Lead zirconate titanate thin films for microwave device applications

The preparation of sol-gel derived thin films of the piezoelectric ceramic lead zirconate titanate (PZT) has been investigated on different substrate configurations for bulk acoustic wave device applications operating at microwave frequencies. Films having a composition of Pb(Zr _0.53Ti_0.47)O₃ have been prepared on platinised silicon (Pt-Si) and platinised gallium arsenide (Pt-GaAs) substrates using a 1,3-propanediol and a novel 1,1,1-tris(hydroxymethyl)ethane based sol-gel technique. Crystalline PZT films were produced on the Pt-GaAs by firing the sol-gel coating at 650°C for a dwell time of 1 second using rapid thermal processing techniques. A single deposition of the precursor sol resulted in films having a thickness of ~0.4 μm. Average values of remanent polarisation for the films were 29 and 24 μC/cm² on Pt-Si and Pt-GaAs, respectively. Microwave characterisation performed on PZT/Pt-Si based BAW resonator structures indicate a fundamental parallel resonance at 0.1 GHz, having an unloaded QF of 1×10¹¹ Hz