Selectivity in atomically precise etching: Thermal atomic layer etching of a CoFeB alloy and its protection by MgO
Selectivity in atomically precise etching: Thermal atomic layer etching of a CoFeB alloy and its protection by MgO
复制标题
DOI：
10.1016/j.apsusc.2021.151751
复制
发表时间：
2021-11-17
影响因子：
6.7
通讯作者：
Teplyakov, Andrew, V
中科院分区：
文献类型：
--
作者：
Konh, Mahsa;Wang, Yang;Teplyakov, Andrew, V
集成存储器件中的中央单元是由两个铁磁层组成的磁性隧道结（MTJ），通常使用诸如CoFeB的复合合金，由诸如MgO的绝缘屏障分隔。原子级精度是制造小型化器件所必需的，而原子层刻蚀（ALE）是实现这一目标的最有前途的方法之一。然而，在纳米级，在蚀刻过程中必须保持合金中每种元素的浓度，并且重要的是不影响绝缘屏障，即蚀刻过程应在MgO处停止。在这里，我们使用热干法蚀刻的CoFeB合金薄膜与顺序剂量的氯和2，4-戊二酮（乙酰丙酮，acacH）。图案化样品以原子级精度进行修改，并且该过程在ALE制度中对CoFeB合金的去除是完全选择性的，而不改变合金成分并且不蚀刻用作保护层的MgO。通过比较ALE工艺前后图案化表面上的膜厚度，使用原子力显微镜（AFM）研究了蚀刻过程。通过程序升温脱附（TPD）实验检测升温过程中的关键脱附片段，提出了反应机理的可行关键特征。用非原位X射线光电子能谱（XPS）对ALE过程中的表面进行了表征。
The central unit in an integrated memory device is a magnetic tunnel junction (MTJ) consisting of two ferromagnetic layers, often using complex alloys such as CoFeB, separated by an insulating barrier such as MgO. Atomic level precision is required to fabricate miniaturized devices, and atomic layer etching (ALE) is one of the most promising methods to do this. However, at the nanoscale, it is imperative to maintain the concentration of each element in an alloy during etching, and it is important to not affect the insulating barrier, i.e. the etching process should stop at MgO. Here we use thermal dry etching of CoFeB alloy thin films with sequential doses of chlorine and 2,4-pentanedione (acetylacetone, acacH). Patterned samples are modified with atomic level precision, and the process is completely selective to the removal of CoFeB alloy in ALE regime without changing the alloy composition and without etching MgO that is used as a protecting layer. The etching process was investigated by comparing the film thickness on a patterned surface before and after ALE process using atomic force microscopy (AFM). The viable key features of the reaction mechanism were proposed by detection of key desorbing fragments during a heating ramp via temperature-programmed desorption (TPD) experiments. Ex-situ X-ray photoelectron spectroscopy (XPS) was performed to characterize the surface during ALE process.