Silicon-On-Insulator (SOI) photonics has become an attractive research topic within the area of integrated optics. This project aims the fabrication of SOI-structures for optical communication technologies with lower costs and less technical requirements compared to standard fabrication processes as well as to provide a higher flexibility with respect to waveguide and substrate material choice. Therefore amorphous silicon is deposited on thermal oxidized silicon wafers by using the dissociation of monosilane (SiH4) in PECVD process, and the material is optimized for compact optical components and circuits in terms of optical light transmission, refractive index and minority carrier lifetime.

The integration of these optical components with the existing CMOS-fabrication technologies even allows the fabrication of highly compact electronic and optical components on the same substrate. This makes the routing of optical signals in microelectronics much easier since the optical layer can be deposited in a last step as a “back-end” process. 

The structures are patterned with DUV/NIL lithography and subsequent anisotropic plasma etching which facilitates the fabrication of highly compact waveguides (photonic wires) as well as of other optical components like couplers, Mach-Zehnder-interferometers (fig.1) tapers (fig. 2), modulators and resonators. Aside from material characterization of the optical layers with XRD, SEM, FTIR, 3-laser- ellipsometry and Raman-spectroscopy, the effects of post thermal treatment with RTA and local laser annealing are investigated.

Fig. 1: Mach-Zehnder interferometer (MZI) made of amorphous silicon

Fig. 2: 3D-tapers which were deposited on top of a-Si:H photonic wires

Contact:

Timo Lipka

Publications:

• A. Harke, M. Krause, J. Müller, Low-loss singlemode amorphous silicon waveguides, Electronics Letters, vol. 41 no. 25, 2005, pp. 1377-1379 
• A. Harke, T. Lipka, J. Amthor, O. Horn, M. Krause, J. Müller, Amorphous silicon 3D-tapers for Si photonic wires fabricated with shadow masks, IEEE PTL, vol.20 no.17, 2008, pp. 1452-1454
• T. Lipka, A. Harke, O. Horn, J. Amthor, J. Müller, Amorphous Waveguides for High Index Photonic Circuitry, OFC/NOEFC, 2009