Orientation control in PZT/Pt/TiN multilayers with various Si and SiO2 underlayers for high performance ferroelectric memories

To suppress fluctuation in capacitor characteristics, highly oriented lead zirconate titanate (or PbZrxTi1-xO3 (PZT) films are required in ultralarge scale ferroelectric memories whose capacitor size is comparable to PZT grai n size. The (111) orientation, which is closely related to spontaneous pola rization, is achieved when PZT film is grown on highly (111) oriented plati num film. The degree of Pt(111) orientation is dependent on the crystallini ty of the underlying TiN barrier metal. Furthermore, the crystallinity of t he TiN is strongly dependent on the type of underlying material. The crysta llinity of the TIN film grown on amorphous Si is much better than the cryst allinity achieved on thermally oxidized Si. The surface energy difference b etween the TiN and underlayer may affect the growth mode of the TiN films. The crystallinity of the TiN film on rougher Si surfaces, such as in situ c rystallized poly-Si, is inferior to the crystallinity observed on amorphous Si. Therefore, a smooth Si buffer layer is required underneath the capacit or to improve performance of the PZT/Pt/TiN capacitor. The modified planari zed stacked structure presented in this article uses a postannealed crystal line Si as a buffer layer underneath the capacitor. (C) 2000 American Vacuu m Society. [S073P-211X(00)08501-2].