Patterning process

A process for forming a pattern, comprising the steps of:

• applying a first positive resist composition comprising a copolymer comprising recurring units having hydroxynaphthyl and recurring units having an alkaline solubility that increases under the action of acid onto a substrate to form a first resist coating, heat treating, exposing the first resist coating to high-energy radiation, heat treating, and developing the exposed resist coating with a developer to form a first resist pattern,
• said copolymer comprising recurring units having hydroxynaphthyl and recurring units having an alkaline solubility that increases under the action of acid comprising recurring units (a1) and recurring units (b) shown by the general formula (1):
• wherein R1 and R2 are each independently hydrogen or methyl, X is a single bond, Y is a single bond or a straight or branched C1-C6 alkylene group, m is 1 or 2, R3 is an acid labile group, a1 and b are numbers in the range:
• 0<a1<1.0, 0<b<1.0, and 0<a1+b<1.0,
• causing the first resist coating to crosslink and cure by irradiation of high-energy radiation having a wavelength of more than 200 nm to 320 nm in air,
• applying a second positive resist composition onto the first resist pattern-bearing substrate to form a second resist coating, heat treating, exposing the second resist coating to high-energy radiation, heat treating, and developing the second resist coating with a developer to form a second resist pattern.