Effect of annealing and hydrogen on properties of electrodeposited platinum electrode and lead-zirconate-titanate films for ferroelectric random access memory applications

The selection of capacitor electrode materials for the nonvolatile ferroelectric random access memory is one of the most important issues because capacitor electrical characteristics are strongly influenced by the electrode materials. The lower Pt electrode was electrodeposited on the Ti seed/Pt seed layer. Two different thicknesses of Ti seed layer (5 and 15 nm) were adopted, and lead-zirconate-titanate (PZT) was deposited on the electrodeposited Pt. The Pt crystal orientation with a 5 nm Ti seed layer is much better than that with a 15 nm Ti seed layer, and the deposited PZT shows much better crystal orientation. Due to better crystal orientation of the PZT layer in the case of a 5 nm Ti seed layer, a Pt/PZT/Pt capacitor well-saturated D-V hysteresis loop was obtained whereas little current was observed in the large electric field. With the 15 nm Ti seed layer, numerous several-mu m-sized voids formed on the lower Pt electrode surface. With the 5 nm Ti seed layer, fewer voids formed on the lower Pt electrode surface. Glow discharge spectrometry measurement with a 15 nm Ti seed layer shows much higher H intensity than that with a 5 nm Ti seed layer, and the H peak coincides with the Ti peak. The H existing in the Ti seed layer must have transmitted into the PZT layer and deteriorated the PZT crystal orientation. (c) 2005 The Electrochemical Society.