High efficiency photoresist-free lithography of UO3 patterns from amorphous films of uranyl complexes

The solid state photochemistry of uranyl carboxylate complexes is presented with the purpose of developing methods for optical lithography of uranium oxide films. These complexes of the general formula, UO2(OOCR)(2) (R = i-C3H7, C5H11, CH2C6H5, CH2OC2H5, C2H4OC2H5), were all photosensitive as thin amorphous films. The primary photochemical reaction for each of these complexes was the extrusion of a CO2 from the ligand and the production of radicals which initiated a chain reaction. The nature of this chain reaction was dependent upon the identity of the organic substituents, R. In some cases the chain reaction required a photochemical step while others were entirely thermal in nature. Of importance are the potentially high quantum yields which can be associated with thermal chain reactions. Some of the systems presented here exhibit quantum yields in excess of 1. This process was shown to be compatible with optical lithography by the patterning of the uranium oxide product on silicon surfaces.