40-nm-particle high-probability detection for bare wafer using side-scattered light

A high probability particle detection system for LSI wafers is proposed. In order to detect fine particles on bare wafers, optical noise from them are studied. Simulation with a diffraction model indicates that the optical noise is caused by diffracted light on the wafer roughness, and can be reduced by a large incident angle illumination and a detector with small pixel size. The side-scattering light detection system which has a illumination of incident angle of 80 degrees and a detector with a pixel size of 0.3 micrometers was confirmed experimentally to detect standard 38-nm particles in high signal-to-noise ratio, and the detection results were verified by SEM. Probability study of detection indicates that the detection probability reduces rapidly as detection light level is low. Two types of systems are proposed, a high detection probability system of 95% with energy of 600 mJ/cm 2 a low illumination energy system of 4 mJ/cm 2 with probability of 10%.