Preparation of Ba(Pb1−xBix)O3 electrode thin films by rf magnetron sputtering

New electrode materials have been explored for Pb(Zr,Ti)O3 (PZT) thin films in ferroelectric random access memory (FeRAM) devices. Among them, Ba(Pb1−xBix)O3 (BPBO) is notable for its improved polarization and fatigue properties. Like PZT, the BPBO conductor contains lead (Pb) and oxygen (O). These structural similarities indicate that it has the same perovskite structure as PZT. BPBO thin films were prepared by rf magnetron sputtering, and the influence of growth conditions (sputtering gas, rf power, substrate temperature, Bi concentration and post-annealing) on crystallization and conductivity was investigated. A perovskite single phase was obtained above 400 °C at x=0, when post-annealing after sputtering was conducted without substrate heating. In the absence of post-annealing, the perovskite single phase was obtained by sputtering on SiO2/Si substrates heated to 350–500 °C. The crystallization temperature decreased with increasing Bi concentration (x), and Ba(Pb0.8Bi0.2)O3 films were prepared at 300 °C. Resistivity of the films also decreased with decreasing sputtering temperature and with increasing Bi concentration. Ferroelectric properties of PZT capacitors used for BPBO electrodes were also evaluated.