JPH0470626B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a pattern forming method for patterning an adhered layer of metal, insulator, etc. by lift-off during the manufacture of semiconductor devices and the like.

(Description of Prior Art) When manufacturing semiconductor devices and the like, there are two conventionally known methods for forming patterns on deposited layers of metals, insulators, etc.: an etching method and a lift-off method. The lift-off method is a simple method, is suitable for forming fine patterns without causing damage due to etching, and has the advantage that even metals that are difficult to etch can be easily patterned. However, the lift-off method has problems with the cross-sectional shape, heat resistance, and solubility of the resist film.
Strict conditions regarding adhesion, etc. are required. For example, in order to be able to easily form a pattern by lift-off, it is necessary that the adhesion layer deposited on the resist film can be easily removed as the resist is dissolved. The cross-sectional shape must be an overhang shape. Furthermore, in order to improve the adhesion to a substrate such as a metal, it is effective to heat the substrate during vapor deposition, so the resist is required to have good heat resistance. Furthermore, it is required that the resist has good adhesion to the substrate to prevent the resist layer from peeling off before and during vapor deposition of metal or the like. Furthermore, in order to form highly integrated fine patterns such as VLSI, it is required that the resist has high resolution.

Currently, in order to form this overhang shape, a multilayer structure is used or a positive photoresist such as AZ-1350J (trade name of a photoresist manufactured by Shipley) treated with chlorobenzene is used. These processes are complicated, have poor throughput, and are difficult to obtain submicrocolon resolution.

(Object of the invention) In view of the above-mentioned conventional drawbacks, the object of the present invention is to
The cross-sectional shape of the resist film that forms the resist pattern is formed into an overhang shape on the order of submicrons, making it easy to dissolve and remove the resist film, and improving the adhesion of the resist to create a beautiful and sharp covering. It is an object of the present invention to provide a resist pattern forming method capable of obtaining a layered pattern.

Still another object of the present invention is to provide a resist having such heat resistance that it is possible to heat the substrate during application of the adhesion layer, and to provide a resist with good adhesion that can be applied to a submicron layer by a lift-off method. The purpose of the present invention is to provide a method for forming patterns so that patterns can be formed to order.

(Structure of the Invention) In order to achieve this object, according to the present invention,
A process of forming a film of quinonediazide sulfonic acid ester of novolac resin as a resist film on the surface of the substrate, a process of selectively exposing this film to deep ultraviolet rays, and a process of developing this film with a solution mainly containing acetate ester. A step of forming a resist pattern, a step of irradiating the resist pattern with ultraviolet rays to photodecompose the quinone diazide groups in the resist pattern, a step of vapor depositing an adhesion layer on the resist pattern and the substrate surface, and a lift-off method. The method is characterized by comprising a step of removing the resist pattern and obtaining a pattern of the deposited layer deposited on the surface of the substrate.

(Explanation of Examples) Examples of the present invention will be described below.

In order to solve the conventional drawbacks of the lift-off method, the present inventors found that the cross-sectional shape of the resist pattern becomes an overhanging shape based on the results of numerous experiments. They found that esters were suitable, and after forming a resist pattern using this material, it was confirmed that the solubility of the resist was increased by irradiating it with ultraviolet light. Furthermore, since this material has excellent heat resistance, it has been confirmed that heating the substrate during deposition of the adhesive layer increases the adhesion of the resist and the adhesive layer to the substrate.

Next, examples and comparative examples of the pattern forming method according to the present invention will be described.

Example 1 Naphthoquinone-1,2-diazide 5, a novolak resin, which is a type of quinonediazide sulfonic acid ester of a novolak resin, was used as a resist material.
-Sulfonic acid ester (hereinafter referred to as LMR)
It was used. In this case, considering that a low degree of polymerization is one of the reasons for improving resolution, naphthoquinone-1,2, a novolak resin with a degree of polymerization of 1 to 10, is used.
-diazide-5-sulfonic acid ester was used. First, this LMR was dissolved in methylcellosolve acetate and applied to a thickness of 0.7 μm on a silicon substrate to form a film, that is, a resist film. next,
After heat-treating (pre-baking) the substrate with the resist film at a temperature of 60°C for 30 minutes, the resist film is
Exposure was carried out using a mask for 10 seconds using a 500W Xe-Hg lamp mainly with deep ultraviolet light of 200 to 300 nm. Next, this resist film is mixed with a solution containing mainly an acetate ester, such as an isoamyl acetate solution (in a volume ratio of 1 isoamyl acetate: 0.2 cyclohexane: water).
0.001) for 30 seconds, a resist pattern with 0.5 μm spaces was obtained. It was confirmed that the cross-sectional shape of the resist film forming the resist pattern had an overhang shape. Next, apply ultra-high pressure Hg at 250W to this sample.
Ultraviolet rays mainly from 350 to 450 nm from the lamp2
Bulk irradiation was performed for minutes. In this case, the output below 300 nm was cut off by the lens system. No deformation of the pattern was observed due to this irradiation. After this ultraviolet irradiation, the substrate was heat-treated at a temperature of 150° C., and a deposit, for example, Ni, which is a metal that is difficult to deposit, was deposited to a thickness of 250 nm by vapor deposition. After that, lift-off was performed with dimethylformamide, and a Ni pattern with a width of 0.5 μm was obtained.

