JP2003140359A - Method for forming pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the etching resistance of a resist pattern. SOLUTION: A resist film made of a chemically amplifying resist material containing a phenol polymer is subjected to pattern exposure, developing and rinsing to form a resist pattern 18A consisting of the non-exposed part of the resist film. Then, the resist pattern 18A is held in a supercritical fluid 16 to desorb a protective group from the phenol polymer constituting the resist pattern 18A. Thus, a resist pattern 18B having improved etching durability is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method for forming a resist film by pattern exposing a resist film made of a chemically amplified resist material.

[0002]

2. Description of the Related Art In the process of a semiconductor integrated circuit device, the size (pattern width) of a resist pattern formed by a lithographic technique is further miniaturized as the semiconductor integrated circuit is highly integrated.

Therefore, there has been proposed a method of forming a resist pattern using a chemical amplification material having a phenyl polymer as the resist material.

The conventional pattern forming method will be described below.
This will be described with reference to FIGS.

First, a chemically amplified resist material having the following composition is prepared.

[0006]   Poly (ethoxyethyloxystyrene-hydroxystyrene) (however, Ciethyloxystyrene: hydroxystyrene = 35mol%: 65mol%) Limmer) ………………………………………………………………………… 1.0g   Triphenylsulfonium tosylate (acid generator) ……………… 0.03g   Propylene glycol monomethyl ether acetate (solvent) ………… 6.0g

Next, as shown in FIG. 6 (a), the above chemically amplified resist material is applied onto the substrate 1 to form 0.2.
After forming the resist film 2 having a thickness of μm, as shown in FIG.
As shown in (b), the numerical aperture for the resist film 2 is:
EUV (Extreme Ultraviolet) with NA of 0.15
The extreme ultraviolet rays 3 emitted from the exposure device are irradiated through a reflection type mask (not shown) having a desired pattern to perform pattern exposure.

Next, as shown in FIG. 6C, the substrate 1 is heated to 105 ° C. by a hot plate (not shown).
The resist film 2 is heated at 90 ° C for 90 seconds.
Then, post exposure bake (PEB) is performed. By doing so, the exposed portion 2a of the resist film 2 is changed to be soluble in an alkaline developing solution because acid is generated from the acid generator, while the unexposed portion 2b of the resist film 2 is changed from the acid generator to acid. Since it does not occur, it remains sparingly soluble in an alkaline developing solution.

Next, with respect to the resist film 2, 2.38 w
When developed with an alkaline developer containing t% tetramethylammonium hydroxide, FIG.
As shown in (d), a resist pattern 4 composed of the unexposed portion 2b of the resist film 2 and having a pattern width of 0.08 μm is obtained.

[0010]

By the way, as the semiconductor integrated circuit is highly integrated, the semiconductor element is further miniaturized, and accordingly, the thickness and width of the resist pattern are further miniaturized. Is required.

However, a resist pattern formed by a conventional pattern forming method and having a reduced thickness and width has a problem that the etching resistance is not sufficient.

In view of the above, it is an object of the present invention to improve the etching resistance of a resist pattern.

[0013]

In order to achieve the above object, the pattern forming method according to the present invention is such that when a protecting group is eliminated by the action of an acid to become an alkali-soluble phenyl polymer and light is irradiated. A step of forming a resist film made of a chemically amplified resist material having an acid generator that generates an acid; a step of selectively irradiating the resist film with exposure light to perform pattern exposure; and a pattern-exposed resist film To develop a resist pattern consisting of an unexposed portion of the resist film, and by holding the resist pattern in a supercritical fluid, the protective groups contained in the phenyl polymer forming the resist pattern are eliminated. And the process.

