JPH01204044A - Pattern forming method - Google Patents

Abstract

PURPOSE:To improve the production yield of a MOSIC, etc., having a fine structure by constituting a positive type photoresist film of an intermediate layer composed of a photoresist film, and an upper and a lower layers composed of a photofading film having the photofading property against an exposure wavelength which are mounted on a substrate and exposing the positive type photoresist film. CONSTITUTION:A high reflection film 22 composed of aluminium and having high reflecting power is mounted on the substrate 10 which is formed a rugged gradation having 1mum in thickness. Next, a lower layer photofading film 32 having the photofading sensitivity of 1,000mj is formed on the film 22 according to a spin coating method. And then, the positive type photoresist film 12 having an average film thickness of about 1mum is formed on the film 32, followed by forming the upper layer fading film 34 having the photofading sensitivity of 350mj on the film 12. Next, the obtd. photoresist film is exposed with an exposure of 400mj, followed by developing it. As the photofading films 32 and 34 formed on the upper and the lower layers respectively are water-soluble, the films dissolve in a developing solution. After developing the films 32 and 34, the films are washed with water, thereby obtaining a positive type photoresist film pattern 14 having a good pattern profile.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pattern forming method, and particularly to a pattern forming method of a photoresist film used in manufacturing semiconductor integrated circuits and the like.

[Prior Art] Conventionally, as a method of improving the pattern resolution of a photoresist film employed in the manufacturing process of MO8ICs such as semiconductor integrated circuits, a substance having a photobleaching effect depending on the exposure wavelength is applied onto the photoresist film by spin coating. A method of coating and patterning is used.

Regarding this conventional method, FIGS. 3 to 5 show schematic cross-sectional views in the order of steps, and FIG. 6 shows a schematic plan view.

First, as shown in FIG. 3(a), a positive photoresist film 12 is coated on a substrate 10 by spin coating, and then exposed using a reduction projection exposure apparatus as shown in FIG. 3(b). However, when development is performed, the upper part 14a of the pattern
A trapezoidal positive photoresist film pattern 14 having different dimensions of the pattern bottom 14b is obtained.

On the other hand, as shown in FIG. 4(a), there is a positive photoresist on the substrate 10! I! After coating 12 by spin coating, a photobleaching substance having photobleaching properties depending on the exposure wavelength is coated by spin coating to form a photobleaching film 20, and then exposure is performed using a reduction projection exposure device. The contrast of the image of the light that is attenuated when passing through the reduction projection system is enhanced by the photobleaching effect of the photobleaching film 20, and when development is performed as shown in FIG. 4(b), a good pattern profile is obtained. A positive photoresist film pattern 14 is formed.

[Problems to be Solved by the Invention] However, even when a photobleaching film is used as shown in FIG. As shown in Figure (a), after forming a positive photoresist film 12 by spin coating on a substrate on which a high reflection film 22 is formed, a photobleaching film 20 having photobleaching properties depending on the exposure wavelength is spun. When a coating film is formed by a coating method and exposed using a reduction projection exposure device as shown in FIG. The transmitted light 26 is irradiated onto the high reflection film surface 22a, and the light with enhanced contrast becomes a large reflected light 26a, which is diffused laterally. Therefore, overexposure is likely to occur, and it is difficult to control the dimensions of the positive photoresist 1 to film pattern 14 with respect to the mask dimensions. In particular, as shown in FIG. 6, the light reflection effect becomes more pronounced at the stepped portion 28, causing pattern breakage 30, and the finer the pattern, the more difficult it becomes to control the pattern dimension relative to the mask dimension, resulting in a significant drop in manufacturing yield, etc. There was a drawback.

An object of the present invention is to provide a pattern forming method that solves this problem.

[Means for Solving the Problems] The present invention includes a step of forming a photobleaching film containing a photobleaching substance having photobleaching properties depending on the exposure wavelength on a substrate, and a process of forming a photoresist film on the photobleaching film. a step of forming a photobleaching film containing a photobleaching substance having photobleaching properties depending on the exposure wavelength on the crotch of the photoresist; a step of exposing the photoresist film to light; and a step of exposing the photoresist film after exposure to the photobleaching material. This pattern forming method is characterized by comprising a step of developing while removing the film.

Effect] When a photobleaching film containing a substance having photobleaching properties depending on the exposure wavelength of the photoresist film is formed on the substrate as a lower layer and an upper layer with the photoresist film as an intermediate layer, and the photoresist film is exposed to light, The contrast of the attenuated image is enhanced by the photobleaching action of the overlying photobleaching film, and this enhanced light is sensitive to the photoresist film. As soon as the sensitivity is completed, the light passes through the photoresist film and is absorbed by the underlying photobleaching material. At this time, by differentiating the photobleaching speed of the photobleaching substances formed on the upper and lower layers, such as faster for the upper layer and slower for the lower layer, exposure can be performed with a constant light amount, and it does not depend on the reflectance of the substrate. , it becomes possible to form a pattern with a good resist profile.

