JP3334662B2 - Chemically amplified negative resist material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a chemically amplified negative resist material, and more particularly to a chemically amplified negative resist material for far ultraviolet light having excellent etching resistance.

[0002]

2. Description of the Related Art Conventionally, a chemically amplified photoresist material has been known. This resist material contains a base resin, a photoacid generator, and a crosslinking agent, and the acid generated from the photoacid generator upon exposure acts as a catalyst to remove one tertiary butoxycarbonyl (tBOC) group. After the reaction has occurred, many resist reactions (chemical amplification reactions) can be successively caused.

As such a resist material, for example,
There is a chemically amplified negative resist material comprising a base resin of polyhydroxystyrene, a photoacid generator, and a crosslinker of hexamethoxymethylmelamine.

[0004] Further, with the recent demand for higher integration and higher speed in integrated circuits, the pattern rule is becoming finer. In response to this, g-line (wavelength 436 nm) or i-line (wavelength 365 nm) is required. Far ultraviolet lithography using far ultraviolet light having a shorter wavelength as an exposure light source has been performed. In this deep ultraviolet lithography, for example, a KrF excimer laser (wavelength: 248 nm) is used as an exposure light source.

Under these circumstances, a conventional chemically amplified negative resist material is subjected to far ultraviolet lithography using a KrF excimer laser beam, whereby the acid generated from the photoacid generator is used as a catalyst to form a resin. Is cross-linked by the cross-linking agent, and the exposed portion is no longer dissolved in the developing solution to form a resist pattern.

[0006]

However, in the case of a resist pattern formed by deep-ultraviolet lithography using a conventional chemically amplified negative resist material, the resist structure is entirely composed of an organic substance and the selectivity to an etching gas is not sufficient. Therefore, when the film is made thin, the residual film ratio of the resist at the time of etching is low, and it has been difficult to secure the function as an etching mask.

As described above, since the etching resistance is weak, it is necessary to increase the thickness of the resist film.
Although patterning was performed with a film thickness of μm, the depth of focus at a line and space (L & S) of 0.15 μm below the wavelength of the KrF excimer laser beam was insufficient at 0.40 μm.

That is, it is difficult to make the resist thinner from the viewpoint of etching resistance, and it is difficult to secure a sufficient depth of focus at a wavelength equal to or less than the wavelength of the KrF excimer laser beam. If the depth of focus conditions become severe and a sufficient depth of focus cannot be obtained, a shape defect will result. In addition, the aspect ratio was increased and the pattern collapsed easily.

An object of the present invention is to provide a chemically amplified negative resist material which can obtain sufficient etching resistance even if the resist is made thinner and can secure a sufficient depth of focus.

[0010]

In order to achieve the above object, a chemically amplified negative resist material according to the present invention comprises:
Polyhydroxystyrene base resin, photoacid generator, and
And a crosslinking agent , and further has the general formula Si (OR) _n R ′ _4-n
(Wherein, R and R ′ are an alkyl group or an aryl group having 1 to 8 carbon atoms which may be the same or different from each other, n represents an integer of 1 to 4, and when n is 2, 3 or 4, R represents All may be the same or different, and similarly, n is 1 or 2
Wherein all R's may be the same or different).

[0011] By having the above structure, the polyhydro
Base resin Kishisuchiren, photoacid generator, and a crosslinking agent
Thus, a negative resist comprising a chemically amplified negative resist material containing a silane monomer represented by the general formula Si (OR) _n R ′ _4-n can be formed. Thereby, even if the negative resist is thinned, sufficient etching resistance can be obtained, and a sufficient depth of focus can be ensured.

[0012]

Embodiments of the present invention will be described below.

[0013] A chemically amplified negative photoresist material according to an embodiment of the present invention comprises a base resin and a photoacid generator (PA).
G), a crosslinking agent, and a general formula Si (OR) _n R ′ _4-n (wherein R and R ′ may be the same or different and each may be an alkyl or aryl group having 1 to 8 carbon atoms; 1 to
Represents an integer of 4, and when n is 2, 3 or 4, all R may be the same or different, and when n is 1 or 2, all R's may be the same or different. Silane monomer (monomer).

Examples of such a silane monomer include an alkoxysilane represented by the general formula Si (OR) ₄ and a general formula Si (OR) _n R ′ _4-n [where n = 1, 2, 3 And the alkoxyalkylsilane represented by the formula:

The alkoxysilane represented by the general formula Si (OR) ₄ includes, for example, (1) tetramethoxysilane, (2) tetraethoxysilane,
(3) Dimethoxydiethoxysilane and the like.

