Degradation of the thermal oxide of the Si/SiO2/Al system due to vacuum ultraviolet irradiation

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Abstract
The generation of point defects in Si/SiO2/Al capacitors due to exposure to vacuum ultraviolet (VUV) (10 eV) radiation has been investigated by studying the electron and hole trapping properties and electron‐spin‐resonance spectroscopy for exposures ranging from 1014 up to 1019 photons cm−2 absorbed in the oxide. At low VUV exposures, the generation of hydroxyl groups and electron traps with cross section ≥10−16 cm2 is observed; however, for exposures larger than 1017 cm−2 these centers are subsequently eliminated. For exposures larger than 1018 cm−2 the oxide network is gradually destroyed; oxygen atoms are removed from their network positions and decorated with hydrogen atoms, thus producing water molecules and trivalent silicon centers in comparable numbers. At an exposure of 1019 cm−2, of the order of 1014 cm−2 of oxygen atoms are removed, without any indication that the process would saturate. A tentative model is presented in which the degeneration process takes place at regular network sites; a defect precursor is not invoked. It is proposed that neutralization of self‐trapped hydrogen/hole pairs at the oxygen atoms plays a crucial role in this process.