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 ( 6 ¿ 6 ¿ 0.25 inches, or 15.2 ¿ 15.2 ¿ 0.635 cm). 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. Such measurement traceability can be achieved only by evaluating the measurement uncertainty (not just the repeatability) of each length comparison in the metrology chain between the definition of the meter and the NIST linewidth standard.This process results in a confidence interval about the calibration result that has a 95% probability of containing the true value. 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 paper and presentation will describe how these mask features are measured at NIST and how their measurement traceability is accomplished.
Proceedings of SPIE, 22nd Annual BACUS Symposium on Photomask Technology, Brian J. Grenon, Kurt R. Kimmel, Editors
, Pedulla, J.
and Stocker, M.
New NIST Photomask Linewidth Standard, Proceedings of SPIE, 22nd Annual BACUS Symposium on Photomask Technology, Brian J. Grenon, Kurt R. Kimmel, Editors, Monterey, CA
(Accessed December 2, 2023)