High-aspect-ratio, molded microstructures with electrical isolation and embedded interconnects

A thin film molding process was developed to enable the fabrication of monolithic micromechanical structures with built-in electrical isolation and embedded interconnects. High-aspect-ratio composite structures were created from undoped polysilicon, low stress nitride and doped polysilicon, in a dual micromolding process. These monolithic electro-mechanical microstructures are more resistant to thermal effects and misalignment errors compared to microsystems assembled from discrete elements. In addition, the microstructures are molded in a re-usable mold providing an economical advantage. A gimballed electrostatic microactuator was successfully fabricated using this process. Electrical isolation was achieved with a combination of low stress nitride and undoped polycrystalline silicon. Various isolation geometries were investigated. Current leakages of less than 1 nA at 30 V were measured for isolation structures 40 mum long and 80 mum tall.