Nanopillar process flows for sub-10nm magnetic tunnel junctions and optical access applications

Magnetic Random Access Memory (MRAM) are now available as embedded memory from major CMOS foundries. They are based on nano-pillar Magnetic Tunnel Junction (MTJ) devices, having two electrodes, a storage and a reference layers, separated by an ultrathin tunnel barrier. To move towards high density MRAM at sub-20nm nodes, one major issue to be solved is to increase the thermal stability. Another recent development is the possibility of using femto-second laser pulses to drive the reversal of the storage layer, achieving ultrafast switching of tunnel junction with very low energy. This work describes how a self-aligned nano-pillar process flow has been used to investigate devices that are fabricated to sub-10nm lateral size. The same flow was then modified to allow full optical access to the storage element, such that all optical switching with femto-second laser pulses of fabricated cells could be demonstrated. Thermal stability ratios Δ as high as 200 are obtained in some of these 8nm diameter junctions demonstrating the potential to scale MRAM down to 4nm cells. A developed ITO process flow provides a way to fabricate nano-pillars for all-optical switching cells.