Thermal Chemical Vapor Deposition of Silicon Carbide Films as Protective Coatings for Microfluidic Structures
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THERMAL CHEMICAL VAPOR DEPOSITION OF SILICON CARBIDE FILMS AS PROTECTIVE COATINGS FOR MICROFLUIDIC STRUCTURES
Spyros Gallis, Ulrike Futschik, James Castracane, Alain E. Kaloyeros, and Harry Efstathiadis School of NanoSciences and NanoEngineering, The University at Albany-SUNY, Albany, NY 12203, Walter Sherwood and Susan Hayes Starfire Systems Inc, Watervliet, NY 12189, Costas G. Fountzoulas Army Research Laboratory, Weapons Material Directorate, Aberdeen Proving Ground, MD 21005.
ABSTRACT
Amorphous silicon carbide (SiC) films were deposited on silicon substrates by thermal chemical vapor deposition (TCVD) technique, at substrate temperatures ranging from 620 ºC 850 ºC. A novel, single-source halide free precursor, SP-4000, belonging to the family of polysilenemethylenes (PSM) (nominal structure [-SiH2-CH2-]n, n = 2-8 including branched and cyclic isomers) was used as source. Argon was used, as both the precursor carrier gas and the dilution gas. Other reactants, such as hydrogen or hydrocarbons, were not used. The deposition yielded films with Si/C ratio of 1 ± 0.2. The highest achieved growth rate was 83 nm/min. The modulus of elasticity and the nanohardness of the SiC films were measured with the aid of a nanoindenter at various depths, which did not exceed 25% of the film thickness. The average nanohardness at indentation depths of approximately 10% of the film thickness was measured up to 13 ± 4 GPa. The results of the nanoindentation will be discussed in conjunction with the microstructural analysis of the films. In addition, the development of a viable TCVD SiC process presents significant opportunities in the nano/micro systems field. In particular, the ability to custom tailor the surfaces of microfluidic structures allows for the development of valves, pumps and channels for use in corrosive or high temperature environments. Initial results from the deposition of SiC films on prototype microfluidic components will be presented.
INTRODUCTION
The use and application of micro-electro-mechanical systems (MEMS) has expanded significantly over the last several years. This technology has been used to fabricate valves, pumps, high temperature sensors, actuators, and motors. There is a need for mechanically and electrically robust materials to construct and coat such devices. Currently, silicon is the primary building material for MEMS applications, but the lifetime of silicon-based MEMS devices can be reduced by wear (e.g., by friction). To improve the microcomponent properties, different materials can be used as part of the device or as a coating for existing devices. SiC has recently
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been recognized as a potential material that can be used to enhance the mechanical and electrical properties of MEMS microcomponents. Its hardness and electrical behavior make it an ideal material for a variety of applications and such properties are likely to extend the lifetime of the device. With high hardness and high mechanical stability it has the capability to withstand friction and wear. Combined with i
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