JPS60230136A - Positive type resist composition - Google Patents

Abstract

PURPOSE:To enhance dry etching resistance and to improve sensitivity and resolution by defining the use range of esterification degree and mol.wt. of the ester produced from an alkali-soluble resin and an aromatic sulfonic acid by the fractional precipitation method. CONSTITUTION:When the ester is produced from the alkali-soluble resin and the aromatic sulfonic acid, the ranges of the esterification degree and the mol.wt. of the product to be used are defined. As such a ester, polyvinylphenol p-toluenesulfonate (VTE) obtained from polyvinylphenol (PVP) and p-toluenesuofonic acid (p-TS) has the main chains of a large number of molecules aligned in a straight chain, and the side chains are formed by the combinations of the -C6H5 groups and the p-TS groups. Such VTE esters are decomposed at the ester bonds by irradiating electron beams and solubilized in alkali, thus exhibiting the characteristics of the positive type resist. Moreover, this VTE has excellent dry etching property.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to the construction of a positive electron beam resist that has improved not only tri-etching resistance but also sensitivity and resolution.

(b) Background of the Technology Various semiconductor elements, filter elements, and other circuit elements are manufactured using semiconductor crystals, dielectric crystals, and the like as substrates.

Taking semiconductor devices such as ICs and LSIs as an example, integration is progressing more and more due to miniaturization of unit elements, and extremely fine conductor patterns are being produced.

Thin film formation technology and photolithography are used to form such fine patterns.

That is, a semiconductor layer is grown by epitaxial growth or heteroepitaxial growth on a substrate to be processed, or a thin layer made of metal or an insulator is formed by a method such as vacuum evaporation or sputtering, and then photoresist and photoetching are used for this. A fine pattern is formed by selectively etching a thin layer on a substrate using photolithographic technology.

Photo-etching technology uses photoresist coating on the substrate to be processed using a method such as a spin cord, which is then selectively exposed to ultraviolet light through a mask, and takes advantage of the difference in solubility of the light irradiated areas to the developing solution. There are two types of image forming molds: a negative type in which the light irradiated area is insoluble in the developer, and a positive type in which the light irradiated area is soluble.

In conventional ultraviolet exposure to form fine patterns, the wavelength used is 350 to 450 nm, so the theoretical limit of resolution is 0.5 μm, but since it involves diffraction and scattering of light, the practical limit is 1 μm. It is difficult to form a pattern with a line width of 1 μm or less.

On the other hand, the wavelength of the electron beam varies depending on the accelerating voltage, but is 0.1
Since the wavelength is much shorter, it is possible to form a pattern with a chain width of 0.1μ.

The present invention relates to improvements in positive electron beam resists for forming fine patterns.

(C) Conventional technology and problems There are chemical and physical methods for etching semiconductor layers and insulating layers, but the latter dry etching method is particularly suitable for forming fine patterns in terms of accuracy. Reactive ion etching method with directional etching (
The abbreviation RIE) is suitable.

This method performs sputter etching by bombarding gas ions using a resist film with windows opened by photoetching as a mask, and takes advantage of the property that the etching rate of the resist film is much lower than that of the substrate to be processed.

Here, as conventional positive electron beam resists, acrylic resin-based ones such as polymethyl methacrylate (abbreviated as PMMA), or poly(butene-1-sulfone) (abbreviated as PMMA) are used.
Sulfone-based compounds such as BS) are known.

Although these resists are useful as so-called electron beam resists that are sensitive to ionizing radiation such as electron beams and X-rays, when etching is performed by RIE using this resist pattern as a mask, dry etching resistance against sputtered ions is low. cannot be used.

For example, when forming a wiring pattern made of a deposited aluminum (AI) film on a silicon (Si) semiconductor substrate by photolithography, using these resists as a mask results in a thick resist film being formed due to the high etching rate. If this happens, the pattern accuracy will decrease and the purpose will not be met.

As described above, conventional positive type electron beam resists have poor dry etching resistance, which has caused problems in use.

(d) Object of the Invention An object of the present invention is to provide a positive electron beam resist structure that has high dry etching resistance and excellent sensitivity and resolution.

(e) Structure of the Invention The purpose of the present invention is to determine the degree of esterification and molecular weight distribution of the product by a fractional precipitation method when producing a positive electron beam resist made of an esterified product of an alkali-soluble resin and an aromatic sulfonic acid. This can be achieved by using a positive resist composition characterized in that it contains a limited number of .

The inventors have long proposed a positive electron beam resist made of an alkali-soluble resin and an aromatic sulfonic acid.

That is, sensitivity, resolution and dry etching resistance can be mentioned as necessary conditions for an electron beam resist sensitive to ionizing radiation.

Now, considering the reason why the dry etching resistance of conventional positive electron beam resists such as PMMA and PBS described earlier is inferior, when these polymer compounds are irradiated with ionizing radiation, the polymer in the irradiated area becomes weaker. As a result of the decomposition into molecules or the cutting of bonds connecting the constituent atoms, the irradiated area changes to a state that is soluble in the developer, but both of these positions occur at the main chain position in the molecular structure. There is.

Therefore, when subjected to ion bombardment during dry etching treatment, decomposition also occurs at the main chain position, resulting in a high etching rate.

Therefore, the inventors have improved the dry etching resistance by developing a resist in which decomposition or dissociation occurs at the side chains of the polymer upon irradiation with ionizing radiation.

