Stress Degradation Characteristics Of MOS Devices And Ring Oscillator Circuits Based On 65 - Nm Process

With the continuous development of integrated circuits toward miniaturization and high integration density, Negative Bias Temperature Instability (NBTI) of pMOSFET and Hot Carrier Injection (HCI) of nMOSFET have become more and more serious, which influences the reliability of CMOS devices and circuits much heavier, making them be one of the most important limiting factors of CMOS devices’ performance and circuits’ lifetime. The conventional reliability evaluation focuses on discrete devices, however the research of devices should serve for circuits. This paper studies the reliability issues mentioned above by reliability test circuit system based on ring oscillator (RO).We proposed a degradation model of ring oscillator based on NBTI and HCI degradation mechanisms of CMOSFETs. The model is demonstrated by comparing the experimental results of discrete devices and ROs which were fabricated using the same process technology (SMIC65nm). We also proposed two kinds of improved multi-function RO systems.The main conclusions of the thesis are:(1) We separated the contribution of NBTI and HCI to the frequency degradation of RO with the help of the model and the experimental results of discrete devices and RO.(2) After dynamic stress, the RO with shorter device channel length (60nm) shows more evident frequency degradation than the result of static stress, indicating that HCI dominates the degradation quantity. After dynamic stress, the RO with longer device channel length (130nm) shows similar frequency degradation to the result of static stress, indicating that HCI and NBTI contribute comparably to the frequency degradation of RO.(3) The improved multi-function RO system can not only separate NBTI of pMOSFET, HCI of pMOSFET, PBTI of nMOSFET and HCI of nMOSFET, but also use charge pumping measurement to small size devices profiting from the high frequency of RO.These studies are important for understanding the key degradation mechanisms of CMOSFETs and circuits, as well as predicting the lifetime of integrated circuits.