Degradation of direct-tunneling gate oxide under hot hole injection

The degradation of ultrathin SiO2 films accompanied by the hole direct tunneling 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 oxides in p-channel MOSFETs with p+ poly-Si gates, while the gate bias 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, whereas no degradation occurs due to the hole direct tunneling from the inversion layer. These experimental findings indicate the existence of threshold energy for trap creation process, which has been predicted by the theoretical study of hole-injection-induced structural transformation of oxygen vacancy in SiO2. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(4): 54–61, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.2008