STEP MEASURING INSTRUMENT

摘要

PURPOSE:To measure a step stably by converging the 1st coherent light reflected by the surface of a sample to be measured and allowing it to interfere with the 2nd coherent light which is varied in optical path length or frequency, and detecting interference fringes generated at this time. CONSTITUTION:Light shifted in frequency is reflected by a light splitting element 10 and superposed as the 2nd coherent light upon the 1st coherent light. Their interference light 14 is split by the light splitting element 15; part of it is detected by a photodetector and the remainder is detected by photodetectors 17-1 and 17-2 respectively. Those photodetectors and a signal processing circuit which processes signals of those photodetectors are provided to obtain lateral resolution of about 1mum when the coherent light is stopped down sufficiently through an objective. The surface of a semiconductor device which varies in structure in a micron order plane direction can be measured and the step is therefore measured stably.