Defect detection system

Abstract

Scattered radiation from a sample surface is collected by means of a collector that collects radiation substantially symmetrically about a line normal to the surface. The collected radiation is directed to channels at different azimuthal angles so that information related to relative azimuthal positions of the collected scattered radiation about the line is preserved. The collected radiation is converted into respective signals representative of radiation scattered at different azimuthal angles about the line. The presence and/or characteristics of anomalies are determined from the signals. Alternatively, the radiation collected by the collector may be filtered by means of a spatial filter having an annular gap of an angle related to the angular separation of expected pattern scattering. Signals obtained from the narrow and wide collection channels may be compared to distinguish between micro-scratches and particles. Forward scattered radiation may be collected from other radiation and compared to distinguish between micro-scratches and particles. Intensity of scattering is measured when the surface is illuminated sequentially by S- and P-polarized radiation and compared to distinguish between micro-scratches and particles. Representative films may be measured using profilometers or scanning probe microscopes to determine their roughness and by the above-described instruments to determine haze in order to build a database. Surface roughness of unknown films may then be determined by measuring haze values and from the database.