A wafer-integrated array of micromachined electrostatically-driven ultrasonic resonators for microfluidic applications

A distributed micromachined ultrasound source is presented. Electrostatic actuators operating at frequencies exceeding 100 kHz are coupled to a Helmholtz resonator in order to achieve high output velocities. They consist of a 1200 μm×1200 μm×1.36 μm composite diaphragm, a perforated P++ backplate and a 3 μm air gap. The actuators cover the entire surface of a 4" wafer and are grouped in four individually addressable quadrants. A robust micromachining technology with >80% yield, employing anodic glass-silicon bonding, dissolved wafer process and advanced deep silicon etching has been developed for fabrication of the actuator array. The dynamic behavior of the diaphragm was studied using laser interferometry, and operation was verified at 96 kHz by acoustic measurement