Edge determination methodology for cross-section STEM image of photoresist feature used for reference metrology

Abstract

The novel method of sub-nanometer uncertainty for the line width measurement and line profile measurement using STEM (Scanning Transmission Electron Microscope) images is proposed to calibrate CD-SEM line width measurement and standardization of line profile measurement as reference metrology. In accordance with the proposed method, we already have established the methodology of Si line profile and line width measurement for reference metrology. In this article, we applied the proposed method to edge determination methodology of the photoresist feature. Using the proposed method, a specimen of photoresist feature is coated with metal, and then it is sliced as a thin specimen of 100 nm thickness by FIB (Focused Ion Beam) micro sampling system. Then the dark-field cross-sectional images of the specimen are obtained by STEM. The edge position of the photoresist is defined at the distance of half metal coating thickness from the peak positions of metal coating area. Then the detected line profiles are compared with the measurement results by CD-AFM. From series of analyses, we established the edge detection methodology of photoresist feature for reference metrology.