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 V_TH defined by subthreshold constant current (V_THC) deviates from the normal distribution, extrapolated V_TH (V_THEX) roughly follows the normal distribution. It is also found that some transistors show extraordinary low on-current (I_ON) 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.