CALIBRATION OF A SMALL ANGLE X-RAY SCATTEROMETRY BASED METROLOGY SYSTEM

摘要

A method and system for calibrating an X-ray beam incident position on a specimen in an X-ray scatterometry metrology system are described herein. The exact location of incidence of the illumination beam on the wafer surface is determined based on occlusion of the illumination beam by two or more occlusion elements. The center of the illumination beam is determined based on the measured value of the transmitted flux and the model of the beam's interaction with each occlusion element. The position of the axis of rotation that orients the wafer over a range of angles of incidence is adjusted to align with the surface of the wafer and intersect the illumination beam at the measurement position. An exact offset value is determined between the normal angle of incidence of the illumination beam with respect to the wafer surface and the zero angle of incidence measured by the sample positioning system.