Charge Trapping in Oxide Grown on Polycrystalline Silicon Layers

Shifts in tunneling I-V characteristics are used to study electron trapping in oxides thermally grown on silicon layers deposited in both amorphous and polycrystalline phases. The electron trapping resulted from charge injection by tunneling from either the bottom or top electrodes of capacitors constructed of two deposited silicon layers separated by thermal oxide. It is observed that upon injection from the top electrode, the resulting trapped-charge centroid is located close to the middle of the oxide layer. On the other hand, injection from the bottom electrode results in an apparent trapped-charge centroid which is located near the bottom silicon-oxide interface. This difference may be attributed to the existence of asperities on the bottom silicon layer.