The reduced critical dimensions of semiconductor devices place more stringent requirements on the precision and accuracy of overlay metrology tools used to monitor stepper feature placement. The use of mix and match stepper techniques and step and scan exposure tools further stress the need for accuracy in overlay metrology tools. It is widely recognized, however, that overlay measurement accuracy can be compromised by misalignments and measurement errors in the optical measurement tool, referred to as tool-induced-shift. Further errors in the measurement process result from asymmetries of the specimen creating an erroneous overlay shift, referred to as wafer-induced-shift. Our optical overlay metrology program at NIST is currently addressing these measurement concerns with the development of a high-accuracy overlay measurement system. This system will be used for overlay measurement research and the calibration of standard reference artifacts designed to improve standard optical alignment procedures as well as artifacts specifically designed for overlay instrument calibration.
Proceedings Title: Proceedings of SPIE, Metrology, Inspection, and Process Control for Microlithography X, Susan K. Jones, Editor
Conference Dates: March 11, 1996
Conference Location: Santa Clara, CA
Pub Type: Conferences
instrument design, overlay metrology, overlay standards