JPH04142544A - Photosensitive composition - Google Patents

Abstract

PURPOSE:To obtain the photosensitive compsn. which has a high sensitivity and can form fine resist patterns even when light of a near UV region is used as a light source by incorporating an alkali-soluble resin and specific silyl ketone into this compsn. CONSTITUTION:This compsn. contains the alkali-soluble resin and at least one kind of the silyl ketone expressed by formula I and the silyl ketone expressed by formula II. In the formulas I and II, R1 denotes a hydrogen atom, 1 to 10C unsubstd. or substd. alkyl group, 6 to 14C unsubstd. or substd. aryl group; R2 to R7 may be the same or different and respectively denote a hydrogen atom, 1 to 10C unsubstd. or substd. alkyl group, 6 to 14C unsubstd. or substd. aryl group, silyl group; n is 1 to 8 integer. A sensitizer, dye surfactant, and a polymer for reforming coated films, etc., may be compounded in addition to the alkali- soluble resin and the silyl ketone with this compsn.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to photosensitive compositions that are sensitive to ultraviolet light.

(Prior Art) In the manufacturing process of semiconductor devices such as LSIs, microfabrication technology using photoetching has been employed for some time, but with the recent trend toward higher integration of LSIs.

More fine processing technology is required in the manufacturing process as described above. In response to these demands, attempts are currently being made to shorten the wavelength of the exposure light source, for example using ultraviolet light such as a KrF excimer laser as the light source. However, when using a KrF excimer laser as a light source, conventional photoresists
Since absorption is too large for the 480 rays of light, the laser cannot sufficiently reach parts far from the surface of the resist film. As a result, the cross-sectional shape of the resist pattern after development becomes triangular, so even if such a resist pattern is used as an etching mask, it is not possible to transfer an etching pattern that is faithful to the intended pattern.

In view of these circumstances, the applicant has been developing a photosensitive composition suitable for use in KrF excimer lasers, and has previously developed photosensitive compositions (representing the general formula or unsubstituted alkyl group or aryl group). A photosensitive composition using a silyl ketone represented by the following as a photosensitizer was disclosed in JP-A-2-59752. However, although such photosensitive compositions exhibit excellent properties for KrF excimer lasers, their sensitivity to light in the near-ultraviolet region is not high, and for example, the sensitivity to light in the near-ultraviolet region is not high.
There was a problem in that it did not show sufficient sensitivity to rays such as n+m) and i-line (365 nm).

(Problems to be Solved by the Invention) As mentioned above, conventional photosensitive compositions do not have high sensitivity to light in the near-ultraviolet region.

For example, when a mercury lamp, a halogen lamp, or the like is used as a light source, a photosensitive composition that exhibits higher sensitivity to light in the near-ultraviolet region has been desired.

An object of the present invention is to solve these problems and provide a photosensitive composition that has high sensitivity and can form a fine resist pattern even when light in the near-ultraviolet region is used as a light source. .

[Structure of the invention]

(Means and effects for solving the problems) The photosensitive composition of the present invention contains an alkali-soluble resin and a silyl ketone represented by the following general formula (I) or (II), and in the silyl ketone, , is characterized in that an unsaturated group having a double bond or triple bond is introduced at one end of the carbonyl group.

(However, R in the formula represents a hydrogen atom, an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, or an unsubstituted or substituted aryl group having 6 to 14 carbon atoms, and R2-R1 may be the same or different. hydrogen atom, carbon number 1-1
0 unsubstituted or substituted alkyl group, unsubstituted or substituted aryl group having 6 to 14 carbon atoms, or silyl group, and n is an integer of 1 to 8. ) The alkali-soluble resin that can be used in the present invention is a polymer having at least one of a phenolic hydroxyl group and a carboxylic acid residue in the molecule, and specifically,
Phenolic novolac resin.

