LENGTH MEASURING METHOD IN ELECTRONIC BEAM LENGTH MEASURING INSTRUMENT

摘要

PURPOSE:To enable high-precision length measurement in a frame memory with a small number of picture elements by splitting a preset measured area into several areas for sequencial scanning in each of the split areas while shifting respective scanning centers to combine one image information with another. CONSTITUTION:The information of secondary electrons generated by irradiating electron beams 2 to a sample 3 is stored in a frame memory 11 and appears on a display 13. A measured area is equally split into, e.g. four in vertical and horizontal, the equivalent of 16 screens is scanned in each of split areas with, e.g. 512X512 picture elements and the information is respectively stored in 16 frame memories M1-M16 with a small number of picture elements. Which split area a pattern is located in is judged from images projected by the display 13, and therefore the length is measured. For example, a 2048X2048 picture element can be measured with ten thousands magnifying power in a 10cmX10cm display screen at the resolution of 0.005mum using a low-cost memory.