JPH07111964B2 - Fine pattern formation method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a fine pattern of metal wiring.

[Prior Art] In the manufacture of a semiconductor integrated circuit device, lithography is used as a technique for forming a pattern of a metal, a semiconductor or the like required for a circuit configuration on a substrate. In this technique, a resist such as a photoresist, an electron beam resist or an X-ray resist is applied on a substrate, and then exposure and development are performed to form a desired fine pattern, and the fine pattern is used as an etching mask to etch the substrate. The film is finely processed. Among these techniques, a three-layer film of an organic film, an intermediate film, and a resist film is formed on a film to be etched to form a pattern in order to accurately process a fine pattern even when there is a step on the underlying substrate. A three-layer resist process (hereinafter referred to as this) to be performed is used. First
2A to 2F are sectional views showing a three-layer resist process disclosed in, for example, Japanese Patent Laid-Open No. 60-43827.

Hereinafter, the steps of the three-layer resist process will be sequentially described with reference to this drawing. As shown in FIG. 2A, first, a film 1 to be etched such as an aluminum (Al) alloy is formed on a substrate 1, and then an organic film 3 such as a photoresist or a polyimide resin is applied to a spinner or the like to have a thickness of about 1 to 3 μm. Apply to thickness and bake. Then, an intermediate film 4 such as silicon dioxide (SiO ₂ ) or SOG is formed thereon. further,
On top of that, a resist such as a photoresist is 0.2 to 0.4 μm.
The resist film 5 is formed by applying the coating solution and baking.
As a result, a three-layer film including the organic film 3, the intermediate film 4, and the resist film 5 is formed.

Next, a pattern forming process using the above three-layer film will be described. As shown in FIG. 2B, the resist film 5 is exposed and developed by a pattern forming method such as photolithography to form a fine pattern 5a of the resist. Then, as shown in FIG. 2C, the intermediate film 4 is formed using the resist pattern 5a as a mask.
Is dry-etched to form a fine pattern 4a of the intermediate film 4. Then, using the fine pattern 4a of the intermediate film 4 as a mask, the organic film 3 is anisotropically etched by reactive ion etching using oxygen (O ₂ ) plasma to form the fine pattern 3a of the organic film. At this time, at the same time, the resist pattern 5a is also removed by etching, as shown in FIG. 2D.
Further, the etching target film 2 is anisotropically etched by reactive ion etching using chlorine (Cl) based plasma to form a fine pattern 2a of the etching target film. In this step, at the same time, the fine pattern 4a of the intermediate film is also removed by etching, as shown in FIG. 2E. Finally, the fine pattern 3a of the organic film is removed by etching with O ₂ plasma to form the fine pattern 2a of the film to be etched as shown in FIG. 2F.

[Problems to be Solved by the Invention] However, the conventional three-layer resist process has a problem in the step of removing the intermediate film 4 and the fine pattern 4a of the intermediate film. That is, silicon dioxide (SiO ₂ ) is often used as the material of the intermediate film. Then, in the steps shown in FIGS. 2D to 2E, that is, in the step of simultaneously etching the Al alloy film 2 to be etched and the fine pattern 4a of the intermediate film, the etching rate of the fine pattern 4a of SiO ₂ is increased. Is slower than the etching rate of the Al alloy film 2,
The fine pattern 4a of SiO ₂ may remain without being completely removed.

Further, during the above process, the intermediate SiO ₂ film becomes a volatile substance by the plasma reaction, and oxygen atoms are generated in the process of volatilizing. The oxygen atoms decompose the side wall protective film formed by attaching atoms such as carbon (C) and nitrogen (N) generated during etching to the etched side wall of the Al alloy film 2. For this reason, side etching is likely to occur on the side wall of the fine pattern 2a of the Al alloy film 2, and there is a problem that the precision of the fine pattern is deteriorated.

Therefore, the present invention is a three-layer resist process,
An object of the present invention is to obtain a method for forming a fine pattern of a semiconductor device in which an intermediate film can be completely removed at the same time during etching of a film to be etched and etching processing can be performed without causing side etching on a pattern side wall portion of the film to be etched. .

[Means for Solving the Problems] A method for forming a fine pattern according to the present invention is a method of sequentially forming an organic film on a surface of an etching target film formed on a semiconductor substrate,
A three-layer film of an intermediate film and a resist film is formed, the resist film is exposed and developed to form a desired resist pattern, the intermediate film is etched using the resist pattern as a mask, and the organic film is formed using the intermediate film as a mask. The film is etched, the resist film is removed at the same time, the film to be etched is etched using the organic film as a mask, the intermediate film is removed at the same time, the organic film is finally removed, and the film to be etched is finely divided. In the method of forming a pattern, the organic film is formed in direct contact with the surface of the film to be etched, and the intermediate film is a non-oxygen containing material that can be etched under the same conditions as the film to be etched. It has the characteristic that it is formed.

[Operation] In the conventional method of forming a fine pattern, the cause of adverse effect in the etching process of the pattern of the film to be etched is oxygen atom.

Therefore, according to the present invention, of the three-layer film formed on the semiconductor substrate, the intermediate film is formed of a material containing no oxygen atoms, so that the film to be etched such as an aluminum (Al) alloy is etched. At this time, the protective film attached to the side wall of the fine pattern formed on the film to be etched is formed without being destroyed by oxygen atoms.

Furthermore, since the organic film is formed in direct contact with the film to be etched, the number of films to be formed is smaller than that in which another film is formed between the film to be etched and the organic film. Become.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings. 1A to 1F are cross-sectional views of a semiconductor device showing the method for forming a fine pattern of a semiconductor device according to the present invention for each step.

