Oxygen diffusion in Pt bottom electrodes of ferroelectric capacitors

Oxygen diffusion through the grain boundaries of Pt films during the crystallization annealing of Pb(Zr, Ti)O-3 (PZT) was investigated for the stacked structure of PZT/Pt/TiN. If the Pt film was sputtered on the TIN film by an in-vacuum process, then columnar (111)-oriented grains were grown with continuous grain boundaries normal to the substrate. On the other hand, a Pt film deposited on a TiN film exposed to air after the TiN deposition consisted of granular grains with a random orientation, because the Pt film was grown on the native oxide surface of the TiN film. The degree of oxygen diffusion in the Pt film deposited on the exposed TiN Blm was lower than that on the nonexposed TiN film after the PZT was crystallized at 650 degrees C in O-2. Differences in the grain boundary structure, such as the diffusion length, are considered to determine the oxygen diffusion rate.