On the microscopic structure of hole traps in pMOSFETs

Hole trapping in the gate insulator of pMOS transistors has been linked to a wide range of detrimental phenomena, including random telegraph noise (RTN), 1/ f noise, negative bias temperature instability (NBTI), stress-induced leakage currents (SILC) and hot carrier degradation. Since the dynamics of hole trapping appear similar in various oxides such as pure SiO₂, SiON, and high-k, the responsible defects should have a related microscopic structure. While a number of defects have been suspected to be responsible for these phenomena, such as oxygen vacancies/E´ centers, K centers, hydrogen bridges or hydrogen-related defects in general, the chemical nature of the dominant charge trap remains controversial. Based on extended time-dependent defect spectroscopy (TDDS) data, we investigate the statistical properties of a number of defect candidates using density functional theory (DFT) calculations. Our results suggest hydrogen bridges and hydroxyl E´ centers to be very likely candidates.