Method and system for enhancing image quality

摘要

This invention relates to methods and systems for enhance the signal-to-noise ratio of an image scanned by a charged particle beam. In an embodiment, a sequence of grayscales of a pixel is recorded first, extreme values of the sequence of grayscales are then identified and removed, and the remained grayscales are used to determine a nominated grayscale of the pixel.

主权项

1. An inspection system for inspecting a sample comprising:
a charged particle beam generator for generating a primary charged particle beam; a condenser lens module arranged below the charged particle beam generator and adapted for condensing the primary charged particle beam; a probe forming objective lens module arranged below the condenser lens module and adapted for focusing the condensed primary charged particle beam into a charged particle beam probe; a charged particle beam deflection module arranged below the condenser lens module for deflecting the charged particle beam probe to a surface of the sample; a secondary charged particle detector module for detecting a secondary charged particle detection signal generated from the sample; an image forming module communicated with the secondary charged particle detector module for receiving the secondary charged particle detection signal and forming at one or more frames; and a noise-filtering module communicated with the image forming module and encoded with a computer program for determining a defect, wherein the computer program performs the following steps: recording a sequence of grayscales of a pixel of the frames scanned by the charged particle beam; removing extreme values from the sequence of grayscales; and determining a nominated grey level of the pixel from remained grayscales.