Study on fabrication tolerances of SOI based directional couplers and ring resonators

• The effect of manufacturing tolerances on directional couplers is studied in detail.
• Effects of wet chemical cleaning and substrate quality are studied in particular.
• 3D full wave FEM simulations have been carried out using Ansoft HFSS.
• Simulation results are emphasized by an analytical calculation of a ring resonator.
• Actions to compensate for fabrication tolerances have been proposed and discussed.

In this study the effect of waveguide shape deviation due to manufacturing tolerances on the performance of lateral directional couplers for ring resonators based on SOI-rib-waveguides is investigated. The effect of deviations of the waveguide width, slab thickness and the waveguide sidewall angle and wet chemical cleaning procedures on the device performance are investigated by using Full Wave 3D Finite Element Method. Furthermore deviations of the top silicon thickness determined by the substrate quality are included in the investigations. Possible measures against systematic process tolerances are proposed and modifications of the fabrication process to improve device stability and reproducibility are discussed.

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