New development strategies for high aspect ratio microstructures

Abstract

 In the first step of the LIGA process a resist layer, typically PMMA (polymethylmethacrylate), is pattered by deep X-ray lithography. The exposed parts are subsequently dissolved by an organic developer. The quality and the achievable height of the microstructure is decisively determined by the development process. In order to increase the aspect ratio and maintain the quality of the microstructures the parameters influencing the development process were investigated. In the case of dip development and ultrasound development a strong dependency of the development rate on the temperature, dose value and depth of deposition has been noticed. The development rate increases with increasing dose value and temperature and decreases with increasing depth of deposition. In case of dip development the development course can be described by a phenomenological equation which considers the three mentioned parameters. In the case of ultrasound further parameters have to be taken into account: the geometry and the dimensions of the strucutres.