Thermally stimulated current in SiO2

Thermally stimulated current (TSC) techniques provide information about oxi de-trap charge densities and energy distributions in MOS (metal-oxide-semic onductor) capacitors exposed to ionizing radiation or high-field stress tha t is difficult or impossible to obtain via standard capacitance-voltage or current-voltage techniques. The precision and reproducibility of measuremen ts through repeated irradiation/TSC cycles on a single capacitor is demonst rated with a radiation-hardened oxide, and small sample-to-sample variation s are observed. A small increase in E-delta(') center density may occur in some non-radiation-hardened oxides during repeated irradiation/TSC measurem ent cycles. The importance of choosing an appropriate bias to obtain accura te measurements of trapped charge densities and energy distributions is emp hasized. A 10 nm deposited oxide with no subsequent annealing above 400 deg rees C shows a different trapped-hole energy distribution than thermally gr own oxides, but a similar distribution to thermal oxides is found for depos ited oxides annealed at higher temperatures. Charge neutralization during s witched-bias irradiation is found to occur both because of hole-electron an nihilation and increased electron trapping in the near-interfacial SiO2. Li mitations in applying TSC to oxides thinner than similar to 5 nm are discus sed, (C) 1999 Elsevier Science Ltd. All rights reserved.