In-line Raman Spectroscopy for Stacked Nanosheet Device Manufacturing

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

In-line Raman spectroscopy for compositional and strain metrology throughout front-end-of-line manufacturing of nextgeneration
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