Poly(methacrylic acid-co-t-butylmethacrylate-co-bornylmetharcylate) was synthesized and its application to a crosslinkable positive photoresist was investigated. The existence of pendant alicyclic bornyl groups increased the thermostability of copolymers; however, a decrease in the acid-catalyzed deprotection of pendant t-butyl groups led to a decrease in the sensitivity of the positive-tone photoresist. The thermostability of the relief polymeric patterns of the positive-tone photoresist was appreciably improved effectively because of the acid-catalyzed dehydration crosslinking of pendant carboxyl groups. Thermogravimetric properties of binder resins, exposure characteristics, and sensitivity and resolution of the photoresist were all investigated. Lithographic evaluation of the curable positive-tone photoresists was also estimated.