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EP-4492143-B1 - ONIUM SALT, CHEMICALLY AMPLIFIED POSITIVE RESIST COMPOSITION, AND RESIST PATTERN FORMING PROCESS

EP4492143B1EP 4492143 B1EP4492143 B1EP 4492143B1EP-4492143-B1

Inventors

  • FUKUSHIMA, MASAHIRO
  • WATANABE, SATOSHI
  • MASUNAGA, KEIICHI
  • KOTAKE, MASAAKI
  • MATSUZAWA, YUTA

Dates

Publication Date
20260513
Application Date
20240701

Claims (15)

  1. An onium salt having the formula (1): wherein n1 is 0 or 1, n2 is 1, 2 or 3, n3 is 1, 2, 3 or 4, n4 is an integer of 0 to 4, with the proviso that n2+n3+n4 is from 2 to 5 in case of n1=0, and n2+n3+n4 is from 2 to 7 in case of n1=1, n5 is an integer of 0 to 4, R alk is a C 6 -C 18 alkyl group or C 4 -C 18 fluorinated alkyl group, with the proviso that when R alk is a C 6 -C 18 alkyl group, the alkyl group has at least one straight chain structure of 6 or more carbon atoms, and when R alk is a C 4 -C 18 fluorinated alkyl group, the fluorinated alkyl group has at least two groups selected from -CF 2 - and -CF 3 , some -CH 2 -in the alkyl or fluorinated alkyl group may be replaced by an ether bond or carbonyl moiety, and the alkyl or fluorinated alkyl group may contain a cyclic structure selected from cyclopentane, cyclohexane, adamantane, norbornane and benzene rings at the end or in a carbon-carbon bond thereof, R 1 is a halogen exclusive of iodine or a C 1 -C 20 hydrocarbyl group which may contain a heteroatom, L A , L B , and L C are each independently a single bond, ether bond, ester bond, sulfonate ester bond, carbonate bond, or carbamate bond, X L is a single bond or a C 1 -C 40 hydrocarbylene group which may contain a heteroatom, Q 1 and Q 2 are each independently hydrogen, fluorine or a C 1 -C 6 fluorinated saturated hydrocarbyl group, Q 3 and Q 4 are each independently fluorine or a C 1 -C 6 fluorinated saturated hydrocarbyl group, and Z + is an onium cation.
  2. The onium salt of claim 1 wherein Z + is a sulfonium cation having the formula (cation-1) or iodonium cation having the formula (cation-2): wherein R ct1 to R ct5 are each independently halogen or a C 1 -C 30 hydrocarbyl group which may contain a heteroatom, and R ct1 and R ct2 may bond together to form a ring with the sulfur atom to which they are attached.
  3. A photoacid generator comprising the onium salt of claim 1 or 2.
  4. A chemically amplified positive resist composition comprising the photoacid generator of claim 3.
  5. The chemically amplified positive resist composition of claim 4, further comprising a base polymer containing a polymer which is decomposed under the action of acid to increase its solubility in alkaline developer.
  6. The chemically amplified positive resist composition of claim 5 wherein the polymer comprises repeat units having the formula (B1): wherein a1 is 0 or 1, a2 is an integer of 0 to 2, a3 is an integer satisfying 0 ≤ a3 ≤ 5+2(a2)-a4, a4 is an integer of 1 to 3, R A is hydrogen, fluorine, methyl or trifluoromethyl, R 11 is halogen, an optionally halogenated C 2 -C 8 saturated hydrocarbylcarbonyloxy group, optionally halogenated C 1 -C 6 saturated hydrocarbyl group, or optionally halogenated C 1 -C 6 saturated hydrocarbyloxy group, and A 1 is a single bond or C 1 -C 10 saturated hydrocarbylene group in which some -CH 2 -may be replaced by -O-.
  7. The chemically amplified positive resist composition of claim 5 or 6 wherein the polymer further comprises repeat units having the formula (B2-1): wherein b1 is 0 or 1, b2 is an integer of 0 to 2, b3 is an integer satisfying 0 ≤ b3 ≤ 5+2(b2)-b4, b4 is an integer of 1 to 3, b5 is 0 or 1, R A is hydrogen, fluorine, methyl or trifluoromethyl, R 12 is halogen, an optionally halogenated C 2 -C 8 saturated hydrocarbylcarbonyloxy group, optionally halogenated C 1 -C 6 saturated hydrocarbyl group, or optionally halogenated C 1 -C 6 saturated hydrocarbyloxy group, A 2 is a single bond or C 1 -C 10 saturated hydrocarbylene group in which some -CH 2 -may be replaced by -O-, X is an acid labile group when b4 is 1, and X is each independently hydrogen or an acid labile group, at least one being an acid labile group, when b4 is 2 or 3.
