Abstract: An overlay measurement recipe is checked for reliability as follows. A first pair of overlay layers (130, 150) is formed (610), and the recipe is used to obtain alignment measurements for the two layers. Then another pair of overlay layers (130, 150) is obtained (630), possibly using the same masks, but this time at least one of the layers (150) is offset from its previous position. The overlay measurement recipe is used again to obtain alignment measurements (640). The two sets of measurements are checked against the offset of the layers from their previous positions to validate the recipe. Other embodiments are also provided.

Abstract: Critically representative features (CRF's) for use in mask-making verification and/or resist development verification are defined and/or copied into the in-scribe area used by wafer CD features. The placement of mask-CRF's in the wafer CD bar region eliminates the problem of correctly and quickly locating mask-CRF's at different positions in the in-die areas of a manufactured mask. On-wafer counterparts of the mask-CRF's may be used for fine-tuning lithography and patterning processes.