The role of etching gas purity in C4F8/Ar plasma to optimize SiO2 etching process

• Published in: Microelectronic engineering Vol. 299; p. 112353
• Main Authors: Liu, Anhan, Yu, Shijun, Nakamura, Shingo, Sugiyama, Akinari, Nishikawa, Takashi, Xu, Dongwei, Jin, Xiao, Wu, Daixuan, Tian, He
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.09.2025
• Subjects: C4F8; Etching; High-purity gas; SiO2; Etching; C4F8; High-purity gas; SiO2
• ISSN: 0167-9317
• DOI: 10.1016/j.mee.2025.112353

The relentless miniaturization of critical feature sizes in integrated circuits has set increasingly stringent demands on the precision of via etching processes. Current research predominantly focuses on the development of gases and optimization of processes. However, the role of etching gas purity and the impact of gas impurities have not yet been the subject of dedicated studies. Here, the etching behavior of silicon dioxide using two different purities of etching gases is investigated, examining the etching rate and morphology of SiO2 films under identical etching parameters. Compared to 99.999 % purity, the 99.99999 % purity C4F8 gas achieves a more stable and uniform etching rate with sidewall angles of 86.6° (closer to a 90° angle). This is primarily attributed to the reduction of etch-active impurities in the C4F8 gas, which decreases etching variability and minimizes damage to the sidewall fluorocarbon protective layer. Our research provides theoretical and experimental support for the advancement of subsequent etching simulation studies and the application of high-purity etching gases. [Display omitted] •Comparative experiments and analysis of silicon dioxide etching under 5 N (99.999 %) and 7 N (99.99999 %) purity conditions.•High uniformity etching process achieved using 7 N purity etching gas, with sidewalls approaching 90° at 200 nm feature size.•A detailed impact analysis of gas impurities on dielectric etching processes, including discussion and evaluation methods.