JPS6010250A - Formation of pattern - Google Patents

Abstract

PURPOSE:To obtain a resist pattern superior in resolution and heat resistance by using a polyacetal type polymer solubilizable in alkali by irradiation of electron beams. CONSTITUTION:A resist material to be used contains (A) an alkali-soluble polymer, such as novolak resin or polyhydroxystyrene, and (B) a polyacetal type polymer (solubility controller) usually forming an alkali-insoluble mixture when it is mixed with said polymer (A), and solubilizable in alkali by irradiation of electron beams. The preferably polyacetal resin (B) is poly-o-nitrobenzaldehyde acetal, especially, poly-o-nitrobenzaldehyde-1,4-dimethylcyclohexylacetal. Said mixture is dissolved in a solvent and applied, and after the irradiation of electron beams, it is developed with an alkaline developing soln.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a pattern forming method, and more particularly, to forming a positive image after development by irradiating a resist material with high-energy radiation such as an electron beam. The present invention relates to a method of forming a mold resist pattern. This method of forming a mother turn can be particularly advantageously used in a microfabrication process for manufacturing a conductor device.

BACKGROUND OF THE TECHNOLOGY In the field of manufacturing conductor devices, it is well known that high-energy radiation, particularly electron beams, is used to perform microfabrication on the order of saramicrons. For such microfabrication, various types of positive resist materials for electron beam exposure have been proposed and are commercially available.

What are typical positive resist materials for electron beam exposure?
It consists of degradable polymers such as remethyl methacrylate.

This polymer is made by irradiating the electron beam to cut the main chain of the polymer in the irradiated area and reduce the molecular weight of that part.
In other words, the solubility in the developer used in the subsequent development process is increased even in the non-irradiated area, and this solubilized area is selectively dissolved and removed during the subsequent development.

Prior Art and Problems As is clear from the above, pattern forming methods using positive resist materials are based on introducing solubility differences into the materials as a result of electron beam irradiation. However,
The solubility difference between the electron beam irradiated region and non-irradiated region introduced in this way is not very large, and therefore, sufficient resolution cannot be expected. Furthermore, the resist materials used here generally have poor heat resistance and therefore often suffer from undesirable changes in properties during, for example, electron beam exposure or plasma processing steps. In the field of photoresists, attempts have been made to obtain solubility differences by using naphthoquinone diazide, which is normally insoluble in alkali but exhibits alkali solubility when irradiated with light, without relying on solubility differences caused by cleavage of the polymer main chain. be. However, EB resist (electron beam resist)
Such a system did not exist.

OBJECTS OF THE INVENTION An object of the present invention is to provide a method for forming a positive resist pattern by electron beam exposure, in which the pattern obtained is excellent in both resolution and heat resistance.

Structure of the Invention The present inventor has recently discovered that, without relying on the solubility difference caused by the cleavage of the polymer main chain due to electron beam irradiation, an alkali-soluble polymer and a normally alkali-insoluble polymer can be combined with an alkali-insoluble polymer by electron beam irradiation. It has been found that the above object can be achieved when electron beam irradiation is performed using a resist material containing a polyacetal polymer (herein referred to as an inhibitor, i.e., a dissolution inhibitor) that can be converted to be soluble in alkali. Ta.

When carrying out the present invention, there will be no cases where the coating has a high viscosity and cannot be coated onto the substrate, or the case where the coating has a particularly low viscosity and undesirably reduces the electron beam sensitivity. However, any of the various alkali-soluble polymers commonly used in the art can be used. Specifically, for example, -OH, -COOI (,
Polymers with alkali-soluble functional groups such as -NH2 and the like can be used. The molecular weight of such a polymer is generally several 400 to several 400,000, preferably i
oo.

~100,000. Especially, several hundred to several thousand
It has been found that a novolac tung fat having a molecular weight of 1.0 can be advantageously used as an alkali-wettable polymer.

When the polyacetal dissolution inhibitor is mixed with the above-mentioned soluble polyester, the mixture usually has the following properties:
exhibits alkali insolubility; however, upon irradiation with an electron beam, i.e., by decomposition of the polyacetal in the irradiated area,
It exhibits alkali solubility. here,
It is thought that the decomposition of polyacetal proceeds by the following reaction mechanism.