Cresol novolac resin, xyresol novolac resin, vinyl phenol resin, isopropenyl phenol resin, polyamic acid, vinyl phenol and acrylic acid,
Copolymers of methacrylic acid derivatives, acrylonitrile, styrene derivatives, etc., copolymers of isopropenylphenol and acrylic acid, methacrylic acid derivatives, acrylonitrile, styrene derivatives, etc., acrylic resins, methacrylic resins, acrylic acid or methacrylic acid and acrylonitrile , copolymers with styrene derivatives, copolymers of malonic acid and vinyl ether, and those containing silicon in these polymers.

Further, a reduced novolac resin obtained by reducing the quinone of a novolac resin with phenol, or a reduced vinyl phenol resin obtained by reducing the quinone of a vinyl phenol resin with phenol can be used. Such reduced novolak resins include reduced phenol novolac resins, reduced metaparacresol novolak resins, and reduced metaparacresol (3
, 5-xyresol) novolak resin, etc.

Furthermore, in the photosensitive composition of the present invention, a silyl ketone having an unsaturated group introduced at one end of a carbonyl group is used as a photosensitizer, as described above. In the photosensitive composition of the present invention, after the silyl ketone is photodecomposed by exposure,
A latent image is formed by addition reaction with the phenolic hydroxyl group or carboxylic acid residue in the alkali-soluble resin. After this, by performing wet development or dry development,
A resist pattern having a good pattern profile can be formed. In the present invention, the silyl ketone as a photosensitizer has a carbon-carbon double bond or a positional bond, and the π electrons of such a bond are conjugated with the π electrons in the carbonyl group. Compared to conventional silyl ketones that do not have double or triple bonds, the light absorption region is shifted toward longer wavelengths. Furthermore, due to the conjugation of π electrons as described above, the reactivity of the silyl ketone itself is improved, so the photosensitive composition of the present invention has high sensitivity even to light in the near-ultraviolet region. . Further, in the silyl ketone used in the present invention, n in the above general formula (I) or (II) is preferably 2 or more. The reason for this is that by setting n to 2 or more, the reactivity of the silyl ketone after it is photodecomposed can be selectively increased only with respect to phenolic hydroxyl groups and carboxylic acid residues. Specifically, the silyl ketone used in the present invention is CH.

CH3C8゜CH3CH30 CH3-5i -5i -C-C=CHCH, CH3C
H30 CH, -5i -5i -5i -C-C:CH3H3
CH.

CH, CH3CH3 CH.

etc.

The blending amount of the silyl ketone is 10% of the alkali-soluble resin.
0 parts by weight, 5 to 70 parts by weight, more preferably 2 parts by weight
It is desirable to blend 0 to 40 parts by weight.

The reason for this is that if the amount of silyl ketone blended is too small, there is a risk that the photosensitivity of the resulting photosensitive composition will be reduced or may be lost.

In addition to the alkali-soluble resin and silyl ketone, the photosensitive composition of the present invention may optionally contain a sensitizer, a dye, a surfactant, and a polymer for modifying the coating film (e.g., epoxy resin, polymethyl methacrylate resin). , propylene oxide-ethylene oxide copolymer, polystyrene, silicone ladder polymer, etc.).

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

First, a resist solution consisting of the photosensitive composition of the present invention dissolved in an organic solvent is applied onto a substrate by a spin coating method or a dipping method.
A resist film is formed by drying at 120°C. Examples of the substrate used here include a silicon single crystal wafer 5 on which various coatings such as an insulating film and a conductive film are deposited, or a mask blank. Examples of the organic solvent include ketone solvents such as cyclohexane, acetone, methyl ethyl ketone, and methyl isobutyl ketone, cellosolve solvents such as methyl cellosolve, methyl cellosolve acetate, and ethyl cellosolve acetate, and ester solvents such as ethyl acetate, butyl acetate, and isoamyl acetate. A solvent or a mixed solvent thereof is preferred.

