Deposition Behavior of Pb(ZrxTi1-x)O3 Thin Films by Metaorganic Chemical Vapor Deposition

Abstract

Polycrystalline Pb(ZrxTi1-x)O3 (PZT) thin films with a well-developed perovskite structure have been prepared on p-type (100) Si wafers by the metalorganic chemical vapor deposition process. Bisdipivalomethanato lead {Pb(DPM)2}, zirconium tetra-t-butoxide {Zr(O-t-C4H9)4}, titanium tetra-i-propoxide {Ti(O-i-C3H7)4}, and oxygen were used as source materials. The film composition could be controlled easily by simply adjusting each source temperature and the carrier gas-flow rates. A perovskite PZT phase was obtained at substrate temperatures above 550-degrees-C. Scanning electron micrographs showed dense and noncolumnar growth with good surface morphologies. We investigated the effect of each element on the sticking of other elements, and the structural changes of the PZT thin films with composition variation. At the initial stage of deposition, the sticking of Pb was strongly restricted by Zr, therefore, the films were lead deficient and the pyrochlore phase was formed. With increasing Zr/Ti ratio, the structure of PZT thin films transformed from the tetragonal phase, and tetragonal and rhombohedral mixed phase, to the rhombohedral phase. The oxygen partial pressure also played an important role in the formation of perovskite PZT. With increasing oxygen partial pressure, the sticking of Pb was promoted so the perovskite PZT phase was easily formed. For the formation of perovskite PZT thin films, the most important step was the sticking of the Pb-containing radical.