[0016]

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The alkoxyalkylsilane represented by the general formula Si (OR) ₃ R 'includes, for example, (4) trimethoxymethylsilane, (5) trimethoxyethylsilane, and (6) dimethoxyethoxy represented by the following chemical structures. Ethylsilane, (7) trimethoxyphenylsilane, (8) triethoxyethylsilane, (9) triethoxymethylsilane, (10) methoxydiethoxymethylsilane, (1
1) Triethoxyphenylsilane and the like.

[0018]

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The alkoxyalkylsilane represented by the general formula Si (OR) ₂ R ′ ₂ includes, for example, (12) dimethoxydimethylsilane, (13) dimethoxymethylethylsilane, and (14) dimethoxy represented by the following chemical structures. Diethylsilane, (15) dimethoxydiphenylsilane, (1
6) diethoxydiethylsilane, (17) diethoxymethylethylsilane, (18) diethoxydimethylsilane, (19) methoxyethoxydiphenylsilane, (2)
0) methoxyethoxydimethylsilane, (21) methoxyethoxymethylethylsilane, (22) methoxyethoxydiethylsilane, (23) diethoxydiphenylsilane, (24) dimethoxymethylphenylsilane, (2)
5) Dimethoxyethylphenylsilane, (26) methoxyethoxymethylphenylsilane, (27) methoxyethoxyethylphenylsilane, (28) diethoxymethylphenylsilane, (29) diethoxyethylphenylsilane and the like.

[0020]

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[0021]

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[0022]

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[0023] The alkoxyalkyl silanes represented by the general formula Si (OR) R _'3, for example, represented by the chemical structure shown below, (30) methoxy trimethyl silane, (31) methoxy dimethylethyl silane, (32) methoxymethyl diethyl Silane, (33) methoxydimethylethylsilane, (34) ethoxytrimethylsilane, (35) ethoxydimethylethylsilane, (36) ethoxymethyldiethylsilane, (37) ethoxytriethylsilane,
(38) methoxydimethylphenylsilane, (39) methoxymethylethylphenylsilane, (40) methoxydiethylphenylsilane, (41) ethoxydimethylphenylsilane, (42) ethoxymethylethylphenylsilane, (43) ethoxydiethylphenylsilane,
(44) methoxymethyldiphenylsilane, (45) methoxyethyldiphenylsilane, (46) ethoxymethyldiphenylsilane, (47) ethoxyethyldiphenylsilane, (48) methoxytriphenylsilane, (4
9) Ethoxytriphenylsilane and the like.

[0024]

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[0025]

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[0026]

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The silane monomer containing an alkoxyl group contained in the chemically amplified negative photoresist material comprises one or more of these alkoxysilanes or alkoxyalkylsilanes.

As the photoacid generator, for example, (50) triphenylsulfonium trifluoromethanesulfonic acid, (51) triphenylsulfonium methanesulfonic acid, and (52) diphenyliodonium trifluoromethanesulfonic acid represented by the following chemical structures: , (53) diphenyliodonium methanesulfonic acid, (54) phthalimide trifluoromethanesulfonic acid, (55) phthalimide trimethanesulfonic acid, (56) naphthalimide trifluoromethanesulfonic acid, (57) naphthalimide methanesulfonic acid, etc. Can be used.

[0029]

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Similarly, as the photoacid generator, for example, (58) triphenylsulfonium toluenesulfonic acid, (59) triphenylsulfonium cyclohexylsulfonic acid, (60) diphenyliodonium toluenesulfonic acid represented by the following chemical structure: It is possible to use any of (61) diphenyliodonium cyclohexylsulfonic acid, (62) phthalimidotoluenesulfonic acid, (63) phthalimidocyclohexylsulfonic acid, (64) naphthalimidotoluenesulfonic acid, (65) naphthalimidocyclohexylsulfonic acid, and the like. it can.

[0031]

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[0032]

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As the crosslinking agent, for example, (66) hexamethoxymethylmelamine represented by the following chemical structure:
(67) tetrakis (methoxymethyl) glycoluril, (68) 1,3-bis (methoxymethyl) -4,5
-Bis (methoxy) ethylene urea, (69) 1,3-
Any one of (methoxymethyl) urea and the like can be used.

[0034]

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Next, polyhydroxystyrene (PHS) as a base resin (resist composition resin), a photoacid generator,
Using hexamethoxymethylmelamine as a cross-linking agent, a chemically amplified negative-type deep ultraviolet photoresist material containing, for example, 10% by weight of tetramethoxysilane to resin was prepared.

