US Patent 7670750 Polymer, resist protective coating material, and patterning process

A resist protective coating material comprises a polymer comprising repeat units having formulae (1a) and (1b) and having a Mw of 1,000-500,000. R1a and R1b are H, F or alkyl or fluoroalkyl, R2a, R2b, R3a and R3b are H or alkyl, or R2a and R2b, and R3a and R3b may bond together to form a ring, 0<a<1, 0<b<1, a+b=1, and n=1 to 4. The protective coating material is improved in water repellency and water slip. In the ArF immersion lithography, it is effective in preventing water penetration and leaching of additives from the resist.