Electrical Charge Storage in Irradiated Insulating Films

Charge storage in single (SiO2) and double-layer (SiO2: Al2O3) insulating films has been investigated by observing the thermal annealing of the radiation-induced space charge in IGFET structures. Evidence presented indicates that the anneal in both films is characterized by a two-step process. The first appears to involve a spatial redistribution of the space charge. This is followed, at a somewhat higher temperature, by neutralization of the added space charge induced by the radiation. Observations on the single-layer insulating films of SiO2 yield activation energies for both processes on the order of 0.3 eV. Experiments on the double-layer films of A1203, pyrolytically deposited on SiO2, indicate that the dominant activation energies for both processes lie in the range from 0.6 to 0.7 eV. However, there is evidence of a small admixture of lower energy processes.