Damage Recovery by Reductive Chemistry after Methanol-Based Plasma Etch to Fabricate Magnetic Tunnel Junctions

Abstract

The damage recovery process for magnetic tunnel junctions (MTJs) after methanol- (Me-OH) based plasma etch has been demonstrated. Me-OH and O2 plasma, which contain oxygen in the molecule, caused unavoidable modification of magnetic materials in the MTJ stack. For example, the magnetization saturation and MR ratio decreased. H2 base reductive plasma treatment was effective in recovering from this deterioration. No harmful side effects were observed in other aspects of MTJ performance such as MTJ resistance, hysteresis loop offset, and switching field. Heavier initial damage required a longer treatment time for recovery. Other types of reductive chemistry such as NH3 plasma deteriorated the MTJ when the treatment lasted more than 15 s, probably due to nitridation. The use of a highly selective Ar/Me-OH etch process along with He/H2 plasma recovery treatment is very promising for the MTJs' etch process to fabricate high-density magnetic random access memory (MRAM) and non-volatile logic devices.