Optimization of plasma nitridation for reliability enhancement of low-temperature gate dielectric in MOS devices

Abstract

Silicon MOS capacitors fabricated solely by low-temperature processes (under 600 °C) are treated with plasma nitridation under different processing conditions. Their properties are investigated at room temperature under high-field stress. It is found that gas flowrate has limited effect on the plasma nitridation process, while an increase in RF power produces more damages to the devices. Chamber pressure is shown to be the critical factor. Moreover, NO-nitrided device gives better performance than N 2O-nitrided one. Both kinds of plasmas are effective in improving the hardness of the gate oxide against stress-induced damage, which is characterized by a smaller shift in flatband voltage and a smaller increase in interface states after the stress. These results show that plasma nitridation has positive effects on the reliability of low-temperature-fabricated devices, which play an important role in flat-panel display systems on glass. © 2003 Elsevier Ltd. All rights reserved.