Drift-Free Micromirror Arrays Made of Monocrystalline Silicon for Adaptive Optics Applications

In this paper, we report on the heterogeneous integration of monocrystalline silicon membranes for the fabrication of large segmented micromirror arrays for adaptive optics applications. The design relies on a one-level architecture with mirrors and suspension formed within the same material, employing a large actuator gap height of up to 5.1 μm to allow for a piston-type mirror deflection of up to 1600 nm. Choosing monocrystalline silicon as actuator and mirror material, we demonstrate a completely drift-free operation capability. Furthermore, we investigate stress effects that degrade the mirror topography, and we show that the stress originates from the donor silicon-on-insulator wafer. The novel heterogeneous integration strategy used in this work is capable of reducing this stress to a large extent.