Image processing using shape recognition for alignment to damaged registration marks in electron beam lithography

Abstract

Shape locate mark registration, a novel image processing technique to accurately locate even damaged registration marks, has been used to resolve alignment challenges in aggressively scaled lithography levels for sub-32 nm complementary metal oxide semiconductor devices. The achievable overlay using traditional registration hardware and software is ultimately limited by the quality of the registration marks and any changes in the registration mark signals caused by device process steps between overlay critical exposure levels. This article discusses the details in the shape locate mark registration and results achieved for the device program. The shape locate mark registration system has been implemented and tested on a Vistec VB6 electron beam lithography tool. Mark locate repeatabilities of better than 5 nm (3σ) across 200 mm wafers and better than 10 nm overlay for device lithography have been demonstrated. Highly scaled 22 nm node fin field effect transistor (FinFET) static random access memory cells of area down to 0.099 μ m2 were fabricated using all e-beam lithography and shape locate registration to demonstrate the scalability of FinFET technology (Kawasaki, Tech. Dig.-Int. Electron. Devices Meet, 2008, p. 237). © 2009 American Vacuum Society.