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Abstract

Surface micromachined structures having a relatively thick silicon nitride layer and a relatively thin conductive polysilicon layer bonded together. Preferably, the silicon nitride layer and conductive polysilicon layer are made in the same low pressure chemical vapor deposition (LPCVD) step. The polysilicon layer is thin enough compared to the silicon nitride layer so that the mechanical properties of the microstructure are primarily determined by the silicon nitride layer. This provides superior mechanical properties for many applications. The thin conductive polysilicon layer provides conductivity for the microstructure (silicon nitride is an electrical insulator). The polysilicon layer has a thickness less than 1/5 the thickness of the silicon nitride layer. Preferably, the polysilicon layer is much thinner than this. The polysilicon layer can be located on a top surface or bottom surface of the silicon nitride layer. Also, the polysilicon layer can be located within the silicon nitride layer. Alternatively, the polysilicon layer covers the sidewalls of the silicon nitride layer, or completely encloses the silicon nitride layer.

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First Claim