Properties of reactively sputtered IrOx for PZT electrode applications

The use of IrOx for electrodes in PbZrxTi1-xO3 (PZT) capacitors for ferroelectric memory applications has proven to be advantageous in several respects. In comparison with Pt, IrOx often exhibits improved fatigue and provides resistance to hydrogen induced degradation at elevated temperatures. Since IrOx is often produced by sputtering in an oxygen containing environment, several forms of IrOx can be produced depending on the process conditions. This work concentrates on an analysis of the DC reactive sputtering of IrOx from an Ir metal target. As with ether oxidizable metals, Ir exhibits a transition between metal and oxide mode sputtering when sputtered in oxygen containing atmospheres. Variations in the Ar/O-2 gas flow ratio were used to produce Ir and IrO(x)films on both sides of the metal-to-oxide mode reactive sputtering transition. Changes in the IrOx film properties were quantified by using a combination of metrics including X-ray diffraction, sheet resistance, and stress. It was found that the, IrOx crystalline structure and other IrOx properties could be directly related to the ferroelectric switching performance of PZT capacitors with IrO(x)top electrodes. A relationship between IrOx deposition processes and resistance to etch induced damage of the ferroelectric properties was also observed.