Improvement of TMR Effect of MTJ Films With Very Thin MgO Barrier Sputtered by Ar-Ne Gas Mixture at Low RA Product Below 1.0 $\Omega \mu{\hbox {m}}^{2}$

The atomic weight of a sputtering gas is very effective for crystallographic characteristics of a sputter-deposited magnesium oxide (MgO) film. The calculations of an elementary process of a collision cascade in a sputtering of MgO suggested that neon (Ne) is more suitable for a sputtering gas than argon (Ar) in the aspect of an energy transfer efficiency. However, damages on the film surface caused by an increase of a number of recoiled Ne atoms should be considered. The experimental results of the magnetoresistive (MR) characteristics of magnetic tunnel junction films with the MgO barrier sputtered by Ar-Ne gas mixture revealed that these suggestions were certified. An improved MR-ratio of 90% was obtained at a very low resistance-area product as low as 1.0 Omegamum² with an optimized mixing ratio in Ar-Ne gas mixture. It is true that we could expect the good physical properties by selecting the most suitable sputtering gas species for improving the crystallographic orientation in oxide thin films.