An Improved Analysis Method on Si-Photonics Waveguide Sidewall Roughness

Low propagation loss waveguides are always preferred when making Si-photonics waveguide devices. However, light scattering due to sidewall roughness of waveguide contributes to the majority of signal losses. To reduce the loss, a reliable approach to measure the sidewall roughness is critical to fine-tune the fabrication process. In this paper, we report a direct sidewall roughness measurement method by using Atomic Force Microscopy (AFM) incorporated with a special scanning mode (Peakforce Tapping mode) and a point-terminated probe. This method has been successfully applied to measure the sidewall roughness of Si-Photonics waveguides for production process monitoring. The present method can also be applied to characterize the sidewall roughness of other nanostructures with similar requirements or situations.