  8. The chemically amplified positive resist composition of any one of claims 5 to 7 wherein the polymer further comprises repeat units having the formula (B2-2): wherein c1 is an integer of 0 to 2, c2 is an integer of 0 to 2, c3 is an integer of 0 to 5, c4 is an integer of 0 to 2, R A is hydrogen, fluorine, methyl or trifluoromethyl, R 13 and R 14 are each independently a C 1 -C 10 hydrocarbyl group which may contain a heteroatom, R 13 and R 14 may bond together to form a ring with the carbon atom to which they are attached, R 15 is each independently fluorine, C 1 -C 5 fluorinated alkyl group or C 1 -C 5 fluorinated alkoxy group, R 16 is each independently a C 1 -C 10 hydrocarbyl group which may contain a heteroatom, and A 3 is a single bond, phenylene group, naphthylene group, or *-C(=O)-O-A 31 -, wherein A 31 is a C 1 -C 20 aliphatic hydrocarbylene group which may contain hydroxy, ether bond, ester bond or lactone ring, or a phenylene or naphthylene group, * designates a point of attachment to the carbon atom in the backbone.
  9. The chemically amplified positive resist composition of any one of claims 5 to 8 wherein the polymer further comprises repeat units of at least one type selected from repeat units having the formula (B3), repeat units having the formula (B4), and repeat units having the formula (B5): wherein d is an integer of 0 to 6, e is an integer of 0 to 4, f1 is 0 or 1, f2 is an integer of 0 to 2, and f3 is an integer of 0 to 5, R A is hydrogen, fluorine, methyl or trifluoromethyl, R 17 and R 18 are each independently hydroxy, halogen, an optionally halogenated C 1 -C 6 saturated hydrocarbyl group, optionally halogenated C 1 -C 6 saturated hydrocarbyloxy group, or optionally halogenated C 2 -C 8 saturated hydrocarbylcarbonyloxy group, R 19 is a C 1 -C 20 saturated hydrocarbyl group, C 1 -C 20 saturated hydrocarbyloxy group, C 2 -C 20 saturated hydrocarbylcarbonyloxy group, C 2 -C 20 saturated hydrocarbyloxyhydrocarbyl group, C 2 -C 20 saturated hydrocarbylthiohydrocarbyl group, halogen, nitro group, or cyano group, R 19 may be a hydroxy group when f2 is 1 or 2, and A 4 is a single bond or C 1 -C 10 saturated hydrocarbylene group in which some -CH 2 -may be replaced by -O-.
  10. The chemically amplified positive resist composition of any one of claims 5 to 9 wherein the polymer further comprises repeat units of at least one type selected from repeat units having the formulae (B6) to (B9): wherein R A is each independently hydrogen, fluorine, methyl or trifluoromethyl, X 1 is a single bond or phenylene group, X 2 is * 1 -C(=O)-O-X 21 -, * 1 -C(=O)-NH-X 21 - or * 1 -O-X 21 -, X 21 is a C 1 -C 6 aliphatic hydrocarbylene group, phenylene group, or divalent group obtained by combining the foregoing, which may contain a carbonyl moiety, ester bond, ether bond or hydroxy moiety, * 1 designates a point of attachment to X 1 , X 3 is each independently a single bond, phenylene group, naphthylene group or * 2 -C(=O)-O-X 31 -, X 31 is a C 1 -C 10 aliphatic hydrocarbylene group, phenylene group, or naphthylene group, the aliphatic hydrocarbylene group may contain a hydroxy moiety, ether bond, ester bond or lactone ring, * 2 designates a point of attachment to the carbon atom in the backbone, X 4 is each independently a single bond, * 3 -X 41 -C(=O)-O-, * 3 -C(=O)-NH-X 41 - or * 3 -O-X 41 -, X 41 is a C 1 -C 20 hydrocarbylene group which may contain a heteroatom, * 3 designates a point of attachment to X 3 , X 5 is each independently a single bond, * 4 -X 51 -C(=O)-O-, * 4 -C(=O)-NH-X 51 - or * 4 -O-X 51 -, X 51 is a C 1 -C 20 hydrocarbylene group which may contain a heteroatom, * 4 designates a point of attachment to X 4 , X 6 is a single bond, methylene, ethylene, phenylene, fluorinated phenylene, trifluoromethyl-substituted