AIR-BRIDGES, AIR-RAMPS, PLANARIZATION, AND ENCAPSULATION USING PYROLYTIC PHOTORESIST IN THE FABRICATION OF 3-DIMENSIONAL MICROSTRUCTURES

Pyrolyzation of photolithographically patterned photoresist on semicon ductor substrates such as silicon, gallium arsenide, and indium phosph ide, results in a convex-shaped, chemically inert, temporary form that functions as a mold upon which to lift-off evaporated thin films such as metals. The pyrolyzation process is simply a bake on a standard la boratory hot-plate that is ramped from room temperature to 300 degrees C air. The pyrolytic-photoresist form is subsequently removed in an o xygen plasma stripper leaving behind the three-dimensional lifted off thin films of free-standing, convex-shaped, full-arch air-bridges or h alf-arch air-bridges that we call air-ramps. Some applications are int erconnects for high-speed devices; inter-level interconnects; out-of-p lane coils for out-of-plane inductors; microdomes for eletromagnetic s hielding; electrodes for field-emitter tips; and microelectromechanica l structures. Pyrolyzing photoresist does not alter the good planariza tion capabilities of photoresist. Because pyrolytic photoresist is a v ersion of the earliest form of synthetic thermoset resin called Bakeli te, it can also be used as a reasonably good encapsulation material. ( C) 1997 American Vacuum Society.