Mechanical and optical properties of surface micromachined torsional mirrors in silicon, polysilicon and aluminum

This paper presents a comparative study of surface micromachined structures fabricated in three different materials, using torsional micromirrors as test vehicle. The devices are realized in single-crystal silicon, polycrystalline silicon and aluminum. Mechanical properties such as internal strains, sticking phenomena, yield strains and endurance test resistance as well as optical properties such as surface reflectivities and scattering characteristics are investigated on the devices. the characterization points out that the silicon and polysilicon structures present higher yield strains and are less prone to surface sticking while the aluminum mirrors have higher surface refiectivities.

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