phenylene, * 2 -C(=O)-O-X 61 -, * 2 -C(=O)-N(H)-X 61 -, or * 2 -O-X 61 -, X 61 is a C 1 -C 6 aliphatic hydrocarbylene group, phenylene group, fluorinated phenylene group, or trifluoromethyl-substituted phenylene group, which may contain a carbonyl moiety, ester bond, ether bond or hydroxy moiety, * 2 designates a point of attachment to the carbon atom in the backbone, R 21 and R 22 are each independently a C 1 -C 20 hydrocarbyl group which may contain a heteroatom, R 21 and R 22 may bond together to form a ring with the sulfur atom to which they are attached, L 1 is a single bond, ether bond, ester bond, carbonyl group, sulfonate ester bond, carbonate bond or carbamate bond, Rf 1 and Rf 2 are each independently fluorine or a C 1 -C 6 fluorinated saturated hydrocarbyl group, Rf 3 and Rf 4 are each independently hydrogen, fluorine or a C 1 -C 6 fluorinated saturated hydrocarbyl group, Rf 5 and Rf 6 are each independently hydrogen, fluorine or a C 1 -C 6 fluorinated saturated hydrocarbyl group, excluding that all Rf 5 and Rf 6 are hydrogen at the same time, M - is a non-nucleophilic counter ion, A + is an onium cation, g1 and g2 are each independently an integer of 0 to 3.
  11. The chemically amplified positive resist composition of any one of claims 5 to 10, further comprising an organic solvent.
  12. The chemically amplified positive resist composition of any one of claims 5 to 11, further comprising a fluorinated polymer comprising repeat units of at least one type selected from repeat units having the formula (D1), repeat units having the formula (D2), repeat units having the formula (D3) and repeat units having the formula (D4) and optionally repeat units of at least one type selected from repeat units having the formula (D5) and repeat units having the formula (D6): wherein j1 is an integer of 1 to 3, j2 is an integer satisfying 0 ≤ j2 ≤ 5+2(j3)j1, j3 is 0 or 1, k is an integer of 1 to 3, R B is each independently hydrogen, fluorine, methyl or trifluoromethyl, R C is each independently hydrogen or methyl, R 101 , R 102 , R 104 and R 105 are each independently hydrogen or a C 1 -C 10 saturated hydrocarbyl group, R 103 , R 106 , R 107 and R 108 are each independently hydrogen, a C 1 -C 15 hydrocarbyl group, C 1 -C 15 fluorinated hydrocarbyl group, or acid labile group, and when R 103 , R 106 , R 107 and R 108 each are a hydrocarbyl or fluorinated hydrocarbyl group, an ether bond or carbonyl moiety may intervene in a carbon-carbon bond, R 109 is hydrogen or a C 1 -C 5 straight or branched hydrocarbyl group in which a heteroatom-containing moiety may intervene in a carbon-carbon bond, R 110 is a C 1 -C 5 straight or branched hydrocarbyl group in which a heteroatom-containing moiety may intervene in a carbon-carbon bond, R 111 is a C 1 -C 20 saturated hydrocarbyl group in which at least one hydrogen is substituted by fluorine, and in which some -CH 2 - may be replaced by an ester bond or ether bond, Z 1 is a C 1 -C 20 (k+1)-valent hydrocarbon group or C 1 -C 20 (k+1)-valent fluorinated hydrocarbon group, Z 2 is a single bond, *-C(=O)-O- or *-C(=O)-NH-, * designates a point of attachment to the carbon atom in the backbone, Z 3 is a single bond, -O-, *-C(=O)=O-Z 31 -Z 32 - or *-C(=O)-NH-Z 31 -Z 32 -, Z 31 is a single bond or C 1 -C 10 saturated hydrocarbylene group, Z 32 is a single bond, ester bond, ether bond, or sulfonamide bond, and * designates a point of attachment to the carbon atom in the backbone.
  13. The chemically amplified positive resist composition of any one of claims 5 to 12, further comprising a quencher.
  14. A resist pattern forming process comprising the steps of: applying the chemically amplified positive resist composition of any one of claims 5 to 13 onto a substrate to form a resist film thereon, exposing the resist film to high-energy radiation, and developing the exposed resist film in an alkaline developer.
  15. The process of claim 14 wherein the substrate is a photomask blank.

