Investigation and Modeling of Hot Carrier Effects on Performance of 45- and 55-nm NMOSFETs With RF Automatic Measurement

Abstract

Effects of hot carriers on dc and RF reliabilities for both 45- and 55-nm negative metal-oxide-semiconductor field-effect transistors with in-line ground-signal-signal-ground test-pad structures were investigated in detail. The investigations were evaluated by an RF automatic testing system with a proprietary control program in Agilent's Integrated Circuit Characterization and Analysis Program software. After a hot carrier stress, we found that the increase in Cgs is larger than the decrease in Cgd for 55- and 45-nm devices, and the difference increases as the process technology keeps advancing. Thus, the degradations of cutoff frequency fT and maximum oscillation frequency fmax are dependent on transconductance gm and gate capacitance Cgg (= Cgs + Cgd) for 45- and 55-nm devices. This is different than many conventional studies that used low-frequency equipment. We propose a surface channel resistance model to comprehensively interpret the observations and verify it by the slope changes in the curves of measured fT versus gm.