Inductively coupled plasma reactive ion etching of magnetic tunnel junction stacks using H2O/CH4 mixture

• Investigation on the etching of magnetic tunnel junction (MTJ) using H2O/Ar gas.
• Understanding of etching of MTJ using H2O/Ar gas.
• Use of H2O/CH4 gas mix to etch MTJ patterned with nanometer-size of 90 × 90 nm2.
• Etching of MTJ with high degree of anisotropy without redepositions.

Magnetic tunnel junction (MTJ) stacks patterned with hard masks of 90 × 90 nm2 were etched and the etch characteristics were investigated using inductively coupled plasma ion etching (ICPRIE) in a H2O-based gas mix. As the H2O concentration in H2O/Ar mixtures increased, the etch profile of MTJ stacks improved and the redeposition decreased. Field emission transmission electron microscopy revealed that etching of the MTJ stacks in H2O plasma was stopped on a MgO barrier layer on which heavy redeposition occurred; however, the addition of CH4 gas to H2O solved this issue. Specifically, as the CH4 concentration in the H2O/CH4 gas mixture increased, the etch profile became more vertical and the redeposition was reduced considerably. Overall, the etching of MTJ stacks with a high degree of anisotropy without any redeposition was accomplished using a H2O/CH4 gas mixture in an ICPRIE system.