The Electrical Properties of MOS Devices with Nitrogen Implanted Gate Oxides

• Main Authors: Chih-Yuan Hsiao, 蕭智元
• Other Authors: Jenn-Gwo Hwu
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/61991253291699617491

碩士 === 國立臺灣大學 === 電子工程學研究所 === 92 === To obtain high performance and low power device, gate oxide thickness shrinkage is a main stream in modern ULSI industry. There are many approaches to achieve ultra thin gate oxide in the state of art. Nitrogen implantation prior to gate oxidation is one of the famous techniques in ultra-thin oxide engineering. With this technique, SOC process becomes feasible. In this thesis, we are going to discuss the characteristics of nitrogen implanted gate oxide. Chapter one is an introduction of nitrogen implanted gate oxide experiment. The process flow design, device structure and measurement tool are also introduced to realize this experimental background. The oxide thickness effect of different nitrogen implantation dosage is described in chapter 2. The oxide thickness result of process combinations of different dosage and different oxidation temperature are investigated. And by way of SIMS analysis, we can figure out the nitrogen dopant profile in Si substrate. Then we propose a mechanism to explain the oxidation retardation effect due to nitrogen implantation. Chapter 3 is the C-V characteristics of nitrogen implanted gate oxide. Basic theory is described first to understand the following properties well. Different frequencies of gate capacitance are measured for comparison. The flat band voltage and interface trap density can be extracted from the C-V plot. According to high frequency capacitance result, the boron doping distribution in Si substrate is used to examine the effect of boron penetration suppression. Chapter 4 is the I-V characteristics of nitrogen implanted gate oxide. The theory of direct and F-N tunneling current is introduced to realize the mechanism. According to the gate current result, the direct tunneling and F-N tunneling regime will be discussed. From gate tunneling current uniformity result, we also realize the oxide thickness uniformity performance of nitrogen implantation. From F-N tunneling current, the barrier height is extracted. It gives the information of the possible process that introduces a low barrier height and therefore results in a high gate leakage current. Finally, the conclusion of this study is given in chapter 5.