High resolution photoresist of imide containing polymers

Abstract

Photoresist compositions suitable for deep UV and excimer laser lithography are disclosed that are mixtures of a photoacid and a polymer having imide residues to which acid labile groups are attached. These compositions provide high resolution, high contrast and high sensitivity in the deep UV (wavelength of 250-300 nm), mid-UV (wavelength of 300-350 nm) or conventional (wavelength of 350-450 nm) exposure bands. The compositions are also suitable for exposure at wavelengths commonly associated with excimer laser sources (248, 308 nm) or for exposure by X-radiation. In the compositions disclosed, the imide group ##STR1## can be blocked with certain groups, X, to form compounds containing the structure ##STR2## which have solubility properties different from the unblocked imide. These groups, X, can be cleaved by acid under the proper conditions to regenerate the unblocked imide. Also, where the imide group is incorporated in a polymer, the polymer with blocked imide groups can be made to function as a resist when compounded with a substrate capable of forming an acid upon exposure to radiation. The exact nature of the imide containing polymer is not critical, providing that: (1) in the unblocked state, the polymer is completely soluble in aqueous alkali; (2) in the blocked state, it is insoluble in the same aqueous solution, while simultaneously; (3) in the blocked state, it is soluble in a solvent capable of dissolving a suitable sensitizer; and (4) it is film forming. Other secondary properties may be selected (to enhance the characteristics of the resist) by varying the structure of the imide or a comonomer.