Generation and relaxation phenomena of positive charge and interface trap in a metaloxidesemiconductor structurePositive charge and interface state generation in a thin gate oxide (30 nm) metaloxidesemiconductor capacitor J. Appl. Phys. 75, 1592 (1994; 10.1063/1.356396 Interface and bulk trap generation in metaloxidesemiconductor capacitorsThis work examines the electrical behavior of metal-oxide-semiconductor capacitors in which positive charge has been generated in the silicon dioxide layer using either avalanche hole injection, avalanche electron injection, or Fowler-Nordheim Tunneling injection. It is concluded on the basis of flatband voltage measurements made as a function of time following charge injection that two distinct species of positive charge are generated in the oxide layer, depending on the nature of charge generation. In particular, avalanche hole injection results in the generation of trapped holes, while avalanche electron injection and Fowler-Nordheim Tunneling result in so-called "slow-states'* or anomalous positive charge centers. The electrical behavior of these two species is discussed. In addition, interface trap density measurements following avalanche hole injection show that both a background level of interface traps and a peak at approximately 0.8 eV above the valence band edge build with time following injection. Further, the dependence of the interface trap density on injection fluence and time supports a model in which a neutral species is released from the bulk of the oxide during hole injection and subsequently generates an interface defect.

Lightly doped n-GaN samples were etched with reactive ion etching (RIE) in BCl3/Cl2/Ar and BCl3/Cl2/N2 plasmas. Replacing the argon by nitrogen in the plasma chemistry resulted in better etch rates, and in addition reduced etch damage for relatively low values of the plasma power. By treating the samples in a nitrogen plasma following etching, we dramatically reduced surface damage, as determined from Schottky IV characteristics measurements. Specifically, the reverse breakdown voltages returned to 70% to that measured from control diode samples. Further, x-ray photoelectron spectroscopy analysis showed that the post-etch nitrogen step decreased the Ga/N ratio. These results suggest that much of the damage induced by RIE plasma etching comes from a nitrogen loss mechanism.

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We have analyzed oxide charging and interface trap generation induced by high-field tunnel injection in thin (200 to 250 A) thermal oxides of silicon prepared using rapid thermal oxidation (RTO). Constant-current Fowler-Nordheim tunnel (FNT) injection was used to stress aluminum gate MOS capacitors and to generate oxide and Si-SiO~ interface trapped charge. Analysis of both the flatband voltage and the gate voltage necessary to maintain constant current aIlows us to separate oxide charge generation from charge generated near and at the Si-SiQ interface. The analysis reveals, in addition to background electron trapping at water-related trapping centers, the trapping of holes near the Si-SiO2 interface as well as the generation of interface charge and anomalous positive charge (APC) near the Si-SiO2 interface. The appearance of these charge components is consistent with a comprehensive model of oxide and interface charging proposed recently by DiMaria and co-workers, ad we make use of this model in discussing the extraction of information on oxide charging from FNT charging curves. In particular, we show that under simplifying assumptions consistent with device processing on a particular oxide, useful information concerning generation of specific charge species can be obtained.

Electron paramagnetic resonance, in conjuction with electrical measurements, has been used to study Si-SiO2 interface defects produced as a result of negative bias, high-field electron injection into the SiO2 layer of metal-oxide-semiconductor capacitors. In particular, a search was made for Pb centers, previously identified as a source of interface traps in unannealed SiO2 on Si, and for E′ centers, which have been associated with trapped holes in SiO2. The results of the EPR experiments show no change in the density of Pb centers following injection, despite the presence of interface traps as indicated by the electrical measurements. Further, no E′ centers are detected in samples for which an analysis of the current-voltage and capacitance-voltage data suggest the presence of 5×1012 cm−2 positively charged centers. We conclude that interface traps generated in the present samples are not of the same microscopic nature as those found in unannealed SiO2 on Si, and that positive charging under the present conditions is not due to trapped holes. It is suggested that the source of positive charge is the so-called ‘‘anomalous positive charge’’ (APC) center. The microscopic nature of the present defects has not been identified.