Capacitance-voltage characteristics of MOS capacitors with Ge nanocrystals embedded in ZrO2 gate material

Capacitance versus voltage (C-V) curves of Ge-nanocrystals (NCs)-embedded metal-oxide-semiconductor (MOS) capacitors are characterized in this work. Ge NCs were formed in 20-nm thick ZrO2 gate layers by ion implantation and subsequent annealing procedures. The formation of the Ge NCs in the ZrO2 gate layers was confirmed by high-resolution transmission electron microscopy and energy dispersive spectroscopy. The C-V curves obtained from a representative MOS capacitor embedded with the Ge NCs exhibit a 3 V memory window as bias voltage varied from 9 to -9 V and then back to the initial positive voltage, whereas MOS capacitors without Ge NCs show negligible memory windows at the same voltage range. This indicates the presence of charge storages in the Ge NCs. The counterclockwise hysteresis observed from the C-V curves implies that electrons are trapped in Ge NCs presented inside the ZrO2 gate layer. And our experimental results obtained from capacitance versus time measurements show good retention characteristics of Ge-NCs-embedded MOS capacitors with ZrO2 gate material for the application of NFGM. (C) 2007 Elsevier B.V. All rights reserved.