JPH11271965A - Pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to obtain an adequate pattern shape in a pattern forming method of forming resist patterns by subjecting a chemical amplification type resist contg. a polymer having an acid dissociation group of an acetal type to pattern exposure in a vacuum, thereby forming the patterns. SOLUTION: The chemical amplification type resist contg. the polymer having the acid dissociation group of the acetal type and an acid generating agent to generate an acid by irradiation with an energy beam is applied on a semiconductor substrate 11 to form a resist film 12 and thereafter, the resist film 12 is subjected to pattern exposure with electron rays 13 in the vacuum. The resist film 12 subjected to the pattern exposure is transferred from the inside of the vacuum into an atmosphere of about 50% in humidity and is rested for a suitable time, for example, 5 seconds in the atmosphere to humidify the resist film 12 and thereafter the semiconductor substrate 11 is placed at 100 deg.C and is heated for 60 seconds by a hot plate. When the exposed parts 12a of the resist film 12 are removed by developing the resist film 12 by the alkaline developer, the resist patterns 14 of the good pattern shape are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pattern forming method for forming a resist pattern on a semiconductor substrate in a manufacturing process of a semiconductor integrated circuit device.

[0002]

2. Description of the Related Art In recent years, with the increase in density and integration of semiconductor integrated circuit devices, the necessity of microfabrication technology has been increasing. As a measure for enabling microfabrication in a lithography process, A chemically amplified resist that uses an ArF excimer laser (wavelength: 193 nm) or a mercury lamp as an exposure light source, and contains a polymer having an acetal-type acid leaving group as a resist material and an acid generator that generates an acid when irradiated with an energy beam. Has been proposed.

A method of forming a resist pattern by exposing an excimer laser to the chemically amplified resist will be described below with reference to FIGS. 2 (a) to 2 (c).

First, as shown in FIG. 2A, a chemically amplified resist having the following composition is applied on a semiconductor substrate 1 to form a resist film 2.

Polymer: poly (ethoxyethyloxystyrene (35 mol%)-co-hydroxystyrene (65 mol%)) 10 g Acid generator: 2,4-dinitrobenzyl tosylate 0.3 g Solvent: diglyme 50 g Next, as shown in FIG. 2B, an excimer laser 3 is applied to the resist film 2 by using a mask 4 having a desired pattern shape.
Exposure through By doing so, an acid is generated from the acid generator in the exposed portion 2a of the resist film 2.

Next, as shown in FIG. 2C, when the semiconductor substrate 1 and thus the resist film 2 are heated, the resist film 2 is heated.
In the exposed portion 2a, the acetal-type acid leaving group is eliminated from the polymer by the action of the acid generated from the acid generator, so that the polymer becomes soluble in the alkaline developer while the unexposed portion 2b In, no acid is generated, so the polymer remains alkali-insoluble.

Next, when the resist film 2 is developed with an alkaline developer, the exposed portions 2a of the resist film 2 are removed as shown in FIG. A very fine resist pattern 5A can be formed.

[0008]

By the way, in order to meet the demand for higher integration and downsizing of the semiconductor integrated circuit device, it is desired to form a fine resist pattern of about 0.1 μm. Therefore, in order to increase the resolution of exposure light in the lithography process, use of an electron beam as an exposure light source is considered.

In the case of exposing with light such as excimer laser light, the resolution is limited by the wavelength of the exposing light source.
This is because, in electron beam exposure, the resolution can be theoretically improved to the beam diameter of the electron beam.

In order to improve the throughput, a pattern forming method for exposing a resist film made of a chemically amplified resist to an electron beam to form a resist pattern is desired.

A method of forming a resist pattern by patternwise exposing an electron beam to a chemically amplified resist containing an acetal-type polymer having an acid leaving group and an acid generator that generates an acid upon irradiation with an energy beam. Will be described with reference to FIGS.

First, as shown in FIG. 3A, a chemically amplified resist having the above composition is applied on a semiconductor substrate 1 to form a resist film 2 having a thickness of 0.5 μm. After forming a resist film 2 made of a chemically amplified resist and having a thickness of 0.5 μm on a semiconductor substrate 1,
As shown in FIG. 3B, the resist film 2 is subjected to pattern exposure with an electron beam 6 in a vacuum to generate an acid from an acid generator in an exposed portion 2a of the resist film 2. in this case,
In the unexposed portion 2b of the resist film 2, no acid is generated from the acid generator.

