Detecting and classifying surface defects with multiple radiation collectors

Abstract

A system to detect and classify defects on a surface of a substrate. A first targeting assembly directs radiation in a first beam onto the substrate. A first collecting assembly collects first radiation specularly reflected from the substrate and produces first signals, a second collecting assembly collects first radiation scattered from the surface of the substrate by defects and not micro-roughness and produces second signals, and a third collecting assembly collects first radiation scattered from the surface of the substrate by defects and micro-roughness and produces third signals. A second targeting assembly directs radiation in a second beam onto the substrate. A fourth collecting assembly collects second radiation scattered from the substrate and produces fourth signals. A processor receives the first, second, third, and fourth signals. A module coupled to the processor has logic instructions stored in a computer-readable medium, which configure the processor to analyze the signals to detect and classify the defects on the substrate.