Oxygen ECR stream etching of dichromated gelatin films

Abstract

An experimental study of the development of dichromated gelatin (DCG) films using an ECR source with oxygen is presented in order to evaluate DCG as a photoresist material in microlithography. The kinetics of the etching process shows saturation behavior for high exposure levels and long development times. From the initial linear dependence, values for development rate are obtained ranging from 300 nm/min for an unexposed film to 25 nm/min for exposed films, depending on ammonium dichromate concentration of the gelatin film, exposure energy and the operation variables of the etching tool—an ECR source—mainly microwave power and oxygen pressure/flow. The etching behavior can be explained using a model based on the formation of a stop layer on the surface of the DCG film, as a result of the modification produced by the O 2 stream. The analysis of the characteristic curve of DCG films gives a threshold energy of 10 mJ/cm 2 and a contrast of 0.65, at 365 nm.