Enhanced optical CD metrology by hybridization and azimuthal scatterometry

Abstract

Reducing parameter correlations to enhance scatterometry measurement accuracy, precision and tool matching is a crucial component of every modeling effort. Parameter sensitivity can largely depend on the orientation of the plane of incidence relative to the grating orientation. Conventional scatterometry is done with the plane if incidence normal to the grating orientation, whereas azimuthal scatterometry allows measurements at an arbitrary angle or set of angles. A second technique examined in this paper is hybrid metrology where inputs from source tools such as CD-SEM and CD-AFM are used to determine values of critical parameters. The first examples shows LER sensitivity gains by measuring narrow resist lines in an orientation parallel with the long axis of the grating. Hybridization of LER results in a CD and SWA FMP improvement of about 60%. We also showcase the benefits of azimuthal scatterometry measuring resist lines with CD larger than the wavelengths of the incident light. A CD and SWA FMP reduction of about 60% and 30% is obtained using azimuthal scatterometry at 0, 45 and 90 degrees azimuth angles. Hybridization of the ARC SWA after RIE results in CD and resist SWA FMP improvements by over 60% and 30%, respectively.

Scatterometry performance improvement by parameter and spectrum feed-forward

“…A multiple POI solution, also known as azimuthal scatterometry, may be used for enhanced metrology performance at the expense of throughput [2]. For post RIE structures, NISR spectra are collected after SE measurements for each wafer, and the combined SE and SR spectra are used in the analysis, which has better performance than using just one of them.…”