According to the pattern forming method of the present invention,
Since the resist pattern is held in the supercritical fluid, the protective group contained in the phenyl polymer forming the resist pattern is efficiently eliminated. This is considered to be because when the resist pattern is held in the supercritical fluid, the protective group having a smaller molecular weight than the polymer dissolves in the supercritical fluid. That is, since there is a large difference in the molecular weight between the phenol polymer having a benzene ring and having a large molecular weight and the protecting group bonded to the phenyl polymer and having a small molecular weight, the protecting group can be efficiently used in the supercritical fluid. It is thought to dissolve and desorb. In addition, the supercritical fluid in the present invention means a critical temperature (Tc) or higher and a critical pressure (Pc).
A supercritical fluid in a supercritical state in the above state and a subcritical state (Tc) or higher and lower than the critical pressure (Pc), or a subcritical state (lower than the critical temperature (Tc) and higher than the critical pressure (Pc). Means both supercritical fluids in the critical state.

Further, the resist pattern containing phenyl polymer as a main component from which the protective group has been removed has improved etching resistance. The reason will be described below.

Usually, the protective group bonded to the base polymer contains oxygen atoms and hydrogen atoms, and these oxygen atoms and hydrogen atoms reduce etching resistance.
This is because the polymer etching rate is N _T / (N _C −
N _O ) (where N _T is the total number of atoms in the polymer unit, N _C is the total number of carbon atoms in the polymer unit,
N _O is the total number of oxygen atoms in the polymer unit. ) Empirical formula (T. Ohfuji, et.al., Proc. SPI
E, 3333, 595 (1998)). Therefore,
Removal of the protective group from the phenyl polymer improves the etching resistance.

Further, since the phenol polymer has a benzene ring, it is more excellent in etching resistance than other polymers.

In the pattern forming method according to the present invention,
The step of removing the protective group may include the step of releasing the protective group by holding the resist pattern in a supercritical fluid that is in a supercritical state by being kept at a critical temperature or higher and a critical pressure or higher. preferable.

By doing so, it is possible to surely improve the etching resistance of the resist pattern.

In the pattern forming method according to the present invention,
The supercritical fluid is preferably a carbon dioxide supercritical fluid.

By doing so, the supercritical fluid can be easily and surely obtained.

In the pattern forming method according to the present invention,
The supercritical fluid is preferably flowing.

In this case, the protective group which is replaced with the supercritical fluid and is dissolved in the supercritical fluid is discharged to the outside together with the flowing supercritical fluid, so that it is efficiently desorbed by the supercritical fluid. Let go.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A pattern forming method according to the first embodiment will be described below with reference to FIG.
2 (a) to 2 (c) and FIGS. 2 (a) to 2 (c).

First, a chemically amplified resist material having the following composition is prepared.

[0026]   Poly (ethoxyethyloxystyrene-hydroxystyrene) (however, Ciethyloxystyrene: hydroxystyrene = 35mol%: 65mol%) Limmer) ………………………………………………………………………… 1.0g   Triphenylsulfonium tosylate (acid generator) ……………… 0.03g   Propylene glycol monomethyl ether acetate (solvent) ………… 6.0g

Next, as shown in FIG. 1A, the substrate 10
The chemically amplified resist material described above is applied to
After forming the resist film 11 having a thickness of 2 μm, as shown in FIG.
As shown in (b), the extreme ultraviolet rays 13 emitted from the EUV exposure apparatus having a numerical aperture NA of 0.15 are applied to the resist film 11 with a reflective mask (not shown) having a desired pattern. Exposure) to perform pattern exposure.

Next, as shown in FIG. 1C, the substrate 10
105 with a hot plate (not shown)
Post-exposure heating (PEB) is performed on the resist film 11 by heating at a temperature of 90 ° C. for 90 seconds. By doing so, the exposed portion 11a of the resist film 11 changes to be soluble in an alkaline developing solution because acid is generated from the acid generator, while the unexposed portion 11b of the resist film 11 becomes
Since no acid is generated from the acid generator, it remains sparingly soluble in alkaline developers.

Next, with respect to the resist film 11, 2.38.
After developing for 60 seconds with an alkaline developing solution composed of wt% tetramethylammonium hydroxide, rinsing with pure water is performed, and as shown in FIG. 2A, the unexposed portion 11b of the resist film 11 is removed. Becomes
Resist pattern 1 having a pattern width of 0.08 μm
8A is obtained.

