STEM tomography study on structural features induced by MTJ processing

The influence of the sidewall damage on the thermal stability factor (Δ) of quad-interface magnetic tunnel junctions (quad-MTJs) was investigated through a string method-based micromagnetic simulation. The quad-MTJs consist of a reference layer/MgO-barrier/CoFeB/middle-MgO/CoFeB/MgO-cap, which has four CoFeB/MgO interfaces to enhance the interfacial perpendicular magnetic anisotropy for large Δ. Experimentally obtained magnetic parameters at room temperature [e.g., saturation magnetization ( Ms), stiffness constant ( As), interfacial perpendicular magnetic anisotropy constants ( Ki), and exchange coupling ( Jex)] in blanket multilayer films of the quad-MTJs were used in micromagnetic simulation. The influence of the sidewall damage on the quad-MTJs, which is difficult to be analyzed in the experimental way, was investigated. The quad-MTJs without damaged layers having relatively higher Ki show the split of the energy barrier into two, resulting in a decrease in Δ. When the decrease in magnetic anisotropy energy ( Eani) is more than the increase in the static magnetic energy ( Esta), the antiferromagnetically (AF) coupled state of two free layers is formed at the midpoint to minimize the total energy ( Eall). This causes the split of the energy barrier. The sidewall damage plays a role in lowering Ki in each layer, consequently avoiding the formation of the AF state. Note that the value of Δ with the sidewall damage, which shows the unified energy barrier, is comparable to non-damaged Δ, which shows the split of the energy barrier; these quad-MTJs have the same volume of free layers.

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Influence of sidewall damage on thermal stability in quad-CoFeB/MgO interfaces by micromagnetic simulation

Naganuma

Honjo

Kaneta

et al. 2022

AIP Advances

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First Demonstration of 25-nm Quad Interface p-MTJ Device With Low Resistance-Area Product MgO and Ten Years Retention for High Reliable STT-MRAM

Nishioka

Miura

Honjo

et al. 2021

IEEE Trans. Electron Devices

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Structural Analysis of CoFeB/MgO-Based Perpendicular MTJs With Junction Size of 20 nm by STEM Tomography

et al. 2021

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STEM tomography study on structural features induced by MTJ processing

Cited by 5 publications

References 21 publications

Influence of sidewall damage on thermal stability in quad-CoFeB/MgO interfaces by micromagnetic simulation

Influence of sidewall damage on thermal stability in quad-CoFeB/MgO interfaces by micromagnetic simulation

First Demonstration of 25-nm Quad Interface p-MTJ Device With Low Resistance-Area Product MgO and Ten Years Retention for High Reliable STT-MRAM

Structural Analysis of CoFeB/MgO-Based Perpendicular MTJs With Junction Size of 20 nm by STEM Tomography

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