Drain bias effects on statistical variability and reliability and related subthreshold variability in 20-nm bulk planar MOSFETs

Abstract

Statistical variability and reliability due to random discrete dopants (RDD), gate line edge roughness (LER), metal gate granularity and N/PBIT associated random charge trapping has limited the progressive scaling of bulk planar MOSFETs beyond the 20-nm technology node. In this paper, their impacts on device figures of merit are studied through comprehensive 3-D simulation. It is found that raised drain-bias can exacerbate threshold-voltage fluctuations, mainly due to LER and RDD. Subthreshold slope (SS) variations resulting from each variation source is studied: RDD and LER generate most of the SS variation and are primarily responsible for its skew. Drain induced barrier lowering (DIBL) is examined against each intrinsic variation source, and RDD and LER are found to cause most of the DIBL variability. The correlation of DIBL with threshold-voltage is fully analysed with respect to each source of statistical variability and reliability. Except for LER, all major sources of variability exhibit de-correlation of DIBL against threshold-voltage.