METHOD TO MEASURE ALIGNMENT USING LATENT IMAGE GRATING STRUCTURES

摘要

A method for facilitating alignment measurements in a semiconductor fabrication process that uses a combination of underlying and latent images on a substrate to indicate alignment between a lithographic mask and the substrate. In an example embodiment of the method for measuring alignment, a substrate has a layer of photoresist disposed on it and illuminated through a reticle element resulting in the formation of a first plurality of underlying grating images. The first plurality of images has a repetitive and symmetrical pattern with equal spacing between images. A second plurality of latent grating images is formed in the photoresist having substantially the same pattern of images as the first plurality of images. The second plurality of images is disposed above from the first plurality of images, the first and second plurality of images serving as an indicator of alignment between the mask and the substrate when the combined images forming a repetitive pattern. The system includes an energy source, an optical element and a reticle element for forming the plurality of images on the substrate to aid in alignment.