Next, as shown in FIG. 2B, the substrate 10
After the resist pattern 18A and the resist pattern 18A are transferred into the chamber 14, carbon dioxide (C
The supercritical fluid 16 is supplied from a cylinder 15 that stores a supercritical fluid of O ₂ (which is in a supercritical state by being kept at a temperature of 40 ° C. and an atmospheric pressure of 80 atm. The critical fluid 16 is discharged to the outside by the discharge pump 17. As a result, the supercritical fluid 16 in the chamber 14 continues to flow and has a temperature of 40 ° C. and a temperature of 8 ° C.
It is in a supercritical state by being maintained at 0 atm. The critical temperature of carbon dioxide is 31.0 ° C. and the critical pressure of carbon dioxide is 72.9 atm.

In this way, inside the chamber 14, the protective group (ethoxyethyl group) of the phenol polymer forming the resist pattern 18A has a benzene ring and has a much higher molecular weight than the phenol polymer having a large molecular weight. Since it is small, it dissolves and desorbs efficiently in the supercritical fluid.

Next, as shown in FIG. 2C, the substrate 10
Is taken out of the chamber 14, the protective group is removed to obtain a resist pattern 18B having improved etching resistance.

Resist pattern 1 after removal of the protective group
The etching resistance of 8B is about 1.5 compared to the etching resistance of the resist pattern 18A before the protective group is eliminated.
Doubled.

In the first embodiment, the protective group is eliminated in the supercritical fluid of carbon dioxide in the supercritical state, but instead of this, the supercritical fluid of carbon dioxide in the subcritical state is used. The protecting group may be removed therein.
Hereinafter, this method will be described with reference to FIG.

First, a temperature lower than the supercritical temperature (Tc), eg, 28 ° C., and a pressure higher than the supercritical pressure (Pc), eg, 8
By keeping at 0 atm, the resist pattern 18A is kept for 40 seconds in the supercritical fluid of carbon dioxide in the subcritical state, and the protective group of the phenol polymer is kept in the supercritical fluid of carbon dioxide in the subcritical state. Dissolve. In this case, since the protective group is in a subcritical state, it is efficiently dissolved and desorbed in a high density supercritical fluid.

Next, the carbon dioxide supercritical fluid in the subcritical state is heated to a temperature higher than the supercritical temperature (Tc), for example 40 ° C., while being kept at a pressure higher than the supercritical pressure (Pc). After changing the supercritical fluid in the subcritical state to the supercritical fluid in the supercritical state, the pressure is returned from the supercritical pressure (Pc) or higher to the normal pressure while keeping the temperature at the supercritical temperature (Tc) or higher. The supercritical fluid in the supercritical state is changed to the supercritical fluid in the subcritical state, and then the temperature is returned from the supercritical temperature (Tc) to room temperature, and the supercritical fluid in the subcritical state is changed to a normal fluid.

(Second Embodiment) Hereinafter, a pattern forming method according to a second embodiment will be described with reference to FIGS.
Also, description will be given with reference to FIGS.

First, a chemically amplified resist material having the following composition is prepared.

[0039]   Poly (t-butyloxystyrene-hydroxystyrene) (however, t-butyl Oxystyrene: Hydroxystyrene = 40mol%: 60mol%) (phenolic polymer ) …………………………………………………………………………………… 1.2g   Triphenylsulfonium triflate (acid generator) ……………… 0.03g   Propylene glycol monomethyl ether acetate (solvent) ………… 6.0g

Next, as shown in FIG. 3A, the substrate 20
The chemically amplified resist material described above is applied to
After forming the resist film 21 having a thickness of 2 μm, as shown in FIG.
As shown in (b), a resist mask 21 is provided with a reflection type mask (not shown) having extreme ultraviolet rays 23 emitted from an EUV exposure apparatus having a numerical aperture NA of 0.15. Exposure) to perform pattern exposure.

