Search

EP-4455118-B1 - POLYMER, CHEMICALLY AMPLIFIED POSITIVE RESIST COMPOSITION, AND RESIST PATTERN FORMING PROCESS

EP4455118B1EP 4455118 B1EP4455118 B1EP 4455118B1EP-4455118-B1

Inventors

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

Dates

Publication Date
20260506
Application Date
20240315

Claims (13)

  1. A polymer adapted to turn alkali soluble as a result of deprotection under the action of acid, the polymer comprising repeat units A1 having the formula (A1): wherein a1 is 0 or 1, a2 is an integer of 0 to 4 in case of a1=0, and an integer of 0 to 6 in case of a1=1, a3 is an integer of 1 to 3, with the proviso that a2+a3 is from 1 to 5 in case of a1=0 and a2+a3 is from 1 to 7 in case of a1=1, R A is hydrogen, fluorine, methyl or trifluoromethyl, X 1 is a single bond, *-C(=O)-O- or *-C(=O)-NH-, * designates a point of attachment to the carbon atom in the backbone, X 2 is a single bond, ether bond, ester bond, carbonyl group, sulfonic ester bond, carbonate bond or carbamate bond, A 1 is a single bond or a C 1 -C 10 saturated hydrocarbylene group in which some constituent -CH 2 - may be replaced by -O-, R 1 is halogen or a C 1 -C 20 hydrocarbyl group which may contain a heteroatom, and R is an acid labile group having formula (AL-1) or (AL-2), wherein R L1 , R L2 , R L6 , R L7 and R L8 are each independently hydrogen or a C 1 -C 15 hydrocarbyl group, R L1 and R L2 may bond together to form a ring with the carbon atom to which they are attached, and any two of R L6 to R L8 may bond together to form a ring with the carbon atom to which they are attached, R L3 , R L4 , R L9 and R L10 are each independently hydrogen or a C 1 -C 20 hydrocarbyl group which may contain a heteroatom, R L3 and R L4 may bond together to form a ring with the carbon atom to which they are attached, and R L9 and R L10 may bond together to form a ring with the carbon atom to which they are attached, R L5 and R L11 are each independently hydrogen or a C 1 -C 15 hydrocarbyl group, m1 and m2 are each independently an integer of 1 to 3, and the broken line designates a point of attachment to the oxygen atom of the aromatic hydroxy group.
  2. The polymer of claim 1, further comprising phenolic hydroxy group-bearing repeat units A2 having the formula (A2): wherein b1 is 0 or 1, b2 is an integer of 0 to 4 in case of b 1=0, and an integer of 0 to 6 in case of b1=1, b3 is an integer of 1 to 3, with the proviso that b2+b3 is from 1 to 5 in case of b1=0 and b2+b3 is from 1 to 7 in case of b1=1, R A is hydrogen, fluorine, methyl or trifluoromethyl, X 3 is a single bond, *-C(=O)-O- or *-C(=O)-NH-, * designates a point of attachment to the carbon atom in the backbone, X 4 is a single bond, ether bond, ester bond, carbonyl group, sulfonic ester bond, carbonate bond or carbamate bond, A 2 is a single bond or a C 1 -C 10 saturated hydrocarbylene group in which some constituent -CH 2 - may be replaced by -O-, and R 2 is halogen or a C 1 -C 20 hydrocarbyl group which may contain a heteroatom.
  3. The polymer of claim 1 or 2, further comprising repeat units of at least one type selected from repeat units having the formula (A3-1) and repeat units having the formula (A3-2): wherein c1 is 0 or 1, c2 is an integer of 0 to 2, c3 is an integer satisfying 0 ≤ c3 ≤ 5+2(c2)-c4, c4 is an integer of 1 to 3, c5 is 0 or 1, d1 is an integer of 0 to 2, d2 is an integer of 0 to 2, d3 is an integer of 0 to 5, d4 is an integer of 0 to 2, R A is each independently hydrogen, fluorine, methyl or trifluoromethyl, A 3 is a single bond or a C 1 -C 10 saturated hydrocarbylene group in which -CH 2 -may be replaced by -O-, A 4 is a single bond, phenylene group, naphthylene group or *-C(=O)-O-A 41 -, A 41 is a C 1 -C 20 aliphatic hydrocarbylene group which may contain hydroxy, ether bond, ester bond or lactone ring, or a phenylene group or naphthylene group, * designates a point of attachment to the carbon atom in the backbone, R 3 is 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 4 and R 5 are each independently a C 1 -C 10 hydrocarbyl group which may contain a heteroatom, R 4 and R 5 may bond together to form a ring with the carbon atom to which they are attached, R 6 is each independently fluorine or a C 1 -C 5 fluorinated alkyl group or C 1 -C 5 fluorinated alkoxy group, R 7 is each independently a C 1 -C 10 hydrocarbyl group which may contain a heteroatom, and X A is an acid labile group in case of c4=1 and X A is hydrogen or an acid labile group, at least one being an acid labile group, in case of c4=2 or 3.
  4. The polymer of any one of claims 1 to 3, further comprising repeat units of at least one type selected from repeat units having the formula (B1), repeat units having the formula (B2), and repeat units having the formula (B3): wherein e and f are each independently an integer of 0 to 4, g1 is an integer of 0 to 5, g2 is an integer of 0 to 2, R A is hydrogen, fluorine, methyl or trifluoromethyl, X 5 is a single bond, *-C(=O)-O- or *-C(=O)-NH-, * designates a point of attachment to the carbon atom in the backbone, A 5 is a single bond or a C 1 -C 10 saturated hydrocarbylene group in which some constituent -CH 2 - may be replaced by -O-, and R 11 and R 12 are each independently a hydroxy group, halogen, an optionally halogenated C 2 -C 8 saturated hydrocarbylcarbonyloxy group, optionally halogenated C 1 -C 8 saturated hydrocarbyl group, or optionally halogenated C 1 -C 8 saturated hydrocarbyloxy group, R 13 is an acetyl group, 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 13 may also be a hydroxy group in case of g2=1 or 2.
  5. A chemically amplified positive resist composition comprising the polymer of any one of claims 1 to 4.
  6. The resist composition of claim 5, further comprising an organic solvent.
  7. The resist composition of claim 5 or 6, further comprising a photoacid generator capable of generating an acid having an acid strength (pKa) of -2.0 or larger.
  8. The resist composition of any one of claims 5 to 7, further comprising a quencher.
  9. The resist composition of any one of claims 5 to 8, 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 R B is each independently hydrogen, fluorine, methyl or trifluoromethyl, R C is each independently hydrogen or methyl, R 301 , R 302 , R 304 and R 305 are each independently hydrogen or a C 1 -C 10 saturated hydrocarbyl group, R 303 , R 306 , R 307 and R 308 are each independently hydrogen, a C 1 -C 15 hydrocarbyl group, C 1 -C 15 fluorinated hydrocarbyl group, or acid labile group, with the proviso that when R 303 , R 306 , R 307 and R 308 each are a hydrocarbyl or fluorinated hydrocarbyl group, an ether bond or carbonyl moiety may intervene in a carbon-carbon bond, R 309 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 310 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 311 is a C 1 -C 20 saturated hydrocarbyl group in which at least one hydrogen is substituted by fluorine, and in which some constituent -CH 2 - may be replaced by an ester bond or ether bond, n is an integer of 1 to 3, x is an integer of 1 to 3, y is an integer satisfying 0 ≤ y ≤ 5+2z-x, z is 0 or 1, Z 1 is a C 1 -C 20 (n+1)-valent hydrocarbon group or C 1 -C 20 (n+1)-valent fluorinated hydrocarbon group, and 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.
  10. A resist pattern forming process comprising the steps of: applying the chemically amplified positive resist composition of any one of claims 5 to 9 onto a substrate to form a resist film thereon, exposing the resist film to a pattern of high-energy radiation, and developing the exposed resist film in an alkaline developer.
  11. The process of claim 10 wherein the substrate has the outermost surface of a material containing at least one element selected from chromium, silicon, tantalum, molybdenum, cobalt, nickel, tungsten, and tin.
  12. The process of claim 10 or 11 wherein the substrate is a mask blank of transmission or reflection type.
  13. A mask blank of transmission or reflection type which is coated with the chemically amplified positive resist composition of any one of claims 5 to 9.