Comparative Example 1 After patterning the resist film in the same manner as in Example 1, the substrate was heated in the same manner as in Example 1 without irradiating ultraviolet light with an Hg lamp.
Ni was vapor-deposited. Subsequently, when the sample obtained in the same manner was immersed in dimethylformamide,
The resist did not dissolve and therefore no resist pattern was obtained.

Comparative Example 2 A resist film was patterned in the same manner as in Example 1, but this time Ni was evaporated and lift-off was performed without both ultraviolet irradiation and substrate heating, and the resist peeled off. This was confirmed by microscopic observation.

These Examples and Comparative Examples will be discussed.

As is clear from Example 1, LMR has high resolution with respect to ultraviolet light and can form an overhang shape. Furthermore, since this LMR has a quinonediazide group, a crosslinking reaction occurs when heated at a temperature of 130°C or higher. However, according to the present invention, after the resist pattern is formed, the resist is
The quinonediazide group is irradiated with ~450nm ultraviolet rays, so the quinonediazide group undergoes photodecomposition, and therefore no crosslinking reaction occurs even when heated.
Even after heat treatment, the resist is dissolved in dimethylformamide and can be easily lifted off.

In Comparative Example 1, the resist was not irradiated with ultraviolet rays in this wavelength range, so the quinonediazide group caused a crosslinking reaction due to the heat treatment at a temperature of 150°C and became insoluble in dimethylformamide.
This makes it impossible to lift off.

In addition, in Comparative Example 2, Ni was evaporated without heating the substrate, so Ni contracted during evaporation and caused stress, which deteriorated the adhesion between the substrate and resist, causing the resist to deteriorate during evaporation. It is thought that it will peel off.

By the way, the thermal crosslinking of quinonediazide in LMR is
This occurs at temperatures above 120°C, but when photodecomposed by ultraviolet rays, the resist will dissolve in dimethylformamide even if heat treated at a temperature of 170°C.
Experiments have confirmed that as the temperature rises further, the adhesion between the resist and the substrate becomes stronger, making it difficult for the resist to peel off. It was also confirmed that the overhang shape of the LMR resist was not impaired even by heat treatment at a temperature of 170°C.

In addition, experiments have confirmed that this heating of the substrate also increases the adhesion of the resist to the substrate, preventing deposits from getting between the resist layer and the substrate during vapor deposition, resulting in a clean and sharp pattern of the deposited layer. Ta.

In this way, lift-off is possible even when heated to 170° C., and heating the substrate during deposition increases the adhesion between the resist and the substrate, as well as the adhesion between the substrate and the adherend.

(Effects of the Invention) According to the present invention, since the quinonediazide sulfonic acid ester of novolac resin is used as the resist material, the cross-sectional shape of the resist after patterning becomes an overhang shape.
Moreover, it has the advantage that after forming a resist pattern using this material, the solubility of the resist can be increased by irradiating it with ultraviolet rays. Further, since this material has excellent heat resistance, there is an advantage that the adhesion of the resist and the adhesion layer to the substrate can be improved by heating the substrate when the adhesion layer is applied.

Further, according to the present invention, after patterning the resist, a resist pattern suitable for lift-off is formed by a simple and easy process of irradiating ultraviolet rays with a wavelength of 350 to 450 nm and heating the substrate at a temperature of up to 170°C. It has the advantage of being possible.

Furthermore, since there is an advantage that the substrate can be heated up to 170°C during the above-mentioned deposition, the resist pattern forming method of the present invention is suitable for use in manufacturing semiconductor devices, magnetic bubble elements, surface acoustic wave devices, etc. .

Claims (1)

[Claims] 1 (a) a step of forming a film of quinonediazide sulfonic acid ester of novolac resin as a resist film on the surface of the substrate; (b) a step of selectively exposing the film to deep ultraviolet rays; c) developing the film with a solution mainly containing acetate ester to form a resist pattern; (d) irradiating the resist pattern with ultraviolet rays;
(e) depositing an adhesion layer on the resist pattern and the substrate surface; (f) removing the resist pattern by a lift-off method; A method for forming a pattern, comprising the step of obtaining a pattern of the deposited layer deposited on the surface of the substrate.