Study of the SiO{sub 2}-to-Si{sub 3}N{sub 4} etch selectivity mechanism in inductively coupled fluorocarbon plasmas and a comparison with the SiO{sub 2}-to-Si mechanism
- Department of Physics, University at Albany, State University of New York, Albany, New York, 12222 (United States)
- Lam Research Corporation, Fremont, California, 94538-6470 (United States)
The mechanisms underlying selective etching of a SiO{sub 2} layer over a Si or Si{sub 3}N{sub 4} underlayer, a process of vital importance to modern integrated circuit fabrication technology, has been studied. Selective etching of SiO{sub 2}-to-Si{sub 3}N{sub 4} in various inductively coupled fluorocarbon plasmas (CHF{sub 3}, C{sub 2}F{sub 6}/C{sub 3}F{sub 6}, and C{sub 3}F{sub 6}/H{sub 2}) was performed, and the results compared to selective SiO{sub 2}-to-Si etching. A fluorocarbon film is present on the surfaces of all investigated substrate materials during steady state etching conditions. A general trend is that the substrate etch rate is inversely proportional to the thickness of this fluorocarbon film. Oxide substrates are covered with a thin fluorocarbon film ({lt}1.5 nm) during steady-state etching and at sufficiently high self-bias voltages, the oxide etch rates are found to be roughly independent of the feedgas chemistry. The fluorocarbon film thicknesses on silicon, on the other hand, are strongly dependent on the feedgas chemistry and range from {approximately}2 to {approximately}7 nm in the investigated process regime. The fluorocarbon film thickness on nitride is found to be intermediate between the oxide and silicon cases. The fluorocarbon film thicknesses on nitride range from {approximately}1 to {approximately}4 nm and the etch rates appear to be dependent on the feedgas chemistry only for specific conditions. The differences in etching behavior of SiO{sub 2}, Si{sub 3}N{sub 4}, and Si are suggested to be related to a substrate-specific ability to consume carbon during etching reactions. Carbon consumption affects the balance between fluorocarbon deposition and fluorocarbon etching, which controls the fluorocarbon steady-state thickness and ultimately the substrate etching. {copyright} {ital 1999 American Vacuum Society.}
- OSTI ID:
- 300144
- Journal Information:
- Journal of Vacuum Science and Technology, A, Vol. 17, Issue 1; Other Information: PBD: Jan 1999
- Country of Publication:
- United States
- Language:
- English
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