Silicon-carbide microfabrication by silicon lost molding for glass-press molds

This paper describes two silicon carbide (SiC) microfabrication processes for SiC glass-press molds. One is silicon lost molding combined with SiC chemical-vapor deposition (CVD) and SiC reaction sintering (RS). The other is silicon lost molding combined with SiC CVD and SiC solid-state reaction bonding (SSRB). In both of these processes, an original pattern on a silicon substrate is transferred to a CVD SiC film, and then the film is backed by bulk SiC to obtain rigidity and robustness against pressing force. Finally, the silicon substrate is etched away to release a SiC mold. In the process using SiC CVD and RS, an original pattern on a silicon substrate was transferred to a SiC mold, but the surface roughness of the SiC mold was 0.05-0.08 mum Ra, and worse than required by the glass-press mold. This was caused by the transformation of amorphous SiC to polycrystalline SiC in RS, which was confirmed by the X-ray diffraction (XRD) data of the CVD SiC film before and after RS. In the process using SiC CVD and SSRB, the surface of the SiC mold was smooth (0.004-0.008 mum Ra) without the crystallization of the amorphous CVD SiC film. The SiC mold was pressed to Pyrex glass to demonstrate its high-temperature strength. The Pyrex glass was deformed by the SiC mold at 850 degC without a void, and no significant deformation of the SiC mold was observed