Imaging, Modeling and Engineering of Strain in Gate-All-Around Nanosheet Transitors

We combine advanced transmission electron microscopy (TEM) and numerical models to draw the evolution of strains over the integration of horizontally stacked Gate-All-Around Nanosheet transistors (GAANS). In particular, we measured compressive strains of -0.5% to -1% after channel release in transistors at 10 nm design rule. With support on model calculations, we speculate that the effect is related to a compressive inter-layer dielectric (ILD). As another method to manipulate channel stresses, in a specifically designed GAANS we demonstrate a transition from compressive to tensile strain introduced by a gate stack/contact test modules. Finally, a demonstration of GAANS Si-channel cladded with SiGe opens a way for the co-integration of compressive SiGe channels with limited modification of the integration flow. The findings provide insights and guidelines for strain engineering in GAANS.