Thermal effects in PZT: diffusion of titanium and recrystallization of platinum

This paper shows temperature dependent hillocks and cracks on the piezoelectric thin film lead-zirconate-titanate (PZT). The PZT thin film is deposited on Pt/Ti/SiO2/Si substrate by metal organic decomposition (MOD) where platinum is a bottom electrode and titanium is an adhesive layer. Experimental results demonstrate that if the annealing temperature exceeds 700 deg. C, titanium diffuses into the platinum layer, and platinum recrystallizes. In addition, partially volatilizable solution in PZT evaporates and thus, causes volume change and residual stresses. Hillocks and cracks in PZT are primarily caused by the above-mentioned thermal effects and make the top electrode and the bottom electrode electrically short. Two methods are applied to improve the thermal effects of platinum and titanium. PZT thin film with perovskite structure is well characterized by X-ray diffractometer (XRD) and a hysteresis loop. The remnant polarization is 20.448 μC/cm2, and the coercive field is 183.299 V/cm. The resonant and anti-resonant frequencies are 14.95 and 20.2 kHz, respectively. The piezoelectric constants, d31 and d33, and the electromechanical coupling coefficient are 159.57 pC/N, -72.86 pC/N, and 0.672, respectively