Reticle/Mask Particle Detection System

The system detects particles by analyzing the scattering of laser light when the laser hits them. Evaluation of the scattered light enables detection of the size and location of the particles. The surface undergoing inspection is scanned by laser beams via spinning galvanometer mirrors and detectors measure the amount of light coming off the surface. An exclusive low-pass filter developed by HORIBA is used to analyze signal data for light reflected from the patterned surface and light scattered by particle contaminants. This improves discrimination. Argon lasers (488 nm) are used to increase operation reliability even further.

A function that measures pellicle transmissivity enables particle detection scanning to be carried out at the proper sensitivity. By switching the light paths, measurement can be done free of the influence of shadows from within the pellicle.