Reactive ion etching of CoSi in a CF rAr plasma

A CF4rAr RF plasma has been applied to etch epitaxial CoSi2films as well as 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 CorTi bilayer 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 to 90 W the etch rate increases linearly up to 20 nmrmin. The disturbing top layer could be removed easily at 60 W with an estimated etch rate of 15 nmrmin. But, at the beginning of the etching process there is formed a new fluorine containing uniform overlayer on top of the CoSi2 film. This nonvolatile overlayer is partially removed at its surface by sputtering. But, it grows simultaneously at the interface to CoSi2by the reaction of CoSi2with F diffused through the overlayer. Consequently the thickness of the overlayer 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. q1999 Elsevier Science B.V. All rights reserved.