Electrical properties and noise characterization of HfO ₂ gate dielectrics on strained SiGe layers

Ultra thin HfO ₂ high-k gate dielectric has been deposited directly on strained Si _0.81Ge _0.19 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 HfO ₂ films when annealed between 400 and 500 °C. Interface trap density was found to be in the range of 4.0-5.6 × 10 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 HfO ₂/Si0 _.81Ge _0.19 stacks annealed in different gas ambient have been measured using metal-insulator-semiconductor capacitors (contact area ∼ 2 × 10 ^{- 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.