Next, the resist film is exposed to irradiation with rF excimer laser, i-line, g-line, etc. at a wavelength of 248n+s through a mask having a desired pattern. Subsequently, when wet development is performed, 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. In addition, when performing dry development, the cyst film after the exposure is
After heating at 50°C or less, preferably under reduced pressure to remove the silyl ketone in the unexposed area and make the silicon content in the unexposed area significantly lower than that in the exposed area, oxygen reactive ion etching (02RTE) is performed. The pattern is formed by etching the unexposed area due to the difference in silicon content between the exposed area and the unexposed area.

In the photosensitive composition of the present invention, a fine resist pattern having a good pattern profile can be formed by the resist pattern forming process as described above. In the present invention, it is possible to obtain an insulating film having a desired pattern by subjecting such a resist pattern to a heat treatment or the like, or to perform etching of a substrate, etc. using the resist pattern as an etching mask.

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

Example 1 First, polyamic acid as an alkali-soluble resin was synthesized by the steps shown below. i.e. stirring bar,
Pass nitrogen gas dried with phosphorus pentoxide into a reaction flask equipped with a thermometer and a dropping funnel to add 4.635 g (0,021 mol) of pyromellitic dianhydride, 3.3', 4
．． 4'-benzophenone tetracarboxylic dianhydride 19
．． 993 g (0,062 mol), maleic anhydride 0.
333 g (0,003 mol) and N-methyl-2-
100 g of pyrrolidone was charged, thoroughly stirred, and cooled to -5°C. Next, 15.996 g (0,081 mol) of 4,4'-diaminodiphenyl ether and bis(
γ-7 Minoprovil) Tetramethyldisiloxane 1.1
A solution prepared by dissolving 99 g (0,003 mol) of N-methyl-2-pyrrolidone in 69 g of N-methyl-2-pyrrolidone was gradually dropped into the flask from the 17+1 lower funnel. Subsequently, the mixture was maintained at -5 to 0°C for 4 hours, and then reacted at room temperature (20°C) for 4 hours to obtain polyamic acid as an alkali-soluble resin. When an N-methyl-2-pyrrolidone solution of this polyamic acid was prepared and the logarithmic viscosity was measured at 30°C, it was found to be 0.82.
It was dl/g.

Next, the polyamic acid Log and 2 g of the silyl ketone represented by the general formula % were uniformly stirred and dissolved in 40 g of N-methylpyrrolidone to prepare a resist solution comprising the photosensitive composition of the present invention.

Note that the above silyl ketone is r Tetrahedro
n, Vol.

39 (I983), P, 949J. The resulting resist solution was filtered through a 0.5p membrane filter, applied onto a silicon wafer using a spinner, and heated on a hot plate at 90°C for 10 minutes.
Dry for 5.0 minutes. A resist film was formed.

Subsequently, the resist film was subjected to pattern exposure (light irradiation amount: 350+*J/al) using a contact exposure machine (manufactured by Cobilt; CA300) using a mercury lamp as a light source, and then a tetrafluorocarbon film with a concentration of 2.38% was applied. A resist pattern was formed by immersing it in an aqueous methyl ammonium hydroxide solution for 60 seconds to develop it, and then washing it with water for another 20 seconds.

When the cross section of the obtained resist pattern was observed using an electron microscope, the 5- line and space were resolved and had sufficient resolution.

In addition, to evaluate the adhesion to the substrate, the resist film before exposure was placed in a constant temperature dryer at 150°C for 1 hour.

Heat curing was performed by increasing the temperature sequentially for 1 hour at 250°C and 1 hour at 320°C, and then for 12 hours in saturated steam at 2 atm.
After heating at 0°C for 24 hours, a cross-cut test was conducted. When the above-described cross-cut test was conducted on 100 samples, the film and silicon wafer did not peel off in any of the samples, and good adhesion was obtained between the resist film and the substrate in this example. It was getting worse. Separately, we peeled off the heat-cured resist film from the silicon wafer with a razor and conducted thermogravimetric analysis (TGA).
No weight loss due to thermal decomposition is observed up to around 0°C, and the resist film has sufficient heat resistance, and can be used as a passivation film or an interlayer insulating film formed in a semiconductor device, for example. It was confirmed that it can be used effectively.

