The current material of choice for microelectromechanical (MEMS) devices is silicon. This derives primarily from the fact that methodologies for micromachining silicon are mature and well established. Silicon is not, however, suited for all applications. For example, it is susceptible to oxidation and creep above 900°C and, therefore, of limited use in high-temperature devices such as microengines. NWhile ceramics, such as SiC and Al2O3 would appear to be ideal for high-temperature mechanical applications, reliable techniques for ceramic microfabrication do not exist.
The goal of this project is to establish methods for chemically micromachining oxide ceramics, with a current focus on magnesia (MgO) and sapphire (Al2O3). One particular Interest is identifying surface orientations that etch in an anisotropic manner. The MgO(1 10) surface appears to be particularly promising as it can be etched rapidly (~75 min/ min) with acids and, under some conditions, wall angles approaching 85° have been attained. A significant challenge in this work has been identifying photoresist materials compatible with the oxide surfaces, which are significantly more basic than SiO2. Another area of interest is the development of substrate joining process that will allow for the fabrication of multi layer oxide structures and the integration of oxide layers into silicon MEMS devices.