Liquid Delivery MOCVD of Ferroelectric PZT

Abstract

ABSTRACTFerroelectric PbZrxTi1-x O3 (PZT) films have been deposited by chemical vapor deposition using flash vaporized metalorganic precursors. Crystalline perovskite films approximately 3000Å thick were deposited on Pt/Si substrates at 550–590°C and had dielectric coefficients in the range of 600–1900. Dielectric constant was found to increase with increasing Zr/Ti ratio, rising to the largest values near the morphotropic phase boundary. Remanent polarizations of the PZT were between 20–27 μC/cm2 and the coercive field decreased with increasing Zr/Ti ratio from 43 to 21 kV/cm. Pyroelectric coefficients were measured using the Byer-Roundy technique and ranged from 20–30 nC/cm2K. At 550°C, a direct relationship was observed between precursor composition and film composition. At 590°C, volatility of PbO became appreciable and composition of films with Zr/(Zr+Ti) = 0.3 remained near stoichiometry over a wide range of excess Pb in the precursor. However, this effect was found to diminish for higher ratios of Zr/Ti. The orientation of the PZT films deposited over a range of precursor compositions was similar with some [100] preferred orientation. In contrast, the orientation of a PbTiO3 films could be manipulated by the Pb/Ti ratio in the precursor, with [111] preferred orientations predominating at lower Pb/Ti and [ 100/001]–[111] mixed orientations at higher Pb/Ti ratios.