Using this chemically amplified negative-type deep-ultraviolet photoresist material, the initial thickness of the photoresist is set to 0.1.
5 μm, with a laser stepper under the following conditions:
0.15 μmL & S was formed on the organic antireflection film provided on the polysilicon substrate.

Substrate: Polysilicon substrate Exposure conditions: KrF excimer laser, numerical aperture (NA) of projection lens 0.60, numerical aperture (σ) of lens toward reticle 0.75 Development condition: 2.38% tetra Methylammonium hydroxide (TMAH) aqueous solution / 60 seconds Etching condition: Cl ₂ -based gas FIG. 1 is a process diagram showing a resist pattern forming process using a chemically amplified negative resist according to the embodiment of the present invention. . As shown in FIG. 1, first, the above-mentioned negative photoresist material is applied onto a polysilicon substrate 10 by a spin coating (rotational coating) method (see (a)). An organic antireflection film (not shown) is provided on the polysilicon substrate 10.

Next, at a temperature of about 80 ° C. for 90 seconds, a prebaking (Prebak: P) is performed by a heating means such as a hot plate.
B) A process is performed to form a negative photoresist film 11 having a thickness of about 0.15 to 0.35 μm (see (b)).

After the PB process, the negative type photoresist film 11 is selectively exposed through a photomask 12 using a KrF excimer laser beam by an exposure device (not shown) (see (c)). By this exposure, in the exposed area of the negative photoresist film 11, the acid (H
⁺ ) Occurs.

After the exposure, the negative photoresist film 11 is
Heat treatment at about 105 to 115 ° C. for 90 seconds ((d)
reference). Heat treatment after this exposure (Post-Expos)
At the time of ure bake (PEB), in the exposed region of the negative photoresist film 11, tetramethoxysilane causes a condensation polymerization reaction by an acid catalyzed reaction by an acid (H ⁺ ) generated from a photoacid generator.

By this condensation polymerization reaction, Si—O bonds are generated to cause cross-linking of the resin, and the cross-linking reaction causes the organic polymer to cross-link in the negative photoresist film 11,
A chain network of silica (SiO ₂ ) is formed. The chemical reaction formula is shown below.

[0042]

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The pattern shape changes due to the difference in the photoacid generator, and the change affects the depth of focus and the resolution. If the photoacid generator generates a large amount of acid, the diffusion length becomes short and the irregularities on the side walls become large. Conversely, if the diffusion length is too long, image sag occurs.

Thereafter, it is immersed for 60 seconds in a developing solution comprising a 2.38% aqueous solution of tetramethylammonium hydroxide (TMAH). As a result, the unexposed portions of the negative photoresist film 11 are selectively dissolved and removed, and the negative resist pattern 1 is formed on the polysilicon substrate 10.
3 is formed (see (e)).

The above-mentioned negative type photoresist film 11 is
Development by TMAH is possible by optimizing the amount of tetramethoxysilane added. Then, when the organic anti-reflection film and the polysilicon were etched with a Cl ₂ -based gas, the remaining film ratio of the photoresist film 11 was 50%, and the etching could be performed without any problem.

That is, the silica is not etched by Cl ₂ gas, and the negative photoresist film 11 is an organic-inorganic hybrid material containing silica in the internal structure. For example,
In the case of an organic antireflection film, polysilicon, or the like, the etching resistance is dramatically improved. Incidentally, the etching rate by this Cl ₂ gas was 0.50 in terms of i-line resist made of novolak resin.

Since the negative type photoresist film 11 can be made thinner, the transmittance is increased by making the film thinner. Therefore, the depth of focus at 0.15 μmL & S is 0.8 μm.
This is higher than the depth of focus of 0.40 μm of the conventional resist having a thickness of 0.50 μm.

Further, since the aspect ratio is lowered and stabilized by thinning, there is no pattern collapse at all, and the TMAH
As a result, a rectangular resist pattern having a smaller roughness than that of the silylation process could be obtained.
Further, there is no possibility that a residue, that is, a development residue is left out.

Similarly to the above negative photoresist film 11, a negative deep ultraviolet photoresist containing a silane monomer containing an alkoxyl group (alkoxysilane or alkoxyalkylsilane) in addition to a photoacid generator and a crosslinking agent. The following Table (1) shows an example in which each of the above materials is combined with each other for the alkoxysilane or alkoxyalkylsilane, the photoacid generator, and the crosslinking agent.

