A SIMPLE OPTICAL-SYSTEM TO OPTIMIZE A HIGH DEPTH TO WIDTH ASPECT RATIO APPLIED TO A POSITIVE PHOTORESIST LITHOGRAPHY PROCESS

The fabrication of micro electro mechanical systems by electrodepositi on inside resist moulds has provided much interest in recent years. In this paper, we propose a method to optimize the lithography process o f a thick positive photoresist. This technique is based on the variati on of transparency of the photoresist during exposure. During exposure the absorption of the light-sensitive compound decreases due to its c onversion into indene carboxylic acid. A very good aspect ratio (heigh t:width) of up to 10:1 and high edge steepness (88 degrees) has been o btained from one coat and one UV exposure.