Decoupling of alignment and overlay metrology errors, and layer-to-layer overlay metrology errors for overlay optimization using machine learning approaches

摘要

A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). Driven by the growing demand of manufacturing modern integrated circuits with ever shrinking sizes, lithographic technologies thai can offer higher resolution und botter reliabilily are under a fast-paced and extensive development. One of such advancing lithographic technologies is the extreme ultra-violet lithography (also known as EUV or EUVL), which allows for sub-10 nanometre (nm) scale resolution. In lithographie processes, it is desirable frequently to make measurements of the structures created, e.g., for process control and verification. Driven by such a demand, various inspection and metrology toots have been made available, including scanning electron microscopes, which are often used to measure critical dimension (CD), and specialized optical metrology tools, such as various forms of scatterometers, to measure overlay, a measure of the accuracy of alignment of two layers in a device.