Microphotonic resonators are very sensitive to sidewall roughness. Several structures with sub-100-nm gap between bus and ring have been patterned on silicon-on-insulator wafer with 50 keV electron-beam lithography at different doses. The authors' direct Monte Carlo (DMC) model has been used to model the electron scattering and energy deposition to predict proximity effects and image modulation. By comparing the point spread function from DMC with independent experimental results, the DMC model has been validated. Experimentally, the line edge roughness (LER) study has been carried out to include both the first order (standard deviation) and the second order of statistical analysis (correlation length). The authors found that the LER is not uniform and varies with the position along the pattern-this nonlocal LER may have profound implications for the performance of the devices. The highest local LER is obtained at the position when the bus is closest to the ring. This phenomenon will be exacerbated when the gap size becomes smaller and will affect coupling efficiency of the waveguides. (c) 2007 American Vacuum Society.