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.