etching process of be stack 201 is divided into two sub processes 1 deposition deposit a protection layer to conformally cover the etched ta hm 203 mtj stack 202 and be stack 201 using cvd or ald 2 etching etch the bottom of the protection layer and un etched be stack 201 using ibe or rie the 1 deposition 2 etching flow could be repeated until the exposed be is completely etched away the protection layer is a dielectric such us sio2 sion sin sicn sic mgo or al2o3 the thickness is between 2 nm and 50 nm the rie etch process is taken place in an inductively coupled plasma icp or capacitively coupled plasma ccp chamber with a high precise controllable vacuum range from 1 mtorr to 100 mtorr the source power is adjusted from 200 watt to 3000 watt the bias power is adjusted from 100 watt to 1500 watt the main etchant of rie could be selected from ch4 h2 co nh3 ch3oh or c2h5oh with the gas flow rate from 5 sccm to 100 sccm optionally the rie etchant could be also added by some other chemistries such us ar kr and xe etc with the gas flow.