Bi-stable planar polysilicon microactuators with shallow arch-shaped leaf springs

摘要

Bi-stable microactuators are necessary to implement optical switch and microrelay with low power and high reliability. In this work, we analyzed the buckling and vibration characteristics of a planar microactuators with shallow arch-shaped leaf springs. To investigate elastic stability of the proposed microactuator, we derived static buckling modes. A concentrated force of 0.35μN at the center of beam was required for the snap-through motion for the beam length of 1600μm, thickness of 3μm, beam width of 6.5μmm and initial rise of 15μm considering only the 1{sup}st buckling mode. We also analyzed vibration characteristics of arch-shaped leaf spring. The resonant frequencies of the 1{sup}st modes across over the 2{sup}nd mode and keeps constant resonant frequencies over the cross point On the contrary, the resonant frequencies of 2{sup}nd modes become almost constant regardless of initial rise. The planar microactuator with shallow arch-shaped leaf springs at both sides were fabricated using silicon micromachining technology. The vertical structure of the planar microactuator features simplicity and consists of p-doped polysilicon as a structural layer and LTO (Low Temperature Oxide) as a sacrificial layer. The polysilicon was annealed for the relaxation of residual stress and HF GPE (gas-phase etching) process was finally employed in order to release the microactuators. These bi-stable planar microactuators with shallow arch-shaped leaf springs showed a high stiffness against external disturbance, and would be very useful for the stable operation of micro optical switch and microrelay.