JPH02248952A - Photosensitive composition - Google Patents

Abstract

PURPOSE:To enhance sensitivity and resolution to radiations, especially, exicimer laser beams by incorporating a specified resin and a compound to be allowed to release an acid by photoirradiation. CONSTITUTION:The photosensitive composition contains a resin obtained by substituting the hydroxy group of an alkali-soluble resin with tetrahydropyranyl ether group and the compound to be allowed to release an acid by photoirradiation, thus permitting the composition film exposed to radiation to release the acid from a photo-acid-generating agent in the photoirradiation part of the film, to replace the tetrahydropyranyl ether group by the hydroxy group of the resin, to dissolve the photoirradiation parts of the film by developing it with an aqueous alkaline developing solution, thus to form a positive image, and consequently, the obtained photosensitive composition to be high in sensitivity to radiations, especially to excimer laser beams.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a photosensitive composition, and particularly to a photosensitive composition useful for forming a fine resist pattern.

(Prior Art) In the manufacturing process of semiconductor devices such as ICs, microfabrication technology using photoetching is employed.

This technique involves forming a photoresist film on a substrate such as a silicon single crystal wafer by spin coating, exposing the resist film to ultraviolet light through a mask with a desired pattern, and then developing and In this method, a rinse pattern is formed by performing a process such as rinsing, and then the exposed wafer is etched using the resist pattern as an etching mask, thereby forming lines or windows with minute widths. In such microfabrication techniques, the accuracy of semiconductor devices is influenced by the performance of the photoresist used, such as resolution on the substrate, accuracy of photosensitivity, adhesion to the substrate, or resistance to etchants.

By the way, due to the demand for higher density and higher integration of resist patterns, exposure methods using light with shorter wavelengths are attracting attention. Specifically, 308n■, 248nl, 19
Excimer laser exposure using 3 n1% light source, X m
If light is attracting attention. However, conventionally, there has been no resist that has sufficient sensitivity and resolution to light of such wavelengths.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems. It tries to provide something.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides (a) a resin obtained by replacing the hydroxyl group of an alkali-soluble resin with a tetrahydropyranyl ether group, and (b) a resin obtained by replacing an acid with a tetrahydropyranyl ether group by light irradiation. This is a photosensitive composition characterized by containing the resulting compound.

The alkali-soluble resin used in the above component (a) is preferably a polymer containing an aryl group or a carboxyl group into which a hydroxy group has been introduced. Specifically, phenol novolac resins, cresol novolac resins, xyresol novolac resins, vinyl phenol resins, impropenyl phenol resins, copolymers of vinyl phenol with acrylic acid, methacrylic acid derivatives, acrylonitrile, styrene derivatives, etc. Copolymers of propenylphenol with acrylic acid, methacrylic acid derivatives, acrylonitrile, styrene derivatives, etc., acrylic resins, methacrylic resins, copolymers of acrylic acid or methacrylic acid with acrylonitrile, styrene derivatives, malonic acid and vinyl ethers, etc. Copolymers and the like can be mentioned. Further, as the alkali-soluble resin, those containing silicon can also be used.

In order to protect the hydroxyl group of each of the above alkali-soluble resins with tetrahydropyranyl ether, 2,3-dihydro-4H-bilane (DIP>) is combined with an acid catalyst (e.g. HC
I, POCj! *, p-toluenesulfonic acid, oxalic acid, etc.) in a suitable solvent (e.g. TIIF, chloroform, ethyl acetate, DMF) with an alkali-soluble resin as shown in the following formula (1). . For details, see 11. Grant, N.
,V,Prelog,R,P,5needon,)Ie
lv.

Chls, Acta, 48.415 (1963).

RR It is desirable that 10 to 100% of the hydroxyl groups in the alkali-soluble resin be replaced with tetrahydropyranyl ether groups in the resin serving as component (a).

The reason for this is that if the introduction rate of the tetrahydropyranyl ether group is less than 10%, the difference in solubility between the exposed and unexposed areas cannot be sufficiently maintained, and as a result, resolution may decrease. . More preferably, the introduction rate of the tetrahydropyranyl ether group is in the range of 20 to 70%.

