A Simulation Study on Process Sensitivity of a Line Tunnel Field-Effect Transistor

A process sensitivity study of a steep subthreshold swing line tunnel field-effect transistor is presented for the first time using 2-D quantum-mechanical device simulations. The impact of various process parameters on the device transfer characteristics is presented with the help of process splits. A study of the thermal budget also shows that an increase in epitaxial growth thermal budget degrades the device performance by increasing the tunneling onset voltage V_TON and the off-current. Through process simulation and Plackett-Burman design of experiment (PB-DOE), the epitaxial layer thickness of the channel was identified as the most critical parameter in device processing. A thickness variation from 2 to 3 nm in the highly ( 7 × 10¹⁹ cm^-3) doped epitaxial was found to cause ~ 500-mV change in the tunneling onset voltage. It was found that an increase in doping concentration in the epitaxial layer to reduce quantum confinement effects will lead to an increase in the sensitivity of the device to the thickness of the epitaxial layer. A thicker epitaxial layer (5-6 nm) with lower doping concentration is recommended for reduced epitaxial layer variation sensitivity.