A chemically amplified positive resist composition is used for semiconductor microfabrication.
In semiconductor microfabrication, especially, in liquid immersion lithography process, it is desirable to suppress the formation of defect.
It has been known that one of big problems in liquid immersion lithography process is defect caused by residual fluid droplets on the resist film (e.g. C. V. Peski et al., “Film pulling and meniscus instability as a cause of residual fluid droplets”, Presentation at the 2nd International Symposium on Immersion Lithography, September, 2005, and D. Gil et al., “The Role of Evaporation in Defect Formation in Immersion Lithography”, Presentation at the 2nd International Symposium on Immersion Lithography, September, 2005). The defect is the specific one in liquid immersion lithography and the defect is formed by conducting post-exposure baking of the resist film on which fluid droplets was remained.
It has been known that number of the defect caused by residual fluid droplets on the resist film is associated with the receding contact angle of the resist film and it is possible to suppress the formation of the defect caused by residual fluid droplets on the resist film by using the resist composition forming the resist film having higher receding contact angle (e.g. K. Nakano et al., “Defectivity data taken with a full-field immersion exposure tool”, Presentation at the 2nd International Symposium on Immersion Lithography, September, 2005).
US 2007/0218401 A1 discloses a chemically amplified resist composition comprising: a resin (A) which contains no fluorine atom and a structural unit (a1) having an acid-labile group in a side chain, a resin (B) which contains a structural unit (b2) having a fluorine-containing group in a side chain and at least one structural unit selected from the group consisting of a structural unit (b1) having an acid-labile group, a structural unit (b3) having a hydroxyl group and a structural unit (b4) having a lactone structure in a side chain, and an acid generator. US 2007/0218401 A1 also discloses that the content of the structural unit (b1) based on the total units of the resin (B) is 10 to 80 mol %.