Electromagnetic analysis for optical coherence tomography based through silicon vias metrology

W. A Iff (1, 2) , J.-P. Hugonin (2) , Christophe Sauvan (2) , M. Besbes (2) , P. Chavel (3) , G. Vienne (4) , L. Milord (4) , Dario Alliata (4) , E. Herth (1) , P. Coste (1) , A. Bosseboeuf (1)

1 C2N (UMR_9001) - Centre de Nanosciences et Nanotechnologies
2 Laboratoire Charles Fabry / Nanophotonique
3 Laboratoire Charles Fabry / Spim
4 UnitySC - UnitySC

This paper reports on progress in the analysis of time-domain optical coherence tomography (OCT) applied to the dimensional metrology of through-silicon vias (TSVs), which are vertical interconnect accesses in silicon, enabling three-dimensional (3D) integration in microelectronics, and estimates the deviations from earlier, simpler models. The considered TSV structures are 1D trenches and circular holes etched into silicon with a large aspect ratio. As a prerequisite for a realistic modeling, we work with spectra obtained from reference interferograms measured at a planar substrate, which fully includes the dispersion of the OCT apparatus. Applying a rigorous modal approach, we estimate the differences to a pure ray tracing technique. Accelerating our computations, we focus on the relevant fundamental modes and apply a Fabry–Perot model as an efficient approximation. Exploiting our results, we construct and present an iterative procedure based on the minimization of a merit function, which concludes TSV heights reliably, accurately, and rapidly from measured interferograms.

Domains: Optics [physics.optics]; Optics / Photonic

W. A Iff, J.-P. Hugonin, Christophe Sauvan, M. Besbes, P. Chavel, et al.. Electromagnetic analysis for optical coherence tomography based through silicon vias metrology. Applied optics, 2019, 58 (27), pp.7472-7488. ⟨10.1364/AO.58.007472⟩. ⟨hal-02348227⟩