Influence of the excess Al content on memory behaviors of Worm devices based on sputtered Al-rich aluminum oxide thin films

• Main Authors: Liu, Z., Liu, P., Li, H. K., Chen, T. P.
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Materials::Microelectronics and semiconductor materials::Thin films
• Online Access: https://hdl.handle.net/10356/104149; http://hdl.handle.net/10220/24656
• Institution: Nanyang Technological University

Reactive sputtering has been used to synthesize Al-rich Al2O3 thin films. After post-deposition thermal annealing, the excess Al content forms Al nanocrystals (nc-Al) which are dispersed in the Al2O3 matrix. In the Al/Al-rich Al2O3/p-Si structure, the current conduction which follows a Schottky emission process can be greatly enhanced by a charging process with negative voltage pulses and then maintained for considerable duration, realizing write-once-read-many-times (WORM) memory behaviors. The current conduction enhancement is attributed to the reduction of effective Schottky barrier caused by charging-induced hole trapping in the nc-Al related defects near the oxide/p-Si interface. It is found that the sample with lower concentration of nc-Al has a larger memory window due to the lower initial current. In addition, the retention is also better since the release of trapped charges is more difficult with less nc-Al related leakage paths present in the oxide film. The concentration of excess Al content in the Al-rich Al2O3 thin film can be optimized to achieve large memory windows as well as good retention characteristics in the associated WORM memory devices.