Identification of current transport mechanism in Al2O3 thin films for memory applications

Abstract

The effect of oxygen anneal on the electrical characteristics, especially on the current transport mechanism, of Al2O3 films in the thickness range of 10–30 nm was examined in detail. The analyses were performed at electric fields of ≤2.5 MV/cm to effectively address the reliability of Al2O3-based devices operating in the low electric field regime. The general conduction mechanism equations were used to simulate the expected current density (J) values for a given electric field (E) range. The characteristic linear plots of the conduction mechanisms were then used to compare the experimental and simulated data to identify the most probable mechanism occurring in the dielectric. Parameters like barrier height and activation energy were extracted from the fit. It was found that oxygen anneal has profound effects on the electrical properties of Al2O3 films, with annealed films demonstrating a different conduction mechanism than their unannealed counterparts, along with significant improvement in the leakage current and barrier height. This kind of analyses will help optimize the process conditions for Al2O3 deposition and provide an optimal range for device operation, thus improving the reliability of Al2O3 films for applications in CMOS logic and Flash memory.