JP3444326B2 - Positive resist composition for far ultraviolet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deep UV positive resist composition containing a (meth) acrylic polymer, a photoacid generator and a dissolution inhibitor. For more details,
The present invention relates to a high-resolution positive resist composition for deep ultraviolet rays.

[0002]

2. Description of the Related Art In a photolithographic process for manufacturing a semiconductor integrated circuit, a so-called g-line (436 nm) or i-line (365 nm) is used up to a circuit design rule (resolution) of about 0.6 to 0.7 μm. As the exposure light,
A resin composition comprising a phenol novolac resin having an aromatic ring having good dry etching resistance and naphthoquinonediazide as a photosensitizer having a dissolution suppressing function is used as a positive resist.

By the way, in order to further improve the degree of integration of semiconductor integrated circuits, in recent years, it has been required to set the circuit design rule to 0.5 μm or less. Therefore, far-ultraviolet light having a shorter wavelength such as far-ultraviolet light of 248 nm from a KrF excimer laser or 193 nm far-ultraviolet light from an ArF excimer laser is used as exposure light for a conventional phenol novolac resin-naphthoquinone diazide-based positive resist. Attempted to apply.

However, in such a positive resist, the phenol novolac resin contained therein is not transparent in the deep ultraviolet region (Deep UV region), and in particular, 19
Since it has a considerable absorption at 3 nm, the surface layer portion of the exposed portion of the resist coating film is dissolved in a developing solution (tetramethylammonium hydroxide (TMAH) aqueous solution or the like), but the exposure light reaches the lower layer portion of the exposed portion. However, there was a problem in that it did not dissolve or did not dissolve completely because it did not reach enough. Therefore, it is practically impossible to improve the resolution by using deep ultraviolet rays.

Therefore, it is conceivable to use a methacrylic resin or an acrylic resin (hereinafter referred to as a (meth) acrylic resin) having a high transmittance for far ultraviolet rays of 193 nm instead of the phenol novolac resin. However, there is a problem that sufficient sensitivity cannot be obtained even if a (meth) acrylic resin is used instead of the phenol novolac resin. Therefore, the sensitivity is improved by adding a chemical amplification modification to the (meth) acrylic resin. For example, a carboxyl group of a (meth) acrylic resin into which an acid-eliminating protective group (eg, t-butyl ester group) is introduced (chemical amplification modification), and a photoacid generator that generates an acid by light irradiation. A chemically amplified positive resist composition is formed from the agent. In this case, when the resist coating film is irradiated with light, the photo-acid generator generates an acid, and the acid desorbs the protective group of the carboxyl group of the (meth) acrylic resin to generate a free carboxyl group. . As a result, the solubility of the resist coating film irradiated with light in an alkali developing solution is dramatically increased, and the sensitivity of the resist is improved. But like this (meta)
The chemically amplified positive resist composition containing an acrylic resin has a problem that its dry etching resistance is insufficient as compared with a positive resist composition containing a conventional phenol novolac resin.

Therefore, recently, in addition to a chemically amplified (meth) acrylic resin and a photoacid generator, a positive resist composition containing a cholesterol derivative excellent in dry etching resistance as a dissolution inhibitor is added. (J. Photopolymer Sci., Technol., 8 (4), 623 (199)
Five)).

[0007]

However, a positive resist composition comprising the above-mentioned chemical amplification type (meth) acrylic resin, a photo-acid generator and a cholesterol derivative is used as an exposure light for ArF excimer of 193 nm. When applying photolithography technology using laser light, the resolution (L (line) / S (space)) is about 0.25.
Although it was possible to improve to μm, it was very difficult to further improve the resolution.

The present invention is intended to solve the above-mentioned problems of the prior art and is a positive electrode for deep ultraviolet rays which is excellent in dry etching resistance and has a high resolving power such that L / S is less than 0.25 μm. An object is to provide a type resist composition.

[0009]

The present inventor uses a specific photobleaching compound as a dissolution inhibitor instead of a cholesterol derivative while maintaining the dry etching resistance of a positive resist composition. Also found that the resolving power can be improved, and completed the present invention.

That is, the present invention is a positive resist composition for deep ultraviolet rays containing a (meth) acrylic polymer, a photoacid generator and a dissolution inhibitor, wherein the dissolution inhibitor is selected from vitamins A or vitamins D. A far-ultraviolet positive resist composition comprising at least one photobleachable compound.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

In the deep UV positive resist composition of the present invention, at least one photobleaching compound selected from vitamins A or vitamins D is used as a dissolution inhibitor.

