Dry-etch of As{sub 2}S{sub 3} thin films for optical waveguide fabrication
- Laser Physics Center, Australian National University, Canberra 0200 (Australia)
Plasma etching to As{sub 2}S{sub 3} thin films for optical waveguide fabrication has been studied using a helicon plasma etcher. The etching effects using the processing gases or gas mixtures of O{sub 2}, Ar, and CF{sub 4} were compared. It was found that the O{sub 2} plasma had no chemical etching effect to the As{sub 2}S{sub 3}, but it could oxidize the surface of the As{sub 2}S{sub 3}. The Ar plasma provided a strong ion sputtering effect to the films. The CF{sub 4} plasma exhibited a too strong chemical etch to the As{sub 2}S{sub 3}, leading to serious undercutting and very rough sidewalls of the waveguides. Ar and O{sub 2} gases were compared as the additives to dilute the CF{sub 4} processing gas. The etch rate of the As{sub 2}S{sub 3} was reduced dramatically from over 2000 nm/min to a few hundred nm/min when the pure CF{sub 4} gas was heavily diluted with 70% Ar or O{sub 2} gas. The undercutting and sidewall roughness of the etched waveguides were also decreased greatly when above dilution was made, which was associated with an enormous weakening of the isotropic chemical etch induced by neutral reactants in the plasma. In addition, the O{sub 2} showed a better dilution effect than the Ar in reducing the etch rate of the As{sub 2}S{sub 3}; and the O{sub 2}/CF{sub 4} plasma also enabled a much lower erosion rate to Al mask layers than the Ar/CF{sub 4} plasma at similar plasma conditions. The As{sub 2}S{sub 3} waveguides with near vertical and very smooth sidewalls were obtained using an optimized O{sub 2}/CF{sub 4} plasma. Moreover, the etching behaviors and mechanisms were explained base on the etching results, and on the characteristics of the applied plasma diagnosed using Langmuir probe and optical spectroscopy techniques.
- OSTI ID:
- 20723209
- Journal Information:
- Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films, Vol. 23, Issue 6; Other Information: DOI: 10.1116/1.2049308; (c) 2005 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0734-2101
- Country of Publication:
- United States
- Language:
- English
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