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 O 2 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. H 2 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 NH 3 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/H 2 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. #

Failure Analysis in Magnetic Tunnel Junction Nanopillar with Interfacial Perpendicular Magnetic Anisotropy

“…As the introduction of C–O-based chemistries, ferromagnetic layers could be oxidized during etching, resulting in the degradations of magnetic properties and reduction in TMR ratio [54]. Kinoshita et al , investigated this degradation and proposed post-etching recovery treatment for the CoFeB/MgO-based MTJ by using reductive He/H 2 plasma to reduce the oxide [64,65]. In their study published in 2014, a TMR ratio of 102% was achieved, which is 5% higher than that of the sample without the He/H 2 treatment.…”

Tunnel Junction with Perpendicular Magnetic Anisotropy: Status and Challenges

“…Wafer tilt and rotation can improve the device profile, but limits its application in high-density array patterning [31]. Besides, enlarging the size of ion source to deal with 300 mm wafer while maintaining beam uniformity and directionality remains a challenge [32,33]. In contrast, RIE/ICP are more suited for mass production.…”

LLG Micromagnetic Simulation on STT Efficiency of sub 30nm Perpendicular MTJs with etching damage

“…This article suggested that this is attributed to an edge-fringe-field related reduction in demagnetization energy. On the other hand, several reports suggested that etching damage has an effect on the properties of MTJs, such as coercive force or MR ratio [9,10]. In addition, the real shape of a MTJ is not completely cylindrical.…”