Mechanism of TiN barrier-metal oxidation in a ferroelectric random access memory

In the stacked structure of PbZr1-xTixO3 (PZT)/Pt/TiN/poly- Si, utilised for ferroelectric random access memory (RAM) application, the mechanism of TiN barrier-metal oxidation was investigated by TEM. In the cross-sectional TEM images of PZT/Pt/TiN/Si, titanium oxide was observed beneath the Pt grain boundary. The oxygen was diffused through the Pt grain boundary during the heat treatment in an oxygen atmosphere for crystallisation of PZT films. The annealing of the TiN film in ammonia resulted in the suppression of the oxidation during the crystallisation annealing of PZT. The minimum required Pt film thickness to protect TiN from oxidation can be reduced from 200 nm to 100 nm. 11 refs.