THE ETCH MECHANISMS OF MAGNETIC-MATERIALS IN AN HCL PLASMA

The etch rates of CoNbZr and Fe/FeCrB soft-magnetic materials have been determined in an RF HCl plasma as a function of pressure. The bombardment energy flux towards the powered electrode and the surface temperature of the material being etched, are both dependent on applied power and pressure. At lower surface temperatures the etch mechanism is shown to be chemically-assisted sputter etching (CASE). At higher temperatures a temperature dependent etch rate is observed, with an activation energy that can be ascribed to the desorption of metal chlorides. When using an alumina mask, selectivities up to 8 and steep side walls can be obtained. A general two-step etch mechanism is proposed, which correlates the side wall profile to the rate-determining step and explains the observed temperature dependencies of the etch rates.