The behavior of hot hole stressed SiO2/Si interface at elevated temperature is investigated. Although an exposure to an elevated temperature does not affect a fresh device, considerable damages occur in a stressed device for temperature above 300 °C. The damage is caused by two thermally activated processes, which are triggered by hole injection and continued after the injection. One of them is the post-stress interface state generation and the other is the unexpected creation of interface state precursors. These new precursors can only be electrically detected when the device is stressed again. The effects of temperature, exposure time and hole injection time on these processes are studied. At 400 °C, annealing of interface states is also significant. It is found that the annealing of the states created post-stress is much faster than the annealing of the states generated during the hole injection, indicating these two have different structures. Roles played by electron injection and hydrogen in the annealing are studied and the hole detrapping process is addressed. The precursor generation follows the first order kinetics with a single characteristic time. The generated precursor is found to be different from the original one existed in a fresh device. These new precursors enhance the degradation in the subsequent stress.
This article reports new experimental results on the continuing interface trap generation post-hot hole injection and investigates the generation mechanism. The generation post-hole injection is found to be two orders of magnitude slower than that post-irradiation and cannot be satisfactorily explained by the transportation of hydrogen species across the gate oxide. The role played by the recombination of trapped holes with free electrons is examined. There is a lack of correlation between the trapped hole removal and the interface trap creation, which is against the prediction of the trapped hole conversion model. The results indicate that the interface traps generated during and post-stress originate from two different defects. The defect responsible for post-stress generation is excited by hole injection and then converted into an interface trap if a positive gate bias is applied. It is found that generation in a poly-Si gated metal-oxide-semiconductor field effect transistor behaves differently from that in an Al-gated device. The possible causes for this difference are discussed.
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