Materials science and fabrication processes for a new MEMS technology based on ultrananocrystalline diamond thin films

Abstract

Received (received date) Revised (revised date) Most MEMS devices are currently based on silicon because of the available surface machining technology. However, Si has poor mechanical and tribological properties that makes it difficult to produce high-performance Si-based MEMS devices that could work reliably, particulary in harsh environments, Diamond as a super-hard material with high mechanical strength, exceptional chemical inertness, outstanding thermal stability and superior tribological performance, and could be an ideal material for MEMS. A key chal- lenge for Diamond-MEMS is the integration of diamond films with other materials. Con- ventional CVD thin film deposition methods produce diamond films with large grains, high internal stress, poor intergranular adhesion, and very rough surfaces, and are conse- quently ill-suited for MEMS applications. Diamond-like films offer an alternative, but are deposited using physical vapor deposition methods unsuitable for conformal deposition on high aspect ratio features, and generally they do not exhibit the outstanding mechani- cal properties of diamond. We describe a new ultrananocrystalline diamond (UNCD) film technology based on a microwave plasma technique using argon plasma chemistries that produce UNCD films with morphological and mechanical properties that are ideally suited for producing reliable MEMS devices. We have developed lithographic techniques for the fabrication of UNCD-MEMS components, including cantilevers and multi-level devices, acting as precursors to micro-bearings and gears, making UNCD a promising material for the development of high performance MEMS devices. We also review the mechanical, tribological, electronic transport, chemical and biocompatible properties of UNCD, which make this an ideal material for reliable, long endurance MEMS device