OXYGEN ECR STREAM ETCHING OF DICHROMATED GELATIN FILMS

An experimental study of the development of dichromated gelatin (DCG) films using an ECR source with oxygen is presented in order to evaluat e DCG as a photoresist material in microlithography. The kinetics of t he 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 unex posed film to 25 nm/min for exposed films, depending on ammonium dichr omate concentration of the gelatin film, exposure energy and the opera tion variables of the etching tool-an ECR source-mainly microwave powe r and oxygen pressure/flow. The etching behavior can be explained usin g 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 thresho ld energy of 10 mJ/cm(2) and a contrast of 0.65, at 365 nm. (C) 1998 E lsevier Science S.A.