Influence of a combination of random noise and pattern-edge width (in pixels) on contrast-to-gradient image resolution in scanning electron microscopy

Abstract

The contrast-to-gradient (CG) method has been proposed previously for the evaluation of image resolution in scanning electron microscopy (SEM). In the CG algorithm, the image to be evaluated is gradually reduced to form the 1/r-reduced image (r = 1, 2, 3, ...) until the representative features of local patterns are accurately recognizable after the corresponding r-th noise reduction. We have studied the influence of a combination of random noise and pattern-edge width (in pixels) on the CG resolution R using both PC-made test images and typical SEM images. As the random noise is larger, the value of R becomes larger (or poorer). The increase in R due to the noise influence is more significant for the narrower width of the pattern edge. This satisfactorily agrees with the common idea that the image resolution is to reflect the sharpness of the pattern edge recognized in the image noise. By revising the form of DeltaR from the weighted standard fluctuation of R to the differential of R, a significantly weak N(dot)-dependency on R has been favorably confirmed, with keeping firmly the noise-dependency on R. Here, N(dot) is the number of pattern dots in the image.