A Fast, Large-Stroke Electrothermal MEMS Mirror Based on Cu/W Bimorph

• Main Authors: Xiaoyang Zhang, Liang Zhou, Huikai Xie
• Format: Article
• Language: English
• Published: MDPI AG 2015-12-01
• Series: Micromachines
• Subjects: microelectromechanical systems (MEMS) mirror; electrothermal actuation; Cu/W bimorph; lateral-shift-free (LSF); vertical scan; multimorph frame; large range; fast response; backside release
• Online Access: http://www.mdpi.com/2072-666X/6/12/1460

This paper reports a large-range electrothermal bimorph microelectromechanical systems (MEMS) mirror with fast thermal response. The actuator of the MEMS mirror is made of three segments of Cu/W bimorphs for lateral shift cancelation and two segments of multimorph beams for obtaining large vertical displacement from the angular motion of the bimorphs. The W layer is also used as the embedded heater. The silicon underneath the entire actuator is completely removed using a unique backside deep-reactive-ion-etching DRIE release process, leading to improved thermal response speed and front-side mirror surface protection. This MEMS mirror can perform both piston and tip-tilt motion. The mirror generates large pure vertical displacement up to 320 μm at only 3 V with a power consumption of 56 mW for each actuator. The maximum optical scan angle achieved is ±18° at 3 V. The measured thermal response time is 15.4 ms and the mechanical resonances of piston and tip-tilt modes are 550 Hz and 832 Hz, respectively.