Here, the photobleaching compound selected from vitamins A or vitamins D means deep ultraviolet rays, especially 19
When it is irradiated with 3 nm ultraviolet light, it has a property of initially absorbing the ultraviolet light but gradually decreasing the degree of absorbing the ultraviolet light (decoloring property). Such decoloring property is
It is considered that the conjugate system in the molecules of vitamins A and vitamins D is caused by the reaction with light. Therefore, when a resist coating film made of a positive resist composition containing a photo-bleaching compound is exposed to deep ultraviolet rays, the light transmittance of the exposed area is longer than the light transmittance of the surrounding non-exposed area. Therefore, the contrast of the light transmittance between the exposed portion and the non-exposed portion can be increased, and the resolution of the positive resist can be improved.

Further, since vitamins A and vitamins D are alicyclic compounds, they can impart good dry etching resistance to the resist composition as well as a cholesterol derivative.

In the present invention, vitamins A which can be preferably used as a dissolution inhibitor are represented by the formulas (1) to (3)

[0016]

[Chemical 4] (In the formula (1), the aldehyde group may be acetalized with a lower monoalkanol (eg, methanol, ethanol, etc.) or a lower dialkanol (eg, ethylene glycol, etc.), and in the formula (2), R ¹ is a hydrogen atom or a lower atom. Alkyl (eg, methyl, ethyl, butyl,
t-butyl and the like), and in the formula (3), R ² is a hydrogen atom, a lower alkoxycarbonyl (eg, methoxycarbonyl, ethoxycarbonyl, butoxycarbonyl, t
-Butoxycarbonyl etc.) or lower alkanoyl (eg acetyl, propionyl, pivaloyl etc.). ) Can be mentioned. here,
R ¹ is preferably t-butyl, which is easily removed by an acid.
Similarly, R ² is preferably t-butoxycarbonyl or pivaloyl.

Further, as vitamin Ds, formulas (4) to
(7)

[0018]

[Chemical 5]

[0019]

[Chemical 6] (In the formulas (4) to (7), R ³ , R ⁴ , R ⁵ and R ⁶ are
Each independently a hydrogen atom, lower alkoxycarbonyl (eg, methoxycarbonyl, ethoxycarbonyl,
Butoxycarbonyl, t-butoxycarbonyl, etc.) or lower alkanoyl (acetyl, propionyl, pivaloyl, etc.). ) Can be mentioned. Here, R ^3, examples of R ^4, R ⁵ and R ^6, is easily eliminated t- butoxycarbonyl or pivaloyl is preferable acid.

In addition, it is preferable to use vitamin D as a dissolution inhibitor from the viewpoint that higher resolution can be realized between vitamin A and vitamin D as described above.

In the present invention, when the content of the photobleaching dissolution inhibitor in the solid content of the positive resist composition for ultraviolet rays is too small, the dissolution inhibition is insufficient and the film edge during development is large. If the amount is too large, residues are generated and the sensitivity is lowered to lower the development rate. Therefore, it is preferably 5 to 40% by weight, more preferably 10 to 30% by weight.

As the (meth) acrylic polymer used in the positive resist composition for ultraviolet rays of the present invention,
Methacrylic acid, acrylic acid, or those obtained by polymerizing esters thereof can be used. Above all,
It is preferable to use a copolymer composed of methyl methacrylate capable of improving the mechanical properties of the resist coating film and methacrylic acid capable of improving the alkali developability and the glass transition point. In this case, methyl methacrylate 20-70% by weight and methacrylic acid 30
It is preferred to use a copolymer consisting of -80% by weight.

Further, the (meth) acrylic polymer used in the present invention has a substituent capable of leaving by an acid in addition to methylmethacrylate and methacrylic acid, and therefore has an alkali developability of the exposed portion of the resist coating film. It is more preferred to use terpolymers obtained using tunable t-butyl methacrylate. In this case 5 to 20% by weight of methyl methacrylate, 15 to 50% by weight of t-butyl methacrylate and 3 of methacrylic acid.
Preference is given to using terpolymers which consist of 0 to 80% by weight.

As the (meth) acrylic polymer used in the present invention, adamantyl ester of methacrylic acid, alicyclic ester such as camphor ester or norbonyl ester is further used for the purpose of further improving the dry etching resistance of the resist. What used as a monomer component can be used preferably.

In the present invention, when the content of the (meth) acrylic polymer in the solid content of the positive resist composition for deep ultraviolet rays is too small, the film-forming property is lowered, and when it is too large, the resolution is lowered. It is preferably 60 to 95% by weight, more preferably 70 to 90% by weight.

If the molecular weight (number average) of the (meth) acrylic polymer used in the present invention is too small, the heat resistance of the resist composition will decrease, and if it is too large, the viscosity will increase and the coatability will be poor. Therefore, it is preferably 10,000 to 20
0000, more preferably 40,000 to 100,000.

