Complex Metrology on 3D Structures Using Multi-Channel OCD

Authored by: Taher Kagalwalaa, Sridhar Mahendrakara, Alok Vaida, Paul K. Isbesterb, Aron Ceplerb, Charles Kangb, Naren Yellaib, Matthew Sendelbachb, Mihael Koc, Ovadia Ilgayevc, Yinon Katzc, Lilach Tamamc, Ilya Osherovc | SPIE 2017, February 1, 2017

Device scaling has not only driven the use of measurements on more complex structures, in terms of geometry,
materials, and tighter ground rules, but also the need to move away from non-patterned measurement sites to patterned
ones. This is especially of concern for very thin film layers that have a high thickness dependence on structure geometry
or wafer pattern factor. Although 2-dimensional (2D) sites are often found to be sufficient for process monitoring and
control of very thin films, sometimes 3D sites are required to further simulate structures within the device. The
measurement of film thicknesses only a few atoms thick on complex 3D sites, however, are very challenging. Apart
from measuring thin films on 3D sites, there is also a critical need to measure parameters on 3D sites, which are weak
and less sensitive for OCD (Optical Critical Dimension) metrology, with high accuracy and precision. Thus, state-ofthe-
art methods are needed to address such metrology challenges. This work introduces the concept of Enhanced OCD
which uses various methods to improve the sensitivity and reduce correlations for weak parameters in a complex
measurement. This work also describes how more channels of information, when used correctly, can improve the
precision and accuracy of weak, non-sensitive or complex parameters of interest.
Keywords: OCD, Scatterometry, Enhanced OCD, XPS, high-K, 3D, Proximity, TMU