Next, as shown in FIG. 3C, the substrate 20
120 by hot plate (not shown)
The resist film 21 is subjected to post-exposure heating (PEB) by heating at a temperature of ° C for 90 seconds. By doing so, the exposed portion 21a of the resist film 21 changes to be soluble in an alkaline developing solution because acid is generated from the acid generator, while the unexposed portion 21b of the resist film 21 becomes
Since no acid is generated from the acid generator, it remains sparingly soluble in alkaline developers.

Next, with respect to the resist film 21, 2.38.
After developing for 60 seconds with an alkaline developing solution composed of wt% tetramethylammonium hydroxide, rinsing with pure water is performed. As a result, as shown in FIG. Becomes
Resist pattern 2 having a pattern width of 0.08 μm
8A is obtained.

Next, as shown in FIG. 4B, the substrate 20
And, the resist pattern 28A is kept inside the chamber 24 in a supercritical fluid of carbon dioxide (CO ₂ ) (subcritical state by being kept at a temperature of 20 ° C. and 80 atm) for 30 minutes.

In this way, inside the chamber 24, the protective group (t-butyl group) of the phenolic polymer forming the resist pattern 28A has a benzene ring and has a molecular weight larger than that of the phenolic polymer having a large molecular weight. Since it is extremely small, it is efficiently dissolved and desorbed in the supercritical fluid 26.

By the way, the supercritical fluid has a higher density at low temperature under the same pressure. Therefore, as in the second embodiment, when the resist pattern 28A is held in the supercritical fluid of carbon dioxide, which is in a subcritical state by being maintained at a temperature of 20 ° C. and 80 atm, the protective group is in a subcritical state. The carbon dioxide is efficiently dissolved and desorbed in the supercritical fluid 26.

Next, as shown in FIG. 4C, the substrate 20
Is taken out of the chamber 24, the protective group is removed, so that a resist pattern 28B having improved etching resistance is obtained.

Resist pattern 2 after removal of the protective group
The etching resistance of 8B is about 1.3 compared with the etching resistance of the resist pattern 28A before the protective group is removed.
Doubled.

As the phenol polymer, poly (ethoxyethyloxystyrene-hydroxystyrene) was used in the first embodiment, and poly (t-butyloxystyrene-hydroxystyrene) was used in the second embodiment. Instead, poly (ethoxyethyloxystyrene-hydroxystyrene) (however, ethoxyethyloxystyrene: hydroxystyrene = 35 mol%: 65mo
l%), poly (methoxymethyloxystyrene-hydroxystyrene) (however, methoxymethyloxystyrene:
Hydroxystyrene = 40 mol%: 60 mol%), poly (tetrahydropyranyloxystyrene-hydroxystyrene)
(However, tetrahydropyranyloxystyrene: hydroxystyrene = 35 mol%: 65 mol%), poly (phenoxyethyloxystyrene-hydroxystyrene) (however, phenoxyethyloxystyrene: hydroxystyrene =
32 mol%: 68 mol%), poly (t-butyloxystyrene)
Hydroxystyrene) (however, t-butyloxystyrene: hydroxystyrene = 30 mol%: 70 mol%), poly (t
-Butyloxycarbonyloxystyrene-hydroxystyrene) (however, t-butyloxycarbonyloxystyrene: hydroxystyrene = 30 mol%: 70 mol%) or poly (t-butyloxycarbonylmethyloxystyrene-hydroxystyrene) (however, t-Butyloxycarbonylmethyloxystyrene: hydroxystyrene = 28 mol%: 72 mol%) or the like may be used.