Here, sensitivity and resolution are achieved by the side chain portion of the polymer,
On the other hand, dry etching resistance is achieved in the main chain portion.

That is, alkali-soluble resins such as phenol novolac resin, Talezol novolac resin, polyvinyl phenol, poly[p-hydroxy α-methylstyrene] and benzenesulfonic acid, 0-2m-, p-toluenesulfonic acid, o-, m- −.

Dry etching resistance has been achieved by resists composed of esters of alkoxyhenzenesulfonic acids such as p-methoxy and ethoxy, and aromatic sulfonic acids such as α and β-naphthalenesulfonic acids.

Here, as a representative example, polyvinylphenol toluenesulfonic acid ester (hereinafter abbreviated as VTE) is an esterified product of polyvinylphenol and p-toluenesulfonic acid.
The explanation is as follows.

The figure shows the decomposition reaction when a VTR is irradiated with an electron beam.The main chain of a VTR is composed of a large number of vinyl phenol molecules arranged in a straight line, and this phenyl group and toluenesulfonic acid A side chain is formed by bonding with a hydrogen group.

When such a VTR is irradiated with an electron beam, the VTR decomposes at the ester bond between polyvinylphenol and toluene sulfonic acid, and this reacts with water constituting the developer to form polyvinylphenol with a hydroxyl group (-011). It decomposes into toluenesulfonic acid having a sulfonic acid group (-S03Fl), becomes soluble in an alkaline developer, and exhibits the characteristics of a positive resist.

By adopting such a configuration, the VTR can be used as a conventional PM
Dry etching resistance is improved compared to MA and PBS.

The present invention further improves the sensitivity and resolution of such VTE, which can be achieved by narrowing the degree of esterification and the molecular weight distribution.

In other words, when the inventors were conducting research on realizing fine patterns using a positive resist made of an ester of an alkali-soluble resin and an aromatic sulfonic acid, it was found that limiting the esterification and molecular weight distribution could only improve resolution. They found that the sensitivity also increased.

This method can be carried out by a fractional precipitation method during the manufacturing process.

The present invention will be explained below by taking VTE as a representative example.

(f> Examples of the invention Example 1 Polyvinylphenol (weight average molecular weight 19000) 6
g and p-) luenesulfonylchloride IJF10 [50
g of tetrahydrofuran, and 10 g of dehydrated pyridine was added dropwise over 30 minutes while stirring at 40°C. After continuous stirring for 4 hours, the reaction solution was poured into 1 liter of deionized water, and the resulting precipitate was washed with deionized water, filtered with suction, and dried to obtain a VTR. Ta.

Next, as a fractionation method, after dissolving the obtained precipitate in 2-butanone, isopropyl alcohol (hereinafter abbreviated as IP
A) is added until cloudiness occurs, heated at 60° C. for 20 minutes, and left to stand overnight.

The liquid separates into two layers, so the upper layer is separated using the decanting method and S
Add PA until cloudiness occurs.

Next, after heating at 60°C for 20 minutes, the lower layer was separated into two layers by standing for day and night. The lower layer was separated using a decanting method, dissolved in 1,4-dioxane, and dried by freeze-drying. do.

Next, a resist solution is prepared by dissolving the obtained powder in cyclohexanone.

The dispersion of the degree of esterification of the resist solution thus separated was 0.98, and the degree of dispersion was 1.25.

Next, as a method for evaluating the characteristics of the resist solution, the resist solution was coated with a silane coupling agent in advance and dried on a Si substrate using a spin code method, and then
A resist film is formed by heating at 00° C. for 30 minutes.

This was irradiated with an electron beam at an accelerating voltage of 20 KV,
A resist pattern can be obtained by developing with an IPA developer.

The sensitivity in this case is 20 μc/cflI, and 1 μc/cflI.
It can be seen that it is possible to resolve a line and space of 1.5 μm at a sensitivity of 10 μc/d using the conventional method, which is improved compared to the resolution of a line and space of 1.5 μm.

Example 2 6g of polyvinylphenol with a weight average molecular weight of 9000
and 7 g of p-toluenesulfonyl chloride were dissolved in 50 g of tetrahydrofuran. Thereafter, a VTR was prepared in the same manner as in Example 1, and fractionated in the same manner as in Example 1 by fractional precipitation using IPA as a good solvent and water as a poor solvent. Separately, the intermediate portion of the esterification degree and molecular weight distribution was collected.

Here, the dispersion of the degree of esterification was 0.98, and the degree of dispersion was 1.25.

Next, in the same manner as in Example 1, a resist solution was adjusted, a resist film was formed, and electron beam exposure was performed, and Microposite MF-312 manufactured by Sisopre Co., Ltd. was used as a developer.
The resist film was developed by immersion for 0 seconds and rinsed using deionized water.

The sensitivity in this case is 30 μ(/Ca, and 1 μm
was able to resolve lines and spaces.

(g) Detailed Description of the Invention As described above, the present invention improves the sensitivity and resolution of a VTR with excellent dry etching resistance.
Implementation of the present invention facilitates the formation of fine patterns for semiconductor ICs and the like.

[Brief explanation of drawings]

The figure shows a decomposition reaction caused by VTR electron beam irradiation. ShiFj3

Claims (1)

[Claims] When producing a positive electron beam resist made of an esterified product of an alkali-soluble resin and an aromatic sulfonic acid, the positive electron beam resist is characterized in that the degree of esterification and molecular weight distribution of the product are limited by a fractional precipitation method. Type resist composition.