Surface kinetics of Bi4-xLaxTi3O12 films etched in a CF4/Ar gas chemistry

The surface reactions and the etch rate of Bi4-xLaxTi3O12(BLT) films in a CF4/Ar plasma were investigated in an inductively coupled plasma (ICP) reactor in terms of the gas mixing ratio. The variation of relative volume densities for the F and the Ar atoms were measured with optical emission spectroscopy (OES). The maximum etch rate of 803 A/min was obtained in a CF4(20 %)/Ar(80 %) plasma. The presence of a maximum in the BLT etch rate at CF4(20 %)/Ar(80 %) may be explained by the concurrence of two etching mechanisms, physical sputtering and chemical reaction. Ar-ion bombardment played roles of destroying the metal (Bi, La, Ti)-O bonds and assisting the chemical reaction between metal and fluorine atoms. The chemical states of BLT were investigated using X-ray photoelectron spectroscopy (XPS), which confirmed the existence of nonvolatile etch byproducts (La-fluorides).