Wu Lei, Yu Bingjun, Zhang Pei, Feng Chengqiang, Chen Peng, Deng Liang, Gao Jian, Chen Siming, Jiang Shulan, Qian Linmao
Tribology Research Institute, State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031, China.
Phys Chem Chem Phys. 2020 Jun 21;22(23):12987-12995. doi: 10.1039/d0cp01370f. Epub 2020 Jun 1.
Amorphous silicon (a-Si) is a type of common surface damages during the ultra-precision machining of monocrystalline Si. However, it is difficult to identify the amorphous damage of several nanometers by traditional detection methods, which severely hinders the performance improvement of Si-based products. In this study, ultrathin a-Si was found to act as a mask against etching in HF/HNO mixtures, resulting in the formation of protrusive hillocks. Reciprocating sliding on an atomic force microscope (AFM) was employed to simulate a material removal event in surface manufacturing. The effects of normal load, etching time and etchant concentration on selective etching were investigated to optimize the parameters for amorphous damage detection. The mechanisms for selective etching were further addressed based on high-resolution transmission electron microscopy (HRTEM) detection and comparative etching of different surface structures. Further analysis demonstrated that a lower dangling bond density of a-Si could result in the reduction of the dissolution rate, while deformed Si lattices, including stacking faults, dislocations and microcracks, could facilitate rapid selective etching. By the proposed selective etching, ultrathin amorphous damage and its spatial distributions can be rapidly identified with high resolution and low destruction. This study sheds new light on achieving a high-quality Si surface in ultra-precision machining.
非晶硅（a-Si）是单晶硅超精密加工过程中常见的一种表面损伤类型。然而，采用传统检测方法难以识别几纳米的非晶损伤，这严重阻碍了硅基产品性能的提升。在本研究中，发现超薄非晶硅在HF/HNO混合液中可作为蚀刻掩膜，导致形成突出的小丘。利用原子力显微镜（AFM）进行往复滑动模拟表面制造中的材料去除过程。研究了法向载荷、蚀刻时间和蚀刻剂浓度对选择性蚀刻的影响，以优化非晶损伤检测参数。基于高分辨率透射电子显微镜（HRTEM）检测和不同表面结构的对比蚀刻，进一步探讨了选择性蚀刻的机制。进一步分析表明，非晶硅较低的悬空键密度会导致溶解速率降低，而包括层错、位错和微裂纹在内的变形硅晶格则有助于快速选择性蚀刻。通过所提出的选择性蚀刻方法，能够以高分辨率和低损伤快速识别超薄非晶损伤及其空间分布。本研究为在超精密加工中实现高质量硅表面提供了新的思路。
