Photoresist characteristics of polyurea films prepared by vapor deposition polymerization Depolymerization of polyurea

Aromatic polyurea was prepared by vapor deposition polymerization of 4, 4′-diaminodiphenyl methane and 4, 4′-diphenylmethane diisocyanate. Mass spectrometric analysis revealed depolymerization of the polyurea. The polyurea evaporated completely at 300°C or lower in vacuum. UV exposed polyurea did not evaporate even at temperatures greater than 300°C. To exploit the thermal resistance of the exposed and unexposed polyurea, patterned films were prepared with 5 μm resolution. It was found that the polyurea could be used as a negative resist material, and that an all-dry lithographic process was possible.