Surface metrology must increasingly contend with sub-micron films, whose prevalence now extends to products well beyond semiconductor devices. For optical technologies such as coherence-scanning interferometry (CSI), transparent sub-micron films pose a dual challenge: film effects can distort the measured top surface topography map, and metrology requirements may now include 3D maps of film thickness. Yet CSI’s sensitivity also presents an opportunity: modeling film effects can decode surface and thickness from the distorted signal. Early model-based approaches entailed practical trade-offs between throughput and field of view, and restricted the choice of objective magnification. However, more recent advances allow full-field surface films analysis using any objective, with sample-agnostic calibration and throughput comparable to film-free measurements. Beyond transparent films, model-based CSI provides correct topography for any combination of dissimilar materials with known visible-spectrum refractive indices. Results demonstrate single-nm self-consistency between topography and thickness maps.

Date Published: 28 August 2016
PDF: 9 pages
Proc. SPIE 9960, Interferometry XVIII, 996005 (28 August 2016); doi: 10.1117/12.2238997

Published in SPIE Proceedings Vol. 9960:
Interferometry XVIII
Katherine Creath; Jan Burke; Armando Albertazzi Gonçalves Jr., Editor(s)