Frequency Variation of the Small-Signal Output Conductance of Decananometer MOSFETs Due to Substrate Crosstalk

Frequency variation of the output conductance in advanced fully depleted SOI and multiple-gate MOSFETs related to the electrical coupling between drain and Si substrate underneath the buried oxide (BOX) is analyzed through measurements and 2-D simulations. A low-frequency (LF) conductance variation in these devices, which could be erroneously attributed to the self-heating effect, is proved to be related to the presence of the Si substrate underneath the BOX. Suppression of this substrate-related LF transition in narrow-fin FinFET's output conductance is experimentally demonstrated. Furthermore, the substrate-related transitions are shown to be increasing with device downscaling, as well as BOX thinning, suggesting that this effect becomes more important for the future device generations