Increase of wafer inspection tool throughput with computational imaging

To increase the throughput of image-based wafer quality inspection tools, we propose to use computational imaging methods to address two main bottlenecks: the mechanical alignment of the wafer with the imaging plane and pixel size of the imager. The former requires significant time but is crucial for a reliable quality check, and the latter introduces a trade off between the wafer scanning speed and the minimum detectable defect size. We demonstrate application of our recently developed SANDR algorithm for obtaining a wafer image with sub-pixel resolution from a series of not-perfectly aligned low-resolution images. The wafer misalignment creates a varying over the field of view depth-of-focus, which poses a significant obstacle for the state-of-the-art methods, but is successfully processed with SANDR. The method is tested on simulated images.