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Tibor Grasser

Abstract

Title: Reliability Impact and Scaling Trends
 
A number of reliability issues in semiconductor devices such as the bias temperature instability (NBTI/PBTI) or hot carrier degradation are linked to defects at the semiconductor/oxide interface or in the bulk of the oxide. Although in scaled devices the number of active defects becomes relatively small, each of them has a much larger impact on the device reliability and performance. While larger devices degrade in a relatively uniform manner, this is no longer the case in scaled devices. There, a considerable spread in the gradation characteristics is observed, including such extreme cases as no degradation at all compared to devices that degrade by multiples of the mean. This is a consequence of the discreteness of the defects which becomes crucial. For example the trapping of a single hole has been observed to cause a threshold voltage shift of more than 30 mV, which is occasionally used as a lifetime criterion.
While the discreetness and stochastic nature of defect creation and charge trapping are a challenge for product design, they offer a unique opportunity to study the physics behind these phenomena. Of particular importance is that the defect properties show a wide dispersion and many peculiarities are lost in the averaged large area device degradation behavior. In scaled devices, however, individual defects can be traced and studied. A summary of our latest results on the negative bias temperature instability in MOS transistors will be given, where a number of astonishing peculiarities in the defect behavior have been observed.