From Computational Lithography to Computational Inspection: Inverse Lithography Technology (ILT) and Inverse Inspection Technology (IIT)

Abstract

For semiconductor manufacturers moving toward advanced technology nodes -32nm, 22nm and below - lithography presents the greatest challenge, because it is fundamentally constrained by basic principles of optical physics. Because no major lithography hardware improvements are expected over the next couple years, Computational Lithography has been recognized by the industry as the key technology needed to drive lithographic performance. This implies not only simultaneous co-optimization of all the lithographic enhancement tricks that have been learned over the years, but that they also be pushed to the limit by powerful computational techniques and systems. Inspection presents another great challenge; Most mask rules are imposed not because of mask manufacturing constraints, but due to limitations of mask inspection tools. In addition, at the most advanced technology nodes, such as 32nm and 22nm, aggressive OPC and Sub-Resolution Assist Features (SRAFs), ILT, and SMO are required. Their use results in significantly increased mask complexity, making mask defect inspection and disposition more challenging than ever. In this paper, a single computational lithography and computational inspection framework based on Level Set Method is presented and explained in non-mathematical language. Results at the 32nm node and below are presented which demonstrate the benefits of Level-Set-Method-based ILT and IIT in design rule optimization, SMO, full-chip correction, and mask inspection.

Inverse lithography technology: 30 years from concept to practical, full-chip reality

“…Luminescent continued working on computational inspection and metrology technologies to enable mask inspection, mask review, and mask repair ready for ILT masks, until it was acquired by KLA in 2012, and TSMC EBO presented a number of papers together with Luminescent showing such capabilities deployed in production. [92][93][94][95][96][106][107][108][109][110][111][112][113][114] ILT was the topic of panel discussion at the SPIE Photomask Technology Conference for two consecutive years in 2015 and 2016. The industry also recognized the issue of using VSB mask writers to write curvilinear ILT masks.…”