Etch characteristics of CeO2 thin films as a buffer layer for the application of ferroelectric random access memory

Abstract

Cerium oxide (CeO2) thin film has been proposed as a buffer layer between the ferroelectric film and the Si substrate in metal-ferroelectric-insulator- silicon structures for ferroelectric random access memory applications. In this study, CeO2 thin films were etched with a Cl-2/Ar gas combination in an inductively coupled plasma. The etch properties were measured for different gas mixing ratios of Cl-2/(Cl-2 + Ar) while the other process conditions were fixed at rf power (600 W) dc bias voltage (-200 V), and chamber pressure (15 mTorr). The highest etch rate of the CeO2 thin film was 230 Angstrom /min and the selectivity of CeO2 to YMnO3 was 1.83 at a Cl-2/(Cl-2 +Ar) gas mixing ratio of 0.2. The surface reaction of the etched CeO2 thin films was investigated using x-ray photoelectron spectroscopy (XPS) analysis. There is a Ce-Cl bonding by chemical reaction between Ce and Cl. The results of secondary ion mass spectrometer analysis were compared with the results of XPS analysis and the Ce-Cl bonding was discovered at 176.15 (arnu). These results confirm that the Ce atoms of the CeO2 thin films react with chlorine and a compound such as CeCl remains on the surface of the etched CeO2 thin films. These products can be removed by Ar-ion bombardment. (C) 2001 American Vacuum Society.