JPS613140A - Radiation sensitive composition - Google Patents

Abstract

PURPOSE:To obtain a radiation sensitive compsn. superior in heat and dry etching resistances as a resist high in sensitivity to light, X-rays, electron and ion beams by using a phenol resin contg. no low mol. wt. component in the radiation sensitive compsn. contg. a phenol resin and a dissolution inhibitor. CONSTITUTION:For example, a novolak resin is used and as the dissolution inhibitor, poly(2-methylpentene-1-sulfone) is used, and they are dissolved in isoamyl acetate to form a resist. A silicon oxide film 5 is formed on a silicon substrate 4, and the film 5 is coated with a resist film 6. The film 6 is irradiated with electron beams 18, developed with an aq. soln. of tetramethylammonium hydroxide, and further, the film 5 is dry etched in fluorine type plasma to form a hole 7. Denaturalization of the resist film using the resin A contg. no lower mol. wt. component of trimer or below is not found at all and no deformation of the hole is not found, too.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a composition sensitive to radiation such as light, electron beams, X-rays, and ion beams, and particularly to heat-resistant compositions.

This invention relates to a radiation-sensitive composition with excellent dry etching resistance.

[Background of the invention]

As a radiation-sensitive composition used in conventional electron beam resist film formation, a mixture of an alkali-soluble resin and a dissolution inhibitor is generally used. In this case, the alkali-soluble resin is:

Phenolic resins such as polyvinylphenol resin and novolak resin are used.

However, when a desired pattern is formed on an electron beam resist film using the above-mentioned radiation-sensitive composition and used as a mask 2, for example when dry etching a thick silicon oxide film on a substrate, the resist film changes in quality due to heat. However, there was a drawback that the shape of the silicon oxide film, which is the material to be processed, was deformed.

[Purpose of the invention]

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and provide excellent heat resistance and dry etching resistance. The object of the present invention is to provide a highly sensitive radiation-sensitive composition as a resist for light, electron beams, X-rays, and ion beams.

[Summary of the invention]

The present inventors have discovered the above-mentioned drawbacks of the electron beam resist film in the prior art. In order to investigate the cause of deterioration during dry etching, we focused on the molecular weight distribution of the phenolic resin used and conducted various studies. As a result, we discovered that the cause was the low molecular weight components contained in the phenolic resin, and completed the present invention. I ended up doing it.

As a result of experiments, it was found that the resist film deteriorates only when the phenolic resin contains low molecular weight components, and conversely, when only high molecular weight components are included, the radiation irradiated area and non-irradiated area are different. The difference in solubility in alkaline developing solutions is small.

In other words, it was also revealed that the sensitivity was low.

As a result of more detailed experiments, we found that in the molecular weight distribution of phenolic resins, for example, when using novolac resins, which do not contain low molecular weight components below trimers, there is less deterioration in sensitivity, heat resistance, and dry resistance. It has become clear that a resist film with excellent etching properties can be formed.

The present invention is characterized in that, in a radiation-sensitive composition containing a phenolic resin and a dissolution inhibitor, a phenolic resin containing no low molecular weight components is used as the phenolic resin. This is a radiation-sensitive composition that uses a phenolic resin that does not contain low molecular weight components of trimers or less.

A resist film using a phenol resin containing a low molecular weight component of trimer or less is subjected to dry etching, for example, plasma etching.

A phenomenon occurs in which the substrate surface temperature rises, low molecular weight components are vaporized, the resist film is thereby altered, and the shape of the resist pattern is deformed.

[Embodiments of the invention]

An example of the present invention will be given below and will be described in more detail.

Table 1 shows the composition of the radiation-sensitive composition solution for resist film formation used in this example.

Table 1 As shown in Table 1, novolak resin was used as the alkali-soluble phenol resin, and poly(2
-methylpentene-1-sulfone) and were mixed at a weight ratio of 88:12.

It was dissolved in the solvent isoamyl acetate.

A resist film formed with this composition is exposed to light.

Works as a positive resist with high sensitivity to electron beams, X-rays, or ion beams. Here, as novolak resin,
Resin A, resin B, and resin C having three types of molecular weight distributions shown in Figure 1 (a), Figure 2 (a), and Figure 3 (a).
A resist film was manufactured using the following method. Resin A is shown in Figure 1 (a
) As shown in Figure 2(a), resin B does not contain any low molecular weight components of trimer or less, and as shown in Figure 2(a), resin B does not contain monomer molecular weight component 1, dimer molecular weight component 2, It contains trimer molecular weight component 3, and resin C is shown in Figure 3(a).
As shown in the figure, the resin contains molecular weight component 1 of monomer, molecular weight component 2 of dimer, and molecular weight component 3 of trimer.

