Degradation of direct-tunneling gate oxide under hot-hole injection

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The degradation of silicon-dioxide thin films induced by the hole direct-tunneling process is investigated using a substrate hot-hole (SHH) injection technique. Hot holes from the substrate, as well as cold holes in the inversion layer, are injected into the gate oxide in p-channel metal–oxide–semiconductor field-effect transistor with a p+ polycrystalline-silicon gate. The gate bias used is kept low enough to avoid simultaneous electron injection from the gate. During the SHH stress, in contrast to the case of thicker oxide films, a strong correlation is observed between the oxide film degradation and the injected hole energy, while no degradation occurs due to the direct tunneling of holes from the inversion layer. These experimental findings indicate the existence of threshold energy for the trap creation process, which has been predicted by the theoretical study of the hole-injection-induced structural transformation of oxygen vacancies in silicon dioxide.