Evaluating Performance Using kϕ Index Parameter for a Symmetrical Junction NADGFET: A 3D TCAD Simulation Analysis

This work uses a 3D model of a symmetrical junction non-aligned double gate n-channel field effect transistor (NADGNFET) to examine the effects of the metal work function and dielectric constant on different figure of merit (FOM) responses. The NADGNFET device measured 90 nm in overall length, 40 nm in channel length, and 50% non-alignment. The concentration of impurities in the donor and acceptor were set at 10
¹⁸
and 10
¹²
cm-3, respectively, during the doping process. FOM measurements of different parameters were recorded while the device was simulated for a voltage range of 0-1 V. This study uses three dielectric constants (k) for the gate oxide: 3.9 for silicon dioxide, 7.2 for silicon nitride, and 24 for hafnium dioxide. It also uses three metal work functions (ϕ) for the gate metal: 4.5 eV for tungsten, 4.75 eV for molybdenum, and 5 eV for gold. The kϕ index is used as the evaluating parameter for the device response analysis. The device response is then analyzed by plotting the recorded peak response of the FOM with respect to kϕ. The analog FOM namely, ON current, ON current by OFF current ratio, threshold voltage, intrinsic gain, is largely affected by metal work function. The analog FOM like drain induced barrier lowering, transconductance, and RF FOM like cut-off frequency, gate delay, transconductance generation factor, and transconductance frequency product, is largely affected by dielectric constant of the gate oxide, and is weakly affected by the metal work function. Whereas, the analog FOM, subthreshold-signal swing parameter is affected by the combined effect of metal work function and dielectric constant. The linearity FOM i.e., intermodulation distortion point-3 (IMD3) shows increasing trend with increased value of kϕ. The study came to the conclusion that the kϕ index may be utilized as a benchmark to describe the device FOM and that it can be helpful in choosing work function and dielectric constant values that balance the trade-off between device FOM.