Scanning micromirrors fabricated by an SOI/SOI wafer-bonding process

MEMS scanning micromirrors have been proposed to steer a modulated laser beam in order to establish secure optical links between rapidly moving platforms. An SOI/SOI wafer-bonding process has been developed to fabricate scanning micromirrors using lateral actuation. The process is an extension of established SOI technology and can be used to fabricate stacked high-aspect-ratio structures with well-controlled thicknesses. Fabricated one-axis micromirrors scan up to 21.8° optically under a dc actuation voltage of 75.0 V, and have a resonant frequency of 3.6 kHz. Fabricated two-axis micromirrors scan up to 15.9° optically on the inner axis at 71.8 V and 13.2° on the outer axis at 71.2 V. The micromirrors are observed to be quite durable and resistant to shocks. Torsional beams with T-shaped cross sections are introduced to replace rectangular torsional beams in two-axis MEMS micromirrors, in order to reduce the cross-coupling between the two axial rotations. Fabricated bidirectional two-axis micromirrors scan up to ±7° on the outer-axis and from -3° to 7° on the inner-axis under dc actuation.