Tunable silicon photonic wires fabricated by contact lithography and thermal oxidation

Oliver Horn; Julia Amthor; Timo Lipka; Jörg Müller

doi:10.1117/12.821694

20 May 2009 Tunable silicon photonic wires fabricated by contact lithography and thermal oxidation

Oliver Horn, Julia Amthor, Timo Lipka, Jörg Müller

Proceedings Volume 7366, Photonic Materials, Devices, and Applications III; 73660C (2009) https://doi.org/10.1117/12.821694
Event: SPIE Europe Microtechnologies for the New Millennium, 2009, Dresden, Germany

Abstract

Contact lithography with i-line (365 nm) or DUV (248 nm) is widely used in laboratories for prototyping. The achievable line width of 300 nm is sufficient for photonic wires, but a process with larger line width is more controllable. The sidewall roughness induced by the lithography and by the following etching steps results in high optical losses. Thermal oxidation is known to smoothen the silicon surface. The oxidation also consumes silicon, so that the photonic wire will shrink and a wider lithography linewidth can be applied. The silicon dioxide is used as a low loss cladding, which further reduces the refractive index contrast, so that the remaining roughness causes less losses. Single mode silicon nanowires with 500nm by 200nm cross section and optical losses of 2dB/cm were produced. The index contrast is still high enough for small bending radii for highly integrated photonic devices. Sharp branches used in Y-couplers can not be fabricated by this oxidation technique, due to the waveguide shrinkage. 3dB-couplers are easily realized by multimode interference (MMI)-couplers, with the output branches sufficiently apart. Using such couplers, Mach-Zehnder interferometers were fabricated. For electric contacts, the SiO₂-cladding is locally removed and ZnO and Al electrodes are applied. The c-axis of sputtered ZnO grows preferentially perpendicular to the surface, which allows to utilize the electro optic effect.

Citation Download Citation

Oliver Horn, Julia Amthor, Timo Lipka, and Jörg Müller "Tunable silicon photonic wires fabricated by contact lithography and thermal oxidation", Proc. SPIE 7366, Photonic Materials, Devices, and Applications III, 73660C (20 May 2009); https://doi.org/10.1117/12.821694

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