In a 3D free space micromirror device, a mirror plate is joined with
actuators through flexible springs where the other ends of the actuators
have fixed support on the substrate. Single crystal silicon and aluminum
are used as bi-morph materials with silicon dioxide providing electrical
isolation between the two. Thickness variation in the microstructure is
achieved by two-step p-n junction formed in a p-type substrate. Thick and
thin n-silicon layer formation and DRIE cut mechanisms are employed in
such a way that all the thick and thin silicon components of the
structure are released simultaneously avoiding overetch which can be
detrimental to the thin flexural springs. Working prototypes of the
device have been found suitable for any optical switching array
architecture where deflections up to 10 degrees are required.