Next, immediately after the semiconductor substrate 1 is moved from the vacuum to the atmosphere, as shown in FIG. 3C, the semiconductor substrate 1 is heated on a hot plate at a temperature of 100 ° C. for 60 seconds. In the exposed portion 2a of the resist film 2, an acetal-type acid leaving group is released from the polymer by the action of an acid generated from the acid generator, so that the polymer becomes soluble in an alkaline developer.

Next, when the resist film 2 is developed with an alkaline developer, the exposed portions 2a of the resist film 2 are removed as shown in FIG. Resist pattern 5B can be formed.

However, in the exposed portion 2a of the resist film 2, since the elimination reaction of the acetal-type acid leaving group from the polymer does not sufficiently occur, as shown in FIG. And the pattern width was larger than 0.1 μm and the pattern shape deteriorated.

In the above-described pattern forming method, an electron beam is subjected to pattern exposure in a vacuum. However, in a vacuum, extreme ultraviolet (light in a 13 nm band or light in a 5 nm band) or ion Also in the case of performing pattern exposure using a beam or the like, there is a problem that the pattern shape is deteriorated as in the case of performing pattern exposure using an electron beam.

As described above, when a pattern defect occurs in a resist pattern, it becomes a cause of a defect in a subsequent process, and thus becomes a major problem in a method of manufacturing a semiconductor integrated circuit device.

In view of the above, the present invention provides pattern exposure in vacuum to a chemically amplified resist containing an acetal-type polymer having an acid leaving group and an acid generator that generates an acid upon irradiation with an energy beam. It is an object of the present invention to obtain a good pattern shape in a pattern forming method of forming a resist pattern by performing a resist pattern.

[0019]

The inventors of the present application have studied the reason why the acetal-type acid leaving group is not sufficiently released from the polymer in the exposed portion of the resist film. In spite of the fact that moisture is required for the leaving group to be eliminated, it has been found that the conventional pattern forming method is caused by insufficient moisture absorption of the resist film.

Next, as a result of various investigations on the reason why the resist film does not absorb moisture sufficiently, in the conventional pattern forming method, a heat treatment is immediately performed after pattern exposure using an energy beam in a vacuum. For this reason, it has been found that the problem is caused by insufficient moisture absorption of the resist film.

The present invention has been made on the basis of the above-mentioned findings, and comprises a step of pattern-exposing an energy beam to a resist film in a vacuum and a step of heating the pattern-exposed resist film. In addition, a step of absorbing moisture in the resist film is added.

More specifically, the pattern forming method according to the present invention relates to a method for forming a chemically amplified resist containing a polymer having an acetal-type acid leaving group and an acid generator that generates an acid by irradiation with an energy beam onto a substrate. A step of applying a resist film by applying the above, a step of pattern-exposing an energy beam to the resist film in a vacuum, and leaving the pattern-exposed resist film in the air,
The method includes a step of absorbing the pattern-exposed resist film and a step of heating and developing the absorbed resist film to form a resist pattern. The time during which the pattern-exposed resist film is left in the air is not particularly limited because it is related to the humidity in the air, but is preferably several seconds in a normal clean room.

According to the pattern forming method of the present invention, after a resist film is exposed to an energy beam in a vacuum in a vacuum, and the resist film subjected to the pattern exposure is left in the air to absorb moisture, a heating step performed later is performed. In the above, in the exposed portion of the resist film, the acetal-type acid leaving group is surely eliminated from the polymer.

In the pattern forming method of the present invention, the acetal-type acid leaving group is preferably an ethoxyethyl group, an isopropoxyethyl group, a methoxyethyl group or a tetrahydropyranyl group.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a pattern forming method according to an embodiment of the present invention will be described with reference to FIGS.

As a resist material, a chemically amplified resist containing a polymer having an acetal-type acid leaving group shown in [Chemical Formula 1], an acid generator that generates an acid by irradiation with an energy beam, and a solvent is prepared. I do.

[0027]

Embedded image

In the chemical formula 1, R and R 'are the same or different alkyl groups, and the oxygen atom in the acetal-type acid leaving group shown in the chemical formula 1 is bonded to the polymer; When the polymer is heated in the presence of an acid, the bond between the oxygen atom and the carbon atom is broken, so that the polymer changes from alkali-insoluble to alkali-soluble.

In the pattern forming method according to one embodiment of the present invention, as the resist material, specifically, a chemically amplified resist having the following composition is used.

