Method and apparatus for beam stabilization and reference correction for euv inspection

An inspection system, comprising:

• an illumination source configured to emit an extreme ultraviolet (EUV) illumination beam for illuminating a sample;
• one or more first multi-cell detectors,
• wherein each of the first multi-cell detectors comprises at least two segments and is configured to generate a first photocurrent when the illumination beam passes through the one or more first multi-cell detectors,
• wherein each of the first multi-cell detectors includes an aperture at a center portion thereof,
• wherein each of the first multi-cell detectors is configured to generate a first illumination intensity distribution signal based on the first photocurrent;
• one or more second multi-cell detectors,
• wherein each of the second multi-cell detectors comprises at least two segments and is configured to generate a second photocurrent when the illumination beam passes through the one or more second multi-cell detectors,
• wherein each of the second multi-cell detectors is configured to generate a second illumination intensity distribution signal based on the second photocurrent;
• a detector assembly configured to receive the illumination beam from the sample and generate images based on the illumination beam;
• and
• a controller communicatively coupled to the detector assembly, the one or more first multi-cell detectors, and the one or more second multi-cell detectors, wherein the controller includes one or more processers configured to execute program instructions causing the one or more processors to:
• receive the images from the detector assembly,
• calibrate the second illumination intensity distribution signal to the images by mapping distortions in the second illumination intensity distribution signal to distorted pixels in the images,
• adjust intensities of the distorted pixels in the images based on the second illumination intensity distribution signal to generate corrected images, and
• detect defects on the sample using the corrected images.