Characterization of atomic-layer-deposited hafnium oxide/SiON stacked-gate dielectrics

Hafnium–oxide films deposited on a thermally grown SiON film and a hydrogen-terminated Si bare substrate by an atomic-layer-deposition technique have been investigated. Capacitance–voltage measurements show equivalent-oxide thicknesses of about 1.79 nm for a 4.2 nm HfO2/SiON stack capacitor and of about 1.84 nm for a 5.2 nm HfO2 single-layer capacitor. These measurements also show a dielectric constant of 18.1 for the HfO2 in the stack capacitor and of 11.2 for the HfO2 single-layer capacitor. The hysteresis of the stack capacitors is measured to be less than 40 mV, whereas that of the single-layer capacitor is 206 mV. Transmission-electron microscopy (TEM) and x-ray photoelectron spectroscopy indicated that the dielectric films are amorphous structure, rather than crystalline or phase-separated silicide and oxide structures. TEM showed that the interface of the stack capacitor can be stable to at least 850 °C.