Development and implementation of PWQ on patterned wafer darkfield inspection systems

Process Window Qualification (PWQ) is a well-established wafer inspection technique used to qualify the design of mask sets and to characterize lithography process windows. While PWQ typically employs a broadband brightfield inspector, novel techniques for patterned wafer darkfield inspection have proven to provide sufficient sensitivity along with noise suppression benefits for lithography layers. This paper describes the introduction and implementation of PWQ on patterned wafer darkfield inspectors. An initial project characterized critical PWQ requirements on the darkfield inspector. The results showed that this new approach meets performance requirements, such as defect of interest (DOI) detection and process window characterization, as well as ease-of-use requirements such as automated setup for advanced design rule products.