AlScN based MEMS quasi-static mirror matrix with large tilting angle and high linearity

Abstract

This paper presents a piezoelectrically (AlScN) driven 3 × 3 quasi-static mirror matrix, where each MEMS mirror utilizes a three-level-construction comprising a mirror plate (diameter = 0.8 mm), a pillar and four AlScN actuators hidden beneath the mirror plate, reducing the chip size to 1.1 × 1.3 mm2. AlScN as a high performance piezoelectric material is used to deliver large force enabling a mechanical tilting angle of ±14° at 150 VDC, in addition to great linearity, repeatability and long-term stability. For realizing the 3D construction three wafers for mirror plate, actuators and a TSV wafer for the vertical electrical contacts are applied. While first demonstrators have been manufactured by a chip-level hybrid assembly to mount the mirror plates onto the actuators, a BEOL triple-wafer-bonding process has been developed to integrate the mirror plates onto the actuators and TSV wafer. This paper will show the design and process efforts for improving the mechanical behavior of the MEMS mirrors, the process effort and current result of triple-wafer-bonding. It concludes by discussing the technological achievements, challenges and outlook for improved performance due to the material development of AlScN.