Patent ID: 7369233
Filing Date: 2008-05-06
Classification: G01N

Abstract:
1. An optical method for measuring characteristics of a sample, comprising: illuminating a surface of the sample by a beam of radiation along an illumination path, radiation in said beam comprising at least one wavelength component in a vacuum ultraviolet (VUV) range; detecting radiation from the surface originating from the beam along a detection path to provide at least one output signal; reducing amount of ambient absorbing gases and moisture present in at least a portion of each of the illumination and detection paths without employing a vacuum chamber, by displacing said gases and moisture with another gas that does not substantially absorb the at least one VUV wavelength component so as to reduce attenuation of the at least one VUV wavelength component, wherein the reducing includes supplying said another gas from a direction transverse to a direction normal to the surface of the sample and to at least one of the illumination and detection paths; and determining the characteristics of the surface from said at least one output signal.