JP3353825B2 - Chemically amplified positive resist and pattern forming method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a lithography process in the manufacture of semiconductor devices, and more particularly to a lithography process having a wavelength of 22 nm.
The present invention relates to a positive resist suitable for lithography using exposure light of far ultraviolet light of 0 nm or less and a pattern forming method.

[0002]

2. Description of the Related Art In the field of the manufacture of various electronic devices requiring fine processing on the order of half microns as represented by semiconductor devices, there is an increasing demand for higher density and higher integration of devices. Therefore, the demand for photolithography technology for forming fine patterns is becoming more and more severe.

In particular, use of photolithography using an ArF excimer laser (193 nm) has recently been considered for the manufacture of a DRAM having an integration of 1 Gbit or more, which requires a processing technique of 0.18 μm or less [Donald. C. Hoffer et al., Journal of Photopolymer Science and Technology
o Photopolymer Science and Technology), Volume 9 (3
No. 387-397 (1996)].

Therefore, development of a resist material corresponding to photolithography using ArF light is desired.
In the development of the resist for ArF exposure, it is necessary to improve the cost performance of the laser because the gas used as the material for laser oscillation has a short life and the laser device itself is expensive. For this reason, there is a high demand for high sensitivity in addition to high resolution corresponding to miniaturization of processing dimensions.

As a method for increasing the sensitivity of a resist, a chemically amplified resist using a photoacid generator as a photosensitive agent is well known. For example, as a typical example, KOKOKU 2-
Japanese Patent No. 27660 describes a resist comprising a combination of triphenylsulfonium hexafluoroarsenate and poly (p-tert-bromocarbonyloxy-α-methylstyrylene). Such chemically amplified resists are currently widely used for KrF excimer laser resists [for example, Hiroshito,
C. Grant Wilson, American Chemical Society Symposium Series 242, 11-2
3 (1984)]. Features of chemically amplified resist
Proton acid generated by light irradiation from a photoacid generator as a contained component causes an acid-catalyzed reaction with a resist resin or the like by heat treatment after exposure. In this way, the photoreaction efficiency (reaction per photon) is significantly higher than that of a conventional resist having less than 1. At present, most of the developed resists are chemically amplified.

[0006]

However, in the case of lithography using short-wavelength light of 220 nm or less typified by an ArF excimer laser, a resist for forming a fine pattern has new characteristics that cannot be satisfied by conventional materials. That is, high transparency to exposure light of 220 nm or less and dry etching resistance are required.

Conventional photoresist materials for i-ray (365 nm) and KrF excimer laser (248 nm) mainly include resins having aromatic rings in their structural units, such as novolak resins or poly (p-vinylphenol). It is used, and the etching resistance of the resin can be maintained by the dry etching resistance of the aromatic ring. However, the resin having an aromatic ring has extremely strong light absorbency for light having a wavelength of 220 nm or less. Therefore, most of the exposure light is absorbed by the resist surface, and the exposure light does not transmit to the substrate, so that a fine resist pattern cannot be formed. For this reason, conventional resins cannot be directly applied to photolithography using short-wavelength light of 220 nm or less. Therefore, a resist material which does not contain an aromatic ring, has etching resistance, and is transparent to a wavelength of 220 nm or less has been desired.

As a polymer compound having transparency to ArF excimer laser light (193 nm) and resistance to dry etching, a copolymer having an adamantyl methacrylate unit which is an alicyclic polymer [Takechi et al., Journal of・ Journal of Photopolymer Science andTec
hnology), 5 (3), 439-446 (199)
2 years), and 9 volumes (No. 3), 509-522 (19
1996)] and copolymers having isobornyl methacrylate units [R. D. RD Allen et al., Journal of Photopolymer Science and Techno
logy), 8 (4), 623-636 (1995)
9) (Vol. 3), pp. 475-488 (199)
6 years)]. However, the (meth) acrylate derivative having an alicyclic group used in the former resin does not have a polar group (for example, a carboxyl group or a hydroxyl group) having substrate adhesion. Therefore, a homopolymer of a monomer having an alicyclic group has strong hydrophobicity and poor adhesion to a substrate to be processed (for example, a silicon substrate), and it is difficult to form a uniform coating film with good reproducibility. Furthermore, a pattern cannot be formed by exposure because there is no adamantane-containing residue having dry etching resistance or a residue capable of exhibiting a difference in solubility before and after exposure in an isobonyl-containing residue unit. Therefore, the former resin is the first resin in the resist resin to be a copolymer with a comonomer capable of exhibiting a difference in solubility, such as t-butyl methacrylate or mevalonic lactone methacrylate, or a co-monomer having substrate adhesion such as methacrylic acid. Available as an ingredient. However, the comonomer content is required to be about 50 mol%, and the dry etching resistance of the comonomer unit is extremely low. Therefore, the dry etching resistance effect of the alicyclic group is significantly reduced, and the practical use as a dry etching resistant resin is poor.

