Study On The Design Of The Measuring And Control System Of Metrological Scanning Electron Microscopy

Nanometer measurement is a precision measuring method on the scale and properties such as shape, optics, electricity, magnetism etc. of material on the nanoscale. The most basic challenge is to precisely measure the scale. With the advantages of high resolution ratio, large depth of field, wide measuring range and fast imaging speed, scanning electron microscopy (SEM) has became one of the major measuring tools in the measurement field of micro-nano geometry structures under 100nm. But the growth in the precisely measurement field of SEM is seriously influenced by the status the measured values of commercial SEM produced by different manufacturers cannot be traced back to the unified benchmark and have big measurement error. The thesis is supported by the National Science-Technology Support Plan Projects (No.2011BAK15B02). In order to establish a complete standard measuring device of Metrology Scanning Electron Microscopy, the key technologies is studied. Therefore, the precisely measurement of the micro-nano geometry structures and the quantity traceability of SEM can be realized. Meanwhile, the implement method of the measuring and control system is proposed.This thesis comprehensively analyzes the present research status on the method of nanometer measurement and quantity transfer. The measuring principle and the present research status at home and abroad of Regular SEM and Metrology SEM are introduced and the structures and performance indexes of the Metrology SEM are analyzed. The structures of the measuring and control system with nanopositioning stage scanning and imaging and interferometer tracing quantities is designed. The optical layout of a two-axes displacement measurement system based on heterodyne laser interferometric method and electronic subdivision method is designed. The control method of the piezoelectric ceramics nanopositioning stage is analyzed and the structure of kinetic control system of stage with two-layers driving and dual-signals controlling is proposed. Then the implement method of high speed data acquisition technology is analyzed and the image acquisition and processing system based on NI-VISION tools is designed and the measuring and control software is programmed using the LabVIEW language.In order to verify the performance of the whole system and each sub system, the standard measurement experiment setup of the whole metrology SEM and its each sub system was constructed and some experiments were conducted as follows:(1) resolution measurement and stability experiments of the laser interferometer measurement sub system. The maximum measurement resolution and static stability are verified while the stage were static and the dynamic stability is verified while the stage was stepping with 5nm. The results demonstrate that the maximum resolution is better than 2nm and static stability is better than 3.5nm and the dynamic stability is better than 2nm. (2) The stability and vibration measurement experiments of the motion control subsystem and the results demonstrate that the motion trajectory of stage meets the design requirement and the vibration error is better than ±6nm. (3) The filtering effect verification experiment of image acquisition and processing subsystem and the results demonstrate the good filtering effect. (4) the stability and measurement accuracy of the whole system of Metrology SEM by imaging measurement of 1μm two-dimensional grid sample. The results demonstrate the good stability, synchronism and repeatability of the whole system and the measurement uncertainty is better 10nm within 10μm scanning range.