JPS6043827A - Formation of fine pattern - Google Patents

Abstract

PURPOSE:To contrive fine formation of a pattern on the film to be etched by a method wherein a triple-layer film consisting of an organic film, an intermediate film and a sensitive resist film is formed on the surface of the film to be etched, and the material and film thickness with which the intermediate film can be removed by etching when an etching is performed on the film to be etched are properly selected for the intermediate film. CONSTITUTION:An organic film 3 is formed on the surface of the film 2 to be etched, and then an intermediate film 4 is formed on the surface. Pertaining to the intermediate film 4, such as a material which can be removed by etching when an etching is performed on the film 2 to be etched is to be selected, and as for the thickness of the film, it is to be thinner than that of the film 2 to be etched. Then, a sensitive resist film 5 is formed, and a resist film 5a to be used for etching mask is formed. An anisotropic etching is performed on the intermediate film 4, and an intermediate film 4a is left under the resist film 5a. An organic film 3a is left in the same manner as above, an anisotropic etching is performed on the film 2 to be etched, and a film 2a to be etched, and a film 2a to be etched is left under the organic film 3a. The intermediate film 4a is removed by etching, and lastly, the organic film 3a is removed by etching.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of forming fine patterns using a sensitive resist film that is sensitive to light, electron beams, and the like.

[Prior art]

In the manufacturing process of semiconductor integrated circuit devices, etc., a film to be etched, such as a polysilicon film, on which a fine pattern is to be formed by etching is formed on the main surface of a semiconductor substrate.
A sensitive resist that is sensitive to light, X-rays, electron beams, or ion beams is coated on the surface of this film to be etched using a spinner method and baked to form a sensitive resist film. This sensitive resist film is irradiated with light, X-rays, electron beams, or ion beams and developed to form a resist film for an etching mask so that the portion of the film to be etched on which the fine pattern is to be formed remains. There is a step of forming a resist film and etching the film to be etched using this resist film as a mask to form a fine pattern of the film to be etched.

By the way, in such a method, if there is a step on the main surface of the semiconductor substrate, the surface of the film to be etched formed on the main surface of the semiconductor substrate also has a step similar to the step on the cut surface of the semiconductor substrate. There will be a step. However, since the surface of the sensitive resist film formed by a spinner method or the like on the surface of the film to be etched that has a step becomes flat, the film on the upper surface side of the step of the sensitive resist film of the film to be etched is The thickness is thinner than the film thickness on the lower surface side of the step.

Therefore, there is a problem in that it is not easy to accurately form a resist film for an etching mask with a fine pattern using the sensitive regime (JIk), which has a thin part and a thick part.

In order to solve these problems, a method called a three-layer resist process has been proposed.

FIGS. 1A to 1F are cross-sectional views showing the main stages of an example of a conventional three-layer resist process.

First, as shown in FIG. 1(A), a film to be etched (2) is formed on the main surface of a semiconductor substrate [++], and then an organic material such as a photoresist is deposited on the surface of the film to be etched (2). A coating liquid is applied using a spinner method or the like and baked to form an organic film (3). Next, an intermediate film (4) such as a silicon oxide film is formed on the surface of the organic film (3) by CVD or the like, and then a light beam is applied onto the surface of the intermediate film (4).

A sensitive resist film (5) sensitive to X-rays, electron beams, or ion beams is coated and rebaked using a spinner method or the like to form a sensitive resist film (5).

Next, as shown in FIG. 1(B), a sensitive resist film (
The sensitive resist film (5) is exposed to light KQ + "" By irradiating and developing, an etching mask (Mk) (5a) is formed on the surface of the intermediate film (4).

Next, as shown in FIG. 1(C), a resist film (5a) is formed.
The intermediate film (4) is etched using the etching mask as an etching mask, and the intermediate film (11M) is etched under the resist Ilu (5a).
4a) remains.

Next, as shown in FIG. 1(D), a resist film (5a) is formed.
Using the intermediate film (4a) as an etching mask, the organic film (3) is subjected to anisotropic etching using rota element (02) plasma to leave the organic film (3a) under the intermediate film (4a).

As shown in FIG. 1(E), a resist film (5a) is applied to the body.
+ Using the intermediate film (4a) and the organic film (3a) as etching masks, the film to be etched (2) is etched to leave the film to be etched (2a) under the organic film (3a,).

Finally, as shown in FIG. 1(F), a resist film (5a
), the intermediate film (4a) and the organic film (3a) are sequentially etched away, completing the work of this conventional three-layer resist process.

In this conventional three-layer resist process, the semiconductor substrate +
Even if there is a step on the 1+ surface and there is a step on the surface of the film to be etched (2), the organic film (3) is formed on the surface of the film to be etched (2) by a spinner method or the like. , the surface of the organic film (3) becomes flat. Therefore, the organic film (
The surfaces of the intermediate film (4) and the sensitive resist film (5), which are sequentially formed on the flat surface of 3), also become flat, and the thickness of the sensitive resist film (5) becomes uniform, so that the sensitivity With the resist film (5), a resist film (5a) for an etching mask having fine notches can be formed with high precision. Then, the notches of the intermediate film (4a), organic film (3a), and film to be etched (2a) formed sequentially under the resist Ilk-(5a) correspond to the pattern of the resist film (5a). Since the pattern is a turn, the pattern of the film (2a) to be etched can be made finer.

