Improving submicron CD measurements through optimum operating points

Mircea V. Dusa; Klaus-Dieter Roeth; Christoph Jung

doi:10.1117/12.29754

1 March 1991 Improving submicron CD measurements through optimum operating points

Mircea V. Dusa, Klaus-Dieter Roeth, Christoph Jung

Proceedings Volume 1496, 10th Annual Symp on Microlithography; (1991) https://doi.org/10.1117/12.29754
Event: 10th Annual Symposium on Microlithography, 1990, Sunnyvale, CA, United States

Abstract

Some problems encountered when measuring submicron CD patterns with white light conventional optical microscopy are presented. These are intended to support the development of a flexible software controlled new high performance optical system, allowing variation in the illumination degree of coherence, numerical aperture, threshold edge detection criteria, focus plane, giving the user opportunities to optimize the measurements. The paper will present results in measuring 0.90 to 0.65 patterns with opposite polarities in different measuring conditions from which an optimum 'operating point' can be defined considering either +/- 0.030 micrometers accuracy criteria or a +/- 0.020 micrometers reproducibility criteria. From such operating points an optimum numerical aperture and illumination aperture can be selected for a given edge detection criteria. NA selection for best resolution and accuracy is also function of the measuring plane position. For small amount of changes in focus plane, increasing the objective NA may actually decrease the quality of the image intensity profile used for measurement, resulting in decreased reproducibility. Such effects, reported also for submicron lithography imaging systems were observed. An increase in overall accuracy when focus plane is moved from the resist upper surface to the bottom resist surface (wafer surface) is observed for windows measurements.

Citation Download Citation

Mircea V. Dusa, Klaus-Dieter Roeth, and Christoph Jung "Improving submicron CD measurements through optimum operating points", Proc. SPIE 1496, 10th Annual Symp on Microlithography, (1 March 1991); https://doi.org/10.1117/12.29754

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