Polymer, resist composition and patterning process

A polymer comprising recurring units of formula (1) and having a Mw of 1,000-500,000 is provided. ##STR1## R.sup.1 is H, methyl or CH.sub.2 CO.sub.2 R.sup.3, R.sup.2 is H, methyl or CO.sub.2 R.sup.3, R.sup.3 is alkyl, R.sup.4 is H, alkyl, alkoxyalkyl or acyl, R.sup.5 and R.sup.15 are acid labile groups, and at least one of R.sup.6 to R.sup.9 is a carboxyl or hydroxyl-containing monovalent hydrocarbon group, and the remainders are H or alkyl, at least one of R.sup.10 to R.sup.13 is a monovalent hydrocarbon group containing a --CO.sub.2 -- partial structure, and the remainders are H or alkyl, R.sup.14 is a polycyclic hydrocarbon group or polycyclic hydrocarbon-containing alkyl group, Z is a trivalent hydrocarbon group, X is --CH.sub.2 -- or --O--, k=0 or 1, x is>0, a, b, c and d are.gtoreq.0, satisfying x+a+b+c+d=1. A resist composition comprising the polymer has significantly improved sensitivity, resolution and etching resistance and is very useful in microfabrication.

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What is claimed is:

1. A polymer comprising recurring units of the following general formula (1) and having a weight average molecular weight of 1,000 to 500,000, ##STR36## wherein R.sup.1 ishydrogen, methyl or CH.sub.2 CO.sub.2 R.sup.3, R.sup.2 is hydrogen, methyl or CO.sub.2 R.sup.3, R.sup.3 is a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, R.sup.4 is hydrogen, a straight, branched or cyclic alkyl group of 1 to 15carbon atoms, a straight, branched or cyclic alkoxyalkyl group of 2 to 15 carbon atoms, or a straight, branched or cyclic acyl group of 1 to 15 carbon atoms, R.sup.5 and R.sup.15 each are an acid labile group, at least one of R.sup.6 to R.sup.9 is acarboxyl or hydroxyl-containing monovalent hydrocarbon group of 1 to 15 carbon atoms, and the remainders are independently hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R.sup.6 to R.sup.9, taken together, may form aring, and when they form a ring, at least one of R.sup.6 to R.sup.9 is a carboxyl or hydroxyl-containing divalent hydrocarbon group of 1 to 15 carbon atoms, and the remainders are independently a single bond or a straight, branched or cyclic alkylenegroup of 1 to 15 carbon atoms, at least one of R.sup.10 to R.sup.13 is a monovalent hydrocarbon group of 2 to 15 carbon atoms containing a --CO.sub.2 -- partial structure, and the remainders are independently hydrogen or a straight, branched or cyclicalkyl group of 1 to 15 carbon atoms, or R.sup.10 to R.sup.13 , taken together, may form a ring, and when they form a ring, at least one of R.sup.10 to R.sup.13 is a divalent hydrocarbon group of 1 to 15 carbon atoms containing a --CO.sub.2 -- partialstructure, and the remainders are independently a single bond or a straight, branched or cyclic alkylene group of 1 to 15 carbon atoms, R.sup.14 is a polycyclic hydrocarbon group of 7 to 15 carbon atoms or an alkyl group containing such a polycyclichydrocarbon group, Z is a trivalent hydrocarbon group of 1 to 10 carbon atoms, or Z forms a ring with R.sup.1, and in this event, R.sup.1 is methylene and Z is a tetravalent hydrocarbon group of 1 to 10 carbon atoms, X is --CH.sub.2 -- or --O--, k isequal to 0 or 1, x is a number of more than 0, a, b, c and d are 0 or positive numbers, satisfying x+a+b+c+d=1.

2. The polymer of claim 1 wherein the acid labile groups represented by R.sup.5 and R.sup.15 in formula (1) are selected from the class consisting of groups of the following general formulae (L1) to (L4), tertiary alkyl groups of 4 to 20 carbonatoms, trialkylsilyl groups in which each alkyl moiety has 1 to 6 carbon atoms, oxoalkyl groups of 4 to 20 carbon atoms, and mixtures of any of the foregoing, ##STR37## wherein R.sup.L01 and R.sup.L02 each are hydrogen or a straight, branched or cyclicalkyl group of 1 to 18 carbon atoms, R.sup.L03 is a monovalent hydrocarbon group of 1 to 18 carbon atoms which may contain a hetero atom such as oxygen atom, a pair of R.sup.L01 and R.sup.L02, R.sup.L01 and R.sup.L03, or R.sup.L02 and R.sup.L03 may forma ring, each of R.sup.L01, R.sup.L02 and R.sup.L03 is a straight or branched alkylene group of 1 to 18 carbon atoms when they form a ring, R.sup.L04 is a tertiary alkyl group of 4 to 20 carbon atoms, a trialkylsilyl group in which each alkyl moiety has 1to 6 carbon atoms, an oxoalkyl group of 4 to 20 carbon atoms, or a group of formula (L1), R.sup.L05 is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms or a substituted or unsubstituted aryl group of 6 to 20 carbon atoms, R.sup.L06 is astraight, branched or cyclic alkyl group of 1 to 8 carbon atoms or a substituted or unsubstituted aryl group of 6 to 20 carbon atoms, R.sup.L07 to R.sup.L16 are independently hydrogen or monovalent hydrocarbon groups of 1 to 15 carbon atoms which maycontain a hetero atom, R.sup.L07 to R.sup.L16, taken together, may form a ring, and each of R.sup.L07 to R.sup.L16 represents a divalent hydrocarbon group of 1 to 15 carbon atoms which may contain a hetero atom, when they form a ring, or two of R.sup.L07to R.sup.L16 which are attached to adjoining carbon atoms may bond together directly to form a double bond, y is an integer of 0 to 6, m is equal to 0 or 1, and n is equal to 0, 1, 2 or 3, satisfying 2m+n=2 or 3.

3. A resist composition comprising the polymer of claim 1.

4. A process for forming a resist pattern comprising the steps of: applying the resist composition of claim 3 onto a substrate to form a coating, heat treating the coating and then exposing it to high-energy radiation or electron beams through aphoto mask, and optionally heat treating the exposed coating and developing it with a developer.