Influence of O2 Gas on Etch Profile of Magnetic Tunnel Junction Stacks Etched in a CH4/O2/Ar Plasma

The etch characteristics of magnetic tunnel junction (MTJ) stacks patterned with W/TiN films were examined using an inductively coupled plasma of a CH4/O-2/Ar gas mix. The effect of the O-2 concentration on the etch rate, etch selectivity and etch profile of the MTJ stacks was examined. The etch profile of the MTJ stacks in 60% CH4/Ar gas appeared to be the best. The addition of 10% O-2 gas in CH4/Ar gas led to an improved etch profile with less redeposition on the sidewall of the MTJ stacks. This was attributed to the increase in [H]/[Ar] and [O]/[Ar] intensity ratios with increasing O-2 concentration to 20%. Transmission electron microscopy of the etched MTJ stacks revealed redeposited materials on the sidewall of the MTJ stacks etched in CH4/Ar gas that were indentified to be mainly Pt, Mn, Co, Ru and Ti. On the other hand, the amount of redeposited materials decreased significantly with the addition of 10% O-2 in CH4/Ar gas. The formation of metal oxides and protection layer in CH4/O-2/Ar gas mix resulted in a high degree of anisotropy without redeposited materials in the etch profile of MTJ stacks. (C) 2012 The Electrochemical Society. All rights reserved.