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

Figures 1 (a) to (1)) show cross-sectional views of a substrate according to an embodiment of the present invention in the order of steps, and Figure 2 shows a schematic plan view of a substrate 1q processed by the method of the present invention. It is something that

First, as shown in FIG. 1(a), a highly reflective film 22 having a high reflectance is placed on a substrate 10 on which uneven steps of approximately 1 μs are formed.
Then, aluminum is deposited to a thickness of 1 μm using sputtering. Next, an exposure wavelength of 436n was applied using a spin coating method.
Styrylpyridinium 2.1mmol110 is dissolved in polyvinyl alcohol and pure water as a photobleaching substance that has a photobleaching effect on m, and a water-soluble solution with a viscosity of 20c is applied onto the high reflection film 22 with an average of about 0.5JJIr1. It is formed with a film thickness and heat-treated at a temperature of 80°C to achieve a photobleaching sensitivity of 100.
A lower photobleaching film 32 of 0IIlj is formed.

Further, a positive photoresist film 12 is coated by spin coating.
was formed with an average thickness of about 11 JIrI, and after heat treatment at a temperature of 80° C., a solution of the same photobleaching material as the lower photobleaching film 32 and having a viscosity of about 10 cps was coated using a spin coating method. Formed with a film thickness of 37#ll, photobleaching sensitivity is 35
An upper photobleaching film 34 of 0 mj is formed.

Next, the wavelength is 436 nm, the numerical aperture is 0.35, and the irradiation output is 500.
When a pattern with a design size of 0.8 μm is exposed at an exposure maximum of 400 mj using a 175 mW/Cm2 reduction projection exposure device and then developed, the photobleaching films 32 and 34 formed on the upper and lower layers become water-soluble. Because it is a resistant material, it dissolves in the developer, and after washing with water after development, it has a good pattern profile of 0.8IJ as shown in Figure 1(b)! A positive photoresist film pattern 14 of rI is obtained. In particular, as shown in FIG. 2, a positive photoresist film pattern 14 is formed with no pattern breakage even at the stepped portion 28.

In the above examples, a solution of styrylpyridinium dissolved in polyvinyl alcohol and pure water was used as a photobleaching substance, but the exposure wavelength was, for example, 436 nm.

A substance having a photobleaching effect in the vicinity of 405 nm, 365 nm and 1245 nm may also be used. In addition, although a water-soluble photobleaching film that is dissolved in the developer of the photoresist film is used, other photobleaching substances and methods for removing photobleaching substances that do not damage the photoresist film or the substrate surface may be used. . In addition, although a 115 reduction projection exposure apparatus was used, other wavelengths were used, for example, 405 nm and 365 nm.

Other reduction projection exposure apparatus capable of irradiating light at 245 nm may be used, and although aluminum is used as the film having high reflectance, other films such as tungsten, molybdenum, etc. may also be used.

[Effects of the Invention] As explained above, according to the present invention, a photoresist film is used as an intermediate layer on a substrate, and photobleaching films having photobleaching properties with respect to the exposure wavelength are formed as upper and lower layers, and then exposed to light. In order to perform this, the contrast of the attenuated image is enhanced by the photobleaching action of the upper photobleaching film after passing through the demagnification projection system, and this enhanced light is sensitive to the photoresist film. After sensing,
The light transmitted through the photoresist film is absorbed by a photobleaching film formed in the lower layer that sufficiently slows down the photobleaching sensitivity.

Therefore, reflection from the substrate can be prevented, and exposure can be performed with a constant light star. Therefore, it is possible to form a pattern that does not depend on the reflectance of the substrate and has a good resist profile, and also to form a resist pattern that faithfully corresponds to the anatomical dimension without pattern breakage in the uneven step part, and it is possible to form a resist pattern that faithfully corresponds to the anatomical dimension without depending on the reflectance of the substrate. This has the effect of significantly improving manufacturing yield.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view showing an embodiment of the present invention in the order of main steps, Fig. 2 is a schematic plan view of a substrate obtained by the method of the present invention, and Figs. 3 to 5 are conventional pattern forming methods. A schematic cross-sectional view showing the method in the order of main steps, and FIG. 6 is a schematic plan view of a substrate obtained by a conventional example. 10...Substrate 12...Positive photoresist film 14...Positive photoresist film pattern 14a...
・Pattern top 14b...Pattern bottom 20...
・Photobleaching film 22...High reflection film 22a...
Highly reflective film surface 26... Light 26a (passed through the photomask)...
Reflected light 28...Stepped portion 30...Pattern cut 32...Lower layer photobleaching film 34...Upper layer photobleaching film

Claims (1)

[Claims] (1) A step of forming a photobleaching film containing a photobleaching substance having photobleaching properties depending on the exposure wavelength on a substrate, a step of forming a photoresist film on the photobleaching film, and a step of exposing the photoresist film to light. a step of forming a photobleaching film containing a photobleaching substance having photobleaching properties depending on the wavelength; a step of exposing the photoresist film; and a step of developing the exposed photoresist film while removing the photobleaching film. A pattern forming method characterized by comprising: