Inductively coupled plasma reactive ion etching of FePt magnetic thin films in a CH4/O2/Ar plasma

Abstract

An inductively coupled plasma (ICP) reactive ion etching of FePt thin films masked with TiN films was carried out in CH4/O2/Ar plasma. As CH4 gas was added to Ar, the etch rates of the FePt thin films and TiN hard mask decreased gradually, and the etch profile of the FePt films improved slightly. The addition of O2 gas to the CH4/Ar gas mixture enhanced the etch profile due to an increase in the etch selectivity of the FePt film to the TiN hard mask. From optical emission spectroscopy (OES) for the CH4/O2/Ar gas mix, the increase in etch selectivity was attributed to the increase in [H] species as well as [O] species due to the addition of O2 gas.With increasing ICP rf power and dc-bias voltage to the substrate, the etch rates increased and the etch profiles improved with a higher degree of anisotropy. X-ray photoelectron spectroscopy (XPS) of the etched FePt films revealed the existence of Fe-containing compounds formed during etching in CH4/O2/Ar plasma. The etch characteristics, OES and XPS analysis of the film surface showed that the etching of FePt films in CH4/O2/Ar plasma follows mainly sputter etching with the assistance of chemical reactions with the films.