Single-Event Effecten in Geïntegreerde Spoelen in CMOS LC-oscillatoren: Mechanismen en Mitigatie

Reliable low-noise clock generation is a fundamental requirement in modern RF and mixed-signal systems operating in radiation-prone environments, including space missions, high-altitude avionics, and high-energy physics instrumentation. CMOS LC-tank oscillators are widely used in phase-locked loops (PLLs) due to their superior phase-noise performance and energy efficiency. However, their susceptibility to single-event effects (SEEs), and in particular single-event frequency transients (SEFTs), remains a critical limitation for maintaining timing stability in mission-critical applications. This dissertation investigates SEFTs in 65 nm bulk CMOS LC-tank oscillators, with a primary focus on a previously underexplored failure mechanism in which the integrated spiral inductor becomes the dominant source of radiation-induced frequency disturbance. While prior work has largely focused on active device sensitivity, this research demonstrates that passive electromagnetic structures can play a central role in radiation response. The central finding of this work is that heavy-ion strikes generate excess carriers in the silicon substrate beneath the inductor, producing transient increases in substrate conductivity. These conductivity perturbations modify the effective inductance and loss characteristics of the spiral inductor, resulting in measurable frequency deviations at the oscillator output. The frequency transient subsequently relaxes as excess carriers recombine or are removed, with recovery dynamics spanning from microseconds to milliseconds. To capture and analyze these effects, this dissertation uses a high-resolution measurement methodology capable of extracting frequency transients with parts-per-million (ppm) accuracy and high time-domain fidelity. Heavy-ion microbeam experiments demonstrate that SEFT sensitivity is localized to the inductor region. The results further reveal that the polarity of the frequency deviation is deterministic and governed by the shielding configuration. The magnitude of the SEFT sensitivity was also found to be influenced by the shielding and inductor geometry. In addition, SEFT sensitivity is shown to be frequency-dependent, establishing oscillator tuning state as not only a functional parameter but also a reliability parameter. To provide a predictive understanding of the observed behavior, a physics-based multi-level modeling framework is introduced. This framework links ion-induced carrier generation and transport in the substrate to conductivity-dependent perturbations in inductor parameters, and ultimately to oscillator-level frequency deviations. Due to the absence of a unified simulation environment capable of simultaneously capturing semiconductor charge transport and full three- dimensional electromagnetic field interactions, the modeling approach combines TCAD simulations, electromagnetic field solvers, and circuit-level transient analysis. This cross-domain methodology is validated against experimental measurements and successfully reproduces key SEFT characteristics, including magnitude and polarity. The modeling framework further identifies an additional amplitude-to-frequency (AM-FM) conversion mechanism, whereby radiation-induced degradation of inductor quality factor contributes to frequency perturbations through nonlinear circuit effects. Building on these insights, this work proposes and experimentally validates mitigation strategies based on substrate engineering beneath the inductor. By introducing reverse-biased junction structures using biased patterned shields and N-well configurations, excess carriers are efficiently collected and removed from the substrate. These techniques reduce SEFT recovery times by more than 50× and suppress peak frequency deviations by approximately an order of magnitude, while maintaining acceptable RF performance. The associated trade-offs, including impacts on inductor quality factor, phase noise, and jitter, are quantitatively evaluated to enable informed design decisions. Overall, this dissertation expands the scope of radiation-hardened-by-design (RHBD) methodologies by demonstrating that passive electromagnetic structures can dominate single-event sensitivity in RF timing circuits. It provides a comprehensive experimental, modeling, and design framework for understanding and mitigating SEFTs in CMOS LC-tank oscillators, thereby contributing to the development of more reliable frequency generation systems in radiation- challenged environments.