AVS 60th International Symposium and Exhibition
    Plasma Science and Technology Tuesday Sessions
       Session PS-TuP

Paper PS-TuP30
Mechanisms of Silicon Nitride (SiN) Etching by Hydrofluorocarbon (HFC) Plasmas

Tuesday, October 29, 2013, 6:00 pm, Room Hall B

Session: Plasma Science and Technology Poster Session
Presenter: K. Miyake, Osaka University, Japan
Authors: K. Miyake, Osaka University, Japan
T. Ito, Osaka University, Japan
M. Isobe, Osaka University, Japan
K. Karahashi, Osaka University, Japan
M. Fukasawa, Sony Corporation, Japan
K. Nagahata, Sony Corporation, Japan
T. Tatsumi, Sony Corporation, Japan
S. Hamaguchi, Osaka University, Japan
Correspondent: Click to Email
Selective etching of silicon nitride (SiN) over silicon dioxide (SiO2) and/or silicon (Si) is widely used in the microelectronics industry. For example, the formation of dual stress liners or etching of dual/triple hard masks (DHM/THM) for dual-damascene structures requires highly selective SiN etching technology. It has been known that the use of plasmas based on hydrofluorocarbon (HFC) gases such as CHF3 and CH2F2 or hydrogen (H) /fluorocarbon (FC) gases can result in higher etching rates of SiN. The goal of this study is to clarify the etching mechanism of SiN and SiO2 by HFC/FC plasmas. For this purpose we have performed molecular dynamics (MD) simulations of SiN and SiO2 etching by HFC/ FC ions with improved interatomic potential functions. In the new interatomic potential functions, electronegativity of fluorine (F) bonded with carbon (C) is taken into account. It has been found that, in MD simulation, electronegativity of F strongly affects the etch rates of SiN by FC ions. Since F is highly electronegative and tends to attract electrons more strongly than C does, the CC bond of C-C-F or C=C-F is weaker than that of C-C-H or C=C-H and the C-F bond of C-C-F or C=C-F is stronger than that of CF4. The bond energy of Si-F is comparable with that of the C-F bond. Therefore, when C and F atoms are provided from the incident beam to a SiN surface, the formation of C-F and Si-F bonds takes place simultaneously and the balance between the C-F and Si-F formation rates determines the total sputtering yield. Since SiFx is a volatile species whereas CFx radicals can form a polymer, if more SiFx bonds are formed, etching proceeds more rapidly and, if more CFx radicals are formed, polymer deposition takes place. In this study, we evaluate the puttering yields of SiN by HFC/FC ions and examine the surface atomic compositions and desorbed products. The results are also compared with data obtained from ion beam experiments. Sputtering yields obtained from MD simulations with the new interatomic potential functions with more accurate electronegative effects of F are found to be in good agreement with those obtained from ion beam experiments.