Abstract
Realizing an optically flat and lightweight high-speed scanning micromirror
still remains as a challenging problem. In this paper, we propose a drum-type
lightweight micromirror that is capable of providing high scanning speed and
retaining optical flatness, simultaneously. The fabrication technique and
surface deformation analysis of the proposed micromirror are described. The
drum-type design is realized using a stretched polycrystalline (poly-) Si
membrane across a rigid crystalline (c-) Si ring. The tensile stress in the
poly-Si membrane is 300–400 MPa that keeps the membrane flat. At the
static condition, the total peak-to-valley surface heights in the center poly-Si
membrane of the designed five distinct shapes of micromirrors are varied from
16 to 29 nm. The stress concentration at mirror edge is investigated by the
amount of surface distortion which is less than 40 nm (i.e., one-tenth wavelength
of the blue light). The maximum total peak-to-valley surface height is about
50 nm and the dominant profile is at the connecting part between the c-Si
ring and the poly-Si membrane. The amount of dynamic deformation in the poly-Si
membrane is less than 40 nm. This satisfies the optical flatness compared
to the wavelength of blue light.
© 2012 IEEE
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