Concentration of Fluorine Atoms and Kinetics of Reactive-Ion Etching of Silicon in CF4 + O2, CHF3 + O2, and C4F8 + O2 Mixtures

• Published in: Russian microelectronics Vol. 52; no. 4; pp. 267 - 275
• Main Authors: Efremov, A. M., Bobylev, A. V., Kwon, K.-H.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.08.2023; Springer Nature B.V
• Subjects: Chemical reactions; Comparative studies; Electrical Engineering; Engineering; Etching; Fluorine; Kinetics; Mixtures; Oxidation; Oxygen atoms; Plasma diagnostics; Polymer films; Reactive ion etching; Silicon; fluorocarbon gases; polymerization; fluorine atoms; etching; plasma; kinetics; mechanism
• DOI: 10.1134/S1063739723700488
• ISSN: 1063-7397

A comparative study of the electrophysical parameters of the plasma, the fluorine atom concentrations, and the kinetics of reactive-ion etching of silicon in CF 4 + O 2 , CHF 3 + O 2 , and C 4 F 8 + O 2 mixtures of a variable (0–75% O 2 ) initial composition is carried out. It is shown that the dominant etching mechanism is always the ion-stimulated chemical reaction Si + x F → SiF x , whose rate has a maximum in the region of 20–50% O 2 . Based on the results of plasma diagnostics, it is found that the similar behavior of the concentration of fluorine atoms is typical only for mixtures of CF 4 + O 2 and CHF 3 + O 2 , while in the C 4 F 8 + O 2 mixture, there is a nonmonotonic change in the probability of the interaction. It is assumed that the latter effect is caused by the competition between the processes of reducing the thickness of the fluorocarbon polymer film and the oxidation of the silicon surface by oxygen atoms.