Optical gratings, lithography tools including such optical gratings and methods for using same for alignment

摘要

Lithography tools and substrates are aligned by generating geometric interference patterns using optical gratings associated with the lithography tools and substrates. In some embodiments, the relative position between a substrate and lithography tool is adjusted to cause at least one geometric shape to have a predetermined size or shape representing acceptable alignment. In additional embodiments, Moiré patterns that exhibit varying sensitivity are used to align substrates and lithography tools. Furthermore, lithography tools and substrates are aligned by causing radiation to interact with optical gratings positioned between the lithography tools and substrates. Lithography tools include an optical grating configured to generate a portion of an interference pattern that exhibits a sensitivity that increases as the relative position between the tools and a substrate moves towards a predetermined alignment position.