Dry etching of magnetic tunnel junctions monitored by spectroscopic reflectance

The dry etching of magnetic tunnel junctions Co/Al2O3/Co/Ni80Fe20 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.

► We study the dry etching of Co/Al2O3/Co/Ni80Fe20 magnetic tunnel junctions.
► The etch process is followed by spectroscopic reflectance.
► Optical Simulations are in good accordance with the experimental curves.
► The etch process can be stopped in the barrier of Al2O3 or in the Co bottom layer.