Throughput optimization for sequential alignment measurements

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). In lithographic processes, it is desirable frequently to make measurements of the structures created, e.g., for process control and verification. Driven by the growing demand of manufacturing modern integrated circuits with ever shrinking sizes, lithographic technologies that can offer higher resolution and belter reliability 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 nanometer (nm) scale resolution. In parallel with the advancement of lithographic technologies, inspection and metrology technologies, such as for example optical scatterometry, are making efforts to keep up with the scaling pace of semiconductor ICs. As such, various inspection and metrology tools have been made available, including scanning electron microscopes (SEMs), 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.