In recent years SU-8 resist attracted a high interest for fabrication of structures with high topography or high aspect ratio structures. The reasons for SU-8 popularity can be found in its unique properties -high chemical and mechanical stability, biological compatibility, optical transparency, high aspect ratio capability and low cost of fabrication. SU-8 can be used as an alternative molding material to LIGA process; in comparison to the standard LIGA process, relatively thick (1 mm range) SU-8 layers can be processed with UV lithography and do not require expensive X-ray light source. Nevertheless, processing of thick layers of SU-8 is not without challenges -coating high viscosity material, critical soft bakes in order of several hours, exposure requiring good contact, critical post exposure bake and extremely long development times. One aspect of the SU-8 processing, which is explored in this paper, is improvement of the development process time -by using single wafer megasonic-enhanced development. In this paper, the experimental results from manufacturing of SU-8 structures with aspect ratio 1:23 by using UV lithography and megasonicenhanced development will be presented. Significant development time reduction from 240 min down to 10 min was achieved.

MEMS-specific processes required to adapt standard IC manufacturing technologies in order to accommodate its custom requirements. Photolithography is one of the standard techniques which had to adapt particularly to the use of thick resists needed for high aspect ratio features fabrication. In order to work with resist thickness varying between few tens and up to few hundreds of micrometers the standard process flow had to be changed to multiple-layers coating, customized (and very long) baking times, special exposure techniques and development. This paper introduces a megasonic-enhanced method used for developing resists. In case of MEMS applications this method brings not only a major yield improvement (better quality features) but also a major decrease of process time.