JPH0293081A - Method for etching multilayer film - Google Patents

Abstract

PURPOSE:To easily and precisely etch a multilayer film at a low cost by using the same resist formed on plural thin-film layers to successively etch the adjacent layers, and removing the pent roof-shaped part of the upper layer. CONSTITUTION:At least two thin-film layers are formed on a substrate, and the respective layers are made of the material incapable of being simultaneously etched by the same liq. etchant. In the film structure, a resist is formed on the upper-layer film, and the first layer is wet-etched. The second layer is then just-etched with the same resist. O2 plasma ashing treatment is then applied to appropriately reduce the shape of the resist pattern. As a result, the overhung part of the upper layer is exposed, and etched by the etchant for the upper layer to remove the pent roof-shaped part of the upper part. By this method, the multilayer film is easily etched, and the highly reliable thin-film pattern free of form defect is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an etching technique for forming thin film wiring, and more particularly to an etching method for preventing geometrical defects and obtaining a highly reliable thin film pattern.

[Conventional technology]

A conventional multilayer wiring pattern forming method is shown in FIGS. 2 and 3. When forming a wiring pattern of a multilayer film by wet etching, there is a method of forming resist layer by layer as shown in FIG. 3, but this method increases the number of steps and has a cost problem. Therefore, when two layers of films are etched using a common resist, side etching of the lower film occurs due to isotropic etching, resulting in overhang of the upper film, which causes defects in subsequent steps.

As a method to solve this problem,
In No. 82, it is stated that this problem can be solved and a stable pattern can be formed by wet etching the upper layer of a common resist and dry etching the lower layer, which is characterized by anisotropic etching. . However, in the case of this method, the process was complicated and no consideration was given to manufacturing costs.

[Problem to be solved by the invention]

When using the above-mentioned conventional technique and etching two layers of films using the same resist with emphasis on cost, the lower layer will be side-etched more than the upper layer, resulting in overhangs at the pattern ends of the upper layer. Therefore, the overhang peels off in a later process, causing short circuits between lines and resist defects, making it difficult to obtain a functional thin film circuit. In addition, other methods increase the number of steps and increase manufacturing costs. An object of the present invention is to solve the above-mentioned problems and obtain multilayer film wiring by an easy method.

[Means to solve the problem]

The above objective is achieved by the following means. First, a pattern is formed on the two-layer film by JAS etching, and then the ends of the resist pattern are set back by 02 ashing process to narrow the resist pattern by 1 to several μm. As a result, the overhang part of the upper layer is exposed, so
By etching this part, the overhang part is removed and a stable wiring pattern is obtained.

[For production]

In the conventional method, the upper layer film is first etched using a resist as a mask, and then the lower layer film is etched using the upper layer film as a mask, so side etching progresses and overhang occurs, which causes defects.

Therefore, the upper and lower layers are just etched as usual, and then the 02 ashing process is performed. By this process, the resist is shaved off by several micrometers, and since the resist is thin at the edges of the pattern, the resist disappears and the pattern becomes narrower. This process exposes the overhanging portion, making it susceptible to etching. This overhanging part is then removed by etching, but because the overhanging part is easily removed, even if the layer further below the lower layer is of the same material as the upper layer, this layer will be removed by etching. If the film thickness is equal to or greater than the film thickness, it is also possible to form a good wiring pattern.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. As shown in the figure, when forming a two-layer interconnection of Cu and Cr, first, a metal film to become the interconnection of Cu and Cr is formed on a substrate by sputtering or the like.

A desired wiring resist pattern film 4 is formed on the formed film. Next, Cr and Cu are just etched using respective predetermined etching solutions.

After drying the substrate, perform 02 plasma ashing for 10 minutes. Through this process, the resist pattern becomes thinner by about 2 to 3 μm than the initial state, and the overhang part of the Cr film that is created as a result of side etching that occurs when etching the Cu film is removed. This will expose the overhang and allow for easy etching.

Next, the overhanging portion of the Cr film exposed by the 02 plasma ashing is etched using a predetermined Cr etching solution. Etching at this time can be performed in a shorter time than the etching time of the Cr film that was performed first. Thereafter, the resist film is removed using a resist removal solution through normal processing. According to this example, two layers of films can be photo-etched into an ideal shape using one layer of resist.
The number of resist film forming steps can be reduced.

〔Effect of the invention〕

According to the present invention, the two-layer film can be ideally etched through the resist forming process twice, so that the number of steps can be reduced to one. Furthermore, compared to the method of forming and etching the resist 1- layer by layer, there is no positional shift in the process of forming the resist, so it is possible to form fine wiring patterns with high accuracy. Furthermore, the subsequent photoetching process can be carried out without any hindrance, increasing reliability and reducing costs.

[Brief explanation of drawings]

FIG. 1 is a process diagram of one embodiment of the present invention, and FIGS. 2 and 3 are process diagrams showing an example of the prior art. DESCRIPTION OF SYMBOLS 1... Upper layer film, 2... Lower layer film, 3... Substrate, 4...
...Resist film, 1'--upper layer film (Cr), 2'--lower layer film (Cu). 3'...Substrate, 4'...Resist film.

Claims (1)

[Claims] 1. In the case of a film structure that has at least two or more thin film layers and the materials constituting each layer cannot be etched simultaneously with the same etching solution, two adjacent layers are patterned by wet etching with the same resist. After just etching the two layers, O_2 plasma ashing is performed to reduce the shape of the resist pattern to expose the overhang part of the upper layer, and then the upper layer is etched with an etching solution to remove the upper layer. A multilayer film etching method characterized by removing the eaves-like parts of the film.