Abstract: A positive working photoresist composition includes at least one thermally cross-linkable photoacid generator, a binder polymer, and a solvent in which the binder polymer and photoacid generator are dissolved. The photoacid generator is represented by the general formula (I): wherein X is methanesulfonate, trifluoromethanesulfonate, 4-toluenesulfonate, 10-camphorsulfonate, cyclohexane sulfamate, perfluoro-1-butanesulfonate, perfluorooctanesulfonate, F, Cl, Br, SbF6, BF4, PF4, or AsF6, R1 is hydrogen or methyl, and R2 is alkyl of C1-10 or vinyloxyethyl. The binder polymer represented by the general formula (II): wherein R1 and R2 are different from each other and are selected from the group consisting of acid labile groups, hydrogen, methoxy, ethoxy, n-butoxy and t-butoxy, R3 is hydrogen or alkyl of C1-10, R4 is hydrogen or methyl, 0<o≦1, 0≦p≦0.7, 0≦q≦0.7, and 0≦r≦0.3, wherein p, q and r are not 0 simultaneously.