Enhancing out-of-plane stroke in piezoelectrically driven micro-lens actuator with residual stress control

Publication date: Available online 16 October 2019Source: Sensors and Actuators A: PhysicalAuthor(s): Ssu-Han Chen, Aron Michael, Chee Yee KwokAbstractThis paper presents the fabrication and characterization of a high performance piezoelectrically driven micro-lens actuator. The fabrication method involves controlling the residual stresses in the structure to predefine the initial deflection of the actuator, resulting in a larger actuation stroke. The residual stress control exploits the unique properties of ultra-high vacuum e-beam evaporated film to form thick tensile polysilicon as the actuator structural layer. This is complemented by a compressive RF-sputtered SiO2 layer on top of the structural layer. Such films are subsequently annealed during various fabrication stages to obtain the designated stress values for compensating the residual moments generated from the electrode and piezoelectric layers of the actuator. Two micro-lens actuators of the same design but with different residual stress levels in the structural layers are fabricated and compared, where one device has an initial deflection close to −47 μm and another −98 μm. The device with a larger downward initial deflection shows 57.2% higher actuation sensitivity than the other device. The actuators exhibit a large out-of-plane stroke of 145 μm and 228 μm, respectively, and at 22 V with a resonant frequency close to 2 kHz.Graphical abstract

Source: Sensors and Actuators A: Physical - October 17, 2019 Category: Physics Source Type: research