DEFECT DETECTION USING TIME DELAY LOCK-IN THERMOGRAPHY (LIT) AND DARK FIELD LIT

摘要

To increase inspection throughput, the field of view (FOV) of an IR camera can be moved over the sample at a constant velocity. Throughout this moving, a modulation (e.g. optical or electrical) can be provided to the sample and IR images can be captured using the IR camera. Moving the FOV, providing the modulation, and capturing the IR images can be synchronized. The IR images can be filtered to generate the time delay LIT, thereby providing defect identification. In one embodiment, this filtering accounts for the number of pixels of the IR camera in a scanning direction. For the case of optical modulation, a dark field region can be provided for the FOV throughout the moving, thereby providing an improved signal-to-noise ratio (SNR) during filtering.