US Patent 7960290 Method of fabricating a semiconductor device

A method for fabricating a semiconductor device. A preferred embodiment comprises forming a via in a semiconductor substrate, filling the via with a disposable material such as amorphous carbon, forming a dielectric layer on the substrate covering the via, performing a back side etch to expose the disposable material in the via. A back side dielectric layer is then depositing, covering the exposed via. A small opening is then formed, and the disposable material is removed, for example by an isotropic etch process. The via may now be filled with a metal and used as a conductor or a dielectric material. The via may also be left unfilled to be used as an air gap.