Electro-deposition for high-quality conformal resist layers for MEMS

Conventional spin-coating methods for photoresist deposition give poor results for MEMS and other applications where a conformal resist layer is required over wafer surfaces with large topography.We have developed a coating tool for use with electro-depositable resist that gives a resist layer with self-limiting uniform thickness across all planes of topography on a wafer surface. High quality, conformal coatings were obtained on wafers with surfaces micromachined to give challenging topography for coating. The resist was successfully patterned on the walls and bottoms of trenches in the micromachined wafers, indicating conformal and uniform resist deposition, even at sharp corners.The tool was also used in the production of a chemical sensor where multiple feedthroughs were successfully formed within single through-wafer holes to give high wiring densities.