New Advanced Process of Ultrathin Oxynitride on the Characteristics of pMOSFET

• Main Authors: Chia-Hua Yeh, 葉佳樺
• Other Authors: Jen-Chung Lou
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/85654928294080021285

碩士 === 國立交通大學 === 電子工程系所 === 96 === According to the scaling rules, aggressive scaling has lead to silicon dioxide (SiO2) gate dielectrics as ultra thin in state-of-the-art CMOS technologies. As a consequence, static leakage current due to direct tunneling through the gate oxide has been increasing at an exponential rate. As technology roadmaps call for sub-10A° gate oxides within the next five years, a variety of alternative high-k materials are being investigated as possible replacements for SiO2. The higher dielectric constants in these materials allow the use of physically thicker films, potentially reducing the tunneling current while maintaining the gate capacitance needed for scaled device operation. Oxynitride(SiON) have been reported to show many advantages over thermal oxide.For example，excellent resistance to penetration of dopant and other impurities such as refractory metal，a higher dielectric strength，and enhanced resistance to damage induced by radiation and high-field stress . As the continuing scaling down of MOS devices has made high-field-induced device degradation a major concern，thin oxynitride seem promising for applications as a replacement for a thermally grown oxide in submicrometer-range ULSI devices. The oxynitrides with high nitrogen content distributed close to the surface are considered to be the best candidates for 65 nm CMOS integration or below. We propose an alternative approach for forming a high-nitrogen ultrathin oxynitride gate dielectric is demonstrated. The oxynitride growth included three process stages－chemical oxide growth, nitridation and subsequent dry oxidation. Meanwhile, chemical oxide as a starting oxide can provide a better controllability in film thickness. Following that, the chemical oxide was nitrided using a furnace in low-pressure NH3 ambient to transfer high-nitrogen oxynitride. The nitrided chemical oxide was then placed in atmospheric O2 ambient to form a robust oxynitride. The process proposed here is simple and fully compatible with current process technology. Finally, by this technique, pMOSFET of oxynitride were fabricated to study electrical characteristics. They demonstrate excellent properties in terms of low leakage current, high endurance in stressing, superior boron diffusion blocking behavior and weak SILC effect, and good performance in HCI effect.