As the acid generator, triphenylsulfonium triflate was used in the first and second embodiments. Instead of this, 1,4-diphenyldiazodisulphone and triphenyls were used. Ruphonium tosylate, camphoriminotosylate, naphthyliminotosylate, camphoriminotrifluoromethanesulfonic acid, naphthyliminotrifluoromethanesulfonic acid, triphenylsulfonium trifluoromethanesulfonic acid, triphenylsulfonium nonafluorobutanesulfonic acid, diphenyliodonium Trifluoromethanesulfonic acid, diphenyliodonium nonafluorobutanesulfonic acid, di (4-t-butylphenyl) iodonium trifluoromethanesulfonic acid,
Di (4-t-butylphenyl) iodonium nonafluorobutane sulfonic acid or the like may be used.

In the first and second embodiments, carbon dioxide is used alone as the supercritical fluid.
Instead of this, a small amount of an organic solvent such as alcohol, hydrocarbon, ether or carboxylic acid may be added to carbon dioxide as an entrainer. In this way, elimination of the protecting group is promoted.

In the first and second embodiments,
Is a supercritical fluid of carbon dioxide (critical temperature: 31.0 ° C.,
(Critical pressure: 72.9 atm) was used, but instead of this,
Water (H ₂O 2) supercritical fluid (critical temperature: 374.2 ° C.,
Critical pressure: 218.3 atmospheres) or ammonia (N
H₃) Supercritical fluid (critical temperature: 132.3 ° C, critical pressure
Force: 111.3 atm) may be used. However, diacid
Carbon dioxide has lower critical temperature and pressure than other fluids.
Therefore, it is easy to bring them into a supercritical state.

[0052]

According to the pattern forming method of the present invention, since the resist pattern is held in the supercritical fluid,
The protective group contained in the phenyl polymer forming the resist pattern is efficiently eliminated, and the resist pattern made of the phenyl polymer with the protective group eliminated is improved in etching resistance.

[Brief description of drawings]

1A to 1C are cross-sectional views showing respective steps of a pattern forming method according to a first embodiment.

2A and 2B are cross-sectional views showing respective steps of the pattern forming method according to the first embodiment.

3A to 3C are cross-sectional views showing respective steps of the pattern forming method according to the second embodiment.

4A and 4B are cross-sectional views showing respective steps of the pattern forming method according to the second embodiment.

FIG. 5 is a diagram illustrating a state of a supercritical fluid.

6A to 6D are cross-sectional views showing respective steps of a conventional pattern forming method.

[Explanation of symbols]

10 substrates 11 Resist film 11a exposure unit 11b Unexposed part 13 extreme ultraviolet 14 chambers 15 cylinders 16 Supercritical fluid 17 Discharge pump 18A Resist pattern before removal of protecting group 18B Resist pattern after elimination of protective groups 20 substrates 21 Resist film 21a exposure unit 21b Unexposed part 23 Extreme UV 24 chambers 26 Supercritical fluid 28A Resist pattern before removal of protective group 28B Resist pattern after removal of protective group

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masaru Sasako             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 2H025 AA09 AB16 AC04 AC08 AD03                       BE00 BE10 CB17 CB41 FA17                 2H096 AA25 BA11 GA08 GA20 HA30                       LA30                 5F046 AA28 LA18

Claims (4)

[Claims] 1. A resist film made of a chemically amplified resist material having a phenyl polymer which is alkali-soluble by removing a protective group by the action of an acid and an acid generator which generates an acid when irradiated with light is formed. And a step of performing pattern exposure by selectively irradiating the resist film with exposure light, and developing the pattern-exposed resist film to form a resist pattern composed of an unexposed portion of the resist film. A method for forming a pattern, comprising: a step; and a step of removing the protective group contained in the phenyl polymer forming the resist pattern by holding the resist pattern in a supercritical fluid. . 2. The step of removing the protective group is carried out by holding the resist pattern in the supercritical fluid in a supercritical state by being kept at a critical temperature or higher and a critical pressure or higher. The pattern forming method according to claim 1, further comprising a step of desorbing. 3. The pattern forming method according to claim 1, wherein the supercritical fluid is a carbon dioxide supercritical fluid. 4. The pattern forming method according to claim 1, wherein the supercritical fluid is flowing.