Etching mechanism of Bi4-xLaxTi3O12 films in Ar/Cl2 inductively coupled plasma

The etching behavior of Bi4-xLaxTi3O12 (BLT) films in inductively coupled Ar/Cl-2 plasma was investigated in terms of etch parameters. The etching rate as a function of Ar/Cl-2 mixing ratio showed a maximum of 50.3 nm/min for the mixture of Ar(80%)/Cl-2(20%). The increase of r.f. power and d.c.-bias voltage caused an increase in BLT etch rate under any fixed gas composition. To understand etch mechanism, the plasma diagnostics were performed using Langmuir probe (LP) and optical emission spectroscopy (OES). The LP measurement indicated that the increase of Ar mixing ratio in Ar/Cl-2 plasma leads to monotonic changes of both electron density and total density of positive ions. The same tendencies were found for chlorine atoms and molecules using OES. The chemical states of BLT were studied using X-ray photoelectron spectroscopy (XPS). XPS narrow scan analysis shows that the La-chlorides remained on the etched surface. The analysis of surface reactions and plasma diagnostics in the frameworks of an ion-assisted etching mechanism confirms the possibility of non-monotonic etch rate behavior due to the concurrence of physical sputtering and chemical etching activated by ion bombardment. (C) 2003 Elsevier B.V. All rights reserved.