Damage mechanisms and related performance degradations induced by ion beam etching (IBE) process in the fabrication of magnetic tunnel junctions (MTJs) were studied systematically. The loss in tunneling magnetoresistance (TMR) and coercive field (Hc) was investigated with different MTJ pillar sizes and IBE incident angles. It is found that IBE-induced damage is the formation of a surficial amorphous shell in the outer rim of an MTJ pillar. This amorphous shell is of low conductivity and TMR, mainly arising from the lattice damage of MgO barrier and partial oxidation of free/reference layers. Based on experimental and theoretical findings, we optimized the IBE process to reduce the damage as well as recover from degradation. As a result, the TMR loss ratio in comparison with a blanket film is reduced from about 18% to 7%, and Hc is increased from 1490 to 2280 Oe for the same stack.

中文翻译：

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自旋转移力矩磁性随机存取存储器制造中蚀刻损伤引起的性能下降

系统地研究了磁隧道结 (MTJ) 制造中由离子束蚀刻 (IBE) 工艺引起的损坏机制和相关性能退化。使用不同的 MTJ 柱尺寸和 IBE 入射角研究了隧道磁阻 (TMR) 和矫顽场 (Hc) 的损失。发现 IBE 引起的损坏是在 MTJ 柱的外缘形成表面无定形壳。这种非晶壳具有低电导率和 TMR，主要由 MgO 势垒的晶格损坏和自由/参考层的部分氧化引起。根据实验和理论发现，我们优化了 IBE 过程以减少损坏并从退化中恢复。结果，与覆盖膜相比，TMR 损失率从大约 18% 降低到 7%，