Sputtered silicon for microstructures and microcavities

This invention relates generally to fabrication of silicon micro mechanical structures. More particularly, it relates to released microstructures made of sputtered silicon that are compatible with pre-fabricated on-chip aluminum circuitry. A sputtered silicon layer and a low temperature fabrication method thereof, is introduced. The sputtered silicon layer is sputtered with predetermined sputtering criteria resulting in a predetermined pre-annealing configuration. The sputtering criteria include sputtering power, ambient sputtering pressure, choice of sacrificial layer and etchant. The initially sputtered layer is transformed during a low temperature annealing process into a post-annealing state. A released structure is micro-machined from the sputtered layer in its post-annealed state. The low temperature annealing leaves pre-fabricated integrated aluminum-metalized circuitry unaffected. Optional conductive sputtered co-layers reduce resistivity and may be used to further tune strain and strain gradient.