Methodology for evaluating the information distribution in small angle scattering from periodic nanostructures
Daniel F. Sunday, Regis J. Kline
Optimizing the extraction of information from X-ray measurements while minimizing exposure time is an important area of research in a variety of fields. The semiconductor industry is reaching a point where the traditional metrological approaches need to be augmented in order to better resolve structures with features sizes below 20 nm. Critical dimension small angle X-ray scattering (CDSAXS) is one measurement technique that has shown to be capable of characterizing detailed features of periodic nanostructures. As currently implemented the measurement utilizes the combined scattering from up to 60 different angles. Reducing that number would dramatically improve the feasibility of CDSAXS for implementation in a fabrication setting, but currently there are no clear guidelines as to which angles provide the most information. In order to develop guidelines for optimizing the angle selection simulation studies were conducted on a wide variety of structures with subsets of the full angular range to identify which angles minimized the overall shape uncertainty. Analyzing sets of two angle pairs (including all combinations between 0° and 60°) provides guidance on which angles best constrain the samples, for select samples higher numbers of angles were included to explore the impact of additional information on the model. Generally, low angles (<3°) best contributed to minimizing the width uncertainty, while higher angles near high curvature regions of the scattering profile best constrained the height of the structure. The minimum uncertainty was general achieved with combinations of the two.
and Kline, R.
Methodology for evaluating the information distribution in small angle scattering from periodic nanostructures, Journal of Micro/Nanolithography, MEMS, and MOEMS
(Accessed May 17, 2022)