New CD-SEM metrology method for the side wall angle measurement using multiple detectors

Abstract

A new metrology method for CD-SEM has been developed to measure the side wall angle of a pattern on photomask. The height and edge width of pattern can be measured by the analysis of the signal intensity profile of each channel from multiple detectors in CD-SEM. The edge width is measured by the peak width of the signal intensity profile. But it is not possible to measure the accurate edge width of the pattern, if the edge width is smaller than the primary electron beam diameter. Using four detectors, the edge width can be measured by the peak width which appears on the subtracting signal profile of two detectors in opposition to each other. Therefore, the side wall angle can be calculated if the pattern height is known. The shadow of the side wall appears in the signal profile from the detector of the opposite side of the side wall. Furthermore, we found that there was the proportional relation between pattern height and the shadow length of the signal on one side. This paper describes a method of measuring the side wall width of a pattern and experimental results of the side wall angle measurements.