Rechargeable E′ centers in silicon-implanted SiO2 films

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Abstract
Implantation of Si in does of 1015–1016 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, Eβ and E’γ variants of bulk amorphous silica.