However, this conventional process has the drawback that it requires a very large number of steps, and also has the drawback that it is very difficult to remove the intermediate film (4a). In other words, the intermediate film (4a) is often a silicon oxide (S102) #aluminum (AL) film, and in this case,
The semiconductor substrate (1) may be damaged by etching when removing the intermediate layer (aa), or the etched layer J[K(2a) may be damaged.
) pattern may deteriorate.

[Summary of the invention]

This invention was made with the aim of eliminating such drawbacks, and involves forming a three-layer film of an organic film, an intermediate film, and a sensitive resist film on the surface of a film to be etched formed on the main surface of a semiconductor substrate. In this method of forming a fine pattern on a film to be etched using this three-layer film, the intermediate film is made of a material and has a thickness that can be removed by etching when etching the film to be etched, thereby forming a fine pattern on the film to be etched. The present invention provides a method for forming a fine pattern with a small number of steps, which can reduce the number of etching steps, and is free from damage to a semiconductor substrate or deterioration of a pattern of a film to be etched.

[Embodiments of the invention]

FIGS. 2A to 2F are cross-sectional views showing the main stages of a method for forming a fine pattern according to an embodiment of the present invention.

First, as shown in FIG.
), on the surface of the film to be etched (2), a coating liquid of an organic material such as a polyimide resin that can be removed at almost the same etching speed as the sensitive resist is applied using a spinner method, and baked. An organic film (3) with a thickness of about 3 μm is formed. Next, an intermediate film (4) is formed on the surface of the organic film (3) by plasma 0VJ) or optical OVD. As this intermediate film (4), in order to be able to remove the etching target Jlq (2+) by etching, for example, when the etching film (2) is a polysilicon film, a polysilicon B bean paste is used. An amorphous silicon film that can be removed at approximately the same etching rate as the polysilicon layer is formed, and its thickness is set to be thinner than that of the polysilicon layer (2).Then, the intermediate film (4) is formed. A sensitive resist that is sensitive to light, X-rays, electron beams, or ion beams is coated on the surface of the film using a spinner method, etc., and baked to a thickness of approximately 0.2 to -0.4 μm, which is thinner than the thickness of the organic film (3). A sensitive resist film (5) is formed.

Next, as shown in FIG. 52(B), the sensitive resist tsukkou [ A resist film (58) for an etching mask is formed on the surface of the intermediate film (4) by irradiating the resist film 5i with an electron beam or an ion beam and developing it.

Next, as shown in FIG. 2(0), a resist film (5a) is formed.
as an etching mask, Freon 115 (C2G
Anisotropic etching with plasma of tF5) is applied to the interlayer film (
4) to form an intermediate film (4a) under the resist film (5a).
leave.

Next, as shown in FIG. 2(D), using the intermediate film (4a) as an etching mask, the organic film (3) is subjected to anisotropic etching using 02 plasma to form an organic layer under the intermediate Jli(aa). Leave the membrane (3a) behind. At this time, the resist film (5
Since the thickness of a) is thinner than the thickness of the organic film (3a), the resist film (5a) is removed by etching.

Next, as shown in FIG. 2(E), using the patterned film (3a) as an etching mask, Freon 115 (1:!207
The film to be etched (2) is subjected to anisotropic etching using the plasma of F5) to leave the film to be etched (2a) under the organic film (3a). At this time, when the film to be etched (2) is a polysilicon film, the intermediate film (4a) is a polysilicon film or an amorphous silicon film, and the thickness of the intermediate film (4a) is that of the film to be etched II! (Since it is thinner than the film thickness of 2i, the intermediate film (4a) is removed by etching.
Finally, as shown in FIG. 2(F), the organic film (3a) is removed by etching with 0□ plasma to complete the process of this embodiment.

In the method of this embodiment, as in the conventional example shown in FIG.
) becomes flat, and 1 is deposited on the surface of this organic film (3).
@ Next formed interlayer film (4) and sensitive resin film (
Since the film thickness of 5) becomes uniform, this sensitive resist film (
5) makes it possible to form a resist film (5a) for an etching mask with a fine pattern with high precision.

