JPH0635195A - Resist composition - Google Patents

Abstract

PURPOSE:To obtain a resist compsn. having polyhydroxy styrene as the resin component having the optimum substitution rate of tertiary butyloxy carbonyloxy group. CONSTITUTION:The resist compsn. consists of 100 pts.wt. of polyhydroxy styrene as the resin component and 1-30 pts.wt. oxygen generating agent. In the resin component, 15-25% of hydroxyl group in the resin is replaced by tertiary butyloxy carbonyloxy groups expressed by formula. By using this resist compsn., a resist pattern of high sensitivity and high contrast is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resist composition and a pattern forming method using the resist composition, and more specifically, a chemically amplified resist composition used for forming a fine pattern of half micron or less in a semiconductor manufacturing process. The present invention relates to an object and a pattern forming method using the composition.

[0002]

2. Description of the Related Art In recent years, wiring has become finer and finer as semiconductor devices have become highly integrated. Latest 64Mbit
The minimum line width of the D-RAM is about 0.4 μm, and the wiring tends to become thinner in the future. Along with this, the exposure light source used for pattern formation is shifting to a KrF excimer laser or an electron beam suitable for fine processing, instead of the conventional g-line and i-line.

In order to deal with this, a new material is being researched which can be replaced with novolak-naphthoquinonediazide as a resist. Among them, a chemically amplified resist is particularly promising. The chemically amplified resist is a general term for resists in which the composition contains an acid generator that generates an acid upon exposure and the generated acid acts catalytically. This type of resist is highly sensitive because it catalyzes a small amount of acid generated by irradiation of ionizing radiation to cause many molecules to decompose or crosslink.

The chemically amplified resist is composed of (1) alkali-soluble resin + crosslinking agent + acid generator (2) alkali-soluble resin + dissolution inhibitor + acid generator (3) alkali-insoluble resin + Acid generator (4) Alkali-soluble resin + acid generator can be roughly divided into four types, but there are many types depending on the developing method and the type of ionizing radiation to be sensitive. Since it has many possibilities as a mechanism, it can be applied to next-generation lithography.

As the base resin of the above type (3), the hydroxy group of polyhydroxystyrene is substituted with a tertiary butyloxycarbonyloxy group, a 2-cyclohexen-1-yloxy group or a trimethylsilyloxy group to give a hydrophobic (alkaline) solution. Insoluble) resins are often used. Among them, the substitution with the tertiary butyloxycarbonyl group can be easily performed even at room temperature, the hydroxyl group is easily returned to the acid, and the change in polarity before and after the substitution is large, which is suitable for a resist.

The present invention belongs to the type (3).

[0007]

Conventionally, as described above, as the base resin of the type (3), resins obtained by substituting hydroxyl groups of polyhydroxystyrene with tertiary butyloxycarbonyloxy groups have been widely used. However, in this resin, the optimum value of what% of the hydroxyl groups should be substituted with tertiary butyloxycarbonyloxy groups has not been clarified. That is, if the substitution ratio is too large or too small, the difference in solubility between the exposed portion and the unexposed portion does not appear, the sensitivity is lowered, and the contrast is also lowered. Therefore, when a pattern is formed by using a conventional resin as a resist material, it is difficult to always obtain optimum sensitivity and contrast.

[0008]

The present invention has been made to solve the above problems, and the resist composition of the present invention contains about 15% to 25% of the hydroxyl groups contained in the following formula I:

[0009]

[Chemical 2]

100 parts by weight of a resin component consisting of polyhydroxystyrene substituted with tert-butyloxycarbonyloxy group and 1 to 30 parts by weight of an acid generator which generates an acid upon exposure. The present invention further relates to a method for forming a positive or negative resist pattern using the resist composition.

This method of forming a positive resist pattern is performed by applying the resist composition of the present invention onto a work to form a resist film, exposing the resist film to a predetermined light pattern, and then heating. To form a latent image corresponding to the pattern in the resist film, and then develop the exposed resist film with an alkaline aqueous solution or an alcohol organic solvent to form a positive resist pattern corresponding to the pattern on the workpiece. And forming. Further, the method for forming a negative resist pattern, the resist composition of the present invention is applied on a workpiece to form a resist film,
The resist film is exposed to a predetermined light pattern and subsequently heated to form a latent image corresponding to the pattern in the resist film, and then the exposed resist film is subjected to a ketone organic solvent or an ether organic solvent. Developing to form a negative resist pattern corresponding to the pattern on the workpiece.

