Electrical characteristics of MIS capacitors with multi-stack thermal-agglomerating Ge nanocrystals in SiO2/SiNx dielectrics

Metal–insulator–semiconductor (MIS) capacitors, having 1-, 2-, or 3-layer Ge nanocrystals (NCs) in SiO2/SiNx dielectrics for charge storage application have been fabricated and characterized. Multi-stack Ge NCs were fabricated by thermal-annealing the amorphous SiGeO/SiNx multilayers deposited with a plasma-enhanced chemical vapor deposition (PECVD) system. Micro-Raman spectra and images of transmission electron microscopy (TEM) demonstrated the presence of Ge NCs after annealing. More holes trapping and storage than electrons were exhibited in capacitance–voltage (C–V) hysteresis curves at room temperature. Increasing the number of layer for Ge NCs in SiO2/SiNx dielectrics from 1 through 2 to 3 improved the memory window from 0.3 through 0.5 to 2.3 V as obtained by C–V hysteresis curves. The current density–voltage (J–V) curves of MIS capacitors exhibited the multi-peak form at the higher negative voltages due to the transient displacement current from the substrate to the Ge NCs.