A key step in the fabrication of free-standing micromechanical devices is often the removal of a sacrificial oxide layer with hydrofluoric acid. As a result, this powerful technique is limited to use on polysilicon and a few HF-resistant metals. The goal of this work is to demonstrate that microdevices can be fashioned from common metals such as aluminum by replacing the oxide layer with a thermally stable polymer. The P.I. recently developed a new family of polyimide materials which have all the requisite properties to serve as sacrificial layers. These include high glass transition temperature, good planarization, excellent thermal stability ( 400 C), good chemical and plasma resistance, and most importantly, rapid solubility in mild, noncorrosive media. In Phase I, the P.I. will use standard IC processing techniques to make simple, free-standing aluminum devices with the aid of these new polyimide materials. Phase II will extend these efforts to include other metals as well as the production of more sophisticated devices. During this same time, he will determine how polymer structure and processing conditions can be altered to improve film adhesion, thermal stability, thermal expansion properties, and wet etch rate.
