In-line Raman spectroscopy for gate-all-around nanosheet device manufacturing

Abstract

In-line Raman spectroscopy for compositional and strain metrology throughout frontend-of-line (FEOL) manufacturing of next-generation gate-all-around nanosheet field-effect transistors is presented. Thin and alternating layers of fully strained pseudomorphic Si ð1−xÞ Ge x and Si were grown epitaxially on a Si substrate and subsequently patterned. Intentional strain variations were introduced by changing the Ge content (x ¼ 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 ð1−xÞ Ge x nanosheets throughout FEOL 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 ð1−xÞ Ge x strain obtained by Raman spectroscopy are in very good agreement with reference metrology and follow trends of previously published simulations.

Taming the Distribution of Light in Gate-All-Around Semiconductor Devices

“…For proper interpretation of this number, it should be compared to the −1% compression expected on fully strained Si .75 Ge .25 due to the smaller lattice constant of Si vs SiGe . The measured lower magnitude of the compressive strain is understood as being mostly due to the three-dimensional nature of our devices, whereby the patterning along the x and y directions induces relaxation . Note that the order of magnitude of the strain obtained in the SiGe and Si layers is in agreement with ref , which focuses on nanosheet transistors.…”

“…The measured lower magnitude of the compressive strain is understood as being mostly due to the three-dimensional nature of our devices, whereby the patterning along the x and y directions induces relaxation . Note that the order of magnitude of the strain obtained in the SiGe and Si layers is in agreement with ref , which focuses on nanosheet transistors.…”

Metrology for 2D materials: a perspective review from the international roadmap for devices and systems

“…[47][48][49] Low-temperature PL is considered a more quantitative method to sense defect concentration thanks to the reduction of phonon-stimulated excitations but is also affected by dielectric environment, laser intensity, and strain thus leaving open a large set of options for the data interpretation. [50][51][52][53] Besides far-eld Raman spectroscopy, which became available as an in-line technique recently, 54 ellipsometry and XPS, which are used in-line, most other options presented here are relatively slow or destructive.…”

Spectral interferometry for fully integrated device metrology

“…The idea is to develop metrology targets that mimic the device architecture as closely as possible but with design simplifications for optimized sensitivity to the desired parameters. Continuously increasing device complexity requires an increased focus on DMCO, which is relevant not only for scatterometry but also for other inline metrology techniques, such as ellipsometry, Raman spectroscopy, 19 and overlay.…”