In Table (1), each crosslinker, each photoacid generator, each alkoxysilane or each combination of alkoxyalkylsilanes are shown together with their respective content ratios. ° C / sec), resist film thickness (μm), PEB temperature / time (° C / sec),
The resolving power (μm), the depth of focus at 0.15 μmL & S, and the etching rate of the i-line resist ratio are shown.

The content ratio by weight of the alkoxysilane or the alkoxyalkylsilane to the resin is approximately 0.1 to 50.
%, Preferably 1 to 20%, but the content is 10%
It seems to be optimized before and after.

For comparison with the examples shown in Table (1), Table (2) shows a conventional example containing neither alkoxysilane nor alkoxyalkylsilane. Table (2) is displayed in the same manner as Table (1), and the combinations of the conventional examples in Table (2) are the same as those in Table (1) except that the alkoxysilane or alkoxyalkylsilane is “none”. Corresponding to the combination of the examples, the same numbers are assigned.

[0053]

[Table 1]

[0054]

[Table 2]

As can be seen from Tables (1) and (2),
In the embodiment (see Table (1)), the conventional example (see Table (2))
In comparison with the above, the resist film thickness is reduced to approximately half, the depth of focus is improved, and the etching rate of the i-line resist ratio is reliably improved.

As an example of improving the etching rate, for example, a crosslinking agent is 10% hexamethoxymethyl melamine, a photoacid generator is 3% triphenylsulfonium trifluoromethanesulfonic acid, and in addition to these, 10% tetramethoxysilane or ethoxy. 9% methyldiphenylsilane
Is contained, the ratio is improved about 1.6 times from 1.6 to 0.5.

As described above, according to the present invention, in addition to a base resin, a photoacid generator and a crosslinking agent, a chemical amplification system containing tetramethoxysilane as a starting composition and containing a silane monomer containing an alkoxyl group. By using the negative resist material, a negative resist film can be formed on the polysilicon substrate.

[0058] The formed polysilicon substrate a negative resist film, will be silica (SiO ₂₎ is generated in the internal structure by passing through a heat treatment, excellent etching resistance, and, about 0.30μm A chemically amplified negative photoresist film for far ultraviolet light that can be thinned as follows.

[0059]

As described above, according to the present invention, a polyhydroxystyrene base resin, a photoacid generator, and a crosslinking agent are contained, and further, the general formula Si (OR)
_{Since a} negative resist composed of a chemically amplified negative resist material containing a silane monomer represented by nR ′ _4-n can be formed, even if the negative resist is thinned,
Sufficient etching resistance can be obtained, and a sufficient depth of focus can be secured.

[Brief description of the drawings]

FIG. 1 is a process diagram showing a resist pattern forming process using a chemically amplified negative resist according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Polysilicon substrate 11 Negative photoresist film 12 Photomask 13 Negative resist pattern

Continuation of the front page (56) References JP-A-4-366958 (JP, A) JP-A-6-59444 (JP, A) JP-A-6-27654 (JP, A) JP-A-7-152156 (JP, A) JP-A-5-204155 (JP, A) JP-A-4-217249 (JP, A) JP-A-7-43899 (JP, A) JP-A-5-204158 (JP, A) 8-76368 (JP, A) JP-A-9-230586 (JP, A) JP-A-8-325455 (JP, A) JP-A-10-7709 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03F 7/038 G03F 7/075

Claims (4)

(57) [Claims] 1. A polyhydroxystyrene base resin, a photoacid generator, and a crosslinking agent , further comprising a general formula Si (O
R) _n R ′ _4-n (wherein, R and R ′ may be the same or different and are each an alkyl group or an aryl group having 1 to 8 carbon atoms, n is an integer of 1 to 4, and n is 2 , 3 or 4, all R's may be the same or different, and similarly, when n is 1 or 2, all R's may be the same or different.) A chemically amplified negative resist material characterized by the following: 2. In the above general formula, R and R 'represent a methyl group,
The negative resist composition according to claim 1, wherein the negative resist composition is an ethyl group or a phenyl group. 3. The method according to claim 1, wherein the silane monomer is contained in an amount of 0.1 to 0.1 by weight.
The chemically amplified negative resist material according to claim 1, wherein the content of the negative resist composition is from about 50% to about 50%. 4. The method according to claim 1, further comprising the steps of:
Applying a chemically amplified negative resist composition according to Zureka, forming a negative photoresist layer, a step of generating an acid from the negative photoresist film to expose the photoacid generator, after exposure Heat-treating the negative-type photoresist film, a post-exposure bake step to cause crosslinking of the resin by an acid-catalyzed reaction, and a tetramethylammonium hydroxide aqueous solution.
And a step of further performing a developing process .