DEGRADATION OF THE THERMAL OXIDE OF THE SI/SIO2AL SYSTEM DUE TO VACUUM-ULTRAVIOLET IRRADIATION

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 10(14) up to 10(19) photons cm(-2) absorbed in the oxide. At low VUV exposures, the generation of hydroxyl groups and electron traps with cross section greater than or equal to 10(-16) cm(2) is observed; however, for exposures larger than 10(17) cm(-2) these centers are subsequently eliminated. For exposures larger than 10(18) 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 10(19) cm(-2), of the order of 10(14) 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. (C) 1995 American Institute of Physics.