A Novel Method of Fabricating SiC-On-Insulator Substrates for Use in MEMS
- PDF / 193,298 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 93 Downloads / 171 Views
A Novel Method of Fabricating SiC-On-Insulator Substrates for Use in MEMS Hung-I Kuo, Christian Zorman, and Mehran Mehregany Department of Electrical Engineering and Computer Science Case Western Reserve University Cleveland, OH 44106, USA ABSTRACT This paper reports on a novel, bonding-free method to fabricate silicon carbide-on-insulator (SiCOI) substrates. The process bypasses wafer bonding by using a high deposition rate polysilicon process in conjunction with wet chemical etching to produce wafer-thick polysilicon layers that serve as substrates for the SiCOI structures. Because wafer bonding is not used, insulators of various material types and thickness can be used. Using this method, transfer percentages over 99% are readily achievable. Various applications could benefit from this technology, including high temperature SiC-based microelectromechanical systems (MEMS) and SiC electronic devices. INTRODUCTION Silicon carbide (SiC) is well known as a wide-band-gap semiconductor with outstanding physical and chemical properties. Compared to silicon (Si), SiC exhibits a larger bandgap, a higher breakdown voltage, a higher thermal conductivity and higher saturation velocity. SiC is also considered to be leading candidate for high temperature microsensor and micro actuator systems, since the 3C-SiC polytype can be epitaxially grown on Si substrates and polycrystalline 3C-SiC (poly-SiC) films can be deposited on SiO 2 and polycrystalline silicon (polysilicon) sacrificial substrate layers [1]. 3C-SiC growth on (100) Si substrates enables the fabrication of bulk micromachined 3C-SiC structures, such as membranes and cantilevers, by selective removal of the Si substrate in various anisotropic etchants. Poly-SiC, when used in conjunction with SiO 2 and polysilicon, enables the fabrication of surface micromachined devices such as electrostatically driven lateral resonant structures and micromotors. Such devices are difficult to fabricate in single crystalline 3C-SiC films since although the Si substrate could be used as a sacrificial layer, it is not sufficiently insulating to support electrostatic actuation. Silicon-on-insulator (SOI) substrates have great potential to enhance the performance of Si microelectronics, especially in the areas of power consumption, operating frequency, and operating temperature due to a significant reduction in leakage currents. Electronic devices fabricated from 3C-SiC films grown on SOI substrates should also have much lower leakage currents, a significant problem that has limited the use of 3C-SiC as an electronic material. Such a substrate would also facilitate the fabrication 3C-SiC MEMS devices, such as the electrostatically actuated devices described previously. Currently, there are four methods that have been used to produce SiCOI substrates. The most direct method is epitaxial growth of 3C-SiC on various commercially available SOI wafers. These substrates include silicon-on-sapphire (SOS) [2], SIMOX [3], and UNIBOND(SmartCut) [4]. The second method combines 3C-SiC growth with Si
Data Loading...