Description

TECHNICAL FIELD This invention relates to a polymer, chemically amplified positive resist composition, and resist pattern forming process. BACKGROUND ART To meet the recent demand for higher integration in integrated circuits, pattern formation to a smaller feature size is required. 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, EUV 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. 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 having a minute area. The operation of successively scanning all finely divided regions on the work surface takes a long time as compared with one-shot exposure through a photomask. To avoid any throughput decline, a resist film having a high sensitivity is required. 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. A small line edge roughness (LER) is another important performance factor. In recent years, the multibeam mask writing (MBMW) process is used in the processing of mask blanks to achieve further miniaturization. The resist used in the MBMW process is a low-sensitivity resist composition (or high-dose region) which is advantageous in roughness while a spotlight is brought to the optimization of the resist composition in the high-dose region. Various improvements in the control of resist sensitivity and pattern profile have been made by a proper selection and combination of resist material components and processing conditions. One improvement pertains to the diffusion of acid that largely affects the resolution of a resist film. In the processing of photomasks, it is required that the profile of a resist pattern formed do not change with a lapse of time from the end of exposure to bake. The major cause of such a change of resist pattern profile with time is diffusion of an acid generated upon exposure. The problem of acid diffusion has been widely studied not only in terms of photomask processing, but also in terms of general resist compositions because the acid diffusion has a significant impact on sensitivity and resolution. Patent Documents 1 and 2 describe acid generators capable of generating bulky acids for controlling acid diffusion and reducing LER. Since these acid generators are still insufficient to control acid diffusion, it is desired to have an acid generator with shorter acid diffusion. Patent Document 3 discloses a resist composition comprising a base polymer having introduced therein repeat units having a sulfonium structure capable of generating a sulfonic acid upon light exposure. This approach of controlling acid diffusion by introducing repeat units capable of generating acid upon exposure into a base polymer is effective in forming a pattern with small LER. However, the base polymer having introduced therein repeat units capable of generating acid upon exposure sometimes encounters a problem with respect to its solubility in organic solvent, depending on the structure and proportion of the repeat units. Polymers comprising a major proportion of aromatic structure having an acidic side chain, for example, polyhydroxystyrene are useful as a base polymer in resist materials for the KrF excimer laser lithography. These polymers are not used in resist materials for the ArF excimer laser lithography because they exhibit strong absorption to radiation of wavelength 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 excimer laser 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. Upon exposure to high-energy radiation, a photoacid generator generates an acid