Conduction mechanisms in Ta2O5 stack in response to rapid thermal annealing

Properties of Ultrathin High Permittivity (Nb[sub 1−x]Ta[sub x])[sub 2]O[sub 5] Films Prepared by Aqueous Chemical Solution Deposition

“…Annealing in oxidative ambient can remove organic residues ͓see X-ray photoelectron spectroscopy ͑XPS͒ results further on͔ as well as reduce the number of oxygen vacancies and structural defects leading to leakage reduction, as reported for Ta 2 O 5 . 4 Crystallization can create leakage current paths along the grain boundaries formed, leading to increased leakage. 28 Here, the effect of annealing at 800°C ͑30 min, 0.5 L/min dry air͒ on the dielectric properties of NbTaO 5 was studied as this composition had the highest permittivity ͑27͒ of all the solid solutions, but still showed a lower leakage current than the composition Nb 2 TaO x also characterized by k = 27 ͓66.6% Nb/͑Nb + Ta͒, see Fig.…”

“…[1][2][3] However, the crystallization temperature increases with decreasing thickness, e.g., only partial crystallization was observed at 800°C for films with a thickness of 9 nm. 4,5 During the high temperature oxidation anneal for crystallization, in metal-insulator-semiconductor devices, oxidation of Si occurs. This SiO 2 with a low permittivity of 3.9 is series-connected to the Ta 2 O 5 , leading to a decrease in the capacitance density and total stack permittivity.…”

“…Amorphous Ta 2 O 5 is characterized by a permittivity that is limited, e.g., only 5-10 in films of 15-40 nm. 4 Because of its more abundant occurrence, higher permittivity, and crystallization at lower temperatures, Nb 2 O 5 has been studied as well. It is characterized by a larger permittivity ͑35-50 6 ͒ than Ta 2 O 5 , but also shows higher conductivity, which is ascribed to a slightly lower bandgap and the possibility of partial reduction of Nb 2 O 5 to suboxides.…”