Updated NIST Photomask Linewidth Standard

Published

May 1, 2003

Author(s)

J Pedulla, James E. Potzick, Michael T. Stocker

Abstract

NIST is preparing to issue the next generation in its line of binary photomask linewidth standards. Called SRM 2059, it was developed for calibrating microscopes used to measure linewidths on photomasks, and consists of antireflecting chrome line and space patterns on a 6 inch quartz substrate. Certified line- and space-widths range from nominal 0.250 ¿m to 32 ¿m, and pitches from 0.5 ¿m to 250 ¿m, and are traceable to the definition of the meter. NIST's reference value, the definition of the meter, is well defined and unconditionally stable. Any replacement or duplicate NIST linewidth standard will be traceable to this same reference, and thus traceable to any other NIST length standard. Establishing such traceability requires evaluation of the effects of all error sources affecting the calibrations. While the meter (and the ¿m) are well-defined, the geometrical width of a chrome line with nonrectangular cross section is not, and so the 'true value' linewidth must be carefully defined to best meet users' needs. The NIST linewidth measurement system and the optical imaging model used have both been updated for this SRM. Remeasurements of previous NIST SRMs 473 and 475 reveal discrepancies which are difficult to reconcile with previous international comparisons between NIST, NPL, and PTB.NIST is preparing to issue the next generation in its line of binary photomask linewidth standards. Called SRM 2059, it was developed for calibrating microscopes used to measure linewidths on photomasks, and consists of antireflecting chrome line and space patterns on a 6 inch quartz substrate. Certified line- and space-widths range from nominal 0.250 ¿m to 32 ¿m, and pitches from 0.5 ¿m to 250 ¿m, and are traceable to the definition of the meter. NIST's reference value, the definition of the meter, is well defined and unconditionally stable. Any replacement or duplicate NIST linewidth standard will be traceable to this same reference, and thus traceable to any other NIST length standard. Establishing such traceability requires evaluation of the effects of all error sources affecting the calibrations. While the meter (and the ¿m) are well-defined, the geometrical width of a chrome line with nonrectangular cross section is not, and so the 'true value' linewidth must be carefully defined to best meet users' needs. The NIST linewidth measurement system and the optical imaging model used have both been updated for this SRM. Remeasurements of previous NIST SRMs 473 and 475 reveal discrepancies which are difficult to reconcile with previous international comparisons between NIST, NPL, and PTB.

Proceedings Title

Proceedings of SPIE, Metrology, Inspection, and Process Control for Microlithography XVII, Daniel J. Herr, Editor

Volume

5038

Conference Dates

February 24, 2003

Conference Location

Santa Clara, CA, USA

Conference Title

Mask-related Metrology

Pub Type

Conferences

Keywords

linewidth, metrology, photomask, standard, traceability

Citation

Pedulla, J. , Potzick, J. and Stocker, M. (2003), Updated NIST Photomask Linewidth Standard, Proceedings of SPIE, Metrology, Inspection, and Process Control for Microlithography XVII, Daniel J. Herr, Editor, Santa Clara, CA, USA (Accessed April 19, 2024)