Sidewall roughness and line profile measurement of photoresist and finFET features by cross-section STEM and TEM image for reference metrology

Abstract

The novel method of sub-nanometer uncertainty for the line width measurement and the line profile measurement using STEM (Scanning Transmission Electron Microscope) images is proposed to calibrate CD-SEM line width measurement and the standardization of line profile measurement as reference metrology. In accordance with the proposed method, we already have established the methodology of profile of Si line and photoresist feature for reference metrology. In this article, we applied the proposed method to the sidewall roughness measurement of photoresist features and line profile measurement of finFET features. Using the proposed method, specimens of photoresist feature and finFET feature are sliced as thin specimens of 100 nm thickness by FIB (Focused Ion Beam) micro sampling system. Then the cross-sectional images of the specimens are obtained by STEM and TEM. The sidewall roughness of photoresist features is estimated by the maximum slope of the image intensity graph at the edge. Then, the sidewall roughness is also measured by CD-AFM (Critical Dimension Atomic Force Microscope); we compared the results by STEM image and CD-AFM. Moreover, the line profile of finFET features is defined using TEM images for reference metrology. We compared the line width of fin measured by the proposed method and CD value by CD-SEM measurement.