目的 研究氧化铝（Al2O3）与二氧化硅（SiO2）的原子层刻蚀（ALE）工艺,明确关键工艺参数对刻蚀精度、表面形貌及材料选择性的影响,推动该技术在半导体器件制造中的应用。方法 采用等离子体增强原子层刻蚀工艺,分别以BCl3气体和CHF3等离子体为改性物质,对Al2O3、SiO2薄膜进行多循环刻蚀处理。通过控制偏压、时间等参数,结合AFM、TEM、AES等表征手段,对刻蚀速率进行定量分析,并结合形貌、区域选择性图像表征其刻蚀效果。结果 Al2O3和SiO2在96~120 V、59~74 V的偏压范围内分别呈现出自限制刻蚀行为,对应单位循环刻蚀速率分别为0.12、0.11 nm/cycle。改性气体显著降低了反应能垒,提高了刻蚀均匀性和选择性。经多循环处理后,薄膜保持良好的结构完整性,表面粗糙度明显降低,且在区域选择性沉积后具有良好的缺陷去除能力。结论 验证了ALE技术在Al2O3、SiO2等介质材料上的高精度加工潜力,具备原子级厚度控制、高选择性、低损伤特性,为ALE在先进节点半导体器件制造中的刻蚀控制提供了研究基础。
Abstract
The work aims to present a comprehensive investigation into atomic layer etching (ALE) processes for aluminum oxide (Al2O3) and silicon dioxide (SiO2), focusing on the effect of process parameters on etching precision, surface morphology, and material selectivity. As the scaling of semiconductor devices continues to push the limits of conventional fabrication techniques, ALE has emerged as a critical process technology capable of delivering sub-nanometer precision, excellent anisotropy, and enhanced control over material interfaces. By combining advanced experimental techniques with plasma simulation, the mechanisms underlying self-limiting etching behavior were analyzed systematically and the optimized ALE conditions were established for both dielectric materials. Special attention was paid to the role of surface modification agents and ion energy control in achieving high selectivity and minimizing physical damage to the etched surfaces. The results demonstrated that Al2O3 and SiO2 each exhibited distinct but well-defined ALE windows under specific bias voltage ranges- 96-120 V for Al2O3 and 59-74 V for SiO2-where the etching per cycle stabilized at approximately 0.12 nm/cycle and 0.11 nm/cycle, respectively. Within these windows, the etching reactions proceeded in a highly controlled, layer-by-layer manner, and the self-limiting nature of the chemical reactions ensured excellent reproducibility and precision. Notably, the use of BCl3 as a surface modification precursor for Al2O3, and CHF3 for SiO2, significantly reduced the threshold energy required for initiating etching reactions. These gases facilitated the formation of volatile byproducts and reactive surface intermediates, which enhanced both the efficiency and the selectivity of the ALE process. Comparative control experiments confirmed that in the absence of these passivation gases, the films either did not etch or exhibited non-uniform sputtering behavior, highlighting the indispensable role of chemical pre-modification in achieving atomic-scale precision. High-resolution transmission electron microscopy (TEM) and atomic force microscopy (AFM) were employed to evaluate film morphology before and after etching. The results revealed that both Al2O3 and SiO2 films maintained excellent structural integrity and surface smoothness after multiple etching cycles, with no significant increase in surface roughness. The ALE process effectively removed nanoscale surface defects and prevented the roughening often associated with conventional plasma etching techniques. The ALE process was further found to effectively remove nanoscale surface defects introduced during prior deposition steps, such as atomic layer deposition (ALD), thereby improving the overall material quality. In addition to process control and surface preservation, ALE also improved material selectivity in patterned structures. Auger electron spectroscopy (AES) analysis showed that ALE treatment could eliminate unwanted deposition in non-growth regions following area-selective deposition (ASD), particularly in Cu/Si test structures. This capability was essential for the fabrication of advanced multi-material semiconductor architectures where nanoscale precision was critical. The findings confirm that plasma-assisted ALE provides a reliable and controllable platform for the precision etching of high-k dielectrics such as Al2O3 and widely used insulators like SiO2. The ability to achieve angstrom-level thickness control, excellent surface uniformity, and improved material selectivity makes ALE a promising candidate for next-generation semiconductor device fabrication. This work lays a solid foundation for further development and integration of ALE into mainstream micro- and nano-fabrication processes.
关键词
原子层刻蚀 /
刻蚀窗口 /
自限制性 /
选择性 /
粗糙度
Key words
atomic layer etching /
etching window /
self-limitation /
selectivity /
roughness
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基金
国家自然科学基金（52350349, 52273237）; 国家重点研发计划（2022YFF1500400）
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