An optical study of alumina films thermal evolution upon ammonia annealing

The physical and structural evolution of alumina films deposited by ALCVD annealed at high temperatures in N₂ has been studied.Low temperature post deposition treatments in NH₃ (PDN) have been performed to evaluate the impact of nitrogen incorporation in the alumina film on its thermal stability. Thermal evolution has been studied by deep UV spectroscopic ellipsometry and grazing X-ray reflectance techniques. AFM measurements were also performed to confirm and complete the ellipsometric and GXR analysis.The change of the crystalline structure was detected by ellipsometry by the different UV refractive index, while the GXR provided a unique thickness evaluation.It was therefore possible to determine the layer densification after the thermal treatment and the impact of the PDN on the transition temperature.