Abstract: Stiffened surface micromachined structures and a method to fabricate the same. A silicon substrate (10) is first etched to produce a mold containing a plurality of trenches or grooves (14) in a lattice configuration. Sacrificial oxide (15) is then grown on the silicon substrate (10) and then a stiffening member (16) (silicon nitride) is deposited over the surface of the substrate, thereby backfilling the grooves with silicon nitride. The silicon nitride is patterned to form mechanical members and metal (40) is then deposited and patterned to form the leads and capacitors for electrostatic actuation of mechanical members. The underlying silicon and sacrificial oxides are removed by etching the mold from underneath the fabricated micromachined devices, leaving free-standing silicon nitride devices with vertical ribs. The devices exhibit increased out-of-plan bending stiffness because of the presence of stiffening ribs. Silicon nitride biaxial pointing mirrors with stiffening ribs are also described.

Abstract: Stiffened surface micromachined structures and a method to fabricate the same. A silicon substrate (10) is first etched to produce a mold containing a plurality of trenches or grooves (14) in a lattice configuration. Sacrificial oxide (15) is then grown on the silicon substrate (10) and then a stiffening member (16) (silicon nitride) is deposited over the surface of the substrate, thereby backfilling the grooves with silicon nitride. The silicon nitride is patterned to form mechanical members and metal (40) is then deposited and patterned to form the leads and capacitors for electrostatic actuation of mechanical members. The underlying silicon and sacrificial oxides are removed by etching the mold from underneath the fabricated micromachined devices, leaving free-standing silicon nitride devices with vertical ribs. The devices exhibit increased out-of-plan bending stiffness because of the presence of stiffening ribs. Silicon nitride biaxial pointing mirrors with stiffening ribs are also described.