Mixed-Signal IC Design addressed to Substrate Noise Immunity in Bulk Silicon ; towards 3D circuits
Résumé
This work investigates substrate coupling effects in mixed IC’s, especially the perturbations on RF blocks. The authors present the impact of low frequency substrate noise perturbations on analog circuits: e.g.: a fully integrated 5 GHz voltage-controlled oscillator (VCO) spectrum. Then, the VCO spurious side-bands due to harmonic substrate noise perturbations are analyzed to find out a relation between the substrate noise characteristics and spur magnitudes. The Impulse Sensitivity Function approach is used to analyze the device sensitivity to substrate noise. A significant link between device sensitivity functions, low frequency substrate perturbations and the VCO side-band spectral power is demonstrated. According to this study, we conclude that a global approach only considering power supply bounces in mixed IC’s is not sufficient to analyze the sensitivity of RF integrated oscillators to low frequency substrate noise. Finally, considered is the 3D integration as a most promising solution to overcome challenges encountered nowadays in planar technologies. As an emerging technology, electrical compact models are notably required for 3D interconnects, including Through-Silicon Via, for accurately evaluating 3D system performances. However, 3D integration implies that the whole electrical context must be considered such as current paths or couplings between chip elements. As a consequence, a substrate extraction method, relying on the Transmission Line Method (TLM) or Green kernels, is proposed to model substrate networks and the entanglement with its interconnects.