MECHANISM OF TIN BARRIER-METAL OXIDATION IN A FERROELECTRIC RANDOM-ACCESS MEMORY

In the stacked structure of PbZr1-xTixO3(PZT)/Pt/TiN/poly-Si for a fer roelectric random access memory (RAM), the mechanism of TiN barrier-me tal oxidation was investigated by transmission electron microscopy (TE M). In the cross-sectional TEM images of PZT/Pt/TiN/Si, titanium oxide was observed beneath the Pt grain boundary. The oxygen was diffused t hrough the Pt grain boundary during the heat treatment in an oxygen at mosphere for crystallization of PZT films. The annealing of the TiN fi lm in ammonia resulted in the suppression of the oxidation during the crystallization annealing of PZT. The minimum required Pt film thickne ss to protect TiN from oxidation can be reduced from 200 nm to 100 nm.