Chemical solution deposition of PZT thin films for microelectronics

Abstract

Research into chemical solution deposition (CSD) methods for ferroelectric thin films is oriented towards higher reliability and lower processing temperatures. In this paper several aspects of CSD PZT thin films related to processing are discussed. The reliability of PZT thin films is related to their chemical homogeneity, which is connected to the chemical homogeneity of the precursor solution. In our investigation we identified the problems of the chemical heterogeneity of PZT thin-film precursors caused by the high reactivity of Zr-alkoxide. By selective modification of the Zr starting compound with acetic acid, the overall chemical homogeneity of the films was increased, which resulted in a higher P r, a lower E c, a higher permittivity and lower losses in the films. By careful control of solution chemistry and annealing conditions, Ti-rich PZT and PLZT films were successfully processed at temperatures as low as 400°C. The crystallization of these films is characterized by rapid nucleation and rapid growth. In contrast, the Zr-rich PZT and PLZT compositions require a lead titanate (PT) seeding layer for further crystallization at a temperature of 400°C. The growth of the perovskite phase is diffusion controlled and, as a consequence, slow.