The present invention will be further described below. The present inventors synthesized resins in which the hydroxyl groups of polyhydroxystyrene were substituted with tertiary butyloxycarbonyloxy groups at various ratios, and examined the sensitivity and contrast of the resist. FIG. 1 is a graph showing the relationship between the tertiary butyloxycarbonyloxy substitution rate and the dissolution rate. The aqueous solution used was a 0.2 N tetramethylammonium hydroxide aqueous solution, and the dissolution rate in this aqueous solution was measured. The polyhydroxystyrene used had a weight average molecular weight of 6,700 and a dispersity of 1.1, but the weight average molecular weight was 3,000.
It was found that the same behavior was exhibited from 0 to 30,000.

From the results shown in FIG. 1, it was found that the optimum value of the substitution rate of hydroxyl groups was 20%. That is, the dissolution rate which was almost unchanged at 5% was 1/10 at 10%.
To 20% and almost zero at 20%. Since this portion corresponds to the boundary between the soluble region and the insoluble region, the polarity is abruptly changed when an acid is generated by exposure and a reaction occurs and becomes soluble in an alkaline developer or an alcohol organic solvent such as isopropanol ( Since it is a positive type), high sensitivity and contrast can be obtained as a resist.

When the substitution rate is much higher than 20%, the decomposition of the tertiary butyloxycarbonyloxy group until the substitution rate reaches 20% does not change the dissolution rate. Therefore, the sensitivity is lowered. When the substitution ratio is much lower than 20%, the resist in the unexposed portion is also dissolved, so that the contrast is lowered or the photosensitivity is not exhibited.

Similarly, in a non-polar organic solvent such as a ketone-based solvent such as methyl isobutyl ketone or an ether-based solvent such as anisole, a phenomenon in which the dissolution rate drastically changes at 20% was observed ( However, in this case the negative type). From the above, it is clear that polyhydroxystyrene having a tertiary butyloxycarbonyloxy substitution rate of 20% is excellent as a resist resin.

The resist performance is not impaired unless the substitution rate is much higher than 20% or lower than 20%. Even if the actual replacement rate is in the range of 15 to 25%, it is practically usable.
The replacement ratio can be controlled relatively easily by adjusting the charging ratio during synthesis, and the replacement ratio and the charging ratio are almost the same. The resist composition of the present invention comprises 100 parts by weight of a resin component of polyhydroxystyrene having tertiary butyloxycarbonyloxy groups in which hydroxyl groups are substituted at a fixed ratio (about 15% to 25%) as described above, and an acid generator. 1 to 30 parts by weight.

The weight average molecular weight of the polyhydroxystyrene of the resin component 1 used in the present invention is 3,000 or more,
It is preferably 30,000 or less. Further, the acid generator used in the present invention is a diphenyliodonium salt,
Triphenylsulfonium salt, benzyl tosylate, nitrobenzyl tosylate, dinitrobenzyl tosylate, 2,4,6-tris (trichloromethyl) -s-triazine, tris (2,3-dibromopropyl) isocyanurate, and tetrabromo It is preferably selected from the group of bisphenol A and the like.

The mixing ratio of the acid generator is 1 to 30 parts by weight with respect to 100 parts by weight of the resin component. If the amount is less than 1 part, the effect is insufficient. If the amount is more than 30 parts by weight, the effect is insufficient and the compatibility with the resin component is poor. Furthermore, according to the resist pattern forming method of the present invention, a positive or negative resist pattern can be obtained depending on the type of the developing solution used.

As the alcohol solvent for obtaining the positive resist pattern, ethanol, butanol, isopropanol or the like is used, and isopropanol is preferable. As a ketone solvent for obtaining a negative resist pattern, for example, methyl ethyl ketone, diethyl ketone, dipropyl ketone, methyl isobutyl ketone, or the like is used, and methyl isobutyl ketone is preferable. Further, as an ether solvent for obtaining a negative resist pattern, dibutyl ether, diethyl ether, anisole, or the like is used, and anisole is preferable.

