Novel approach for nano-patterning magnetic tunnel junctions stacks at narrow pitch: A route towards high density STT-MRAM applications

Nano-patterning magnetic tunnel junction (MTJ) cells at low dimension and very dense pitch remains a challenge for high density STT-MRAM due to the difficulty of MTJ stacks etching. To circumvent this etching issue, this paper demonstrates a novel scalable approach for MTJ nano-patterning at very narrow pitch (pitch = 1.5F, F = MTJ dot diameter) by growing the MTJ material on pre-patterned conducting non-magnetic pillars without post-deposition etching. Advantageously, these pillars could be the vias connecting the different metal levels in CMOS technology. Structural, magnetic and transport properties of so prepared MgO-based MTJs were investigated. The comparison with those obtained by conventional ion beam etching (IBE) shows that this novel approach is quite promising to circumvent the issue of MTJ etching for high density MRAM.