(5x) Growth and Characterization of Sic Films for Mems and Nems Applications

Silicon carbide has properties such as high melting point, large bandgap, chemical resistance, high fracture toughness, and high elastic modulus which make it an attractive material for harsh environment micro- and nanoelectromechanical systems applications (MEMS and NEMS). Silicon carbide is also sought after as a MEMS anti-stiction and wear-reducing coating. A method to deposit SiC thin films on silicon wafers with a single source precursor, 1,3-dislabutane, in a low pressure chemical vapor deposition (LPCVD) reactor has been developed. This method has been scaled-up to realize deposition on 4- and 6-inch wafers, which are compatible with micro- and nanomachining facilities. Amorphous SiC is attained at temperatures of 750°C and below, while polycrystalline films are attained at temperatures of 800°C and above. Uniform films with low surface roughness have been achieved using a closed boat configuration. Films deposited have highly tensile residual stresses (>1.3 GPa), limiting the application of these films to chemically resistant and wear resistant coatings. Using dichlorosilane (DCS) as an additional precursor allows control of residual stress and strain gradient of the polycrystalline SiC. Residual stress, strain, strain gradient, and stoichiometry are characterized in order to better understand the mechanism behind stress control. Stress varies from 240 MPa tensile to 1.2 GPa tensile. The lowest magnitude strain gradient realized is 3.1x10^-5 μm^-1. The biaxial modulus is calculated to be in excess of 1.0 TPa for films with small enough strain gradients to permit the necessary measurements. Such film properties make these SiC films suitable for structural layers in MEMS and NEMS devices.