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In-line Raman Spectroscopy for Stacked Nanosheet Device Manufacturing

February 1, 2021 @ SPIE 2021
Authored by: D. Schmidt, C. Durfee, J. Li, N. Loubet, A. Cepler, L. Neeman, N. Meir, J. Ofek, Y. Oren, D. Fishman

In-line Raman spectroscopy for compositional and strain metrology throughout front-end-of-line manufacturing of next generation stacked gate-all-around nanosheet field-effect transistors is presented. Thin and alternating layers of fully strained pseudomorphic Si(1-x)Gex and Si were grown epitaxially on a Si substrate and subsequently patterned. Intentional strain variations were introduced by changing the Ge content (x = 0.25, 0,35, 0.50). Polarization-dependent in-line Raman spectroscopy was employed to characterize and quantify the strain evolution of Si and Si(1-x)Gex nanosheets throughout front-end-of-line processing by focusing on the analysis of Si-Si and Si-Ge optical phonon modes. To evaluate the accuracy of the Raman metrology results, strain reference data were acquired by non-destructive high-resolution x-ray diffraction and from destructive lattice deformation maps using precession electron diffraction. It was found that the germanium-alloy composition as well as Si and Si(1-x)Gex strain obtained by Raman spectroscopy are in excellent agreement with reference metrology and follow trends of previously published simulations.
Keywords: Raman spectroscopy, strain, stress, gate-all-around, nanosheet FET