Sputter-Metallization-Induced Electronic Defects in Thermal SiO2

The generation of interface states and oxide electron traps in thermal silicon dioxide (SiO2) layers by sputtering metallization has been investigated. The dependence of the samples on electric field and temperature during the sputter process is observed. The interface state density spectra revealed narrow distributions indicating an increased density of band edge states. In the upper part of the Si band gap a peak was observed due to the generation of a particular interface defect site. Three bulk defect centers were found as identified by their capture cross sections of the order of 1 × 10—16, 3 × 10—17 and 3 × 10—18 cm2. The first one is associated with radiation induced neutral centers and is a feature of oxides metallized by sputtering. The other two traps are believed to be related to defects like SiOH and H2O. Post metallization annealing (PMA) resulted in a reduction of the density of the oxide and interface traps and a broadening of the interface trap spectra. A speculation on the defect formation process is included.