Complex Optical Proximity Correction (OPC) must be deployed to meet advanced lithography requirements. The OPC models are used to convert input design shapes into mask data that often deviate significantly from both the initial design and the final wafer image in resist. The process includes selective shape biasing, applying pattern-specific corrections, and, possibly, modeling the effect at multiple exposure conditions. It is important to verify the results of the OPC model and this is done by invoking OPC verification programs. The verification models identify points of failure to specific criteria. Failure can be defined as the simulated resist dimension below which a feature will not survive additional processing. Since these models are built for use in OPC verification, they may only be well-calibrated at feature sizes near target. This can introduce uncertainties in the failure predictions. This paper will explore options for validating the OPC verification models and methods. While wafer prints are an obvious source of feedback on the simulated results, there are also options at mask level. In this paper, we study the effect of programmed defects at wafer level, mask level and through OPC verification method. For each test case, five points in the process window space are chosen to provide comparison data between OPC verification measurements, mask-level intensity contour measurements - e.g. Aerial Image Microscope System (AIMS), and wafer measurement of patterned photoresist. The results permit correlation to measurable metrics and provide an improved understanding of OPC verification validity.

Date Published: 16 November 2007
PDF: 9 pages
Proc. SPIE 6730, Photomask Technology 2007, 67302Q (16 November 2007); doi: 10.1117/12.746685

Published in SPIE Proceedings Vol. 6730:
Photomask Technology 2007
Robert J. Naber; Hiroichi Kawahira, Editor(s)