Deposition of self-polarized PZT films by planar multi-target sputtering

Abstract

A planar multi target sputtering approach was used to deposit self polarized PZT films on TiO₂/Pt bottom electrodes for the use in thin film pyroelectric IR detector arrays. By using elevated substrate temperatures of about 450°C “in situ” growth of tetragonal PZT could be achieved. The films exhibited pyroelectric currents without poling. The pyroelectric coefficient was 2×10⁻⁴ C/m²K, the dielectric constant was 300 and dielectric loss tan δ was 0.01. The self polarization disappears after heating the sample to 600°C. Stresses were studied in the thin film processing for the bottom electrode and the PZT film. The TiO₂/Pt electrode is under high tensile stress of 900 MPa after preparation. PZT has a small compressive stress of -60 MPa, the whole TiO₂/Pt/PZT stack has a tensile stress of +80 MPa. This low stress level together with the self polarization and the good electrical properties makes the films suitable for the use in pyroelectric detector arrays.