Characteristics of TaOxNy Gate Dielectric with Improved Thermal Stability

We report the properties of novel gate dielectric TaO x N y prepared by low-pressure chemical vapor deposition using Ta(OC 2 H 5 ) 5 and NH 3 . The metal-oxide-semiconductor (MOS) characteristics of TaO x N y /SiO 2 gate dielectric are compared with those of Ta 2 O 5 /SiO 2 stack gated with a W/WN electrode. The flat-band voltage shift (Δ V fb ) of TaO x N y in comparison with Ta 2 O 5 is -0.17 V due to the nitrogen-induced positive charges accumulated at the SiO 2 /Si interface. The interface state density of W/WN/TaO x N y /SiO 2 /p-Si nMOS capacitors as determined by the conductance method is in the 0.85–1.5×10 11 eV -1 cm -2 range near the Si midgap. The leakage current level of the TaO x N y /SiO 2 /p-Si MOS capacitor is ∼-10 nA/cm 2 at -2.5 V at the effective oxide thickness ( T eff ) of 31 Å. The leakage current is four to five orders of magnitude lower than that of poly-Si-gated SiO 2 in the -2–-3 V range. The reliable characteristics of TaO x N y over Ta 2 O 5 in terms of a smaller increase in T eff and excellent breakdown field against selective oxidation at 950°C allow us to maintain the standard complementary metal-oxide-semiconductor fabrication process and technology.