Nanoscale Spin-Transfer Torque MRAM Etching Using Various Gases

The magnetic tunnel junction (MTJ)-related materials were etched using He, Ar, and CO/NH3 in an inductively coupled plasma etching system. When the MTJ materials were etched with He, the etch selectivities and the etch profiles of the etched MTJ patterns were significantly improved. The sputter etch characteristics were also investigated using the Stopping and Range of Ions in Matter (SRIM) simulation program. The results showed higher sputter etch selectivity of CoFeB over W using He than those obtained using Ar. Also He exhibited higher energy and narrower angular probability density function of the sputtered atoms. Also, by using He, similar to Ar, magnetic properties of the MTJ were preserved compare to CO/NH3 due to no oxidation of magnetic materials.