For this reason, a new resist resin material having high light transparency to light of 220 nm or less, high etching resistance and improved substrate adhesion has been desired.

[0010]

Means for Solving the Problems The inventor of the present invention has made intensive studies to achieve the above object, and has completed the present invention.

That is, the present invention relates to a chemically amplified positive resist containing at least a polymer having a unit represented by the general formula (1) and a photoacid generator which generates an acid upon exposure.

[0012]

Embedded image (In the above formula, R ¹ is a hydrogen atom or a methyl group, G
Represents an alicyclic hydrocarbon group having a 1,2-diol structure. The present invention also relates to a pattern forming method comprising at least a step of applying the resist on a substrate to be processed, a step of performing exposure, a step of performing baking, and a step of performing development.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the general formula (1), R ¹ is a hydrogen atom or a methyl group. G is an alicyclic hydrocarbon group having a 1,2-diol structure, and specifically, as shown in Table 1, 2,3-dihydroxynorbornyl group, 2,3-dihydroxynorbornylmethyl Group, 2,
3-dihydroxy-5-methyl-5-norbornylmethyl group, 3,4-dihydroxytricyclo [5.2.1.
^0,6 ] decyl group, 3,4-dihydroxy-dimethyltricyclo [5.2.1.0 ^2.6 ] decyl group, 3,4-dihydroxy-tricyclo [5.2.1.0 ^2,6 ] decyl
An oxyethyl group , a 3,4-dihydroxy-dimethyltricyclo [5.2.1.0 ^2,6 ] decyloxyethyl group ,
3,4-dihydroxytetracyclo [4.4.0.1
^2,5 1. ^7,10 ] dodecylmethyl group, 3,4-dihydroxy-8-methyl-8-tetracyclo [4.4.0.1
^2,5 . [ ^17,10 ] dodecylmethyl group and the like, but are not limited thereto.

[0014]

[Table 1] The polymer having the unit represented by the general formula (1) specifically includes a polymer represented by the general formula (2).

[0015]

Embedded image In the general formula (2), R ¹ is a hydrogen atom or a methyl group, G is an alicyclic hydrocarbon group having a 1,2-diol structure, (specifically, an alicyclic hydrocarbon group shown in Table 1) R ² and R ⁴ are a hydrogen atom or a methyl group, R ³ is a group having 7 to 13 carbon atoms having a group decomposable by an acid or a group decomposed by an acid. Bridged cyclic hydrocarbon group (specific examples of the group decomposed by an acid include a t-butyl group, a tetrahydropyran-2-yl group, a tetrahydrofuran-2-yl group,
Methoxytetrahydropyran-4-yl group, 1-ethoxyethyl group, 1-butoxyethyl group, 1-propoxyethyl group, 3-oxocyclohexyl group, 2-methyl-2
Adamantyl group, 2-ethyl-2-adamantyl group,
8-methyl-8-tricyclo [5.2.1.0 ^2,6 ] decyl group or 1,2,7,7-tetramethyl-2-
Examples include a norbornyl group, a 2-acetoxymenthyl group, a 2-hydroxymenthyl group, a 1-methyl-1-cyclohexylethyl group, but are not limited thereto. In addition, having 7 to 7 carbon atoms having a group decomposed by an acid
Specific examples of the bridged cyclic hydrocarbon group of 13 include tricyclo [5.2.1.0 having an ester group as shown in Table 2.
^2,6 ] decylmethyl group, tricyclo [5.2.1.
0 ^2,6 ] decyl group, adamantyl group , norbornyl group,
Methylnorbornyl group, isobornyl group, tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodecyl group, methyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodecyl group, but not limited thereto (provided that R ^{6 in} Table 2 is a group which is decomposed by an acid, and specific examples thereof include a t-butyl group, Tetrahydropyran-2-yl group, tetrahydrofuran-2-yl group, 4-
Methoxytetrahydropyran-4-yl group, 1-ethoxyethyl group, 1-butoxyethyl group, 1-propoxyethyl group, 3-oxocyclohexyl group, 2-methyl-2
Adamantyl group, 2-ethyl-2-adamantyl group,
8-methyl-8-tricyclo [5.2.1.0 ^2,6 ] decyl group or 1,2,7,7-tetramethyl-2-
Examples include a norbornyl group, a 2-acetoxymenthyl group, a 2-hydroxymenthyl group, a 1-methyl-1-cyclohexylethyl group, but are not limited thereto. ) And R ⁵ are a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms or a group having a lactone structure, and specifically, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, Isobutyl group, t-butyl group, cyclohexyl group, dimethylcyclohexyl group, tricyclo [5.2.1.0 ^2,6 ] decyl group, adamantyl group,
Norbornyl group, isobornyl group, tetracyclo [4.
4.0.1 ^2,5 . 1 ^7,10 ] dodecyl group, γ-butyrolactone-α-yl group, 6-hydroxynorbornane-2-
Examples include, but are not limited to, a carboxylic-6-lactone-2-yl group. Also, x, y, and z are respectively x + y + z = 1, 0 <x <
It is an arbitrary number satisfying 1,0 <y <1,0 ≦ z <1.
The weight average molecular weight of the polymer is 2,000 to 200,000.
And preferably 3,000 to 100,000.

