Modeling of Conduction Mechanisms in Ultrathin Films of Al2O3 Deposited by ALD

Abstract

We reported the analysis and modeling of some conduction mechanisms in ultrathin aluminum oxide (Al2O3) films of 6 nm thickness, which are deposited by atomic layer deposition (ALD). This modeling included current-voltage measurements to metal-insulator-semiconductor (MIS) capacitors with gate electrode areas of 3.6 × 10−5 cm2 and 6.4 × 10−5 cm2 at room temperature. The modeling results showed the presence of ohmic conduction, Poole Frenkel emission, Schottky emission, and trap-assisted tunneling mechanisms through the Al2O3 layer. Based on extracted results, we measured a dielectric conductivity of 5 × 10−15 S/cm at low electric fields, a barrier height at oxide/semiconductor interface of 2 eV, and an energy trap level into bandgap with respect to the conduction band of 3.11 eV. These results could be affected by defect density related to oxygen vacancies, dangling bonds, fixed charges, or interface traps, which generate conduction mechanisms through and over the dielectric energy barrier. In addition, a current density model is developed by considering the sum of dominant conduction mechanisms and results based on the finite element method for electronic devices, achieving a good match with experimental data.