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Proceedings Paper

Advanced solutions in silicon photonics using traditional fabrication methods and materials of CMOS technologies (Conference Presentation)
Author(s): Charles Baudot; Maurin Douix; Sylvain Guerber; Sébastien Crémer; Nathalie Vulliet; Jonathan Planchot; Romuald Blanc; Laurène Babaud; Carlos Alonso-Ramos; Diego Pérez-Galacho; Sonia Messaoudène; Sébastien Kerdiles; Daniel Benedikovic; Catherine Euvard-Colnat; Eric Cassan; Delphine Marris-Morini; Laurent Vivien; Pablo Acosta-Alba; Frédéric Boeuf

Paper Abstract

Optical signal modulation is presently done using Si pn junctions which cause phase shifting due to Soref effect and, put in a Mach-Zehnder configuration, produce interference and generate amplitude modulation. The drawback of pn junctions is the relatively low phase shifting efficiency which consequently inflicts high power consumptions on the electrical driver. An alternative device to pn junctions was developed and consists of introducing capacitive structures within the optical waveguide. The proposed device has the same cross-section foot-print but is much shorter due to improved efficiencies. Typical pn-junctions can generate phase shifts of < 20°/mm for given implantation conditions and the capacitive structure developed produces shifts of > 60°/mm for the same implantation conditions. The device is made up of crystal Si, a thin SiO2 capacitor dielectric and poly-Si. Benchmarking the two phase shifters with respect to insertion losses, we observe that the proposed device is promising. Another material exhaustively used in CMOS technologies is Si3N4. In the data-communication bandwidths, the index contrast between Si3N4 (n = 1.95) and SiO2 (n=1.45) is smaller than that with Si (n = 3.5). Thus, nitride waveguides have lower optical mode confinements and are thus less sensitive to insertion losses caused by line edge roughness and wavelength shifting incurred by process variations. Moreover, the temperature induced index variations are 5 times les in Si3N4 than Si. Therefore, the use of nitride to fabricate devices in silicon photonics looks advantageous. However, high speed electro-optic devices are challenging in Si3N4. Consequently, a co-integration of both materials is essential. We developed a fabrication method and associated devices which allow to transfer the signal to and fro Si and Si3N4. We present some devices in each layer to illustrate the benefits.

Paper Details

Date Published: 5 April 2018
Proc. SPIE 10537, Silicon Photonics XIII, 105370G (5 April 2018); doi: 10.1117/12.2290252
Show Author Affiliations
Charles Baudot, STMicroelectronics (France)
Maurin Douix, STMicroelectronics (France)
Sylvain Guerber, STMicroelectronics (France)
Sébastien Crémer, STMicroelectronics (France)
Nathalie Vulliet, STMicroelectronics (France)
Jonathan Planchot, STMicroelectronics (France)
Romuald Blanc, STMicroelectronics (France)
Laurène Babaud, STMicroelectronics (France)
Carlos Alonso-Ramos, Ctr. de Nanosciences et de Nanotechnologies (France)
Diego Pérez-Galacho, Ctr. de Nanosciences et de Nanotechnologies (France)
Sonia Messaoudène, STMicroelectronics (France)
Sébastien Kerdiles, CEA-LETI (France)
Daniel Benedikovic, Ctr. de Nanosciences et de Nanotechnologies (France)
Catherine Euvard-Colnat, CEA-LETI (France)
Eric Cassan, Ctr. de Nanosciences et de Nanotechnologies (France)
Delphine Marris-Morini, Ctr. de Nanosciences et de Nanotechnologies (France)
Laurent Vivien, Ctr. de Nanosciences et de Nanotechnologies (France)
Pablo Acosta-Alba, CEA-LETI (France)
Frédéric Boeuf, STMicroelectronics (France)

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

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