Electrical characterization of metal-oxide-high-k dielectric-oxide-semiconductor (MOHOS) structures for memory applications

Conventional SONOS (polysilicon-oxide-nitride-oxide-silicon) non-volatile memory devices use silicon nitride as the charge storage layer. In this work, metal-oxide-high-k dielectric-oxide-silicon (MOHOS) structures are fabricated using HfO2 and Dy2O3 high-k dielectrics as the charge storage layer. The Al/SiO2/Dy2O3/SiO2/Si capacitors have a C–V memory window of 1.88 V and a leakage current density of 10−8 A/cm2. This leakage current is lower than those of Al/SiO2/HfO2/SiO2/Si capacitors and other similar capacitors reported in the literature. A minimum detection window of 0.5 V for MOHOS capacitors can be maintained up to 2 × 108 s using as-deposited Dy2O3. The better performance of the Al/SiO2/Dy2O3/SiO2/Si structure over Al/SiO2/HfO2/SiO2/Si is attributed to the larger conduction band offset at the Dy2O3/SiO2 interface (2.3 eV) versus 1.6 eV at the HfO2/SiO2 interface.