Photoetching of thin lead films with nitromethane

Abstract

Thin evaporated lead films have been photoetched with gaseous nitromethane activated by ultraviolet radiation. The rate of etching (of the order of 10 Å./min.) varies inversely with the volume of the system, is proportional to the square root of the radiation intensity, and is proportional to the partial pressure of nitromethane and then saturates at a limiting pressure. The presence of nitrogen in the system strongly retards the etching reaction. The rate of reaction has been calculated as a function of the radiation wave length by use of a set of transmission niters. For lead, the wave length band of 2680 ± 50 Å. gives the largest positive contribution to the rate, while a band at 2530 ± 50 Å. inhibits the reaction by about 370% of the observed rate.