Description

TECHNICAL FIELD This invention relates to an onium salt, a chemically amplified positive resist composition, and a resist pattern forming process. BACKGROUND ART Pattern formation to a smaller feature size is required to meet the recent demand for higher integration in integrated circuits. Acid-catalyzed chemically amplified resist compositions are most often used in forming resist patterns with a feature size of 0.2 µm or less. High-energy radiation such as UV, deep-UV or EB is used as the energy source for exposure of these resist compositions. In particular, the EB lithography, which is utilized as the ultra-fine microfabrication technique, is also indispensable in processing a photomask blank into a photomask for use in the fabrication of semiconductor devices. Resist compositions for use in the EB lithography include positive ones wherein exposed regions are dissolved away to form a pattern and negative ones wherein exposed regions are retained to form a pattern. Either one which is easier to use is chosen in accordance with the morphology of the necessary resist pattern. In general, the EB lithography is by writing an image with EB, without using a mask. In the case of positive resist, those regions of a resist film other than the regions to be retained are successively irradiated with EB having a minute area. In the case of negative resist, those regions of a resist film to be retained are successively irradiated with EB. The operation of successively scanning all finely divided regions on the work surface takes a long time as compared with full wafer exposure through a photomask. To prevent any throughput decline, a resist film having a high sensitivity is required. Because of a long image writing time, it is likely that a difference arises between an initially imaged portion and a lately imaged portion. The stability with time of the exposed portion in vacuum is one of the important performance factors. One of the important applications of chemically amplified resist material resides in processing of photomask blanks. Some photomask blanks have a surface material that can have an impact on the pattern profile of the overlying chemically amplified resist film, for example, a layer of a chromium compound, typically chromium oxide deposited on a photomask substrate. For high resolution and profile retention after etching, it is one important performance factor to maintain the profile of a resist film pattern rectangular independent of the type of substrate. Attempts were made to ameliorate resist sensitivity and pattern profile in a controlled way by properly selecting and combining components used in resist compositions and adjusting processing conditions. One outstanding problem is the diffusion of acid, which has a significant impact on the resolution of a chemically amplified resist film. In the processing of photomasks, it is required that the profile of the resist pattern resulting from exposure does not change depending on the time taken until PEB. The major cause for time-dependent changes is the diffusion of acid generated upon exposure. Since the problem of acid diffusion has large impacts on sensitivity and resolution not only in the photomask processing, but also in general resist compositions, many studies are made thereon. Patent Documents 1 and 2 describe acid generators capable of generating bulky acids upon exposure, for thereby controlling acid diffusion and reducing roughness. Since these acid generators are still insufficient to control acid diffusion, it is desired to have an acid generator with more controlled diffusion. Patent Document 3 discloses a resist composition comprising a base polymer having bound thereto an acid generator capable of generating a sulfonic acid upon light exposure whereby acid diffusion is controlled. This approach of controlling acid diffusion by binding repeat units capable of generating acid upon exposure to a base polymer is effective in forming a pattern with reduced LER. However, the base polymer having bound therein repeat units capable of generating acid upon exposure encounters a problem with respect to its solubility in organic solvent, depending on the structure and proportion of the relevant units. Polymers comprising a major proportion of aromatic structure having an acidic side chain, for example, polyhydroxystyrene are useful in resist materials for the KrF lithography. These polymers are not used in resist materials for the ArF lithography since they exhibit strong absorption at a wavelength of around 200 nm. These polymers, however, are expected to form useful resist materials for the EB and EUV lithography for forming patterns of smaller size than the processing limit of ArF lithography because they offer high etching resistance. Often used as the base polymer in positive resist compositions for EB and EUV lithography is a polymer having an acidic functional group on phenol side chain masked with an acid labile group (or acid-decomposab