Tunable Fabry-Pérot cavities fabricated from PECVD silicon nitride employing zinc sulphide as the sacrificial layer

TLDR: In this paper, a Fabry-P?rot cavity has been fabricated using PECVD silicon nitride as the membrane layer with ZnS as the sacrificial material.

Abstract: The construction of self-supporting and suspended structures is one of the fundamental challenges of microelectromechanical systems (MEMS). Many technologies have been developed for the fabrication of such structures, which can be categorized into bulk or surface micromachining. Generally surface micromachining techniques rely on a high-temperature deposition process such as low pressure chemical vapour deposition to produce high-quality films. Plasma enhanced chemical vapour deposition (PECVD) can be used to deposit films at temperatures less than 300??C. PECVD of silicon nitride has not been used extensively in MEMS structures due to the material limitations created via the deposition technique, primarily controllability of the intrinsic stress and etch selectivity of the deposited film. We show here that PECVD silicon nitride can be used successfully in MEMS structures, and that the intrinsic stress is controllable through variations in the PECVD deposition parameters. A MEMS-based Fabry-P?rot cavity has been fabricated using PECVD silicon nitride as the membrane layer with ZnS as the sacrificial material. Devices with an initial 1??m cavity length typically provide a displacement of 240?nm across a 380??m membrane span for an applied bias of only 1.6?V.