Polymer: poly (ethoxyethyloxystyrene (35 mol%)-co-hydroxystyrene (65 mol%)) 10 g Acid generator: 2,4-dinitrobenzyl tosylate 0.3 g Solvent: diglyme 50 g First, as shown in FIG. 1A, a resist film 12 having a thickness of 0.5 μm is formed by applying the above-described chemically amplified resist on a semiconductor substrate 11, and then, as shown in FIG. As shown, in a vacuum (1 × 10 ⁻⁷ Torr), the resist film 12 is subjected to pattern exposure to an electron beam 13 so as to form a desired pattern. In this way, the acid is generated from the acid generator in the exposed portion 12a of the resist film 12, while no acid is generated from the acid generator in the unexposed portion 12b.

Next, the resist film 12 which has been subjected to the pattern exposure is moved from a vacuum to an atmosphere having a humidity of about 50%, and is left in the atmosphere for an appropriate time, for example, 5 seconds.
2 to absorb moisture.

Next, as shown in FIG. 1C, the semiconductor substrate 11 and thus the resist film 12 are heated on a hot plate at a temperature of 100 ° C. for 60 seconds. In this case, since the resist film 12 has been sufficiently absorbed by being left in the air, the ethoxyethyl group, which is an acetal-type acid-eliminating group, is poly (P) in the exposed portion 12a of the resist film 12. Ethoxyethyloxystyrene
Since it is reliably released from co-hydroxystyrene, it changes to alkali-soluble. On the other hand, in the unexposed portion 12b of the resist film 12, since no acid is generated from the acid generator, the ethoxyethyl group does not separate from the polymer, and thus remains insoluble in alkali.

Next, as shown in FIG. 1D, the resist film 12 is developed with an alkaline developer to
When the second exposed portion 12a is removed, a resist pattern 14 composed of the unexposed portion 12b of the resist film 12, having a pattern width of 0.1 μm, and having a good rectangular cross section can be formed.

In the above embodiment, the pattern exposure was performed using an electron beam in a vacuum (1 × 10 ⁻⁷ Torr). However, the present invention is not limited to this.
At 10 ⁻⁶ to 1 × 10 ⁻⁸ Torr, pattern exposure may be performed using extreme ultraviolet light (light having a wavelength of 13 nm or light having a wavelength of 5 nm) or an ion beam.

The acetal-type acid leaving group includes
Instead of an ethoxyethyl group, an isopropoxyethyl group,
A methoxyethyl group or a tetrahydropyranyl group can be used.

[0036]

According to the pattern forming method of the present invention, after an energy beam is pattern-exposed to a resist film in a vacuum, the resist film which has been subjected to the pattern exposure absorbs moisture. In the process, the acetal-type acid leaving group surely leaves the polymer, so that it changes to be soluble in the developer,
In the unexposed portion of the resist film, the acetal-type acid leaving group does not leave the polymer, and thus remains insoluble in the developer. Therefore, it is possible to obtain a resist pattern having a good pattern shape having a rectangular cross section composed of an unexposed portion of the resist film.

In the pattern forming method of the present invention, when the acetal-type acid leaving group is an ethoxyethyl group, an isopropoxyethyl group, a methoxyethyl group or a tetrahydropyranyl group, the acid leaving group is formed when the resist film absorbs moisture. Ensures detachment from the polymer in the presence.

[Brief description of the drawings]

FIGS. 1A to 1D are cross-sectional views showing each step of a pattern forming method according to an embodiment of the present invention.

FIGS. 2A to 2D are cross-sectional views showing respective steps of a conventional pattern forming method.

FIGS. 3A to 3D are cross-sectional views showing respective steps of a pattern forming method which is a premise of the present invention.

[Explanation of symbols]

 Reference Signs List 11 semiconductor substrate 12 resist film 12a exposed part 12b unexposed part 13 electron beam 14 resist pattern

Claims (2)

[Claims] A step of applying a chemically amplified resist containing a polymer having an acetal-type acid leaving group and an acid generator that generates an acid upon irradiation with an energy beam onto a substrate to form a resist film; A step of patternwise exposing the resist film to an energy beam in a vacuum; and a step of leaving the pattern-exposed resist film in the atmosphere to absorb moisture in the pattern-exposed resist film. Heating the resist film and then developing the resist film to form a resist pattern. 2. The pattern forming method according to claim 1, wherein the acetal-type acid leaving group is an ethoxyethyl group, an isopropoxyethyl group, a methoxyethyl group or a tetrahydropyranyl group.