Disclosed are methods and apparatus for detecting a relatively
wide dynamic range of intensity values from a beam (e.g.,
scattered light, reflected light, or
secondary electrons) originating from a sample, such as a
semiconductor wafer. In other words, the inspection
system provides detected output signals having wide dynamic ranges. The detected output signals may then be analyzed to determine whether defects are present on the sample. For example, the intensity values from a target die are compared to the intensity values from a corresponding portion of a reference die, where a significant intensity difference may be defined as a defect. In a specific embodiment, an inspection
system for detecting defects on a sample is disclosed. The
system includes a beam generator for directing an
incident beam towards a sample surface and a
detector positioned to detect a detected beam originating from the sample surface in response to the
incident beam. The
detector has a sensor for detecting the detected beam and generating a detected
signal based on the detected beam and a non-
linear component coupled to the sensor. The non-
linear component is arranged to generate a non-linear detected
signal based on the detected
signal. The
detector further includes a first analog-to-
digital converter (ADC) coupled to the non-
linear component. The first ADC is arranged to digitize the non-linear detected signal into a digitized detected signal.