PURGE GAS FLOW CONTROL FOR HIGH-PRECISION FILM MEASUREMENTS USING ELLIPSOMETRY AND REFLECTOMETRY

摘要

A method and system for measuring sample characteristics using a broadband metrology tool in a purge gas flow environment are disclosed. A beam path for the tool is purged with gas at a first flow rate. The sample surface is illuminated by source radiation having a vacuum ultraviolet (VUV) and/or ultraviolet-visible (UV-Vis) component. The gas flow rate is adjusted between the first flow rate for measurements made with VUV radiation and a second flow rate for measurements made UV-Vis radiation. The system includes a light source, illumination optics, collection optics, detector, gas source and a controller. The gas source can supply gas to a beam path in the light source and/or illumination optics and/or sample and/or collection optics and/or detector. The controller can control a flow rate of the gas in response to an output signal from the detector.