Example 2 A novolak resin containing p-cresol, m-cresol novolak, and 2,5-xyresol at a molar ratio of 0.25:0.45:0.35, respectively, was prepared as an alkali-soluble resin, and the novolak resin 10
0g, add 20g of silyl ketone represented by the general formula % and 400g of acetate cellosolve as a solvent, stir until homogeneous,
A resist solution consisting of the photosensitive composition of the present invention was prepared by dissolving it. The obtained resist solution was filtered through a 0.5-line membrane filter, and then applied onto a silicon wafer in the same manner as in Example 1 and dried to form a resist film with a thickness of 1.0 μs. Next, a KrF excimer laser stepper (NA
; 0.37) to pattern exposure (light irradiation amount: 320 J/cd) on the resist film, and then the density v
, when developed with a 38% aqueous solution of tetramethylammonium hydroxide, the resolution was 0.35. A fine resist pattern was formed with high precision.

Examples 3 to 9 From the raw material compositions shown in Table 1, polyamic acids (I) to (vi
) was synthesized. Table 1 also lists the synthesis conditions and the logarithmic viscosity of the obtained polyamic acid solution. The abbreviations used in Table 1 will be explained below.

BPDA: 3.3',4.4'-bisphenyltetracarboxylic dianhydride.

BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride.

PMDA: Pyromellitic dianhydride.

DPE: 4.4'-diamino V phenylethe AM 5i-a Le.

:4,4'-diaminodiphenylmethane.

: Bis(γ-aminopropyl)tetramethyldisiloxane.

(x=4~5) Nianirin.

-a -b -c -d :0-Toluidine.

: Phthalic anhydride.

: Hexahydrophthalic anhydride.

:4-Methylhexahydrophthalic anhydride.

:maleic anhydride.

(Left below) Next, the above polyamic acids (i) to (vi) and silyl ketones (m) to (VI) each having the structural formula shown below were prepared.
) in the amounts shown in Table 2, Example 1
A resist solution comprising the photosensitive composition of the present invention was prepared in the same manner as described above. Thereafter, a resist film was formed on the silicon wafer in the same manner as in Example 1, followed by exposure and development to form a resist pattern with a resolution of 2-. In the exposure described above, the same contact exposure machine as in Example 1 was used, and Table 2 shows the amount of light necessary to form a resist pattern at a resolution of 2/Jll when using such a contact exposure machine. The amount of light irradiation is shown below. Table 2 also shows, as a comparative example, a case in which a silyl ketone (■) in which no unsaturated group was introduced at one end of the carbonyl group was used.

CH3CH1 As shown in Table 2, in Examples 3 to 9, 250
A resist pattern with a resolution of 2 μs could be formed with a light irradiation amount of ~420+aJ/cj, but in the comparative example, a light irradiation amount of 560 mJ/aJ was required to form the same resist pattern, and the photosensitive composition of the present invention However, it was confirmed that high sensitivity was exhibited even when a mercury lamp was used as the light source. Furthermore, as is clear from comparing Example 3 and Example 7,
In the present invention, particularly high sensitivity is obtained when a silyl ketone having a silyl group having a silicon number of 2 or more is used.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to provide a photosensitive composition that exhibits high sensitivity even to light in the near-ultraviolet region. According to the photosensitive composition of the present invention, a resist pattern with high precision can be formed even when light in the near-ultraviolet region is used as a light source, and its industrial value is great.

Agent: Patent Attorney Noriyuki Chika

Claims (1)

[Scope of Claims] A photosensitive composition comprising an alkali-soluble resin and at least one of a silyl ketone represented by the following general formula (I) and a silyl ketone represented by the following general formula (II). thing. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (However, R_1 in the formula is a hydrogen atom, an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, Represents an unsubstituted or substituted aryl group having 6 to 14 carbon atoms, R_2 to R_7 may be the same or different, and each represents a hydrogen atom, an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, and 6 carbon atoms. ~
represents 14 unsubstituted or substituted aryl groups or silyl groups, and n is an integer of 1 to 8. )