Importance

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Abstract

A method of determining overlay accuracy, using visual inspection, of a first circuit pattern relative to a second circuit pattern. The first circuit pattern and the second circuit pattern are too large to be contained in a single reticle and are formed separately on an integrated circuit wafer and photo stitched together. A first overlay pattern is located adjacent to the first circuit pattern on a mask. A second overlay pattern is located adjacent to the second circuit pattern on a mask, preferably, but not necessarily, the same mask. The first overlay pattern and the second overlay pattern are located so that their images in the layer of developed photoresist will be adjacent to each other after the photoresist is exposed with the first and second circuit patterns and developed. Visual observation of the images of the first and second overlay patterns is then used to determine the overlay accuracy of the first circuit pattern relative to the second circuit pattern.

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First Claim