Diamond, due to its unique mechanical, thermal, chemical and electrical properties, is an excellent material for Microelectromechanical Systems (MEMS). Furthermore, due to its large band gap of 5.5 eV, diamond offers the possibility of making MEMS structures out of a single material by varying the doping level to achieve the semiconducting, metallic and insulating (undoped) properties needed in a typical MEMS structure. Such single-material MEMS (SMM) can alleviate problems of complicated multilayer devices, such as thermal mismatch, adhesion, inter-layer diffusion, contact resistance. Since polycrystalline diamond (poly-C) is inexpensive and retains many of the unique properties of single-crystal diamond, SMM technology based on poly-C has been developed in this research work. Moreover, poly-C can be layered to perform a number of functions, whereas a complex stack of materials would otherwise be required. Consequently, due to poly-C's high etching selectivity to most other materials, the SMM fabrication process developed in the current work can reduce the number of fabrication masks by a factor of 1.5 - 2 as compared to a conventional MEMS process.The development of SMM technology faces three major challenges; (a) production of highly conducting and highly insulating films, (b) the development of dry etching techniques for multilayer poly-C structures without any damage to the sacrificial layers necessary to produce multilayer structures and (c) the surface micromachining technology of building multilayer SMM structures containing insulating, semiconducting and highly conducting layers. All of these challenges and other associated poly-C micromachining technologies are discussed in depth. A number of complex poly-C SMM structures were fabricated using Si or SiO2 as a sacrificial layer to address the initial SMM issues. Additionally, the surface micromachining processes of SMM devices and SMM thin film packaging have been developed.In this research, the design, fabrication and testing of novel poly-C RFMEMS resonators with piezoresistive detection, a potential application for SMM technology, are developed and presented for the first time. These resonator uses undoped poly-C with a resistivity above 109 Ohm·cm as an insulating layer as well as a structural layer. Lightly boron-doped poly-C with a resistivity of 9 Ohm·cm is used as a semiconducting material with piezoresistive properties. Highly doped poly-C with a resistivity on the order of 10-3 Ohm·cm is used as interconnect to reduce the total parasitic resistance in signal transmission. SMM system integration has been achieved for a RFMEMS application with piezoelectric actuation and piezoresistive detection.
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