CONFORMAL PHOTORESIST COATINGS FOR HIGH ASPECT RATIO FEATURES
Authors: Keith A. Cooper and Clif Hamel et al. Company: SUSS MicroTec Date Published: 9/17/2007
IWLPC (Wafer-Level Packaging)
Abstract: The recent proliferation in advanced packaging and MEMS applications has created a need for high aspect ratio lithography processes. This paper will explore some of the alternatives for coating photoresists and dielectrics onto such structures, including conventional spin coating, electrodeposition, and more recently, spray coating. Data will be presented and discussed regarding the relative merits of the competing coating technologies, with real-world application examples for spray coating. This novel technique will be shown to deliver highly conformal resist coatings not only over etched v-groove structures commonly found in the MEMS world, but also over deep trenches and wells with high aspect ratios. The paper will emphasize recent improvements to both hardware and process methodology in an effort to broaden the scope of structures and materials suitable for spray coating. Practical extensions of this new technology will be explored and discussed, along with an assortment of new structures and applications that spray coating has enabled.