Bias temperature instability (BTI) and hotcarrier degradation (HCD) are among the most important reliability issues but are typically studied independently in an idealized setting. However, even though it is well understood that mixed BTI/HC degradation corresponds to a realistic scenario, there is only a limited number of studies available on the impact of mixed stress conditions. In this first part of the work, we present a thorough experimental study of the impact of mixed stress conditions on SiON pMOSFET characteristics, which contain a study at the single defect level. We focus on the contribution of single defects to the recoverable component of degradation. From an electrostatic point of view, recovery after mixed negative BTI (NBTI)/HC stress is typically attributed to charge carrier emissions by oxide defects near the source, which have been charged during stress. However, the experimental characterization of recovery after different stress conditions provides strong evidence that even defects located in the vicinity of the source can remain uncharged after mixed NBTI/HC stress, and thus do not contribute to the recovery signal. Consequently, the recoverable component can be negligibly small after certain stress conditions, which leads to the conclusion that a simple electrostatic model does not properly describe the behavior of recovery after mixed NBTI/HC stress.Index Terms-Device reliability, hot-carrier degradation (HCD), mixed-mode stress, negative bias temperature instability (NBTI), pMOSFET, single oxide defects, timedependent defect spectroscopy (TDDS). I. INTRODUCTIONB IAS temperature instability (BTI) and hot-carrier degradation (HCD) affect the performance of metal-oxide-

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Characterizing mixed hot-carrier/bias temperature instability (BTI) degradation in full {V G , V D } bias space is a challenging task. Therefore, studies usually focus on individual degradation mechanisms, such as BTI and hot-carrier degradation (HCD). However, a simple superposition of these mechanisms at an arbitrary {V G , V D } combination often fails to predict the cumulative damage. We experimentally acquired a large data set covering the full bias space of a pMOSFET which allows us to obtain detailed degradation and recovery maps. Our models for describing oxide and interface defects provide physical insights into the underlying mechanisms and a possible interplay between the degradation modes. Additionally, we perform a dedicated experiment to reveal the implications of different stress regimes onto the various types of defects by switching BTI and HCD stress conditions. The results clearly reveal the conceptual limits of the assumption of independent degradation regimes. Index Terms-Bias temperature instability (BTI), defect modeling, full bias map, hot-carrier degradation (HCD), mixed-mode stress, reliability. I. INTRODUCTION A SSESSING the reliability of a technology typically focuses on idealized device degradation modes, such as bias temperature instability (BTI) and hot-carrier degradation (HCD). Each of these degradation modes is usually assessed in

Given the rapid recovery of the degradation induced by bias-temperature stress, the understanding and modeling of NBTI has been a challenge for nearly half a century. With the introduction of the time-dependent defect spectroscopy (TDDS), NBTI could be studied at the single defect level, confirming that it is dominated by a collection of first-order reactions rather then the previously invoked reaction-diffusion mechanism. The most intriguing feature of these first-order processes is the wide distribution of their time constants, which can be visualized in capture/emission time (CET) maps. In the following we clarify the microscopic link between individual defects seen in TDDS studies and the response of a large ensemble visible in the CET maps. In particular, we show how the distribution of the individual defect parameters can be extracted from measurements on large-area devices.

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