JPH11174669A - Resist composition and pattern forming method using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resist composition for developing, by an alkaline water solution, a positive type pattern, high in sensitivity, high in resolution, and good in stability, and a pattern forming method using it. SOLUTION: In a chemically amplifying resist composition including, at least, an alkali-soluble resin, a medium for changing solubility of an alkaline solution by a reation using an acid as a catalyst, and an acid precursor for producing an acid by radiation exposure, an organic salt having an anion site expressed by a general formula 1 being an alkyl sulfonic acid or an aryl sulfonic acid, is added to the resist composition. In the formula, R1 , R2 , R3 , and R4 are alkyl radicals having 1 to 6 carbon atoms or substituted alkyl radicals, Y<-> stands for an alkyl sulfonic acid or an aryl sulfonic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resist composition used for microfabrication of a semiconductor device or the like, and more particularly to a radiation composition including an electromagnetic wave such as ultraviolet rays, far ultraviolet rays, X-rays or a particle beam such as an electron beam or an ion beam. A process in which an acid is generated in the pattern latent image forming portion by pattern-like irradiation, and the acid-catalyzed reaction changes the solubility of the irradiated portion and the non-irradiated portion in an aqueous alkali solution to form an aqueous alkali solution as a developer. The present invention relates to a resist composition that causes a pattern to appear by using the same, and a pattern forming method using the same.

[0002]

2. Description of the Related Art In recent years, integrated circuits have been miniaturized in accordance with high integration, and patterns of sub-half micron or less have been required, and resist materials having excellent resolution have been demanded. In addition, in order to improve the productivity of wafer processing, it is important to increase the sensitivity of the resist used, as well as to improve the apparatus.

As a resist material for achieving high sensitivity, for example, as a chemically amplified resist composition utilizing an acid catalyzed reaction, US Pat. No. 3,779,778, Japanese Patent Publication No. 2-2766
No. 0, JP-A-2-25850 discloses a composition.

However, in the pattern forming method using such a chemically amplified resist composition, since the amount of acid generated in the exposed portion of the resist film is very small, it is easily affected by the surrounding environment and is stable. It is difficult to form fine patterns. For example, a surface insolubilized layer is formed by a basic substance in the environment, and the cross-sectional shape of the resist pattern becomes a shape having an eaves, or a hem-spread shape in which the vicinity of the substrate surface is widened, There is a problem that a vertical and good pattern shape cannot be obtained. Further, the problem of diffusion of acid generated by exposure also causes a problem that resolution is reduced.

As a method for avoiding this, Japanese Patent Application Laid-Open No. 8-110
As described in JP-A-635, a method of adding a salt of pyridine or a derivative thereof is also known.

As a method for improving contrast, as described in JP-A-4-51243, an ammonium compound is added to a resist to increase a difference in dissolution rate between an exposed portion and an unexposed portion. In some cases, the contrast is improved, and as a result, a good rectangular pattern is obtained.

[0007]

SUMMARY OF THE INVENTION Incidentally, Japanese Patent Application Laid-Open No.
The prior art described in JP-A-110635 has a problem that the film is reduced after the heat treatment due to the acidity of those salts. Further, in the prior art described in JP-A-4-51243, a poorly soluble layer is formed on the resist surface because the influence of the base in the environment is not considered.
In addition, there is a problem that the resist sensitivity is reduced.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a specific organic salt enhances the stability of a resist composition and improves contrast, and the decrease in resist sensitivity is reduced in comparison with other salts and basic substances. Based on this finding, the above problem was solved by adding these organic salts to a resist composition.

That is, the present invention is a chemically amplified resist comprising a compound capable of generating an acid upon irradiation with actinic radiation and a medium having a reactivity that changes the solubility in an aqueous alkali solution by an acid catalyzed reaction. And a method for forming a pattern using the composition.

[0010]

Embedded image

Wherein R ₁ , R ₂ , R ₃ and R ₄ may be the same or different and are an alkyl group having 1 to 6 carbon atoms or a substituted alkyl group, and Y 1 is an alkylsulfonic acid , Arylsulfonic acid) Examples of the organic salt represented by the general formula 1 include tetraethylammonium paratoluenesulfonate, tetraethylammonium trifluoromethanesulfonate, tetrabutylammonium paratoluenesulfonate, and tetrabutylammonium trifluoromethanesulfonate. And the like.

Since these organic salts have previously formed a complex with a paratoluenesulfonic acid anion, which is an arylsulfonic acid, and a trifluoromethanesulfonic acid anion, which is an alkylsulfonic acid, the acid generated by exposure is consumed. Without, compared to basic substances,
A decrease in resist sensitivity can be reduced. At the same time as this effect, as in the case where a basic substance is added, it is characterized in that it is hardly affected by the basic substance in the air. Further, since these organic salts release an acid even by heat treatment before exposure, it is necessary to use a protecting group having a high activation energy for deprotection to some extent.

