Hydrogen-related instabilities in MOS devices under bias temperature stress

Hydrogen plays a central role in several reliability-related phenomena in electronic devices. Here, we review an extensive set of first-principles calculations on H effects in Si-based devices. The results provide a framework for the explanation of the physical processes responsible for bias-temperature instability (BTI). We also examine new results on the dissociation reaction of a Si-H bond at the Si-SiO2 interface. We find that the process has barriers of more than 2.3 eV; this precludes the reaction from being responsible for the creation of interface traps at the moderate temperatures involved in BTI. In contrast, the results suggest as a viable alternative BTI scenario the depassivation of Si-H bonds by extra H species that are released in the Si substrate and reach the interface under the influence of the applied bias. We discuss the theoretical and experimental evidence for H-dopant complexes in Si as the source of H and results on other atomic-scale processes that can influence BTI degradation.