New Insights into TDDB in FinFET Based on Strain Analysis at the Atomistic Scale

Gate dielectric time-dependent dielectric breakdown (TDDB) is a critical reliability concern in FinFET devices. However, the microscopic failure mechanism of on-state TDDB <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\vert \mathbf{V}_{\mathrm{g}\mathrm{s}}\vert &gt; 0,\ \vert \mathbf{V}_{\mathrm{d}\mathrm{s}}\vert &gt; 0)$</tex> is different from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{V}_{\mathrm{g}\mathrm{s}}$</tex> -only TDDB <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\vert \mathrm{V}_{\mathrm{g}\mathrm{s}}\vert &gt; 0,\ \vert \mathrm{V}_{\mathrm{d}\mathrm{s}}\vert =0)$</tex> due to the impact of channel current. In this study, aberration-corrected scanning transmission electron microscopy (STEM) and advanced strain analysis are employed to observe the physical evolution during the breakdown process of FinFETs from an atomic perspective. It is discovered that breakdown-induced silicon epitaxial defects are generated at the corners of the fin for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{V}_{\mathrm{g}\mathrm{s}}$</tex> -only TDDB, while shifted to the middle of the fin for on-state TDDB. The formation of these defects on the Si <110> orientation is accompanied by tensile strain. This work provides new insights into different types of TDDB phenomena in FinFETs at the atomic scale.