Awl spring MEMS switches with nanocrystalline graphite sidewall coating using spacer etch method

Abstract

Long cycling of MEMS switches, especially in a high temperature environment, can degrade the contact resulting in decreased switching reliability. Different contact coatings including metals, amorphous carbon and nanocrystalline graphite (NCG) have been proposed but carbon-based contact appear to greatly increase cycling reliability due to their low stiction and friction coefficient properties. However, establishing a good contact coating on the beam sidewall of an in-plane MEMS switch is still challenging, while out-of-plane MEMS fabrication is complicated as it involves multiple lithography steps and suffers residual stresses in deposited layers. Therefore, we propose a one-step lithography process to define the MEMS switch structure and then use a spacer etch method to create a reliable NCG sidewall coating on the drain contact region. We use plasma enhanced chemical vapour deposition (PECVD) method to deposit undoped NCG coatings on a double-clamp in-plane awl meander spring MEMS switch. The MEMS switch is subjected to cold- and hot-cycling electrical measurements to evaluate which of the NCG coatings is suitable for long switching operation.

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Identifiers

ORCID for Jamie Dean Reynolds: orcid.org/0000-0002-0072-0134

ORCID for Suan-Hui Pu: orcid.org/0000-0002-3335-8880

ORCID for Harold Chong: orcid.org/0000-0002-7110-5761

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