[0016]

[Table 2] In addition, the photoacid generator used in the present invention is preferably a photoacid generator that generates an acid by light irradiation of 400 nm or less, preferably in the range of 180 nm to 220 nm, and the polymer compound according to the present invention described above. Any photoacid generator may be used as long as the mixture with the above is sufficiently dissolved in an organic solvent and the solution can form a uniform coating film by a film forming method such as spin coating. Also, alone
Two or more kinds may be used as a mixture. Examples of photoacid generators that can be used include, for example, Journal of the Organic Chemistry.
mistry) 43, No. 15, pp. 3055-3058 (19
78). V. Crivello (JVCriv
ello) et al., a triphenylsulfonium salt derivative, and other onium salts (eg, compounds such as sulfonium salts, iodonium salts, phosphonium salts, diazonium salts, and ammonium salts), and 2,6-dinitrobenzyl esters [O. Nalamasu (O. Nalamasu)
Et al., SPIE Proceedings, 1262, 32 (1990)], 1,2,3-tri (methanesulfonyloxy) benzene [Takumi Ueno et al., Proceeding of PME '89, Kodansha, pp. 413-424. (1990)] and sulfosuccinimide disclosed in JP-A-5-134416.

The content of the photoacid generator is usually from 0.2 to 30 parts by weight, preferably from 1 to 15 parts by weight, based on 100 parts by weight of all the components including itself. When the content is 0.2 parts by weight or more, sufficient sensitivity is obtained, and pattern formation is facilitated. When the amount is 30 parts by weight or less, formation of a uniform coating film becomes easy, and residue (scum) hardly occurs after development.

The positive resist of the present invention is prepared by dissolving it in a solvent so that the concentration of all the constituents is 5 to 40% by weight at the time of use, followed by filtration with a filter. As a preferable solvent to be used, any solvent may be used as long as the component consisting of the resin and the photoacid generator is sufficiently dissolved, and the solution is an organic solvent capable of forming a uniform coating film by a method such as spin coating. . Moreover, you may use individually or in mixture of 2 or more types. Specifically, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, tert-butyl alcohol, methyl cellosolve acetate, ethyl cellosolve acetate, propylene glycol monoethyl ether acetate, methyl lactate, ethyl lactate, 2-methoxybutyl acetate, Acetic acid 2
-Ethoxyethyl, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, N-methyl-2-pyrrolidinone,
Cyclohexanone, cyclopentanone, cyclohexanol, methyl ethyl ketone , 1,4-dioxane, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, and the like. However, of course, it is not limited to these.

The "basic" constituent components of the positive resist of the present invention are the above-mentioned resin, photoacid generator and solvent, but if necessary, surfactants, dyes, stabilizers, Other components such as an improving agent and a dye may be added.

[0020]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the present invention.

