| 摘要 |
A method for characterizing overlay errors between at least a first and a second mask layer for an integrated circuit. A first primary alignment structure is formed in a first position of the inter-layer region around the first mask layer, and a first secondary alignment structure is formed in a second position of the inter-layer region around the first mask layer. Similarly, a second primary alignment structure is formed in a first position of an inter-layer region around the second mask layer, and a second secondary alignment structure is formed in a second position of the inter-layer region around the second mask layer. The first mask layer and the second mask layer are exposed onto a photoresist coated substrate with a first exposure and a second exposure, where the first position of the first primary alignment structure during the first exposure generally aligns with the second position of the second secondary alignment structure, and the second position of the first secondary alignment structure during the second exposure generally aligns with the first position of the second primary alignment structure. The photoresist on the substrate is developed, and offsets between the first primary alignment structure and the second secondary alignment structure are measured, and offsets between the second primary alignment structure and the first secondary alignment structure are also measured, to determine the overlay errors.
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