Ta2O5 film formation by double ion beam method

Abstract Ta 2 O 5 thin films (20–40 nm thick) were formed on silicon substrates by double ion beam deposition method at room temperature. The films were annealed in a range of 400–600 °C for 15 min in N 2 ambient. I – V and C − V properties of Ta 2 O 5 fil were measured employing Al/Ta 2 O 5 /Si metal-insulator-semiconductor (MIS) capacitors. The smallest conductivity was found for Ta 2 O 5 films annealed at 500°C and was as small as that for the 10 nm thick thermal SiO 2 film. The dielectric constant of Ta 2 O 5 films was about 13 as derived from the high frequency C – V measurements at 100 kHz. However, the Ta 2 O 5 films formed by double ion beam deposition method have a large amount of positive fixed charges and/or oxide trap charges. Therefore, the flat band voltage of MIS capacitors becomes a large negative value. We confirm that these charges are made by irradiation of high energy electrons and high neutral atoms during the film deposition.