Specific examples of resins obtained by substituting the hydroxyl group of the alkali-soluble resin, component (a), with a tetrahydropyranyl ether group are shown in Table 1 below. Also,(
Specific examples of resins obtained by substituting the hydroxyl group of the alkali-soluble resin containing silicon, which is component a), with a tetrahydropyranyl ether group are shown in Table 2 below.

The above component (b) is a compound that generates an acid upon irradiation with light (
The prior generator) is not particularly limited, but onium salts and 0-nitrobenzyl ether are preferable from the viewpoint of sensitivity. Specific examples of such compounds are shown in Table 3 below. Further, it is desirable that the proportion of the component (b) contained in the solid component of the photosensitive composition is in the range of 1 to 20ffi%. The reason for this is that the ratio of component (b) is 1
If it is less than % by weight, a sufficient amount of acid will not be generated during exposure, and
On the other hand, if the proportion exceeds 20% by weight, it may cause deterioration of coating properties and deterioration of storage stability. More preferably, the proportion of component (b) contained in the solid component of the photosensitive composition is 2 to 1%.

The components (a) and (b) above are dissolved in a solvent to prepare the photosensitive composition of the present invention. Such solvents are not particularly limited, but specifically include ketone solvents such as cyclohexane, acetone, methyl ethimeketone, and methyl isobutyl ketone; cellosolve solvents such as ζ methyl cellosolve, methyl cellosolve acetate, and ethyl cellosolve acetate; Ester solvents such as ethyl acetate, butyl acetate, and isoamyl acetate, or mixed solvents thereof are preferred.

In addition, the photosensitive composition according to the present invention has the above-mentioned (a) to (b).
) In addition to the components shown in
Polymethyl methacrylate resin, propylene oxide
(ethylene oxide copolymer, polystyrene, silicone ladder polymer, etc.) may also be blended.

Next, a process for forming a resist pattern using the photosensitive composition of the present invention will be explained.

First, a photosensitive composition of the present invention dissolved in a solvent is applied onto a substrate by a spin coating method or a dipping method, and then dried to form a resist film. Examples of the substrate used here include a single silicon single crystal wafer, the same wafer with various coatings such as an insulating film and a conductive film deposited on its surface, or a mask blank.

Next, the resist film is exposed to radiation, for example, an excimer laser having a wavelength of 248n-, through a mask having a desired pattern, and then the substrate is heated at 70 to 110°C for 30 minutes.
The tetrahydropyranyl ether group in the photosensitive composition is removed by heating for about 0 seconds to 10 minutes. Thereafter, a desired resist pattern is formed by developing with an alkaline aqueous solution. Examples of the alkaline aqueous solution used here include a tetramethylammonium hydroxide aqueous solution.

(Function) According to the present invention, the present invention comprises (a) a resin obtained by replacing the hydroxyl group of an alkali-soluble resin with a tetrahydropyranyl ether group, and (b) a compound (prior generator) that generates an acid upon irradiation with light. Therefore, a photosensitive composition with high sensitivity and high resolution to radiation, particularly excimer laser, can be obtained.

That is, by irradiating a film obtained by applying the photosensitive composition of the present invention onto a substrate, an acid is generated from the prior generator in the light-irradiated portion of the film, and this acid causes the formation of an acid in the film. The tetrahydropyranyl ether group introduced into the resin which is the component (a) is removed, the hydroxyl group of the alkali-soluble resin in the membrane is regenerated, and the tetrahydropyranyl ether group introduced into the resin is removed. The effect of suppressing the solubility of the alkali-soluble resin in an alkaline solution is reduced. As a result, by developing with a developer consisting of an alkaline aqueous solution, only the light irradiated area (exposed area) of the film is dissolved in the developer (alkaline aqueous solution), and a positive image is formed. In addition,
By heating the iris plate at 70-110° C. after exposure, the removal reaction of the tetrahydropyranyl ether group introduced into the resin, which is the component (a), is promoted, and the sensitivity can be further improved.

Furthermore, if an alkali-soluble resin containing silicon is used, a positive image with excellent oxygen reactive etching resistance (oxygen RIE resistance) can be formed by exposure and development.

