RECHARGEABLE E' CENTERS IN SILICON-IMPLANTED SIO2-FILMS

Implantation of Si in does of 1015-10 16 cm-2 into dry thermal oxides on silicon wafers produces a three-state MOS memory device. For both positive- and negative-going traps, gate voltage stress up to ±10 MV/cm -1 generates stable (±) oxide charge near the gate and (∓) charge near the substrate. Electron paramagnetic resonance (EPR) measurement on corona-field (≤11 MV/cm) stressed oxides reveals E' centers in regions of positive charge, which may be recycled between the EPR-visible (+) state and the invisible neutral state. The correspondence of charge and EPR indicates a composite or Feigl-Fowloer-Yip E' center, O3 3/4 Si:.+Si 3/4 O3, arising from nonstoichiometric Si fused into the SiO2 lattice. Upon trapping an electron, the center rebonds to yield O3 3/4 SiSi 3/4 O3. The charging parameters of the E' center suggest tunneling of an electron from the (0→+) state, and are consistent with the theoretical prediction of the energy level and Franck-Condon relaxation. The three types of E' centers observed in this and related studies are compared with the E'α, E 'β and E'γ variants of bulk amorphous silica.