A silicon oxide film on a silicon substrate was dry etched by the dry etching process shown in FIG. 4 using the above three types of novolac resins. That is, as shown in FIG. 4(,), a layer with a thickness of 2.5. A silicon oxide film 5 with a film thickness of 1.
5- resist 6 was applied. Next, the electron beam 18 is
It was irradiated with a dose of c/aI. Then, it was developed with an aqueous solution of tetramethyl hydroxide, and the image shown in Fig. 4 (b) was developed.
) was obtained. Next, the silicon oxide film was dry-etched to a depth of 2p in fluorine gas plasma to form a 2-square hole 7 as shown in FIG. 4(c). Then, the cross-sectional shape of the two-sided hole formed by dry etching the silicon oxide film was observed using a scanning electron microscope. FIG. 1(b) shows Novolac resin A,
FIG. 3(b) shows the case where resin B is used, and FIG. 3(b) shows the case where resin C is used. These are cross-sectional photographs of each hole.

That is, as is clear from FIG. 3(b), the resist film 8 using resin C containing all low molecular weight components undergoes deterioration during dry etching, and the pores 9 in the silicon oxide film are deformed in shape. There are 1.

Furthermore, as can be seen from FIG. 2(b), the resist film 10 using resin B that does not contain a monomer molecular weight component is slightly altered in quality, but no deformation is observed in the pores 11. As is clear from FIG. 1(b), the resist film 12 is made using resin A that does not contain low molecular weight components of trimer or less.
No deterioration was observed at all.

Moreover, there is no deformation in the shape of the hole 13.

FIG. 5 is a graph showing the sensitivity characteristics of resist films depending on the type of novolac resin, and shows the electron beam irradiation amount (c/ad
) and the relationship between the remaining film rate (residual film thickness/coating film thickness). That is, the sensitivity characteristics of resist films using resins A, B, and C are represented by curves 16.15 and 14, respectively. As shown by curve 17, the sensitivity characteristics of a resist film using a novolak resin containing only a high molecular weight component show that the remaining film ratio with respect to the amount of electron beam irradiation is small, indicating that the sensitivity is low. As is clear from curve 16 in this graph, the novolac resin that does not contain low molecular weight components of trimer or less has extremely little decrease in sensitivity.

From the above results, a resist film using a novolak resin that does not contain low molecular weight components of trimer or less.

It has excellent heat resistance and dry etching resistance, and shows no deterioration in sensitivity characteristics due to radiation irradiation.

〔Effect of the invention〕

As explained in detail above, a resist film using the radiation-sensitive composition according to the present invention has good sensitivity to light, electron beams, X-rays, or ion beams.

It has excellent heat resistance and dry etching resistance.

It has great value as a resist material that is effective in microfabrication of semiconductors such as LSI.

[Brief explanation of the drawing]

FIG. 1(a) is a diagram showing the molecular weight distribution of resin A of the present invention,
FIG. 1(b) is a scanning electron microscope cross-sectional photograph of a hole formed by dry etching a silicon oxide film using resin A of the present invention, FIG. 2(a) is a cross-sectional photograph of resin B and FIG. 3(a).
Figure 2(b) shows the molecular weight distribution of resin C, and Figure 2(b) shows the molecular weight distribution of resin B.
3(b) is a cross-sectional photograph taken by a scanning electron microscope of a hole formed by dry etching a silicon oxide film using resin C, and FIG. 4(a), (b), and (c) are taken by an electron beam. A diagram showing the dry etching process, and FIG. 5 is a diagram showing the sensitivity characteristics of resist films to electron beams depending on the type of novolak resin. Explanation of symbols 1... Molecular weight component of monomer 2... Molecular weight component of dimer 3... Molecular weight component of trimer 4... Silicon substrate 5... Silicon oxide film 6... Resist film 7... Hole 8... Resist film using resin C 9... Hole in silicon oxide film formed by resist using resin C 10... Resist film 11 using resin B... Resin B Holes 12 in silicon oxide film formed by resist using Resin A... Resist film 13 using Resin A... Holes 14 in silicon oxide film formed by resist using Resin A... Sensitivity characteristics of Resin C 15. ... Sensitivity characteristics of resin B 16 ... Sensitivity characteristics of resin A 17 ... Sensitivity characteristics of high molecular weight component resin 18 ... Electron beam

Claims (1)

[Scope of Claims] 1. A radiation-sensitive composition containing a phenolic resin and a dissolution inhibitor, characterized in that the phenolic resin is a phenolic resin that does not contain a low molecular weight component. 2. The radiation-sensitive composition according to claim 1, wherein the low molecular weight component not contained in the phenol resin is a trimer or less.