Preparation of positive photoreactive polyimides and their characterization

Polyimide precursors were synthesized from a diamine and a diacid chloride that was derived from the reactant with promellitic dianhydride and o‐nitrobenzyl alcohol. Their thermal properties were studied in nitrogen using dynamic thermogravimetry, and the photoreaction mechanism was investigated by ultraviolet and infrared spectrophotometry. The polyimide precursors were spin‐coated onto silicon wafers, prebaked, and then exposed to UV light from a high pressure Hg–Xe lamp. When the films were dipped into 2% aqueous KOH after irradiation, the exposed area dissolved forming high resolution patterns. Relative sensitivities of the polymers were determined.