Further, these organic salts function as a contrast enhancer for improving the resolution of the resist. In order to improve the contrast, it is necessary to reduce the dissolution rate difference between the low exposure area and the high exposure area in the exposed area, as described in JP-A-4-51243. That is, it is conceivable to add a dissolution-inhibiting component that is easily detached from the resist surface in the low-exposure region and hardly detached from the resist surface in the high-exposure region.

Certain organic salts easily dissolve into the solution in the low exposure region, which is susceptible to attack by hydroxy ions, and in the high exposure region, a reactive medium that changes the solubility by a reaction using an acid as a catalyst. It does not easily leave due to the hydrophobic interaction with and protects the alkali-soluble groups of the medium.
As a result, there is no difference in dissolution rate between the exposed portions, and the contrast can be improved. It is considered that the organic salt represented by the general formula 1 in the present invention also has improved contrast with the same effect.

The amount of the organic salt to be added is preferably 0.01 to 0.5 part by weight based on 100 parts by weight of the alkali-soluble resin. When the amount is 0.01 to 0.5 part by weight, the stability and the resolution can be easily controlled, and a sufficient effect as a stabilizer and a contrast enhancer can be obtained. If the amount of the organic salt is more than 0.5 parts by weight, the dissolution inhibiting effect tends to be large and the contrast tends to be low. If the amount is less than 0.01 part by weight, the stability tends to decrease.

The effect of the present invention can be imparted to the organic salt regardless of whether it is a single type or a multiple type.

The resist composition of the present invention can contain additives such as a surfactant, a storage stabilizer, a sensitizer, a striation inhibitor, a plasticizer, and an antihalation agent, if necessary. .

[0018]

(Example 1) m, p-cresol novolak resin: 89 parts by weight, polyhydroxy compound having a tetrahydropyranyloxy group (average molecular weight: 99)
2, polydispersity: 1.02): 11 parts by weight, and diphenylmethylsulfonium paratoluenesulfonate: 4 parts by weight as an acid precursor. 0.116 parts by weight of tetrabutylammonium paratoluenesulfonate as an organic salt was dissolved in 2-heptanone as a solvent to prepare a solution having a solid concentration of 20% by weight. The solution was filtered through a 0.1 μm membrane filter to prepare a resist solution.

The obtained resist solution was dropped on a silicon wafer, spin-coated, and heat-treated at 120 ° C. for 2 minutes to form a resist solution.
A resist film having a thickness of 7 μm was obtained. The substrate was irradiated with an electron beam using an electron beam lithography system (electron beam acceleration voltage is 30 kV), the irradiation amount was changed stepwise, and then heat treatment was performed at 100 ° C. for 2 minutes to perform an acid-catalyzed reaction of the latent image portion of the resist. Promoted.

After the above heat treatment, the resist on which the latent image was formed was developed for 60 seconds using an aqueous solution containing 2.38% by weight of tetramethylammonium hydroxide as a developing solution. The residual film ratio after development is 100%, the contrast by the sensitivity curve is improved as compared with before addition of tetrabutylammonium paratoluenesulfonate, and the sensitivity is 1 μC / cm ² , compared with the addition of tetrabutylammonium instead of organic salt. The sensitivity was twice as high. Further, even after storage for one month, there was no decrease in film thickness and no decrease in sensitivity, and stability was improved.

(Example 2) In Example 1, the solvent 2-
It carried out according to the method of Example 1 except having used methyl ethyl ketone instead of heptanone. As in Example 1, the improvement in contrast and stability and the decrease in sensitivity were suppressed.

Example 3 The procedure of Example 1 was repeated, except that 5 parts by weight of N-hydroxynaphthalimide trifluoromethanesulfonic acid ester was used in place of the acid generator diphenylmethylsulfonium paratoluenesulfonate. went. As in Example 1, the improvement in contrast and stability and the decrease in sensitivity were suppressed.

Example 4 The procedure of Example 1 was repeated, except that tetrabutylammonium trifluoromethanesulfonate was used instead of tetrabutylammonium paratoluenesulfonate as the organic salt. As in Example 1, the improvement in contrast and stability and the decrease in sensitivity were suppressed.

(Embodiment 5) FIG. 1 shows an embodiment in which the present invention is applied to a process of processing an interlayer insulating film of a silicon semiconductor by using an electron beam lithography technique. An element isolation field insulating film 102 made of SiO ₂ is provided on a semiconductor substrate 101 made of p-type silicon single crystal. In an active region (not shown) surrounded by the field insulating film 102, semiconductor elements such as MOS transistors and bipolar transistors are provided. A first layer aluminum wiring 103 is formed on the field insulating film 102 by a pattern, and an interlayer insulating film 104 is provided on these aluminum wirings. This interlayer insulating film 1
04 is made of SiO ₂ .