First, using FIG. 1A, an organic film, an intermediate film, and
A process of forming a three-layer film of a resist film will be described. Board 1
An aluminum (Al) alloy film 6, which is a film to be etched, is formed on top. Then, a photoresist, a polyimide resin, or the like is applied on the Al alloy film 6 using a spinner or the like to a thickness of about 1 to 3 μm to form the organic film 7. Further, a DC bias is applied to the silicon target in the vacuum chamber by a sputtering method, and the intermediate film 8 of the amorphous silicon film 8 is formed to a thickness of 1500Å to 2000Å by sputtering with argon (Ar) plasma. The amorphous silicon film 8 does not contain oxygen atoms. Further, a resist such as a photoresist or an electron beam resist is applied on the intermediate film 8 to have a thickness of about 0.2 to 0.4 μm to form a resist film 9.

Next, a process of forming a fine pattern on the Al alloy film 6 by etching will be described. As shown in FIG. 1B, the resist film 9 is formed by a pattern forming method such as photolithography.
Is exposed and developed to form a resist film 9a having a desired fine pattern. Next, as shown in FIG. 1C, the intermediate film 8 is dry-etched using a fluorine-based plasma of (CF ₄ + O ₂ ) using the resist film 9a as an etching mask to form an intermediate film pattern 8a. Then, as shown in FIG. 1D, using oxygen (O ₂ ) plasma, RF power 800W, gas pressure 2-5P
The organic film 7 is anisotropically etched by reactive ion etching under the condition of a to form an organic film pattern 7a. Under this etching condition, the resist film 9a is simultaneously etched and removed.

Then, using the organic film pattern 7a as an etching mask, Al
The alloy film 6 is etched. In this process, SiCl ₄ and Cl ₂
The Al alloy film 6 is anisotropically etched by reactive ion etching using a mixed gas plasma of BCl ₃ and BCl ₃ to form a desired fine pattern 6a. In this etching process, the pattern 8a of the amorphous silicon film that is the intermediate film is used.
Are set so that they are simultaneously removed by etching. Further, on the sidewalls of the fine pattern 6a of the Al alloy film, carbon and nitrogen atoms are attached in the etching process to form the sidewall protection film 10, but in the pattern 8a of the amorphous silicon film that is simultaneously etched in this etching process. Since the oxygen atom is not contained, the side wall protection film 10 is not destroyed by the oxygen atom. Therefore, due to the action of the side wall protective film 10, there is no side etching as shown in FIG.
Is formed. Finally, if the organic film pattern 7a is removed by etching with O ₂ plasma or the like, the fine pattern 6a of the Al alloy film is formed as shown in FIG. 1F.

Although amorpha silicon was used as the substance containing no oxygen atoms in the intermediate film in the above example, the factor that adversely affects the etching process of the film to be etched is the oxygen atom, so any substance containing no oxygen atom should be used. Good. Therefore, a substance containing nitrogen atoms, such as a silicon nitride film (Si
₃ N ₄ ) is also acceptable. In this case, the nitrogen atom can further strengthen the side wall protective film on the side wall of the pattern of the Al alloy film which is the film to be etched.

Further, although the sputtering method is used as the method of forming the intermediate film in the above-described embodiment, a method of forming a reactive deposition film by ECR (electron cyclotron resonance) phenomenon may be used.

[Effects of the Invention] As described above, according to the present invention, since the intermediate film is formed of the material containing no oxygen atom, the sidewall protection film of the pattern of the film to be etched is not destroyed at the time of etching the film to be etched. Anisotropic etching is possible, and a fine pattern with good pattern accuracy can be formed.

Further, when the film to be etched is etched, at the same time, the intermediate film is completely removed by etching, so that it is possible to omit the conventional entire surface removing step of the remaining portion of the intermediate film and simplify the fine pattern forming step.

Further, since the organic film is formed in direct contact with the film to be etched, the number of films to be formed is smaller than that of another film formed between the film to be etched and the organic film. The number of steps in the film forming step can be reduced, and the step of removing the film can be omitted.

[Brief description of drawings]

1A, 1B, 1C, 1D, 1E, 1F,
FIG. 6 is a cross-sectional view of a semiconductor device showing a method of forming a fine pattern of a semiconductor device according to an embodiment of the present invention in accordance with the forming steps. 2A, 2B, 2C, 2D, 2E, 2F,
FIG. 11 is a cross-sectional view of a semiconductor device showing a conventional method of forming a fine pattern of a semiconductor device according to the forming steps. In the figure, 1 is a substrate, and 6 and 6a are Al films to be etched.
Alloy films, 7 and 7a are organic films, 8 and 8a are intermediate films, 9 and 9a are resist films, and 10 is a side wall protective film. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] 1. A three-layer film including an organic film, an intermediate film and a resist film is sequentially formed on a surface of a film to be etched formed on a semiconductor substrate, and the resist film is exposed and developed to form a desired resist pattern. Forming, etching the intermediate film using the resist pattern as a mask, etching the organic film using the intermediate film as a mask, simultaneously removing the resist film, etching the etching target film using the organic film as a mask At the same time, removing the intermediate film, finally removing the organic film, in the method of forming a fine pattern on the film to be etched, the organic film is formed in direct contact with the surface of the film to be etched, The intermediate film is a non-oxygen containing material and is formed of a material that can be etched under the same conditions as the film to be etched. The method of forming the turn. 2. The method for forming a fine pattern according to claim 1, wherein the material of the intermediate film is amorphous silicon. 3. The method for forming a fine pattern according to claim 1, wherein the material of the intermediate film is a material containing nitrogen atoms.