Electrical properties and noise characterization of HfO2 gate dielectrics on strained SiGe layers

Ultra thin HfO2 high-k gate dielectric has been deposited directly on strained Si0.81Ge0.19 by atomic layer deposition process. Important electrical properties such as, interface trap density, charge trapping behavior, and low-frequency noise characteristics have been studied in detail. Grazing incidence X-ray diffraction analysis shows that the conversion from amorphous to crystalline phase start to appear in the HfO2 films when annealed between 400 and 500 degrees C. Interface trap density was found to be in the range of 4.0-5.6x10(11) eV(-1) cm(-2). Results of internal photoemission studies on pre-existing charge trapping for different processing conditions; without annealing and annealed in O-2, N-2 and mixed (O-2 and N-2) ambient are presented. Low-frequency noise characteristics of HfO2/Si0.81Ge0.19 stacks annealed in different gas ambient have been measured using metal-insulator-semiconductor capacitors (contact area similar to 2x10(-3) cm(2)). It is found that the sample annealed in N-2 gas ambient shows better electrical properties in general compared to samples annealed in O-2 and/or mixed (O-2 and N-2) gas ambient. (C) 2012 Published by Elsevier B.V.