Low-frequency noise in submicrometer MOSFETs with HfO2, HfO2/Al2O3 and HfAlOx gate stacks

Low-frequency noise measurements were performed on p- and n-channel MOSFETs with HfO2, HfAlOx and HfO2/Al2O3 as the gate dielectric materials. The gate length varied from 0.135 to 0.36 mum with 10.02 mum gate width. The equivalent oxide thicknesses were: HfO2 23 Angstrom, HfAlOx 28.5 Angstrom and HfO2/Al2O3 33 Angstrom. In addition to the core structures with only about 10 Angstrom of oxide between the high-kappa dielectric and silicon substrate, there were double-gate oxide structures where an interfacial oxide layer of 40 A was grown between the high-kappa dielectric and Si. DC analysis showed low gate leakage currents in the order of 10(-12) A(2 - 5 x 10(-5) A/cm(2)) for the devices and, in general, yielded higher threshold voltages and lower mobility values when compared to the corresponding SiO2 devices. The unified number-mobility fluctuation model was used to account for the observed 1/f noise and to extract the oxide trap density, which ranged from 1.8 X 10(17) cm(-3) eV(-1) to 1.3 X 10(19) cm(-3) eV(-1), somewhat higher compared to conventional SiO2 MOSFETs with the similar device dimensions. There was no evidence of single electron switching events or random telegraph. signals. The aim of this paper is to present a general discussion on low-frequency noise characteristics of the three different high-kappa/gate stacks, relative comparison among them and to the Si-SiO2 system.