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 °C. Interface trap density was found to be in the range of 4.0–5.6 × 1011 eV− 1 cm− 2. Results of internal photoemission studies on pre-existing charge trapping for different processing conditions; without annealing and annealed in O2, N2 and mixed (O2 and N2) 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 ~ 2 × 10− 3 cm2). It is found that the sample annealed in N2 gas ambient shows better electrical properties in general compared to samples annealed in O2 and/or mixed (O2 and N2) gas ambient.

► Electrical characterization of ultra thin HfO2 high-k gate dielectric stacks
► Study of interface trap density, charge trapping behavior, and low-frequency noise
► Comparison of electrical properties of samples annealed in N2, N2 + O2, O2 gas
► Trap locations are estimated from bias dependency of random telegraph signal.
► Superiority of N2 annealed sample is demonstrated from electrical characterization.