Reactive ion etching of CoSi2 in a CF4/Ar plasma

A CF4/Ar RF plasma has been applied to etch epitaxial CoSi2 films as well a s compound layers containing mainly Co, Ti and Si. This additional layer is formed on top of the CoSi2 during the solid phase reaction of a Co/Ti bila yer with Si(100). The etch rate for CoSi2 depends strongly on the RF power. Below 18 W the etch rate is negligibly small. By increasing the power up t o 90 W the etch rate increases linearly up to 20 nm/min. The disturbing top layer could be removed easily at 60 W with an estimated etch rate of 15 nm /min, But. at the beginning of the etching process there is formed a new fl uorine containing uniform overlayer on top of the CoSi2 film. This nonvolat ile overlayer is partially removed at its surface by sputtering. But, it gr ows simultaneously at the interface to CoSi2 by the reaction of CoSi2 with F diffused through the overlayer. Consequently the thickness of the overlay er remains constant and the sputtering process determines the etch rate of the underlying CoSi2 film. It was demonstrated, that an in situ control of the etching process is possible using laser interferometry. (C) 1999 Elsevi er Science B.V. All rights reserved.