Laser micromachined high frequency ultrasonic arrays

Piezoelectric ceramics have been patterned by means of laser micromachining to create ultrasonic arrays resonating in the frequency range of 35-45 MHz. The Lumonics PM-844 excimer laser with a KrF gas mixture (248 nm) has been used to micromachine trenches with a width to depth aspect ratio of up to 1:5. By using a projection etch approach, the large aperture of the excimer laser is used to simultaneously ablate the features of a complex geometrical pattern. Pre-poled ceramic structures >20 μm wide and >35 μm thick have been cut and validated with SEM images. The dielectric, piezoelectric and acoustic properties have been evaluated using an impedance analyser and pulse-echo techniques