Waveguide sidewall roughness estimation via shape-from-shading surface reconstruction of SEM pictures

A shape-from-shading algorithm is applied to topography images of silica waveguide sidewalls coming from a Scanning Electron Microscope. The approach is found appropriate to restitute the sidewall profile. The reconstructed relief obtained is then height calibrated via Line Edge Roughness measurement. The technique enables thereafter roughness measurement at arbitrary positions on the sidewall, with the advantage of providing non-destructive testing on full wafer.