(Example) Examples of the present invention will be described in detail below.

Implementation fi11-7 The resin obtained by substituting the hydroxy group of the alkali-soluble resin shown in Table 1 below with a tetrahydropyranyl ether group and the prior generator shown in Table 3 below are shown in Table 4. These mixtures were dissolved in ethyl cellosolve acetate to prepare a 7fJ photosensitive composition.

Next, each of the photosensitive compositions was applied onto a silicon single crystal wafer using a spinner and dried to form a resist film with a thickness of 1.0 μm. Exposure was carried out under the conditions shown in Table 5.

Next, the substrate with the exposed resist film was heated to 110°C.
After heating for 1 minute on a hot plate, the resist film was developed with a tetramethylammonium hydroxide (TMAH) aqueous solution having a concentration shown in Table 5.

A cross section of each of the obtained resist patterns was observed using an electron microscope to examine the resolution. The results are also listed in Table 4 below. As is clear from Table 4, the photosensitive composition according to the present invention has high sensitivity to excimer laser,
It can be seen that it has a high resolution.

Examples 8 to 14 Resins obtained by substituting the hydroxy groups of silicon-containing alkali-soluble resins shown in Table 2 below with tetrahydropyranyl ether groups and the prior generators shown in Table 3 below. They were blended in the proportions shown in Table 5 below, and these mixtures were dissolved with ethyl cellosolve acetate to prepare seven types of photosensitive compositions.

Next, a photoresist (based on novolac resin and naphthoquinone diazide) was deposited on a 5-inch silicon wafer.
0FPR-800 (manufactured by Tokyo Ohka Co., Ltd.) was applied with a spinner at a voltage of 0.5 μm, and then 20
Heat treatment was performed at 0° C. for 30 minutes.

Subsequently, each of the photosensitive compositions was applied to a thickness of 0.5 μm on this first layer resist film using a spinner, and then heated on a hot plate at 90° C. for 5 minutes to form a second layer resist film. did.

Then, NA O,:(7,10:1 reduced projection Kr
Exposure was carried out using an F excimer laser stepper under the conditions shown in Table 5. Subsequently, the substrate having the exposed resist film was heated for 1 minute on a not hot plate, and then the resist film was developed with an aqueous solution of tetramethylammonium hydroxide (TMAll) having a concentration shown in Table 5. An upper layer pattern was formed.

Next, each silicon substrate on which the upper layer pattern was formed was etched using a dry etching device (product name manufactured by Ikeda Seisakusho Co., Ltd.; formerly known as RRI).
B), 2 x 10-” ZOrrs output 0.0
Reactive ion etching (RIB) using oxygen plasma under conditions of 8 W/cs2 was performed to transfer the upper layer pattern to the lower resist film (first resist film).

The resolution of the two-layer patterns formed in Examples 8 to 14 and the etching ratio (oxygen RIE resistance) of the upper layer pattern relative to the lower resist film made of 0FPR-800 manufactured by Tokyo Ohka Co., Ltd. were investigated. Those results are shown in the same 5th column.
Also listed in the table.

As is clear from Table 5, the upper layer pattern made of the photosensitive composition of the present invention has excellent resolution and oxygen-resistant layer E properties. It can be seen that the image can be faithfully transferred to the underlying resist film, and a fine and highly accurate two-layer pattern can be formed.

[Effects of the Invention] As detailed above, according to the present invention, radiation, especially KrF
It is possible to provide a photosensitive composition that has high sensitivity and high resolution to excimer laser (248tv) and is suitable for photoetching processes for semiconductor devices and the like.

Table 1 m, p-cresol novolac resin (tetrahydropyranyl ether group introduction rate: 5o) ... [A] (m, p-cresol) (xyresol) novolak resin (tetrahydropyranyl ether group introduction rate: 40)
...CB) CG) Table (A) (BE CD) Table [B] [Mouth] [C] (2) [H] [G]

Claims (1)

[Scope of Claims] A photosensitive composition characterized by containing (a) a resin obtained by replacing the hydroxyl group of an alkali-soluble resin with a tetrahydropyranyl ether group, and (b) a compound that generates an acid upon irradiation with light. thing.