Electron-beam metrology and inspection

Production of integrated circuits necessitates pattern inspection and measurement of critical dimensions to guarantee yield and quality. The shrinking of pattern size in microelectronics requires progressive employment of electron-beam techniques for this purpose. GaAs technology and integrated optics pose additional challenges.Critical dimensions, e.g. linewidth and pitch, as well as placement accuracy of patterns on wafers or masks are to be examined. The measurement accuracy of any e-beam technique is influenced by the quality of the instrument but also by the process of signal formation and by charging effects. High- and low-voltage operation are possible, both having a certain range of applications. Low-voltage operation requires the electron optics to be adapted, but minimizes charging and damage. The algorithms of peak detection, threshold and automatic threshold crossing as well as linear regression may be used for detection of the pattern edges.Inspection is necessary to monitor pattern fidelity, and in an automated form it is intended to be utilized for defect detection. Pattern-to-pattern comparison, pattern-to-data comparison, and feature extraction are the techniques which have been investigated so far.