Downscaling of Pb(Zr,Ti)O-3 film thickness for low-voltage ferroelectric capacitors: Effect of charge relaxation at the interfaces

In this communication we address two issues essential for low-voltage memory applications of ferroelectric thin films: the size effect on polarization switching, and polarization fatigue. According to the proposed concept, both of these phenomena are controlled by local injection of charge into the interfacial layers of the ferroelectric film. In the experimental part of this work, we show that the entrapped charge relaxation can be enhanced by introducing a thin RuO2 layer into the top interface of the Pt/PZT/Pt ferroelectric capacitor. Capacitors prepared in this way using PZT with a 45/55 Zr/Ti ratio show a substantial improvement of fatigue performance and withstand relatively well the thickness downscaling. As a result, these capacitors exhibited good ferroelectric properties for driving voltage amplitudes as low as 0.6-0.8 V. Our results suggest that control of charge relaxation at the interface is a key issue for development of low-voltage ferroelectric capacitors. (C) 2000 American Institute of Physics. [S0021-8979(00)04016-0].