Analyses of Random Threshold Voltage Fluctuations in MOS Devices

摘要

Though variability of transistor characteristics has always been a matter to consider for integrated circuit manufacturing, recently, its importance dramatically increased as the feature sizes entered sub-100nm regime [1,2]. In particular, the increase of random fluctuations is a serious obstacle for continuing further scaling down of transistors. Random fluctuations refer to a kind of variability that exhibit no correlation between neighboring devices (Fig.1). It is caused by microscopic fluctuations of atomic scale, such as random placement of doped impurities (random dopant fluctuation: RDF), line edge roughness, gate oxide roughness, etc. As a result, it cannot be eliminated by simply improving the long range uniformity of manufacturing process. It is increased by the reduction of channel width and length, because the transistor characteristics become more sensitive to the same amount of microscopic perturbation.