Li Chen, Zhu Huilong, Zhang Yongkui, Yin Xiaogen, Jia Kunpeng, Li Junjie, Wang Guilei, Kong Zhenzhen, Du Anyan, Yang Tengzhi, Zhao Liheng, Huang Weixing, Xie Lu, Li Yangyang, Ai Xuezheng, Ma Shishuai, Radamson Henry H
Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
ACS Appl Mater Interfaces. 2020 Oct 21;12(42):48170-48178. doi: 10.1021/acsami.0c14018. Epub 2020 Oct 9.
A digital etching method was proposed to achieve excellent control of etching depth. The digital etching characteristics of p-Si and SiGe using a combination of HNO oxidation and buffered oxide etching oxide removal processes were investigated. Experimental results showed that oxidation saturates as time goes on because of low activation energy and its diffusion-limited characteristic. An oxidation model was developed to describe the wet oxidation process with nitric acid. The model was calibrated with experimental data, and the oxidation saturation time, final oxide thickness, and selectivity between SiGe and p-Si were obtained. In SiGe/p-Si stacks, the saturated relative etched depth per cycle was 0.5 nm (four monolayers), and variation between experiments was about 4% after saturation. A corrected selectivity calculation formula was also proposed, and the calculated selectivity was 3.7-7.7 for different oxidation times, which was the same as the selectivity obtained from our oxidation model. The proposed model can be used to analyze process variations and repeatability, and it can provide credible guidance for the design of other wet digital etching experiments.
提出了一种数字蚀刻方法，以实现对蚀刻深度的精确控制。研究了采用HNO氧化和缓冲氧化物蚀刻氧化物去除工艺相结合的p-Si和SiGe的数字蚀刻特性。实验结果表明，由于活化能低及其扩散限制特性，氧化会随着时间的推移而饱和。开发了一个氧化模型来描述用硝酸进行的湿法氧化过程。该模型用实验数据进行了校准，得到了氧化饱和时间、最终氧化物厚度以及SiGe和p-Si之间的选择性。在SiGe/p-Si叠层中，每个周期的饱和相对蚀刻深度为0.5 nm（四个单层），饱和后实验之间的变化约为4%。还提出了一个校正后的选择性计算公式，对于不同的氧化时间，计算出的选择性为3.7-7.7，这与从我们的氧化模型中获得的选择性相同。所提出的模型可用于分析工艺变化和重复性，可为其他湿法数字蚀刻实验的设计提供可靠指导。
