Model-based analysis of SEM images to automatically extract linewidth, edge roughness, and wall angle

Abstract

Methods of extracting information regarding critical dimensions (CD) in scanning electron microscopes (SEM) are currently based on image brightness. This brings significant uncertainty of the measured results because image brightness has a complex relation to the size and shape of feature, its material, geometry of the pattern as well as SEM setup. A model based extraction of CDs out of SEM images has been developed. The analysis is based on an understanding of physical principles involved in the formation of the SEM signal. Some parameters, such as beam voltage and materials, should be known to the operator as the input data along with the SEM image. The output results of the myCD software are contours of lines, linewidth at the top, bottom, and in the middle of the line, line edge roughnessess at each edge, line width roughness, and wall angles at each edge. In addition, averaged values over all lines present in the image are also displayed. The model based analysis of SEM images may considerably improve accuracy of CD measurements in SEM.