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

Abstract

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 4.0–5.6×1011eV−1cm−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~2×10−3cm2). 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.