Electrostatically deflectable polysilicon torsional mirrors

• Published in: Sensors and actuators. A. Physical. 1994-07, Vol.44 (1), p.83-89
• Main Authors: Fischer, M., Graef, H., von Münch, W.
• Format: Article
• Language: English
• Subjects: Exact sciences and technology; Fundamental areas of phenomenology (including applications); Lenses, prisms and mirrors; Optical elements, devices, and systems; Optics; Physics
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/0924-4247(94)00785-3

This paper describes the fabrication of electrostatically deflectable structures using surface micromachining with chemical vapour deposition (CVD) polysilicon. Particular attention has been paid to the realization of torsional mirrors. Free-standing structures with a thickness of 1 μm are produced by lateral etching of a 2 μm sacrificial silicon dioxide layer deposited between the substrate and the CVD polysilicon layer. In order to avoid sticking of completely under-etched structures to the substrate, the polysilicon microstructures are fixed by a frozen solvent after etching of the sacrificial layer and rinsing; subsequently a sublimation process under vacuum is applied. The torsional mirrors are deflectable with voltages of about 20 V. The maximum deflection is approximately 2°. Several mirrors with different dimensions have been made. For comparing and optimizing their mechanical properties and behaviour during deformation, mirror designs are modelled using the finite-element program ANSYS.