Electron trapping in aluminum−implanted silicon dioxide films on silicon

Photoelectric and MOS capacitance−voltage techniques were used to study electron trapping in 1400−Å dry−grown silicon dioxide films that were implanted with aluminum ions at 20 keV to a fluence of 1014 cm−2. The photoinjection of electrons into the implanted oxides resulted in the buildup of negative space charge. Data analysis indicated that all injected electrons had been trapped and that the observed transient responses of the photocurrent and flatband voltage were governed by the electric−field dependence of the photoinjected current. The negative space charge could be annealed either optically by photons of energy exceeding 4 eV or thermally at 350 °C. A 600 °C anneal for 30 min considerably reduced the concentration of electron traps. From this it is concluded that a substantial fraction of the traps were associated with displacement damage created by the ion implantation.