The Mechanism Of Hole Trapping In Negative Bias Temperature Instability

Negative Bias Temperature Instability (NBTI) is one of the most important reliability research topics in modern CMOS technologies. Although it has been known for forty years, the degradation mechanism is still under debate and is of great interests. The Negative Bias Temperature (NBT) degradation has been largely attributed to two different traps. One is the interface states due to Pb centers, resulting from the dissociation of Si-H bonds. The other is the hole traps generated in the gate oxide, such as oxide vacancy related E'centers or nitride-incorporated defects. In most cases, both contributions are mixed in the NBTI process. It is of great importance to separate them in order to understand their roles and generation mechanisms, In this study,1) We use the low temperature NBTI measurement technique to assess the hole trapping in NBTI process. Our experimental results show that the|△VT|at relative low temperature are dominated by hole trapping process in both SiO2and PNO pMOSFETs.2) We also Demonstrate the low temperature hole trapping is inelastic LRME tunneling process, which is samilar with the NBTI hole trapping process under high temperature.3) By applying a low temperature sweeping technique, we also can indentify the energy profile of recoverable hole traps for nitrided oxide and SiO2pMOSFETs subject to Negative Bias Temperature Stress (NBTS). It is found that the energy distribution of hole traps for nitrided oxide devices has two obvious peaks, one in the lower and one in the upper half of the silicon band gap. Both peaks gradually develop with increasing the stress time and temperature. We attempt to compare the energy profile for nitrided oxide and SiO2devices to identify the nitrogen effect on the hole traps generated under NBTS.