Patent ID: 6833913
Filing Date: 2004-12-21
Classification: G01N

Abstract:
An inspection system for detecting defects on a sample, the system comprising:a beam generator for directing an incident beam towards a sample surface; a detector positioned to detect a detected beam originating from the sample surface in response to the incident beam, wherein the detector comprises: a sensor for detecting the detected beam and generating a detected signal based on the detected beam; a non-linear component coupled to the sensor, the non-linear component being arranged to generate a non-linear detected signal based on the detected signal; and a first analog-to-digital converter (ADC) coupled to the non-linear component, the first ADC binge arranged to digitize the non-linear detected signal into a first digitized detected signal; a data processor for determining whether there is a defect present on the sample surface based on the first digitized detected signal, wherein the non-linear component is arranged to match a dynamic range of the detected signal to at least a portion of a dynamic range of the first ADC; a transformation mechanism for transforming the first digitized detected signal into a second digitized detected signal that compensates for noise variation associated with different intensity levels of the first detected output signal, and wherein the data processor is further arranged to receive the second digitized signal and the step of determining whether there is a defect is based indirectly on the first digitized detected signal by being based directly on the second digitized detected signal.