Regensburg 2019 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 12: HL Poster I

HL 12.62: Poster

Montag, 1. April 2019, 17:30–20:00, Poster E

Towards Dopant-free MOSFETs by Silicon Nitride Interface Engineering — •Lena Hellmich, Benjamin Richstein, and Joachim Knoch — Institut für Halbleitertechnik, RWTH Aachen University, Germany

Though doping enables conductivity in silicon and low contact resistances, and degenerate doping avoids carrier freeze out in low temperature applications. However, in deep nanoscale MOSFETs even at very high dopant concentrations only a few dopants reside in typical device volumes resulting in strong variability. Furthermore, the nanoscale size leads to deactivation of dopants increasing parasitic source/drain resistances. Thus, the replacement of dopants in nanoscale MOSFETs becomes more and more important. Our approach to replace the degenerate doping in source/drain (S/D)-contacts is a thin Fermi-Level-Depinning layer in the contact area between metal and silicon. In order to suppress the penetration of the metal wave function of S/D-contacts into the bandgap of silicon, very thin silicon nitride layers in sub-nm regime are fabricated. This thin insulating layer results in a Fermi-Level-Depinning; thus, the Schottky-barrier decreases, resulting in a lower contact resistance and suppression of ambipolar behavior. The metal work function, however, can be utilized to obtain N- or PMOS-like behavior. We fabricated dopant-free ohmic contacts are realized and characterized at room temperature and low temperatures. Besides, S/D-contacts with different metals and a thin silicon nitride layer to demonstrate unipolar behavior.