrate by dry etching, The size transfer error becomes large.

An object of the present invention is to provide a method for manufacturing a semiconductor device that can form a fine pattern on a semiconductor substrate having steps without using a deep ultraviolet resist.

[Means for solving problems]

The method for manufacturing a semiconductor device of the present invention includes a step of forming a first photoresist film on a semiconductor substrate having a step, and a step of forming a light absorption film mainly composed of polyimide on the first photoresist film. , and forming a second photoresist film on the light absorption film.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1(a) to 1(d) are cross-sectional views of a semiconductor chip shown in the order of manufacturing steps to explain one embodiment of the present invention, and show an example of forming a fine pattern on a polycrystalline silicon layer. .

First, as shown in FIG. A first photoresist film 3 is formed by coating 800.50CP) to a thickness of 1.8 μm. After that, it is heated on a hot plate at 100" for 60 seconds. Next, polyimide is the main component. A light absorbing material (for example, an anti-reflection material AR manufactured by Brewer 5science)
CPN2) is applied to a thickness of 2000λ and heated for 100'0.60 seconds on a hot plate to form the light absorption film 4. Next, a photoresist is applied on this light absorption film 4. O.J.
Coat to a thickness of m and heat on a hot plate at 100℃ for 40 minutes.
After forming the second photoresist film 5 by heating for seconds, exposure is performed using a predetermined mask.

Next, by developing for 50 seconds using a developer (for example, developer for positive photoresists manufactured by Tokyo Ohka Co., Ltd. NMD-3), the second photoresist film in the exposed area becomes the sound absorbing film 4 under J-5-. are etched anisotropically at the same time. Through this development, a second photoresist pattern 5a and a light absorption film pattern 4a are formed as shown in FIG. 1(b).

Next, when the entire surface of the silicon substrate 1 is irradiated with sufficiently parallel ultraviolet rays, the light-absorbing film pattern 4a serves as a mask in the portion where the pattern exists, and the first photoresist film 3 under that portion is not exposed to light.

Then, by developing with a developer for about 80 seconds, the second
The exposed portions of the photoresist pattern 5a, the light absorption film pattern 4a, and the first photoresist film 3 are removed, and the first photoresist pattern 3a as shown in FIG. 1(C) has a high aspect ratio and a stepped portion. Good line width controllability can be obtained.

Thereafter, using the first photoresist pattern 3a as a mask, the polycrystalline silicon layer 2 is etched by dry etching. At this time, the transfer error in pattern dimensions can be made smaller than when a deep ultraviolet resist such as polymethyl acrylate is used as the lower layer.

[Effects of the Invention] As explained above, the present invention involves forming a light-absorbing film mainly composed of polyurethane between two photoresist films, and using a deep ultraviolet resist as the photoresist. It has the advantage of being able to form fine patterns using the PCM method using only a general ultraviolet resist. Furthermore, since no metamorphic layer is formed at the interface of the photoresist film, the method of patterning the photoresist film can be performed with high precision.

Furthermore, since the ultraviolet resist is used instead of the deep ultraviolet resist, which has poor dry etching resistance, it is possible to reduce transfer errors in pattern dimensions even when a pattern is transferred to a base by dry etching.

[Brief explanation of the drawing]

1) to 1(d) are cross-sectional views of a semiconductor chip shown in the order of steps to explain one embodiment of the present invention, and FIGS. 2(a) to
(cl is a cross-sectional view of a semiconductor chip shown in the order of steps to explain the pattern forming method using the conventional PCM method. 1...Clicon substrate, 2...Polycrystalline 7)
Recon layer, 3...First photoresist film, 4.
・Mark・Light absorption film, 4a...Light absorption film pattern,
5... Second photoresist film, 5a... Second photoresist pattern, 6... Deep ultraviolet resist film, 6a... Deep ultraviolet resist pattern, 7... ...-Photoresist film.・、-3 2nd agent Patent attorney Susumu Uchihara 7Page Figure 1 District 2

Claims (1)

[Claims] A step of forming a first photoresist film on a semiconductor substrate having a step, a step of forming a light absorption film mainly composed of polyimide on the first photoresist film, and a step of forming a second photoresist film on the light absorption film. A method for manufacturing a semiconductor device, comprising the step of forming a photoresist film.