In Situ Impact Analysis of Very High Heat Flux Transients on Nonlinear p-n Diode Characteristics and Mitigation Using On-Chip Single- and Two-Phase Microfluidics

Abstract

The reliable operation of advanced integrated circuits (ICs) is impacted by the presence of randomly generated heat-flux transients. These transients can induce severe nonlinearities in the device response and can result in the degradation of ohmic contacts for p-n diodes as well as gate dielectric for metal-oxide field-effect transistors. In this paper, we focus on the impact and mitigation of steady-state and transient heat flux, with levels ranging from 0 to 250 W/cm 2 . The impact analysis exercise focused on the heat-flux-induced nonlinear variation of the p-n diode power exponent factor (alpha). For the steady-state heat-flux scenario, the alpha- V FB (forward bias voltage) characteristics yield a maxima point (alpha m ) which is observed to decrease monotonically with an increase in diode temperature. The alpha m value is further useful for deriving other parameters, such as saturation current ( Is ), series resistance ( Rs ), and the diode ideality factor (beta) . The transient heat-flux scenario yields a transient power exponent factor (alpha T , maxima-alpha mT ) which is distinct from the steady-state case. The alpha mT shows an inverse dependence on instantaneous diode temperature. Transient mitigation is evident when the diode power exponent parameter is recovered under the application of single-phase as well as two-phase on-chip fluid flows. Finally, while our primary focus has been on transient mitigation, we have also looked at the feasibility of localizing transient heat sources based on temperature profiles generated using an on-chip distributed resistance temperature detector sensor array. In real-life ICs, the systematic localization and characterization of heat sources will be of interest in order to provide information on the origin of transients, thus leading to modifications in circuit design or process integration steps.