Dry etching of magnetic tunnel junctions monitored by spectroscopic reflectance

Abstract The dry etching of magnetic tunnel junctions Co/Al 2 O 3 /Co/Ni 80 Fe 20 was monitored using spectroscopic reflectance. Optical simulations show that the etching of a 2 nm thick layer of alumina is observable on the reflectance curves. It is then confirmed experimentally, by determining the chemical nature of the layer by Auger Electron Spectroscopy at different points of the reflectivity curves. We are then able to stop the etching process precisely in the thin barrier of alumina and in the lower electrode of cobalt. Thereafter, we have calculated the sputtering yield of each thin film, thanks to the simulations of the reflectance curves.