Polyacetals useful in the practice of the present invention include, for example,
Poly(O-nitrobenzaldehyde acetal), especially poly(O-nitrobenzaldehyde-1,4-dimethylcyclohexyl acetal). Incidentally, the molecular weight of such acetal is not particularly limited as in the case of the alkali-soluble polymer described above, and generally ranges from several hundred to several 1.
It's on the order of 0,000. In particular, number IQOOO to number 10Q
It has been found that poly(O-nitrobenzaldehyde 1,4-dimethylcyclohexyl acetal) having a molecular weight of OOO can be advantageously used as dissolution inhibitor.

The alkali-soluble polymer and polyacetal dissolution inhibitor can be advantageously used in any mixing ratio. Such mixing ratio will generally depend on the desired result and the physical and chemical properties of both, especially their compatibility.

The nine-turn forming method of the present invention can be carried out, for example, by the following procedure.

A mixed resist solution is prepared by combining the selected alkali-soluble polymer and a polyacetal dissolution inhibitor, which is applied onto the substrate to be etched. Here, as a solvent for preparing the resist solution, a cellulose solvent such as methyl cellosolve acetate (MCA) or ethyl cellosolve (EC) is used, and as a substrate, Si, SiO□, P
SG etc. can be applied using a spin code method, a spray method, etc., and the preferred film thickness is about 5,000 ~
15,000 K can be raised each.

After the resist film is formed, a desired pattern is exposed using an electron beam exposure apparatus commonly used in this technical field. In the exposed area, as a result of the electron beam irradiation, the dissolution inhibitor contained in that area is changed to be alkali-soluble, thereby significantly improving the alkali solubility of that area.

After electron beam exposure, the resist film is developed with a suitable alkaline developer. Examples of useful developers include quaternized alkali ammonium salts (such as MF 312 from Shipley).
) and other aqueous solutions. As a result of development,
The exposed portion of the resist film having increased alkali solubility can be completely dissolved and removed. Finally, a clear positive resist lean corresponding to the exposed image/turn can be obtained.

Examples of the invention The invention will now be illustrated by the following examples.

Example 1: The following starting materials were prepared and combined.

Starting material Amount used Alkali-soluble polymer Nitsublack resin 90 wt% (molecular weight = 800 to 7ρ00) Polyacetal dissolution inhibitor; Poly(0-nitrobenzaldehyde 1,4-dimethylcyclohexyl 10 wt% acetal) (Molecular weight = lO to 120,000) This Add the mixture to methylcellosolve acetate) QVICA
) to obtain a 10% solution. This resist solution was coated onto a silicon wafer to a film thickness of 500 mm using a spin code method and then baked at 80 DEG C. for 60 minutes. After baking, exposure was performed using an electron beam exposure device at an accelerating voltage of 20 kV. After electron beam exposure, alkaline development was performed using a 70% aqueous solution of MF 312, and a positive resist pattern of SR microns (0.8 μm line and space) was obtained. (D.=1.0×1O-4C/c
In2). As a result of testing, this I-Lean was found to have excellent heat resistance. (Under N2 atmosphere, 220℃,
Even after baking for 80 minutes, no change was observed in the shape of the main turn. ) Example 2: The procedure described in Example 1 above was repeated. However, in the case of this example, the experiment was conducted using the following starting materials. The results obtained were approximately the same as those of Example 1.

Starting material Amount used Alkali-soluble polymer: de' (o-hydroxystyrene) 95wt% (molecular weight = 7000-78000) Polyacetal dissolution inhibitor: (same as Example 1) 5Wt (molecular weight = 190,000-200,000) Invention According to the present invention, it is possible to form a positive resist pattern that is excellent in both resolution and heat resistance. In particular, the resolution is on the order of submicrons and is as good as the commonly used resist (AZ 1350 J). moreover,
According to the invention, it is unnecessary to consider polymer backbone cleavage, so that suitable polymers can be selected from a wide range of alkali-soluble polymers.

Claims (1)

[Scope of Claims] 1. A pattern forming method characterized by forming a positive resist with 9 turns by electron beam irradiation using a resist material containing an alkali-soluble polymer and a polyacetal dissolution inhibitor. 2. The pattern forming method according to claim 1, wherein the dissolution inhibitor is poly(0-nitrobenzaldehyde acetal).