JPH01304457A - Pattern forming method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary of the Invention] Regarding a pattern forming method, particularly a fine pattern forming method using a lift-off method, a pattern forming method that utilizes the characteristics of a two-layer resist and solves the problem of pattern limitations has been developed. A step of forming a lower resist film on a substrate, then forming an electron beam positive type upper resist film n9 on the lower resist film, patterning the upper resist film, and dry etching using oxygen using a vapor deposition method. A process of forming a vapor deposited film of a substance that is resistant to etching, a process of removing the unexposed part of the upper resist film and the vapor deposited film above it using a lift-off method, and anisotropic etching of the lower resist film using the vapor deposited film as a mask. The present invention includes a pattern forming method characterized in that it includes a step of performing.

[Industrial application field]

The present invention relates to a pattern forming method, and particularly to a fine pattern forming method using a lift-off method.

[Conventional technology]

In the production of semiconductor integrated circuits with a pattern rule development target of 0.2 to 0.3 μm, fine pattern formation technology is becoming more important than ever, and it uses an electron beam that can be focused well. One such technique is a combination of electron beam (EB) exposure and two-layer resist.

FIG. 2 shows a conventional two-layer resist process. First, as shown in FIG. 2(a), a lower resist 2 is coated on a substrate 1 using a photoresist or an electron beam resist.

Next, as shown in FIG. 2B, an upper resist 3 made of a silicon-containing negative resist is applied onto the lower resist 2.

Next, the upper resist layer 3 is exposed to an electron beam 4 using an electron beam 4, as shown in FIG.
It is developed to form a pattern of the upper resist 3.

Subsequently, reactive ion etching (R[
), using the pattern of the upper resist 3 as a mask, the lower resist 2 is etched as shown in FIG.

The reason why a silicon-containing negative resist is used as the upper resist 3 is that when the lower resist is etched by 02 during RIE of the lower resist, the upper resist contains silicon, so 5 in 2 is formed in the upper resist by the 02 plasma. This is because the upper resist layer becomes resistant to RIE. In fact, it has been experimentally confirmed that silicon-containing resist has a selectivity of 20 times or more in RIH of the lower layer using 0□ gas.

[Problem to be solved by the invention]

When exposing a negative resist using an electron beam, the electron beam enters the resist and cross-links the molecules of the resist, leaving the areas exposed to the electron beam during development; however, when the electron beam enters the resist, Secondary electrons are generated, the secondary electrons move irregularly and expose the resist,
Furthermore, secondary electrons from the substrate enter the resist and expose the resist, causing a proximity effect in which adjacent resist patterns come into contact with each other due to backscattering, which limits the resolution of the resist. In addition, swelling of the resist occurs during resist development, and in the case of a line-space pattern in which lines and spaces appear alternately, there is a problem that the boundaries between adjacent resist patterns become unclear. Although it has excellent resistance in IH, there is a problem that there is a pattern limit.

The present invention therefore seeks to provide a patterning method that takes advantage of the features of a two-layer resist while solving the problem of pattern limitations.

[Means to solve the problem]

The above-mentioned problems include the process of forming a lower resist film on a substrate, then forming an electron beam positive upper resist film on the lower resist film, patterning the upper resist film, and using a vapor deposition method to resist dry etching using oxygen. a process of forming a vapor deposited film of a substance having a etchant, a process of removing the unexposed portion of the upper resist film and the vapor deposited film thereon by a lift-off method, and a process of performing anisotropic etching on the lower resist film using the vapor deposited film as a mask. The problem is solved by a pattern forming method characterized by including.

[Effect]

That is, in the present invention, since the silicon-containing resist, which is the upper layer resist of the conventional two-layer resist, has poor resolution,
Instead, a high-resolution positive resist is used. However, this positive resist cannot be used as a mask because it has no resistance to dry etching of the underlying resist. Therefore, in the present invention, a thin film of a material having excellent resistance to dry etching using oxygen is formed only in the openings. Then, by removing the positive resist in the unexposed areas with an organic solvent so that the mask material remains only in the openings, it becomes possible to form a fine pattern.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

The steps for carrying out the method of the invention are illustrated in FIG.

Refer to FIG. 1(a): A lower resist film 12 is formed by coating a lower resist film on a substrate 11 and curing it by a method such as light irradiation or baking. Then, the upper resist film 13 is similarly formed by applying and curing the positive resist. The lower layer resist is, for example, a negative resist with the trade name CMS, and the upper layer resist is, for example, a positive resist with the trade name PMMA.

Refer to FIG. 1(b): The upper resist film 13 is patterned by electron beam exposure and development as in the conventional example.

See FIG. 1(C): For example, an aluminum (II l ) film 14 is formed by vapor deposition.
is formed to a thickness of 0.1 μm or less. The thickness of A2 should be as long as it can be used as a mask in the next step of RIH, and although it varies depending on the RIE device, it should not be less than 0.1 μm! Enough. Also,
A! If A2 is deposited thickly, A2 will adhere to the sidewalls of the pattern of the upper resist film 13, which will hinder lift-off, so care must be taken.

Refer to FIG. 1(d): A lift-off process is performed to remove the unexposed portion of the upper resist film 13 and the Aj2 film thereon using an organic solvent (for example, acetone).

Refer to FIG. 1(e): The lower resist film 12 is etched by RIE using 0□ to obtain a lower resist pattern.

In the above steps, the upper resist film 13 has a thickness of 0.2 to 0.3 μm to facilitate lift-off.

Further, gold (Au) may be used instead of l. The thickness of the lower resist layer is 8! It is set in relation to the RIE resistance of
In one example, good results were obtained with a film thickness of 2.0 μm.

〔Effect of the invention〕

As described above, according to the present invention, the pattern width is 0.2 μm with higher accuracy than the conventional two-layer resist (pattern width 0.5 μm).
It became possible to form fine patterns of m.

[Brief explanation of the drawing]

Figures 1 (a) to (e) are cross-sectional views of embodiments of the present invention, and Figure 2 (
a) to (d) are cross-sectional views of conventional examples. In the figure, 11 is the substrate, 12 is the lower resist film, 13 is the upper resist film, and 14 is to! The membrane is shown.

Claims (1)

[Claims] A lower resist film (12) is formed on the substrate (11), and then an electron beam positive type upper resist film (12) is formed on the lower resist film.
Step 3): patterning the upper resist film (13) and forming a deposited film (14) of a substance resistant to dry etching using oxygen using a vapor deposition method; unexposing the upper resist film using a lift-off method; removing the portion and the deposited film (14) thereon, and removing the deposited film (14);
4) A pattern forming method comprising the step of performing anisotropic etching on the lower resist film (12) using the mask as a mask.