Evaluation method of surface roughness using SEM

Surface roughness plays a crucial role in determining the physical and functional properties of materials, particularly in electroplated coatings for semiconductor and manufacturing applications. In this study, we investigate the feasibility of assessing surface roughness by scanning electron microscope (SEM) combined with the photometric stereo (PS) method and using a segmented backscattered electron (BSE) detector-referred to as the SEM-PS method. Conventional SEM-PS method suffers from limited height accuracy due to artifacts such as BSE deflection; therefore, distortion and deflection corrections were introduced to enhance measurement precision. Four electroless Ni-P plated samples with different roughness levels but identical composition were prepared, all exhibiting amorphous structures and low inclination angles suitable for SEM-PS analysis. Height calibration was performed using an atomic force microscope (AFM), with one sample serving as the reference. After corrections, SEM-PS results showed good agreement with AFM measurements, particularly in regions with gentle slopes, and consistent roughness trends were confirmed across all samples. Although sensitivity to surface contamination remains a limitation, the SEM-PS method provides a non-destructive, wide-area approach for reliable evaluation of intrinsic surface morphology, offering clear advantages for plating characterization and other applications requiring contamination-insensitive surface analysis.