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.