AVS 57th International Symposium & Exhibition
    Plasma Science and Technology Thursday Sessions
       Session PS-ThM

Paper PS-ThM9
Characteristics of Silicon Nitride Etching by Reactive Plasmas Containing CHxFy Ions

Thursday, October 21, 2010, 10:40 am, Room Aztec

Session: Plasma Surface Interactions (Fundamentals & Applications) III
Presenter: T. Ito, Osaka University, Japan
Authors: T. Ito, Osaka University, Japan
K. Karahashi, Osaka University, Japan
M. Fukasawa, Sony, Japan
T. Tatsumi, Sony, Japan
S. Hamaguchi, Osaka University, Japan
Correspondent: Click to Email
Selective etching of silicon oxide (SiO2) over silicon nitride (SiN) has been widely used in microelectronics fabrication processes such as contact hole etching in self-aligned processes, formation of a stress liner, and dual/triple hard mask (DHM/THM) etching processes of dual-damascene structures. The etching gases used in these plasma processes typically include fluorocarbon gases and etching chemistry by CxHyFz+ ions emitted from the plasma is considered to play an important role for the determination of etching selectivity. In this work, etching characteristics of SiO2 and SiN by CHxFy+ ion beams are discussed with a special emphasis on effects of hydrogen provided by CHxFy+ ions on etching selectivity. The ion beams are generated by a mass-selected ion beam system and injected with a monochromatic energy into a sample substrate (SiO2 or SiN) placed in an ultra-high vacuum chamber. The multi-beam injection system that we employed for this study also allows simultaneous irradiation of the sample by charge-neutral radical species during ion beam injection. In this way, the system enables us to simulate experimentally plasma-surface interactions that take place during the corresponding plasma etching processes. The change in chemical nature of the substrate surface during the process can be observed in situ by X-ray photoelectron spectroscopy (XPS) that is installed in the reaction chamber. Time of Flight (ToF) measurement of sputtered species from the sample surface is also possible with a mass and energy analyzer placed near the sample. In the experiments, sputtering yields of SiO2 and SiN by CF+,CHF+, CF2+, CF2+, and CH2F2+ ion beams generated from CH2F2 or CHF3 gases were examined. A typical ion dose for each ion irradiation was 1.6´1015 /cm2/sec. It has been found that the sputtering yield of SiN depends on the amount of hydrogen provided by the CHxFy+ ion beam whereas the sputtering yield of SiO2 is less sensitive to such hydrogen. Energy dependence of the sputtering yields and effects of fluorocarbon film deposition by a low-energy ion beam on hydrogen accumulation on the surface will be also discussed.