Since the patterns of the intermediate film (4a), organic film (3a), and etching target 1 (2a) correspond to the pattern of the resist film (5a), the pattern of the etching film (2a) can be made finer. can be achieved. Moreover, the intermediate film (4a) is made of a material that can be removed at approximately the same etching speed M+- as the film to be etched (2), and the thickness of the resist film (5a) is that of the resist IIU.
The thickness of the intermediate film (4a) is set to be thinner than that of the organic film (3), which can be removed with one etching speed at approximately the same etching speed as (5a).
The film thickness of the resist film (5a) and the intermediate film (4a) is set to be thinner than that of the film to be etched (2), which can be removed at approximately the same etching speed as the intermediate film (4a).
) is the organic film (3a) and the film to be etched (
It is automatically etched away by etching during the formation of 2a). Therefore, in the final stage, the organic film (3a
) only need to be removed by etching, so the semiconductor substrate m
There is no risk of damaging the film or deteriorating the pattern of the film to be etched (2a), and the number of steps is smaller than that of the conventional example shown in FIG. r, can be reduced.

In this embodiment, a light beam, XtX, is used to sensitize any one or all of the sensitive resist film (5), the intermediate film (4), and the organic film (3) to the sensitive resist film (5).

Additives such as dyes that can absorb electron beams or ion beams are mixed or combined to reduce the negative effects of reflection of light or X-rays from the semiconductor substrate +1+ or backscattering of electron beams or ion beams. You can also do this.

In this example, the film to be etched (2) is a polysilicon film, but the present invention is not limited to this. Removable Atk, 5in2
It can also be applied to other coatings such as membranes.

In addition, in this example, the etching of the organic film (3) was carried out at zero
2 plasma was used, but this does not necessarily have to be a 0° plasma, and a mixed gas plasma of 02 and a halogen compound such as OF4.0C14 may be used.
In this case, the etching rate for the organic film (3) can be increased.

In this example, the resist film (5a) was etched away when etching the organic film (3).
It is not necessary that the organic film (3) be etched away when etching the organic film (3).

〔Effect of the invention〕

As explained above, in the method for forming a fine pattern of the present invention, a three-layer film of a 1L intermediate resist film and a sensitive resist film is formed on the surface of a film to be etched formed on the main surface of a semiconductor substrate. Since the three-layer rule 4 is used to form a fine pattern on the film to be etched, even if there is a step on the main surface of the semiconductor substrate and a step on the surface of the film to be etched, the organic The surface becomes flat, and the thicknesses of the intermediate film and sensitive resist film that are successively formed on the surface of this organic film become uniform. Therefore, it is possible to form a micropatterned etching mask (cis)IIN with high accuracy using this sensitive resist film, so that the pattern of this etching mask resist film is sequentially transferred to the lower layer by etching and is finally formed. The pattern of the film to be etched can be made finer.

Moreover, since the intermediate plate is made of a material and has a film thickness that can be removed by etching when etching the film to be etched,
] Since the crotch is automatically removed by etching when the pattern of the resist film for the etching mask is transferred to the film to be etched, there is little risk of damage to the semiconductor substrate or deterioration of the pattern of the etched film being handled, and the number of steps is reduced. can be made smaller than the number of steps in the conventional example.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view sequentially showing the main stages of an example of a conventional three-layer resist process, and Figure 2 is a cross-sectional view sequentially showing the main stages of a fine pattern forming method according to an embodiment of the present invention. be. In the figure, (1) is a semiconductor substrate, (2) and (2a
) is the film to be etched, (3) and (3a) are the films to be etched,
(4) O and (4a) are interlayer films, t51 is a sensitive regimen rib, and (5a) is a resist film for an etching mask. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa (C) (E,) (F) (F) Procedural amendment (voluntary) Commissioner of the Japan Patent Office1, Indication of case Patent application No. 151947/19822,
'zl'! JJ (') Name f' Indication Method for forming fine patterns 3, Person making the amendment 5, Detailed explanation of the invention in the specification subject to amendment 6, Contents of the amendment (ll Page 4, line 1 of the specification The word "flat" is replaced by "
"It's relatively flat," he corrected.

Claims (1)

[Claims] +11 An organic film, an intermediate film, and a sensitive resist film are sequentially formed on the surface of a film to be etched formed on the main surface of a semiconductor substrate, and the film to be etched is formed on the sensitive resist film. The sensitive resist film is sensitized and developed to form a resist film for an etching mask so that a portion above the portion where a fine pattern is to be formed remains, and the pattern of the resist film for an etching mask is sequentially etched into the lower layer. In the method of transferring and finally forming a fine pattern of the film to be etched, the fine pattern is characterized in that the intermediate film is made of a material and has a film thickness that can be removed by etching during etching of the film to be etched. How to form. (2) Light rays, X-rays, that sensitize the sensitive resist film. The method for forming a fine pattern according to claim 1, characterized in that an intermediate film mixed with or combined with an additive capable of absorbing an electron beam or an ion beam is used. (3) Light rays, X-rays, that sensitize the sensitive resist film. 2. A method for forming a fine pattern according to claim 1, wherein an organic film mixed with or combined with an additive capable of absorbing an electron beam or an ion beam is used. (4) Light rays or X-rays that sensitize the sensitive resist film. A method for forming a fine pattern according to any one of claims 1 to 3, characterized in that a sensitive resist film mixed with or combined with an additive capable of absorbing an electron beam or an ion beam is used. .