Mask layer structure superimposition accuracy determination, for semiconductor manufacture, involves scanning rear side of substrate and mask layer using radiation, and evaluating images to find positions of alignment marks

摘要

Mask layer`s structure superimposition accuracy determination method involves scanning a rear side of a semiconductor substrate (10) and a mask layer (14) using electromagnetic radiations. The radiations reflected from the substrate and layer are absorbed. Images of the absorbed radiation are evaluated to find positions of alignment marks on the substrate and layer. The accuracy of superimposition of a mask structure in the layer is determined based on the positions. An independent claim is also included for an optical system for determining the accuracy of superimposition of a structure in a mask layer on a semiconductor layer.