Conduction mechanisms responsible for leakage currents in RF sputtered HfO2 high-κ gate-oxide thin film MOS capacitors

Abstract MOS capacitors with HfO2 thin films as a high-κ gate-oxide layer were fabricated by RF sputtering for varied film thicknesses. These films were amorphous with thicknesses ranged from 35.9 to 87.9 nm. XPS confirmed the presence of SiOx interfacial layer. The HfO2 film of physical thickness 49.3 nm had shown a dielectric constant of 26.9 and an effective oxide thickness of 7.1 nm. However, the lowest leakage current was measured as 4.6 × 10−7 A/cm2 at −1 V in the MOS capacitor with a 35.9 nm thick HfO2 gate-oxide layer. The leakage currents were majorly due to the conduction, which is space charge limited and was effective almost in the entire considered region of biasing (0 to −15 V). Additionally, the emissions at different voltage regions are explained based on Poole-Frenkel (from 0 to −3 V), Schottky effect (−3 to −9 V), trap-assisted, and Fowler-Nordheim tunnelling (−9 to −15 V). Complete leakage current mechanisms are discussed.