The heating after the exposure is preferably about 60.
It is in the range of to 150 ° C. Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to these Examples.

[0021]

EXAMPLES Synthesis Example 1 2 g of polyhydroxystyrene having a weight average molecular weight of 5.4 × 10 ³ and a dispersity of 2.0 (equivalent to 0.017 mol of monomer)
And potassium tert-butyloxy as catalyst
8 g (0.0034 mol) was dissolved in 80 ml of distilled dimethylformamide and stirred under a nitrogen stream for 5 minutes. 1.47 g (0.003 g) of ditertiary butyl oxycarbonate dissolved in 20 ml of dimethylformamide.
(4 mol) was added dropwise over 5 minutes, and then 2
Stir for hours. After completion of the reaction, throw it into water to reprecipitate, 1,4-
Lyophilized with dioxane.

It was confirmed by NMR and IR that the tertiary butyloxycarbonyloxy-substituted polyhydroxystyrene thus synthesized had a substitution rate of 20%. The substitution rate was measured from the intensity ratio of the peak (1.5 ppm) due to tertiary butyl in the tertiary butyloxycarbonyloxy group in the NMR measurement chart. In the IR measurement chart, t-B
Since the C═O bond of OC appears near 1755 cm ⁻¹ , t
-It can be seen that BOC is progressing. Example 1 1 g of a resin having a substitution rate of 20% synthesized in Synthesis Example 1 and 0.2 g of diphenyliodonium hexafluoroantimonate
g was dissolved in cyclohexanone and filtered through a 0.2 μm membrane filter to prepare a resist solution.

This is deposited on a silicon wafer to a film thickness of 0.7 μm.
Then, a sample for exposure was obtained by applying the coating solution as described above and baking on a hot plate at 100 ° C. for 1 minute. Immediately after the exposure, it was baked on a hot plate at 110 ° C. for 2 minutes, and then 0.
Immersion development was performed for 1 minute with a 2N alkaline developer. When the electron beam sensitivity was measured in this way, it was 6 μC / cm ²
I found out. It was also found that a substantially rectangular positive pattern with a line and space of 0.2 μm can be resolved.

When the same procedure was performed using methyl isobutyl ketone as the developing solution, it was found that a substantially rectangular negative pattern having 0.2 μm lines and spaces could be resolved. Example 2 The above exposed sample was irradiated with KrF excimer laser to examine the sensitivity and resolution. As a result, the sensitivity was about 80 mJ / cm ² , and the resolution was 0.3 μm line & space which is the minimum line width of the photomask. Example 3 A resist solution was prepared by using 0.2 g of nitrobenzyl tosylate in place of 0.2 g of diphenyliodonium hexafluoroantimonate in Example 1, and sensitivity and resolution were the same as in Examples 1 and 2 below. I investigated the sex.
As a result, the sensitivity is ^{8μC / cm 2, KrF 60mJ /} cm 2 in the excimer laser, the minimum resolution width was the same as in Examples 1 and 2 with the electron beam. Example 4 A resist solution was prepared by using 0.2 g of tris (2,3-dibromopropyl) isocyanurate in place of 0.2 g of diphenyliodonium hexafluoroantimonate in Example 1, and the same procedure as in Examples 1 and 2 was followed. The sensitivity and resolution were investigated. As a result, the sensitivity is 3 μC / c with electron beam.
m ² was 70 mJ / cm ² with a KrF excimer laser, and the minimum resolution width was the same as in Examples 1 and 2. Synthesis Example 2 “Tertiary butyloxy potassium 0.38 of Synthesis Example 1
Instead of g (0.0034 mol), 0.19 g (0.0017 mol) of potassium tert-butyloxy was used, and 1.47 g (0.07 mol) of di-tert-butyloxycarbonate.
The same synthesis was performed using 0.74 g (0.0017 mol) of ditertiary butyloxy carbonate instead of (034 mol). It was confirmed that the tertiary butyloxycarbonyloxy substitution rate of the hydroxyl group was 10%. Comparative Example 1 A resin having a substitution rate of 10% synthesized in Synthesis Example 2 was used in Examples 1 to 1.
The resist performance was evaluated in the same manner as in 4, but none of them showed photosensitivity. Synthesis Example 3 “Tertiary butyloxy potassium 0.38 of Synthesis Example 1
g (0.0034 mol) in place of 0.57 g (0.0051 mol) of potassium tert-butyloxycarbonate, 1.47 g of ditert-butyloxycarbonate (0.0
Instead of (034 mol), 2.21 g (0.0051 mol) of ditertiary butyloxycarbonate was used for the same synthesis. It was confirmed that the tertiary butyloxycarbonyloxy substitution rate of the hydroxyl group was 30%. Comparative Example 2 The resin having a substitution rate of 30% synthesized in Synthesis Example 3 was used in Examples 1 to
The resist performance was evaluated in the same manner as in No. 4, but in each case, the sensitivity was reduced by about 3 to 5 times. In addition, during pattern formation, the difference in dissolution rate between the exposed and unexposed areas was small, and film loss in the line area and omission of the space area were observed.

