Low surface damage laser processing of silicon by laser-induced plasma etching (LIPE)
Low surface damage laser processing of silicon by laser-induced plasma etching (LIPE)
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DOI：
10.1016/j.apsusc.2022.153712
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发表时间：
2022-05
影响因子：
6.7
通讯作者：
Heinke Robert;Ehrhardt Martin;Bauer Jens;Lotnyk Andriy;Lorenz Pierre;Morgenstern Roy;Lampke Thomas;Arnold Thomas;Zimmer Klaus
中科院分区：
文献类型：
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作者：
Heinke Robert;Ehrhardt Martin;Bauer Jens;Lotnyk Andriy;Lorenz Pierre;Morgenstern Roy;Lampke Thomas;Arnold Thomas;Zimmer Klaus
脉冲激光精密加工硅表面是一项具有挑战性的工作。激光烧蚀可实现直接图案化，但会导致表面和亚表面区域的许多修改。随着光学、微电子和微流体等领域对精密结构硅表面的需求不断增加，需要新的基于激光的超精密表面加工技术。为此，本文对最近发展起来的激光诱导等离子体刻蚀工艺(LIPE)在单晶硅刻蚀后的化学修饰和结构修饰方面进行了研究。在研究中，脉冲能量最大为750微焦耳的飞秒激光(775微米，150微秒，1微赫)在大气压下聚焦到CF4/O2气体混合物中，在硅样品前点燃激光诱导的等离子体。通过扫描电子显微镜、透射电子显微镜、X射线光电子能谱和拉曼光谱对激光刻蚀后的硅片表面进行了表征，结果表明，刻蚀后的硅片表面没有熔化特征，没有结构表面或亚表面缺陷，也几乎没有刻蚀产生的化学污染，并且在原子有序的硅片表面覆盖了2 nm厚的氟氧化硅。比较清楚地表明，激光烧蚀硅时可以避免严重的结构和化学变化，从而实现超精密表面加工。
The precise surface machining of silicon by pulsed laser processing is challenging. Laser ablation enables direct patterning but causes numerous modifications of the surface and sub-surface region. Due to the increasing demand of precisely structured silicon surfaces in various fields, such as optics and micro-electronics and micro-fluidics, new laser-based ultra-precise surface machining techniques are required. Therefore, the recently developed laser-induced plasma etching process (LIPE) was studied in relation to chemical as well as structural modifications after the etching of single-crystalline silicon. For the studies, a fs-laser (775 nm, 150 fs, 1 kHz) with a pulse energy of maximum 750 µJ was focused to a CF4/O2gas mixture at atmospheric pressure igniting a laser-induced plasma in front of the <1 0 0> Si sample. For comparison, a silicon surface was also structured by direct laser ablation.The LIP etched surface, that is characterized by SEM, TEM, XPS- and Raman-spectroscopy, shows no melting features, no structural surface or subsurface defects and almost no chemical contamination from etching besides a 2 nm thick silicon oxyfluoride on top of the atomically ordered silicon. The comparison shows clearly that the severe structural and chemical modifications at laser ablation of silicon can be avoided enabling ultraprecise surface machining.