2D Scanning Micromirror with Large Scan Angle and Monolithically Integrated Angle Sensors Based on Piezoelectric Thin Film Aluminum Nitride

Abstract

A 2D scanning micromirror with piezoelectric thin film aluminum nitride (AlN), separately used as actuator and sensor material, is presented. For endoscopic applications, such as fluorescence microscopy, the devices have a mirror plate diameter of 0.7 mm with a 4 mm2 chip footprint. After an initial design optimization procedure, two micromirror designs were realized. Different spring parameters for x- and y-tilt were chosen to generate spiral (Design 1) or Lissajous (Design 2) scan patterns. An additional layout, with integrated tilt angle sensors, was introduced (Design 1-S) to enable a closed-loop control. The micromirror devices were monolithically fabricated in 150 mm silicon-on-insulator (SOI) technology. Si (111) was used as the device silicon layer to support a high C-axis oriented growth of AlN. The fabricated micromirror devices were characterized in terms of their scanning and sensor characteristics in air. A scan angle of 91.2° was reached for Design 1 at 13 834 Hz and 50 V. For Design 2 a scan angle of 92.4° at 12 060 Hz, and 123.9° at 13 145 Hz, was reached at 50 V for the x- and y-axis, respectively. The desired 2D scan patterns were successfully generated. A sensor angle sensitivity of 1.9 pC/° was achieved.