Silicon carbide microfabrication by silicon lost molding for glass press molds

Two novel silicon carbide (SiC) microfabrication processes for SiC glass-press molds were developed. One is silicon lost molding combined with SiC chemical vapor deposition (CVD) and SiC reaction-sintering (RS). A SiC film was deposited on a micromachined silicon mold, and backed with a SiC reaction-sintered body. The surface roughness of the SiC mold was 0.05-0.08 /spl mu/m Ra, and worse than required by the glass-press mold. This was caused by poly-crystal SiC growth during hot isotropic pressing (HIP), which was confirmed from X-ray diffraction (XRD) patterns of the CVD SiC film before/after HIP. The other is silicon lost molding combined with SiC-CVD and SiC solid-state reaction bonding (SSRB). A SiC film deposited on the micromachined silicon mold was bonded with a SiC ceramic substrate using a Ni interface layer. The surface of the SiC mold was very smooth (0.004-0.008 /spl mu/m Ra) without poly-crystallization of the CVD SiC film. The SiC mold was pressed to a glass to confirm its high-temperature strength. The Pyrex glass was shaped by the SiC mold without a void, and no damage to the SiC mold was observed.