Epoxy-based resist SU-8 is widely used in the development and fabrication of high-aspect-ratio (HAR) MEMS structures. It has proven to be a suitable photoresist combining thick layer coating and good adhesion on silicon substrates as well as possessing good mechanical and chemical stability. However, the trend towards minia- turization and increasing packaging density has pushed the demand for challenging micro-machining processes. As an example, a novel design of a MEMS microinductor requires a dielectric permanent layer coated in deep silicon trenches in order to insulate copper windings from the magnetic material deposited in these trenches. This requires the development of a photolithography process which enables the coating of a void-free layer filling the trenches. In this paper, the use of thick SU-8 photoresist for filling deep silicon trenches is investigated. Different SU-8 formulations are analyzed, processed and results are compared. As a result, an optimized process is developed to achieve void-free filled trenches and a uniform planar layer above them, with near vertical sidewall patterns.

Date Published: 20 October 2016
PDF: 5 pages
Proc. SPIE 10032, 32nd European Mask and Lithography Conference, 100320O (20 October 2016); doi: 10.1117/12.2247894

Published in SPIE Proceedings Vol. 10032:
32nd European Mask and Lithography Conference
Uwe F.W. Behringer; Jo Finders, Editor(s)