Circuit Performance Shifts Due to Layout-Dependent Stress in Planar and 3D-ICs

This paper presents an approach for analyzing stress in 2-D and 3-D integrated circuits (ICs) due to postmanufacturing thermal mismatch. For both 2D-ICs and 3D-ICs, shallow trench isolation (STI) induces thermal residual stress in active silicon. For 3D-ICs, through-silicon vias (TSVs) act as an additional source of stress. Together, the sources of stress cause changes in the delay and power of the circuit. We develop an analytical model based on inclusion theory in micromechanics to accurately estimate the stresses and strains induced in the active region by surrounding STI in a layout. The TSV-induced stress depends on the location of the transistor with respect to the TSVs. Therefore, these stresses result in placement-dependent variations in the transistor mobilities and threshold voltages of the active devices, and we propagate these effects to circuit-level performance. At the transistor level, the stress state is translated into mobility and threshold voltage variations using piezoresistivity and band deformation potential models, respectively. At the gate level, the computed changes in transistor electrical parameters are used to predict gate-level delay and leakage power changes for single-fingered and multifingered layout styles, which are subsequently used to predict circuit-level delay and leakage power for a given placement.