Silicon carbide technology for micro- and nano-electromechanical systems applications.

摘要

Micro- and nano-electromechanical systems (MEMS and NEMS) have emerged as a technology that integrates miniaturized mechanical structures with microelectronics components mainly for sensing and actuating applications. Silicon carbide (SiC) has gained great attention as both a coating and a structural material for MEMS applications in harsh environments, due to its superior mechanical strength, chemical stability and excellent performance in high-temperature, high-power electronic components. In addition, because of its high acoustic velocity and stable physicochemical properties, SiC is recently recognized as a promising material for fabricating radio frequency (RF) MEMS used as oscillators and filters in RF signal communications. The goal of this work is to realize a manufacturable SiC technology for MEMS applications.; Using a single precursor 1,3-disilabutane (1,3-DSB), we have been able to deposit polycrystalline cubic SiC films on Si and SiO2 substrates by chemical vapor deposition at relatively low temperatures ranging from 750 to 850°C. The SiC films can be in situ doped by introducing NH3 to the precursor 1,3-DSB. The electrical resistivity of SiC films is controlled by properly adjusting the flow rate ratio of NH 3 to 1,3-DSB. Electrical resistivity as low as 26 mO·cm has been achieved for as-deposited SiC films.; Selective dry etch for SiC has been investigated using SF6/O 2, HBr and HBr/Cl2 transformer coupled plasmas. Nonmetallic materials including SiO2 and Si3N4 have been used as masking materials.; The mechanical, electrical and chemical properties of SiC thin films are characterized using the state-of-the-art material characterization technologies, as well as MEMS-based test structures. It is found that the SiC films possess many desirable properties for MEMS applications, such as high Young's modulus, high fracture strength, and low stiction characteristics.; The developed SiC technology is applied to build SiC-based MEMS resonators with resonant frequencies in both audio- and radio-frequency ranges. A 173 MHz SiC Lame-Mode resonator with a quality factor of 9334 in room ambient is demonstrated.; By combining the "bottom-up" and "top-down" approaches in nanofabrication technologies, SiC and Si nanometer-size structures are fabricated. Assembly processes towards the positional and orientational control over these nanostructures have also been explored. These processes lay the groundwork and provide promising approaches for the low-cost batch-fabrication of nanoscale devices including NEMS.