Regensburg 2019 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 2: Nitrides: Devices
HL 2.15: Vortrag
Montag, 1. April 2019, 13:15–13:30, H31
Silicon Nitride Interface Engineering for the Realization of Dopant-free MOSFETs — •Benjamin Richstein1,2, Thomas Grap1,2, Lena Hellmich1, and Joachim Knoch1 — 1Institute of Semiconductor Electronics, RWTH Aachen, Germany — 2Peter Grünberg Institute 11, FZ Jülich, Germany
Dopants are necessary in standard CMOS-technology as they enable conductivity in silicon and provide low contact resistances. Moreover, 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, new concepts are required to avoid the problems with dopants in small MOSFETs. Therefore we show a study on silicon nitride interface engineering. Very thin silicon nitride layers in the sub-nm regime are fabricated to suppress the penetration of the metal wave function of S/D-contacts into the bandgap of silicon. This leads to a Fermi-Level-Depinning and a decrease of the Schottky-barrier in Schottky-MOSFETs. As a result, the contact resistivity decreases and the ambipolar behavior can be suppressed. The metal work functions of S/D-contact metals are utilized to obtain N-, or PMOS-like behavior. Dopant-free ohmic contacts were fabricated and characterized at room and very low temperatures. Additionally, Schottky-MOSFETs with S/D-contacts consisting of a thin silicon nitride layer and different contact metals are fabricated to demonstrate unipolar behavior.