On the interlayer insulating film 104, m, p-cresol novolak resin: 89 parts by weight, a polyhydroxy compound having a tetrahydropyranyloxy group (average molecular weight:
992, polydispersity: 1.02): 11 parts by weight, diphenylmethylsulfonium paratoluenesulfonate: 4 parts by weight as an acid precursor, and 0.16 parts by weight of tetrabutylammonium paratoluenesulfonate as an organic salt.
A solution having a solid content of 20% by weight was prepared by dissolving in heptanone. The solution was filtered through a 0.1 μm membrane filter to prepare a resist solution.

The obtained resist solution is dropped on a silicon wafer, and after spin coating, heat-treated at 120 ° C. for 2 minutes to form a resist solution.
A resist film 105 having a thickness of 7 μm was formed (see FIG. 1).
(a)). Next, a predetermined position is irradiated with an electron beam 106 to form a latent image on the resist film 105, and then heat-treated at 100 ° C. for 2 minutes to increase the solubility of the latent image portion of the resist in an aqueous alkaline solution. Accelerated (FIG. 1 (b)).

Thereafter, tetramethylammonium hydroxide
The latent image was developed using an aqueous solution containing (a concentration of 2.38%) as a developer to form a resist pattern 107 (FIG. 1).
(c)).

Next, the interlayer insulating film 104 is etched using the resist film 107 as a mask.
07, the first layer aluminum interconnection 1
The through hole 108 for establishing electrical continuity with the second layer aluminum wiring formed in the next step was formed with good dimensional controllability (FIG. 1D).

Comparative Example 1 A positive resist was prepared in the same manner as in Example 1 except that no organic salt was added. Immediately after the preparation of the resist, there was no decrease in the film immediately after the development, and the film was good.
Value) was bad. After storage for 1 month at room temperature after preparation, the film loss after development was 0.4 μm, which was considerably poor in stability.

Comparative Example 2 A positive resist was prepared in the same manner as in Example 1 except that tetrabutylammonium as a basic substance was used instead of tetrabutylammonium paratoluenesulfonate as an organic salt. Prepared. There was no film loss and the contrast was good,
The sensitivity was ² μC / cm ² .

(Comparative Example 3) The procedure of Example 1 was repeated, except that pyridinium paratoluenesulfonate, an acidic organic salt, was used in place of tetrabutylammonium paratoluenesulfonate, an organic salt. A resist was prepared. 100n film loss after development
m.

Comparative Example 4 A positive resist was prepared in the same manner as in Example 1 except that a phenol compound having an ethylvinyl ether group was used instead of the phenol compound having a tetrahydropyranyloxy group. did. The film loss after development was as large as 300 nm.

[0033]

According to the present invention, an alkaline aqueous solution having high sensitivity, high resolution, and high stability to ultraviolet rays, far ultraviolet rays, electron beams, X-rays, and other active actinic rays, using a safe solvent. As a result, a photosensitive composition capable of developing into a positive resist was obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a process in a fifth embodiment of the present invention.

[Explanation of symbols]

101: semiconductor substrate, 102: field insulating film, 10
3 ... aluminum wiring, 104 ... interlayer insulating film, 105 ...
Resist film, 106: electron beam, 107: resist pattern, 108: through hole.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Fumio Murai 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd. Central Research Laboratory (72) Inventor Yasunori Suzuki 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Hitachi, Ltd. Central Research Laboratory

Claims (5)

[Claims] 1. A chemically amplified resist composition comprising an alkali-soluble resin, a medium having a reactivity to increase solubility in an aqueous alkali solution by a reaction catalyzed by an acid, and an acid precursor which generates an acid upon irradiation. So, general formula 1
A resist composition comprising an organic salt such that the anion site represented by is an alkylsulfonic acid or an arylsulfonic acid. Embedded image (Wherein, R ₁ , R ₂ , R ₃ and R ₄ may be the same or different and are an alkyl group having 1 to 6 carbon atoms or a substituted alkyl group, and Y 1 is an alkylsulfonic acid, an arylsulfonic acid, Represents any of the acids) 2. The resist composition according to claim 1, wherein the reactive medium for increasing the solubility in the aqueous alkali solution has a tetrahydropyranyl group or a t-butyloxycarbonyl group. 3. A resist composition according to claim 1, wherein the organic salt has a reactivity to change the solubility in an aqueous alkali solution by a reaction using an acid as a catalyst.
A resist composition comprising 0.01 to 0.5 part by weight based on 00 parts by weight. 4. A step of forming a desired pattern latent image on the resist layer using radiation on a coating film of the resist composition according to claim 1, a step of accelerating a reaction using an acid as a catalyst, and an aqueous alkaline solution. A step of forming a pattern by development using a developer as a developer. 5. A semiconductor substrate having a tetrahydropyranyl group or a t-butyloxycarbonyl group having a reactivity to change solubility in an aqueous alkali solution by a reaction using an alkali-soluble resin or an acid as a catalyst. Forming a resist pattern with a resist composition containing an organic salt represented by the general formula 1 comprising a chemically amplified resist composition containing at least a medium, an acid precursor that generates an acid upon irradiation with radiation, and a solvent. Performing a process of etching the substrate based on the resist pattern, or a process of implanting ions.