Synthesis Example 1 A polymer having the following structure (in the general formula (2), G is 3,4
-Dihydroxytricyclo [5.2.1.0 ^2,6 ] decyl group, R ¹ and R ² are hydrogen atoms, and R ³ is t-butoxycarbonyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodecyl group, x = 0.65, y = 0.35, z = 0)

[0022]

Embedded image In a 100 ml eggplant-shaped flask equipped with a reflux tube, 3,4-
4 g of dihydroxy-tricyclodecyl acrylate and t
- butoxycarbonyl tetracyclododecyl acrylate 3g dissolved in dry tetrahydrofuran 38 ml, there AIBN189mg a (30mmol · 1 ^-1) was added, under argon, is stirred at 60 to 65 ° C.. After cooling for 2 hours, the reaction mixture was allowed to cool with ligroin / ether (1/1).
1) The mixture is poured into 400 ml, and the deposited precipitate is separated by filtration. Further, re-precipitation purification was performed once again to obtain 3.36 of the target substance.
g (yield 48%). The copolymerization ratio at this time was ¹
From the integration ratio of H-NMR, it was 65:35 (x = 0.
65, y = 0.35). GPC analysis revealed that the weight average molecular weight (Mw) was 15,700 (in terms of polystyrene) and the degree of dispersion (Mw / Mn) was 1.86.

Synthesis Example 2-6 A polymer having the structure shown in Table 3 in which G and R ^{1 to} R ⁵ in the general formula (2) were synthesized in the same manner as in Synthesis Example 1.

[0024]

[Table 3] Example 1 Evaluation of etching resistance of polymer 2 g of the resin obtained in Synthesis Example 1 was dissolved in 10 g of ethyl lactate,
Then, the mixture was filtered using a 0.2 μm Teflon filter. Next, spin coating was performed on a 3-inch silicon substrate and baked on a hot plate at 90 ° C. for 60 seconds to form a thin film having a thickness of 0.7 μm. The etching rate of the obtained film with respect to CF ₄ gas was measured using a DEM451 reactive ion etching (RIE) device manufactured by Nidec Anelva (etching condition: Power = 1)
00W, pressure = 5 Pa, gas flow rate = 30 sccm). Table 4 shows the results. Similarly, Synthesis Example 4 and Synthesis Example 6
The etching rate was also measured for the resin obtained in the above. As a comparative example, novolak resist (PFI-1 manufactured by Sumitomo Chemical Co., Ltd.)
5A), the results of a poly (p-vinylphenol) used as a base resin of a KrF resist, and a poly (methyl methacrylate) coating film that is a resin having no bridged cyclic hydrocarbon group in its molecular structure are also shown. The etching rate was standardized for the novolak resist.

[0025]

[Table 4] From the above results, the resin used in the present invention has a lower etching rate with respect to CF ₄ gas than poly (methyl methacrylate) having no bridged cyclic hydrocarbon group, and poly (p-vinyl) which is a base resin of KrF resist. Phenol)
It has an etching rate equivalent to that of, indicating that it has excellent dry etching resistance.

Example 2 Evaluation of Transparency of Polymer 2.5 g of the resin obtained in Synthesis Example 1 was dissolved in 10 g of ethyl lactate, and then filtered using a 0.2 μm Teflon filter. Next, spin-coat on a 3-inch quartz substrate,
Baking was performed on a hot plate at 90 ° C. for 60 seconds to form a thin film having a thickness of 1 μm. About this thin film,
The transmittance at 193.4 nm, which is the center wavelength of ArF excimer laser light, was measured using an ultraviolet-visible spectrophotometer. Similarly, the resins obtained in Synthesis Examples 4 and 6 were measured.

As a result, the transmittance of the polymer obtained in Synthesis Example 1 was 54% / μm, that of the polymer of Synthesis Example 4 was 57% / μm, and that of the polymer of Synthesis Example 6 was 60% / μm. From these results, it was confirmed that the polymer of the present invention exhibited transparency usable as a single-layer resist.

Example 3 Evaluation of resist patterning using polymer A resist having the following composition was prepared.

(A) Polymer (Synthesis Example 1): 2 g (b) Photoacid generator (triphenylsulfonium triflate (TPS)): 0.02 g (c) Propylene glycol monomethyl ether acetate: 11.5 g The above mixture Was filtered using a 0.2 μm Teflon filter to prepare a resist. The resist was spin-coated on a 4-inch silicon substrate, and baked on a hot plate at 120 ° C. for 1 minute to form a thin film having a thickness of 0.45 μm. Then, the formed wafer was allowed to stand still in a contact type exposure experimental machine sufficiently purged with nitrogen. A mask in which a pattern was drawn with chrome on a quartz plate was brought into close contact with the resist film, and ArF excimer laser light was irradiated through the mask. Immediately thereafter, the film was baked on a hot plate at 95 ° C. for 60 seconds, developed with a 2.38% TMAH aqueous solution at a liquid temperature of 23 ° C. for 60 seconds by an immersion method, and subsequently rinsed with pure water for 60 seconds. As a result, only the exposed portion of the resist film was dissolved and removed in the developing solution, and a positive pattern was obtained. Similarly, the resists using the polymers obtained in Synthesis Examples 4 and 6 were evaluated. Table 5 shows the results of sensitivity and resolution.

