Growth-Then-Anodization Technique and Stress Effect of Rapid Thermal Ultra-Thin Gate Oxides

• Main Authors: Wei-Jian Liao, 廖偉見
• Other Authors: Jenn-Gwo Hwu
• Format: Others
• Language: en_US
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/66216204496377674679

碩士 === 國立臺灣大學 === 電子工程學研究所 === 91 === We introduce an alternative oxidation process called growth-then-anodization technique of rapid thermal ultra-thin gate oxide to reduce the gate leakage current. The growth models for DC anodization of silicon are introduced. The anodization technique of direct current superimposed with alternating-current anodization (DAC-ANO) is applied to repair the traps of thermal ultra-thin gate oxides. Effects of anodization time and thermal oxide thickness are inspected. It was experimentally observed that the quality of thermal oxides is well improved by the proposed growth-then-anodization of thermal oxides method. The reliability properties of thermal oxides treated with anodization are also examined. After stress induced leakage current (SILC) test, the thermal oxides treated with anodization exhibit less SILC behavior than thermal oxides without anodization. Growth mechanisms of DAC anodization are proposed to interpret the observed phenomena. Field and oxide thickness dependencies of SILC behavior of ultra-thin gate oxides are also investigated. The reasons of the SILC behavior for thermal oxides treated with anodization and thermal oxides without anodization are the same. Under high field stress the tunneling current will damage oxide structure and increase bulk traps. The damage extent is dependent on the oxide field, oxide thickness and process. The thermal oxides treated with anodization are potential for ultra-thin gate oxide application. Furthermore, thickness-dependent stress effects in p-type MOS capacitor are also discussed in this work. The effects of gate Al thickness and oxide thickness in a p-type MOS capacitor are analyzed by substrate injection current (Jsub). The experimental results exhibit that the Jsub increases with oxide thickness and gate Al thickness. Thus, we can conclude that the substrate injection current is very sensitive to the thickness of gate Al and gate oxide, and the substrate injection current is useful for examining the stress effects in MOS structures.