In the present invention, as the photo-acid generator, far-ultraviolet rays, especially 193 obtained from ArF excimer laser are used.
It is possible to use various compounds capable of liberating an acid by light of nm, for example, onium salts such as phenyliodonium triflate, sulfonates such as o-nitrobenzyl sulfonate, trichloroacetophenone, etc. The halogen-based compounds and the like can be used. Specifically, bis (t-butylphenyl) iodonium triflate, tris (trichloromethyl) -S-triazine, diphenylsulfonium triflate and the like can be preferably used.

If the content of the photo-acid generator in the solid content of the deep UV positive resist composition is too small, the resolution performance will be lowered, and if it is too large, a residue will be generated. %, More preferably 5 to 10% by weight.

In the deep UV positive resist composition of the present invention, various additives may be added as necessary, for example, a fluorine-based surfactant having a striation-preventing effect (eg, Flowrad FC series activator). ) And the like can be added.

The deep UV positive resist composition of the present invention comprises at least a photo-decolorable compound selected from vitamin A or vitamin D as a (meth) acrylic polymer, a photo-acid generator and a dissolution inhibitor. It can be produced by uniformly mixing one kind by a conventional method.

The positive resist composition for far ultraviolet rays of the present invention described above is a KrF excimer laser (248 nm) or an ArF excimer laser (1) that emits deep ultraviolet rays.
It can be preferably used when manufacturing a semiconductor integrated circuit by utilizing a photolithography method using (93 nm). As a result, high resolution (for example, L / S of 0.2
A resist pattern of about μm) can be formed.

[0032]

The present invention will be described in detail below with reference to the following examples.

Examples 1-15 and Comparative Examples 1-2 80 parts by weight of a copolymer of methyl methacrylate and methacrylic acid having a molecular weight of about 65,000 (molar ratio 3: 1) and bis (t-butyl) as a photoacid generator. A deep-UV positive resist composition was prepared by dissolving 5 parts by weight of phenyl) iodonium triflate and 15 parts by weight of the dissolution inhibitor shown in Table 1 in 200 parts by weight of a solvent.

The composition thus obtained was coated on a silicon wafer to a dry thickness of 1 μm and dried to form a resist film, and then ArF was formed through a predetermined mask pattern.
Exposure was performed using an excimer laser stepper (NA = 0.5, manufactured by Nikon Corporation), and the light transmittance of the resist film at the initial stage of exposure was measured using Hitachi U3400 (using a quartz substrate). Further, the light transmittance of the resist film after irradiation with light of 100 mJ / cm ² was measured. The results are shown in Table 1.

After irradiating with light of 100 mJ / cm ² , it was developed with 0.07N tetramethylammonium hydroxide solution. Resolution at this time (L /
S) is shown in Table 1.

Further, with respect to the obtained resist pattern,
Dry etching (O ₂ = 8 sccm, CH ₃ F = 755
sccm, pressure = 5.3 Pa, RF power = 1150
W, Vdc = -500V, etcher / AME811 hexsort type (manufactured by Applied Materials), and phenol novolac type positive resist (THM
The respective etching rates were compared when the etching rate for RiP3300, manufactured by Tokyo Ohka Co., Ltd.) was set to 1.
The results are shown in Table 1.

[0037]

[Table 1] Light transmittance (%) Resolution (L / S) Dry etch resistant dissolution inhibitor Initial irradiation After irradiation (μm) (Etch rate) 3 Bitamin A acid 30 54 0.22 1.5 4 Betamine A acid t-butyl ester 35 52 0.21 1.5 5 Bitamin A ₁ 33 58 0.23 1.5 6 Bitamin A ₁ t-butyl carbonate 34 52 0.23 1.5 7 Bitamin A ₁ hyperbolic ester 30 53 0.22 1.5 8 Bitamin D ₂ 35 62 0.20 1.3 9 Bitamin D ₂ t-Butyl Carbonate 34 62 0.19 1.3 10 Bitamin D ₂ Phabolate 37 65 0.19 1.3 11 Bitamin D ₃ 39 60 0.20 1.3 12 Gitamin D ₃ t-Butyl Carbonate ester 35 63 0.18 1.3 13 human Bu glutamic D ₃ pivalate ester 37 62 0.19 1.3 14 human Bu glutamic D ₄ 40 64 0.22 1.3 15 Purobitami D ₂ 42 63 0.22 1.3 Comparative Example 1 Cholesterol 45 45 0.24 1.3 2 Koresuterorupibaru ester 48 48 0.25 1.3

From Table 1, since the positive resist compositions of Examples 1 to 15 use the decolorizable compound as a dissolution inhibitor, the light transmittance after irradiation with 100 mJ / cm ² is higher than that at the initial exposure. It can be seen that is greatly improved.

