ing, exposure, post-exposure baking (PEB), and develop› ment. If necessary, any additional steps may be added. 

[0154] For example, the positive resist composition is first applied onto a substrate on which an integrated circuit is to be formed (e.g., Si, SiO$_{2}$ , SiN, SiON, TiN, WSi, BPSG, SOG, or organic antireflective coating) or a substrate on which a mask circuit is to be formed (e.g., Cr, CrO, CrON, MoSi$_{2}$ , or SiO$_{2}$ ) by a suitable coating technique such as spin coating, roll coating, flow coating, dipping, spraying or doctor coating. The coating is prebaked on a hotplate at a temperature of 60 to 150° C. for 10 seconds to 30 minutes, preferably at 80 to 120° C. for 30 seconds to 20 minutes. The resulting resist film is generally 0.01 to 2.0 µm thick. 

[0155] The resist film is then exposed to a desired pattern of high-energy radiation such as UV, deep-UV, EB, EUV, x-ray, soft x-ray, excimer laser light, y-ray or synchrotron radiation, directly or through a mask. The exposure dose is preferably about 1 to 200 mJ/cm 2 , more preferably about 10 to 100 mJ/cm 2 , or about 0.1 to 100 µC/cm 2 , more preferably about 0.5 to 50 µC/cm 2 . The resist film is further baked (PEB) on a hotplate at 60 to 150° C. for 10 seconds to 30 minutes, preferably at 80 to 120° C. for 30 seconds to 20 minutes. 

[0156] Thereafter the resist film is developed with a devel› oper in the form of an aqueous base solution for 3 seconds to 3 minutes, preferably 5 seconds to 2 minutes by conven› tional techniques such as dip, puddle and spray techniques. A typical developer is a 0.1 to 10 wt%, preferably 2 to 5 wt % aqueous solution of tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tet› rapropylammonium hydroxide (TPAH), or tetrabutylammo› nium hydroxide (TBAH). The resist film in the exposed area is dissolved in the developer whereas the resist film in the unexposed area is not dissolved. In this way, the desired positive pattern is formed on the substrate. Inversely in the case of negative resist, the exposed area of resist film is insolubilized and the unexposed area is dissolved in the developer. It is appreciated that the resist composition of the invention is best suited for micro-patterning using such high-energy radiation as KrF and ArF excimer laser, EB, EUV, x-ray, soft x-ray, y-ray and synchrotron radiation. 

[0157] In an alternative embodiment, a negative pattern may be formed via organic solvent development using a positive resist composition comprising a base polymer hav› ing an acid labile group. The developer used herein is preferably selected from among 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, butenyl acetate, isopentyl acetate, propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl propionate, ethyl propionate, ethyl 3-ethoxypropi› onate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, pentyl lactate, isopentyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate, benzyl 

acetate, methyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, ethyl phenylacetate, and 2-phenylethyl acetate, and mixtures thereof. 

[0158] At the end of development, the resist film is rinsed. As the rinsing liquid, a solvent which is miscible with the developer and does not dissolve the resist film is preferred. Suitable solvents include alcohols of 3 to 10 carbon atoms, ether compounds of 8 to 12 carbon atoms, alkanes, alkenes, and alkynes of 6 to 12 carbon atoms, and aromatic solvents. Specifically, suitable alcohols of 3 to 10 carbon atoms include n-propyl alcohol, isopropyl alcohol, I-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, t-butyl alcohol, 1-penta› nol, 2-pentanol, 3-pentanol, t-pentyl alcohol, neopentyl alcohol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl- 3-pentanol, cyclopentanol, 1-hexanol, 2-hexanol, 3-hexanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 3,3-dim› ethyl-2-butanol, 2-ethyl-1-butanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pen› tanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl- 1-pentanol, 4-methyl-2-pentanol, 4-methyl-3-pentanol, cyclohexanol, and 1-octanol. Suitable ether compounds of 8 to 12 carbon atoms include di-n-butyl ether, diisobutyl ether, di-s-butyl ether, di-n-pentyl ether, diisopentyl ether, di-s› pentyl ether, di-t-pentyl ether, and di-n-hexyl ether. Suitable alkanes of 6 to 12 carbon atoms include hexane, heptane, octane, nonane, decane, undecane, dodecane, methylcyclo› pentane, dimethylcyclopentane, cyclohexane, methylcyclo› hexane, dimethylcyclohexane, cycloheptane, cyclooctane, and cyclononane. Suitable alkenes of 6 to 12 carbon atoms include hexene, heptene, octene, cyclohexene, methylcyclo› hexene, dimethylcyclohexene, cycloheptene, and cyclooctene. Suitable alkynes of 6 to 12 carbon atoms include hexyne, heptyne, and octyne. Suitable aromatic solvents include toluene, xylene, ethylbenzene, isopropyl› benzene, t-butylbenzene and mesitylene. The solvents may be used alone or in admixture. 

[0159] Rinsing is effective for minimizing the risks of resist pattern collapse and defect formation. However, rins› ing is not essential. If rinsing is omitted, the amount of solvent used may be reduced. 

[0160] A hole or trench pattern after development may be shrunk by the thermal flow, RELACSfi or DSA process. A hole pattern is shrunk by coating a shrink agent thereto, and baking such that the shrink agent may undergo crosslinking at the resist surface as a result of the acid catalyst diffusing from the resist layer during bake, and the shrink agent may attach to the sidewall of the hole pattern. The bake is preferably at a temperature of 70 to 180° C., more preferably 80 to 170° C., for a time of 10 to 300 seconds. The extra shrink agent is stripped and the hole pattern is shrunk. 

[0161] Examples of the invention are given below by way of illustration and not by way of limitation. The abbreviation "pbw" is parts by weight. 

[0162] Thiophenecarboxylic acid sulfonium salts 1 to 20 used in resist compositions are identified below. Sulfonium salts 1 to 20 were synthesized by ion exchange between an ammonium salt of thiophenecarboxylic acid or derivative thereof providing the anion shown below and a sulfonium chloride providing the cation shown below. 

## Example 

