Analysis of transistor characteristics in distribution tails beyond ±5.4σ of 11 billion transistors

Transistors in distribution tails of 11G (11 billion) transistors were intensively measured and compared with transistors in the center of distribution. It is found that, while VTH defined by subthreshold constant current (VTHC) deviates from the normal distribution, extrapolated VTH (VTHEX) roughly follows the normal distribution. It is also found that some transistors show extraordinary low on-current (ION) which deviates from the normal distribution. The origin of abnormal distribution and the impact on yield loss are discussed based on measured results and 3D device simulation.