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6649575 
Journal Article 
Control of Sidewall Profile in Dry Plasma Etching of Polyimide 
Zawierta, M; Martyniuk, M; Jeffery, RD; Putrino, G; Keating, A; Silva, KKMBD; Faraone, L; , 
2017 
Yes 
I E E E Journal of Microelectromechanical Systems
ISSN: 1057-7157 
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC 
PISCATAWAY 
593-600 
WOS:000402736900013 
Spin-on polyimide is an organic thin film often used as a sacrificial layer for surface micromachining due to its high thermal stability, ease of removal, and compatibility with many materials and processes used in the realization of microelectromechanical systems (MEMS). The incorporation of sloped sidewalls in polyimide for fabricating pedestal structures is crucial in order to provide strong anchors in freestanding MEMS devices, especially in cases having a high aspect ratio and/or where structural materials have limited deposition conformality. This paper demonstrates a reliable reactive ion etching (RIE) methodology for tuning the polyimide sidewall angle, ranging from a vertical sidewall up to an angle of about 25 degrees from the vertical. The key modifications to the process parameter space include changes to the process temperature and chamber pressure. This paper also presents a novel lift-off process, which is based on the use of an interfacial polymer layer to facilitate removal of an overlying silicon oxide hard mask. This procedure allows polyimide sacrificial layers employing a silicon oxide hard mask to be used on samples that have exposed silicon oxide layers elsewhere on the chip that are required to remain intact during hard mask removal. Therefore, this lift-off process is applicable in situations where the silicon oxide hard mask removal cannot be accomplished by wet etching in hydrofluoric acid solutions. [2016-0314]