From nanoscale displacement sensing and estimation to nanoscale alignment

Abstract

In this article, the authors present theoretical background and practical procedures for linking displacement sensing and estimation to nanoscale alignment. The authors discuss the application of nanoscale displacement sensing and estimation (nDSE)-based overlay metrology tool. The authors propose a new look at what constitutes displacement and alignment. From there, the authors develop several frameworks to bridge these two concepts based on a set of new pseudodisplacement concepts and on the careful selection of references. Direct displacement-measurement-based alignment (DDMA) is the first method the authors have used to generate reliable alignment results. The authors achieved sub-100-nm (down to 21nm) alignment accuracy. Indirect displacement-measurement-based alignment (IDMA) is the most accurate method in theory. IDMA truly utilizes nDSE to achieve precision coplacement between different layers and processes. IDMA and DDMA, along with a group of other nDSE-based algorithms/procedures, are vibration tolerant, making them ideal as overlay alignment tools for nanoimprint lithography.