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Proceedings Paper

Optimization of H2 thermal annealing process for the fabrication of ultra-low loss sub-micron silicon-on-insulator rib waveguides
Author(s): Cyril Bellegarde; Erwine Pargon; Corrado Sciancalepore; Camille Petit-Etienne; Olivier Lemonnier; Karen Ribaud; Jean-Michel Hartmann; Philippe Lyan
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Paper Abstract

The superior confinement of light provided by the high refractive index contrast in Si/SiO2 waveguides allows the use of sub-micron photonic waveguides. However, when downscaling waveguides to sub-micron dimensions, propagation losses become dominated by sidewall roughness scattering. In a previous study, we have shown that hydrogen annealing after waveguide patterning yielded smooth silicon sidewalls. Our optimized silicon patterning process flow allowed us to reduce the sidewall roughness down to 0.25 nm (1σ) while maintaining rectangular Strip waveguides. As a result, record low optical losses of less than 1 dB/cm were measured at telecom wavelengths for waveguides with dimensions larger than 350 nm. With Rib waveguides, losses are expected to be even lower. However, in this case the Si reflow during the H2 anneal leads to the formation of a foot at the bottom of the structure and to a rounding of its top. A compromise is thus to be found between low losses and conservation of the rectangular shape of the Rib waveguide. This work proposes to investigate the impact of temperature and duration of the H2 anneal on the Rib profile, sidewalls roughness and optical performances. The impact of a Si/SiO2 interface is also studied. The introduction of H2 thermal annealing allows to obtain very low losses of 0.5 dB/cm at 1310 nm wavelength for waveguide dimensions of 300-400 nm, but it comes along an increase of the pattern bottom width of 41%, with a final bottom width of 502 nm.

Paper Details

Date Published: 22 February 2018
PDF: 10 pages
Proc. SPIE 10537, Silicon Photonics XIII, 1053706 (22 February 2018); doi: 10.1117/12.2289564
Show Author Affiliations
Cyril Bellegarde, Univ. Grenoble Alpes (France)
CNRS, LTM (France)
CEA-LETI (France)
Erwine Pargon, Univ. Grenoble Alpes (France)
CNRS, LTM (France)
CEA-LETI (France)
Corrado Sciancalepore, Univ. Grenoble Alpes (France)
CEA-LETI (France)
Camille Petit-Etienne, Univ. Grenoble Alpes (France)
CNRS, LTM (France)
CEA-LETI (France)
Olivier Lemonnier, Univ. Grenoble Alpes (France)
CEA-LETI (France)
Karen Ribaud, Univ. Grenoble Alpes (France)
CEA-LETI (France)
Jean-Michel Hartmann, Univ. Grenoble Alpes (France)
CEA-LETI (France)
Philippe Lyan, Univ. Grenoble Alpes (France)
CEA-LETI (France)

Published in SPIE Proceedings Vol. 10537:
Silicon Photonics XIII
Graham T. Reed; Andrew P. Knights, Editor(s)

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