Ti and TiO x seeding influence on the orientation and ferroelectric properties of sputtered PZT thin films

Abstract

The integration of PZT thin films in MEMS requires a thorough control of nucleation and growth of the Metal/Ferroelectric/Metal multilayer. In this paper, the Ti seeding technology has been used to optimise the nucleation of Pb(Zr 0.52, Ti 0.48)O 3 thin films (PZT) on a stabilized Pt/TiO x /Si bottom electrode. TiO x (20 nm) and Pt (100 nm) films have been deposited on Si substrates by reactive sputtering in Ar+O 2 (90/10) and in pure Ar, respectively. The bottom electrode crystallisation rapid thermal annealing (RTA, 400 °C, 30 s) has been performed in N 2 or (N 2+O 2) atmospheres. A few nanometers thick Ti or TiO x seeding layer has been sputtered in Ar or Ar+O 2. Finally, 0.25 μm thick PZT films have been sputtered in pure Ar plasma and crystallised by RTA (700 °C, 30 s, in air). The PZT XRD measurements have shown the highest (1 1 1) orientation for the samples prepared with the Ti seeding layer deposited on the bottom electrode. Moreover, best ferroelectrics values have been measured for the sample with the air annealed bottom electrode and the Ti seeding layer ( P r=13.8 μC cm −2, E c=153 kV cm −1). These values have been recorded on 400 and 450 μm side length square top electrodes dispatched on a 1.5 cm 2 area. We have found a yield up to 80% with a 450 μm×450 μm top electrode surface. The comparison of these results with PZT/Pt/Ti basic structures point out the influence of the Ti seeding ultra-thin layer and the bottom electrode annealing conditions on the PZT crystallization in the perovskite phase.