The authors analyzed the electrical properties of MOS capacitors with thulium oxide (Tm2O3) gate dielectrics and evaluated the thickness-dependent properties. The authors observed that a thin silicate layer (instead of an SiO2 layer) with a thickness of less than 1 nm had formed between the Tm2O3 and Si substrate after an annealing process at 500 °C. The authors obtained an effective oxide thickness of 0.55 nm with dielectric constants of 18 and 12 for Tm 2O3 and its silicate, respectively. The leakage current properties with different thicknesses have revealed sufficient suppression by 2 orders of magnitude from the required levels. However, conduction mechanism analyses and a model to explain the flatband voltage (Vfb) behavior on different thicknesses showed the presence of charged defects in the oxides, which were mostly located at the Tm2O3 and silicate interface. The effective mobility of nFET showed degraded properties by Coulomb scatterings, which were consistent with the Vfb shift. The less reactive properties of Tm2O3 are advantageous for gate oxide scaling in future MOS devices.
|Journal||Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics|
|State||Published - Nov 2011|