Design-Oriented Modeling of TSV Substrate Noise Coupling to Ring VCOs

2026-05-28

AI Summary

This work addresses the degradation of spectral purity in radio-frequency circuits—specifically ring voltage-controlled oscillators (VCOs)—caused by parasitic coupling from through-silicon vias (TSVs) in three-dimensional integrated circuits. The authors propose a design-oriented compact modeling approach that, for the first time, constructs an explicit three-port RLGC macromodel for signal-ground TSVs with an exposed substrate node. By integrating this model with RF devices from a process design kit (PDK) that support substrate terminal access, the study enables controlled injection and experimental validation of TSV-induced substrate noise. Measurements and simulations of a three-stage ring VCO fabricated in 22 nm FD-SOI technology reveal that a 1 GHz, 0.5 Vpp TSV aggressor generates a −35.2 dBc primary sideband spur at the output. The spur magnitude increases monotonically with aggressor strength and exhibits low-pass coupling behavior, decreasing from −20.2 dBc to −33.1 dBc as the interference frequency rises from 500 MHz to 2 GHz.

Abstract

Through-silicon vias (TSVs) enable dense vertical interconnects in 3D-IC and chiplet systems, but their metal-oxide-silicon structure introduces significant parasitic coupling paths that can degrade the spectral purity of sensitive RF blocks. This paper presents a compact, design-oriented methodology for assessing TSV-induced substrate noise in mixed-signal circuits. We derive a closed-form analytical three-port RLGC macromodel for a Signal-Ground TSV pair that explicitly exposes the substrate node. The methodology is validated using a three-stage Ring VCO designed in a 22 nm FD-SOI technology, where specific RF devices from the process design kit (PDK) provide direct access to the transistor substrate terminals for controlled noise injection. Multi-tone Harmonic Balance simulations in Spectre RF quantify the impact of TSV aggressors on the oscillator's output spectrum. The results indicate that an aggressor of 1 GHz, 0.5 V$_{pp}$ induces a primary sideband spur of -35.2 dBc. Sensitivity characterization reveals that the magnitude of these sideband spurs increases monotonically with the aggressor amplitude. Furthermore, frequency sweeps demonstrate a low-pass coupling response, where the induced spur magnitude decreases from -20.2 dBc at 500 MHz to -33.1 dBc at 2 GHz.

Problem

• TSV
• substrate noise
• noise coupling
• Ring VCO
• spectral purity

Innovation

• TSV substrate noise
• design-oriented modeling
• RLGC macromodel
• Ring VCO
• spectral purity