Thermally actuated optical microscanner with large angle and low consumption
A monolithic silicon integrated optical micro-scanner is presented. The device consists of a mirror located on the tip of a thermal bimorph actuator beam. The fabrication process is very simple and compatible with IC fabrication techniques. The device is excited electrothermally at its resonance frequency, enabling large angular deflections at low power consumption. The technological process consists of basic frontside silicon micromachining steps requiring only three mask levels. The moving part is defined by selective silicon bulk etching. The bimorph beam is made of silicon dioxide and a thin film conductor. The residual stress in the two layers is used to achieve a 45 degrees out-of-plane rest position of the mirror. This allows optical components (e.g., laser diode, collimating lens) to be placed directly on the silicon substrate. Mirrors of 500 x 300 to 800 x 800 mu m(2) with resonant frequencies varying from 600 to 100 Hz were realized. Mechanical scan angles of above 90 degrees were achieved. The devices are very robust and have run through fatigue tests of billions of cycles at 300 Hz and 90 degrees deflection. The power consumption of the device is typically 1 mW for 30 degrees mirror deflection. (C) 1999 Elsevier Science S.A. All rights reserved.