[0030]

[Table 5] From the above results, it was found that the positive resist of the present invention had excellent resolution characteristics. In addition, since there was no phenomenon such as pattern peeling, it was confirmed that the substrate had excellent adhesiveness.

[0031]

As is clear from the above description, the positive resist of the present invention has a dry etching resistance,
The positive resist of the present invention is excellent in transparency and further excellent in resolution and substrate adhesion, and can form a fine pattern required for manufacturing a semiconductor device.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-10-83076 (JP, A) JP-A-7-252324 (JP, A) JP-A-5-72738 (JP, A) JP-A-11- 292822 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03F ^7/ 00-7/42

Claims (6)

(57) [Claims] 1. A chemically amplified positive resist comprising at least a polymer having a unit represented by the general formula (1) and a photoacid generator which generates an acid upon exposure. Embedded image (In the above formula, R ¹ represents a hydrogen atom or a methyl group, and G represents an alicyclic hydrocarbon group having a 1,2-diol structure.) 2. G in the general formula (1) is 2,3-dihydroxy-norbornyl group, 2,3-dihydroxy-norbornylmethyl group, 2,3-dihydroxy-5.
-Methyl-5-norbornylmethyl group, 3,4-dihydroxy-tricyclo [5.2.1.0 ^2,6 ] decyl group,
3,4-dihydroxy-dimethyltricyclo [5.2.
1.0 ^2.6 ] decyl group, 3,4-dihydroxy-tricyclo [5.2.1.0 ^2,6 ] decyloxyethyl group ,
3,4-dihydroxy-dimethyltricyclo [5.2.
1.0 ^2,6 ] decyloxyethyl group , 3,4-dihydroxytetracyclo [4.4.0.1 ^2,5 1. ^7,10 ] dodecylmethyl group, 3,4-dihydroxy-8-methyl-8
-Tetracyclo [4.4.0.1 ^2,5 . The positive resist according to claim 1, which is at least one member selected from the group ^{consisting of} [ ^1,7,10 ] dodecylmethyl groups. 3. The polymer according to claim 1, wherein the polymer has the general formula (2).
The positive resist described in the above. Embedded image (In the above formula, R ¹ is a hydrogen atom or a methyl group, G is an alicyclic hydrocarbon group having a 1,2-diol structure,
R ² and R ^{4 each} represent a hydrogen atom or a methyl group; R ³ represents a group having 7 to 7 carbon atoms having an acid-decomposable or acid-decomposable group
13, a bridged cyclic hydrocarbon group, R ⁵ represents a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms, or a group having a lactone structure. X, y, and z are x + y + z = 1 and 0 <x, respectively.
<1, 0 <y <1, 0 ≦ z <1. The weight average molecular weight of the polymer is 2,000 to 2,000.
00) 4. G in the general formula (2) is 2,3-dihydroxy-norbornyl group, 2,3-dihydroxy-norbornylmethyl group, 2,3-dihydroxy-5
-Methyl-5-norbornylmethyl group, 3,4-dihydroxy-tricyclo [5.2.1.0 ^2,6 ] decyl group,
3,4-dihydroxy-dimethyltricyclo [5.2.
1.0 ^2,6 ] decyl group, 3,4-dihydroxy-tricyclo [5.2.1.0 ^2,6 ] decyloxyethyl group ,
3,4-dihydroxy-dimethyltricyclo [5.2.
1.0 ^2,6 ] decyloxyethyl group , 3,4-dihydroxytetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodecylmethyl group, 3,4-dihydroxy-8-methyl-8
-Tetracyclo [4.4.0.1 ^2,5 . ^4. The positive resist according to claim 3, which is at least one member selected from the group ^{consisting of} [ ^1,7,10 ] dodecylmethyl groups. 5. A positive resist according to claim 1, wherein
Of coating on a substrate to be processed, 180 to 220 nm
Exposing with light of a wavelength of, baking, and
Characterized by containing at least a step of developing.
Pattern formation method. 6. The exposure light is ArF excimer laser light.
The pattern forming method according to claim 5.