Manufacturing miniature Si-based ceramic rotors by micro reaction sintering

Si-based high-temperature ceramics are attractive materials for power microelectromechanical systems (MEMS), such as microscale gas turbines, micro-combustors and micro-reactors. We have developed two novel microfabrication processes for manufacturing miniaturized components of silicon carbide (SiC) and silicon nitride (Si3N4) ceramics. SiC microrotors were successfully fabricated by conducting hot-isostatically pressurized SiC reaction sintering within micromachined silicon molds prepared by photolithography and reactive ion etching, and Si3N4 microrotors were more easily fabricated by directly nitridating porous Si microrotors which were prepared by micromilling pre-sintered silicon powder compacts. The present study shows that Si3N4 reaction sintering is more suitable for the fabrication of miniature Si3N4 components, because the pre-sintered porous silicon polycrystals are mechanically machinable and the following reaction sintering assures the dimensional accuracy by the near-net-shaping characteristic.