Study on ferroelectric thin films for application to NDRO non-volatile memories

Abstract

In this paper we describe an experimental study on ferroelectric non-volatile memory. The test devices using a MFMIS (metal-ferroelectric-metal-insulator-semiconductor) structure were developed for 1-Tr-type NDRO (non-destructive readout) memory. PZT (Lead-zirconate-titanate) and PT (lead-titanate) thin films were deposited on various bottom electrodes by solgel method. As electrodes, Pt, Pt/Ti, Pt/Ti/Ta and Pt/IrO₂ were deposited by RF magnetron sputtering. We found out that a variation in the electrodes caused drastic changes in the C-V characteristics and fatigue characteristics of MFMIS capacitors. The I-V characteristics of Pt/PZT/ Pt/SiO₂/p-Si MFMIS FET showed a hysteresis loop and the direction of the loop corresponded to ferroelectric polarization in the PZT film. A 2.7 V memory window was achieved using a 6 V programming voltage. PZT thin films on Pt/IrO₂ electrodes showed no fatigue after 10¹² switching cycles.