That is, the sensitivity of a resin having a substitution rate of 30% is
Physically it was as follows. 1) Diphenyliodonium hexfluoroantimony
When used with an electron beam; electron beam sensitivity 25 μC / cm² KrF excimer laser feeling
Degree 320mJ / cm ² 2) When nitrobenzyl tosylate is used; electron beam sensitivity 20 μC / cm² KrF excimer laser feeling
Degree 400mJ / cm ² 3) Tris (2,3-dibromopropyl) isocyanurate
When using a sheet; electron beam sensitivity 30 μC / cm² KrF excimer laser feeling
Degree 280mJ / cm ²

[0026]

As described above, in the resist composition of the present invention, about 15 to 25% of the hydroxyl groups of the polyhydroxystyrene of the resin component are replaced with tertiary butyloxycarbonyloxy groups. Therefore, it has an effect of obtaining a resist pattern having high sensitivity and high contrast. Further, both negative and positive resist patterns can be obtained depending on the type of developing solution used.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the tertiary butyloxycarbonyloxy substitution rate and the dissolution rate.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location G03F 7/26 7124-2H H01L 21/027

Claims (7)

[Claims] 1. About 15% to 25% of the contained hydroxyl groups,
The following formula I: A resist composition comprising 100 parts by weight of a resin component consisting of polyhydroxystyrene substituted with tert-butyloxycarbonyloxy group, and 1 to 30 parts by weight of an acid generator that generates an acid upon exposure. 2. The weight average molecular weight of the resin component is 3,000.
It is not less than 30,000 and not more than 1.
The resist composition described. 3. The acid generator is diphenyliodonium salt, triphenylsulfonium salt, benzyl tosylate, nitrobenzyl tosylate, dinitrobenzyl tosylate, 2,4,6-tris (trichloromethyl) -s.
-Triazine, tris (2,3-dibromopropyl) isocyanurate, and tetrabromobisphenol A
The resist composition according to claim 1, which is selected from the group of: 4. A resist composition according to claim 1 is applied onto a work to form a resist film, and the resist film is exposed to a predetermined light pattern and subsequently heated to correspond to the pattern. Forming a latent image in the resist film, and then developing the exposed resist film with an aqueous alkaline solution or an alcohol organic solvent to form a positive resist pattern corresponding to the pattern on the workpiece. And a method for forming a positive resist pattern. 5. The method for forming a resist pattern according to claim 4, wherein the alcoholic organic solvent is isopropanol. 6. A resist composition according to claim 1 is applied onto a work to form a resist film, and the resist film is exposed to a predetermined light pattern and subsequently heated to correspond to the pattern. Forming a latent image in the resist film, and then developing the exposed resist film with a ketone organic solvent or an ether organic solvent to form a negative resist pattern corresponding to the pattern on the workpiece. A method for forming a negative resist pattern, comprising: 7. The method for forming a resist pattern according to claim 6, wherein the ketone organic solvent is methyl butyl ketone and the ether organic solvent is anisole.