Nitrogen incorporation engineering and electrical properties of high-k gate dielectric (HfO2 and Al2O3) films on Si (100) substrate

Abstract

Pt/HfO 2 , HfO2–Al2O3, or Al2O3–HfO2–Al2O3/p-type Si (100) metal oxide semiconductor capacitors, which were fabricated using an atomic-layer-deposition technique, were post-deposition annealed under a NH3 atmosphere in order to investigate the nitrogen incorporation behavior along with their influences on the electrical properties. X-ray photoelectron spectroscopy showed that the binding energy of Hf 4f peak shifts to the lower values with increasing PDA temperature due to the formation of Hf–N bonds. An amorphous Al2O3 interface layer suppressed N diffusion into the Si substrate. The rapid thermally annealed HfO2–Al2O3 film at 800 °C for 30 s, which contained approximately 20 at. % N in the HfO2 layer, showed a flat-band voltage shift of ∼30 mV (corresponding to a negative fixed charge ∼1.6×1011 cm−2), a leakage current density of −4.7×10−10 A/cm2 at −1 V, a hysteresis voltage <20 mV, excellent charge-to-breakdown characteristics and the lowest surface roughness. The single layer HfO2 film did not demonstrate good electrical properties due to excessive N diffusion into the Si substrate. A thin Al2O3 capping layer deteriorates the surface morphology and electrical properties of the HfO2–Al2O3 bilayer.