Two-dimensional microscanner actuated by PZT thin film

This paper introduces the fabrication and characterization of two-dimensional resonant microscanners actuated by sol-gel deposited PZT thin films. The piezoelectric PZT thin films with silicon micromachining technology provide the advantages of high scanning frequencies and low driving voltages. The actuation principle is based on the bimorph beam structure, which consists of an oxide layer and a piezoelectric PZT layer. The two-dimensional scanning performance can be achieved by applying AC voltages with phase shifts at resonance frequencies to the actuating beams. The devices were fabricated through thin film depositions, lithography, dry plasma etching and ICP releasing process. The fabrication processes were improved considerably. A STS ICP system was used instead of KOH or other wet-chemical etching processes to prevent the damages of front side devices whilst the sample was etched through. For a scanner structure with a 300×300 μm² mirror plate, the first four resonance frequencies were measured to be in the range of 10-30 kHz. To investigate the vibration modes, the deflections on different locations of the mirror plate were measured. The two-dimensional scanning angles were determined to be 8° at 16.2 kHz in one direction and 11° at 23.4 kHz in the perpendicular direction.