Scanner and stepper intrafield distortion characterization-A Comparison and correlation of current techniques

摘要

Misregistration occurs to some extent at every printed point on a wafer due to several causes. Intrafield distortion is one aspect of misregistration that is difficult to detect and resolve in a production environment. Historically intrafield distortion was primarily detected by external overlay measurements of box-in-box structures. Distortion data can also be generated via in-situ pattern placement measurements of scanner/stepper alignment marks. In state-of-the-art exposure tools the magnitude of non-correctable intrafield errors has become small due to advances in lens manufacturing, and tool controls. This increase in quality has caused us to re-examine the capability of current distortion measurement techniques and their correlation to product imaging. This paper presents a comparison of distortion measurement techniques for current DUV scanners and steppers. Wafer level distortion errors were gathered via scanner in-situ mark measurements, LMS IPRO, and CD SEM product overlay measurements. Correlation of the scanner in-situ mark measurements and LMS IPRO measurement process will be presented. We will present our comparison of the product wafer across field overlay measurements with the results generated from the distortion measurements. Our conclusion will attempt to derive a figure of merit for the capability of the customary distortion techniques to describe intrafield product overlay variations.