Two-State Current Phenomenon in MOS Device with Al2O3/Al/SiO2 Dielectric Stack Structure

• Main Authors: Ching-Kai Kao, 高靖凱
• Other Authors: 胡振國
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/65283410732371309772

碩士 === 國立臺灣大學 === 電子工程學研究所 === 103 === In this thesis, a MOS capacitor with Al2O3/Al/SiO2 dielectric stack structure was fabricated and it is observed that there is a two-state characteristic in this device. In chapter 2, it is shown that the two-state characteristic results from the two-state transient currents and the two-state transient currents are caused by the charges stored in the embedded aluminum. In order to distinguish the two states clearly, it is suggested to read the device at the "best read voltage". This "best read voltage" would lead to a "symmetrical" two-state current pair. It is also noticeable that the two-state window would be larger if the writing voltages are larger and the retention time of our device is about 1.1s. In chapter 3, three factors that could influence the two-state window are discussed. First, it is observed that the two-state window would be larger if the thickness of SiO2 is smaller. Second, it is found out that after post metallization annealing, the two-state window would be larger, which results from the local thickness reduction of SiO2 after PMA. Third, the oxidation time of embedded aluminum is also an important factor. If the oxidation time of embedded aluminum is very long, the thickness of SiO2 would be larger and the embedded aluminum would be totally oxidized. Owing to the thick SiO2 and the absence of embedded aluminum, the two-state window almost disappears.