HfAlOx high-k gate dielectric on SiGe: Interfacial reaction, energy-band alignment, and charge trapping properties

Ultra thin HfAlOx high-k gate dielectric has been deposited directly on Si1−xGex by RF sputter deposition. The interfacial chemical structure and energy-band discontinuities were studied by using X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectroscopy (TOF-SIMS) and electrical measurements. It is found that the sputtered deposited HfAlOx gate dielectric on SiGe exhibits excellent electrical properties with low interface state density, hysteresis voltage, and frequency dispersion. The effective valence and conduction band offsets between HfAlOx (Eg = 6.2 eV) and Si1−xGex (Eg = 1.04 eV) were found to be 3.11 eV and 2.05 eV, respectively. In addition, the charge trapping properties of HfAlOx/SiGe gate stacks were characterized by constant voltage stressing (CVS).