Perpendicular shape anisotropy spin transfer torque-MRAM: determination of pillar tilt angle from 3D Stoner–Wohlfarth astroid analysis.

The concept of perpendicular shape anisotropy spin-transfer-torque magnetic random access memory (PSA-STT-MRAM) consists of significantly increasing the thickness of the storage layer in STT-MRAM to values comparable to the cell diameter so as to induce a perpendicular shape anisotropy in this layer. This robust source of bulk anisotropy allows us to extend the downsize scalability of STT-MRAM towards a sub-10 nm technological node. However, due to the high aspect ratio of the patterned magnetic tunnel junction pillars, some of them may fall during the etching process or become tilted. To interpret the magnetoresistance loops measured on these PSA-STT-MRAM cells, it is important to know the exact direction of the applied field with respect to the pillar axis. We present here an experimental procedure based on 3D Stoner Wohlfarth astroid analysis which allows us to determine the pillar tilt angle. [ABSTRACT FROM AUTHOR]