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

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 C_gs is larger than the decrease in C_gd for 55- and 45-nm devices, and the difference increases as the process technology keeps advancing. Thus, the degradations of cutoff frequency f_T and maximum oscillation frequency f_max are dependent on transconductance g_m and gate capacitance C_gg (= C_gs + C_gd) 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 f_T versus g_m.