Gas flow sputtered thick layers of columnar lead zirconate titanate on silicon wafers for high frequency ultrasound transducers

The piezoelectric ceramic PZT, lead zirconate titanate, is the most spread material to generate ultrasound in medical and technical applications. Thereby frequencies between 30 MHz and 100 MHz require ceramic thicknesses between 50 mm and 20 mm. The presented gas flow sputtering process permits to deposit PZT of this thickness with a sputtering rate of 100 nm/min at temperatures between 520 °C and 550 °C. The PZT shows a typical columnar structure with a piezoelectric coefficient d33f of about 500 pm/V. An example for the fabrication ultrasound arrays with this sputtering process and lithographic structuring is given.