On the other hand, since the positive resist compositions of Comparative Examples 1 and 2 use a cholesterol derivative that does not exhibit decoloring property as a dissolution inhibitor, they are used as a dissolution inhibitor. It can be seen that there is no change in light transmittance.

Therefore, it can be seen that the positive resist compositions of Examples 1 to 15 have improved resolution as compared with the positive resist compositions of Comparative Examples 1 and 2. In particular, Examples 8 to 15 using a vitamin D derivative as a dissolution inhibitor.
It can be seen that the positive resist composition of No. 2 has a remarkable improvement in resolution. Moreover, it can be seen that the dry etching resistance has performance comparable to that of Comparative Examples 1 and 2.

The dry etching resistance of the positive resist compositions of Examples 1 to 7 was slightly lower than that of the compositions of Comparative Examples 1 and 2, but there was no problem in practical use.

[0042]

According to the positive resist composition for deep ultraviolet rays of the present invention, it is possible to obtain a high resolving power having an L / S of less than 0.25 μm and good dry etching resistance with no practical problems. Becomes

Claims (15)

(57) [Claims] 1. In a deep-UV positive resist composition containing a (meth) acrylic polymer, a photoacid generator and a dissolution inhibitor, the dissolution inhibitor is vitamin A or a conjugated system.
A far-ultraviolet positive resist composition, which is at least one photobleaching compound selected from vitamin Ds having 2. The vitamin Ds are represented by formulas (4) to (7) : [Chemical 2] (In Formulas (4) to (7), R ³ , R ⁴ , R ^5, and R ⁶
Are each independently a hydrogen atom or a lower alkoxycarbo.
It is nil or lower alkanoyl. ) Light extinction represented by
The far-ultraviolet ray according to claim 1, which is at least one of the organic compounds.
Positive resist composition for lines. 3. The vitamin D is represented by the formula (4) to the formula (6).
A photobleaching compound represented by
Item 3. A positive resist composition for deep ultraviolet rays according to Item 2. 4. The vitamin A has the formula (1) to (3): (In the formula (1), the aldehyde group may be acetalized with a lower monoalkanol or a lower dialkanol, in the formula (2), R ¹ is a hydrogen atom or a lower alkyl, and in the formula (3), R ² is hydrogen. Atom, lower alkoxycarbonyl or lower alkanoyl.)
The far-ultraviolet positive resist composition according to claim 1, which is at least one of photobleachable compounds represented by 5. The positive resist for deep ultraviolet light according to claim 2, wherein the dissolution inhibitor is at least one photobleaching compound selected from vitamin Ds represented by formulas (4) to (7). Composition. 6. In the formulas (4) to (7), R ³ , R ⁴ ,
R ⁵ and R ⁶ are each independently t- butoxycarbonyl or far ultraviolet positive-working resist composition of the serial <br/> mounting in any one of claims 2-5 pivaloyl. The content of 7. dissolution inhibitor is, far ultraviolet positive resist according to any one of claims 1 to 6, which is 5 to 40% by weight in solid content of the far ultraviolet positive resist composition for Composition. 8. (meth) acrylic polymer, far ultraviolet positive-working resist composition according to any one of claims 1 to 7, which is a copolymer of methyl methacrylate and methacrylic acid. 9. The (meth) acrylic polymer comprises 20 to 70% by weight of methyl methacrylate and 30 of methacrylic acid.
9. The positive resist composition for deep ultraviolet rays according to claim 8, which is a copolymer composed of about 80% by weight. 10. (meth) acrylic polymer, methyl methacrylate, far ultraviolet positive-working resist composition according to any one of claims 1 to 7, which is a terpolymer consisting of t- butyl methacrylate and methacrylic acid. 11. The terpolymer according to claim 10, wherein the (meth) acrylic polymer is a terpolymer composed of 5 to 20% by weight of methyl methacrylate, 15 to 50% by weight of t-butyl methacrylate and 30 to 80% by weight of methacrylic acid. Positive resist composition for ultraviolet rays. 12. The content of the (meth) acrylic polymer is 60 in the solid content of the positive resist composition for deep ultraviolet rays.
Far ultraviolet positive-working resist composition according to any one of claims 1 to 11, which is a 95% by weight. 13. photoacid generator, according to claim 1 to 12 is bis (t-butylphenyl) iodonium triflate
The positive resist composition for deep ultraviolet light as described in any one of 1. 14. The content of the photo acid generator, far ultraviolet positive-working according to any one of the far ultraviolet positive resist composition according to claim in solids 2 to 20 wt% 1-13 Resist composition. 15. A method of using a photolithographic method using a positive resist and a KrF excimer laser or ArF excimer laser for producing a semiconductor integrated circuit, according to any one of claims 1 to 14 as a positive resist 1. A method for producing a positive type resist composition for deep ultraviolet light.