High resolution soft x-ray photoelectron spectroscopy with synchrotron radiation is used to study the interfaces of SiO 2 /Si(111), SiO 2 /Si(100), Si͑111͒/Si 3 N 4 , and SiO 2 /Si 3 N 4 for device-quality ultrathin gate oxides and nitrides. The thin oxides and nitrides were grown by remote plasma deposition at a temperature of 300°C. Aftergrowth samples were further processed by rapid thermal annealing for 30 s at various temperatures from 700 to 950°C. The Si͑111͒/Si 3 N 4 samples were air exposed and formed a thin ϳ6 Å SiO 2 layer with a Si(2p) core-level shift of 3.9 eV, thus allowing us to study both the Si͑111͒/Si 3 N 4 and SiO 2 /Si 3 N 4 interfaces with a single type of sample. We obtain band offsets of 4.54Ϯ0.06 eV for SiO 2 /Si(111) and 4.35Ϯ0.06 eV for SiO 2 /Si(100) with film thicknesses in the range 8-12 Å. The Si͑111͒/Si 3 N 4 nitrides show 1.78Ϯ0.09 eV valence-band offset for 15-21 Å films. This value agrees using the additivity relationship with our independent photoemission measurements of the nitride-oxide valence-band offset of 2.66Ϯ0.14 eV. However, we measure a substantially larger SiO 2 /Si 3 N 4 ⌬E V value of 3.05 eV for thicker ͑ϳ60 Å͒ films, and this indicates substantial differences in core-hole screening for films of different thickness due to additional silicon substrate screening in the thinner ͑15-21 Å͒ films.

Device-grade ultrathin ͑9-22 Å͒ films of silicon dioxide, prepared from crystalline silicon by remote-plasma oxidation, are studied by soft x-ray photoelectron spectroscopy ͑SXPS͒. The 2p core-level spectra for silicon show evidence of five distinct states of Si, attributable to the five oxidation states of silicon between Si 0 ͑the Si substrate͒ and Si 4ϩ ͑the thin SiO 2 film͒. The relative binding energy shifts for peaks Si 1ϩ through Si 4ϩ ͑with respect to Si 0 ͒ are in agreement with earlier work. The relatively weaker signals found for the three intermediate states (I 1 , I 2 , and I 3 ͒ are attributed to silicon atoms at the abrupt interface between the thin SiO 2 film and substrate. Estimates of the interface state density from these interface signals agree with the values reported earlier of ϳ2 monolayers ͑ML͒. The position and intensity of the five peaks are measured as a function of post-growth annealing temperature, crystal orientation, and exposure to He/N 2 plasma. We find that annealing produces more abrupt interfaces ͑by reducing the suboxide interface state density͒, but never more abrupt than ϳ1.5 monolayers. We observe a 15%-20% drop in the interface thickness ͑in particular the ''Si 2ϩ '' peak intensity͒ with increasing annealing temperature. Somewhat different behavior is observed with small amounts of nitrogen in the SiO 2 film where an apparent increase in interface state density is seen. A quantitative analysis is presented which explores the effects of these sample preparation parameters in terms of relative interface state density and modeling of the SXPS data.

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Hot-carrier-induced oxide charge trapping and interface trap creation in metal-oxide-semiconductor devices studied by hydrogen/deuterium isotope effectThe substitution of deposited alternative gate dielectrics for thermally grown SiO 2 in aggressively scaled complementary metal-oxide-semiconductor devices requires separate and independent processing steps for ͑i͒ the oxidation of the Si substrate to form the Si-dielectric interface and ͑ii͒ the deposition of thin film dielectric. Ultrathin plasma-oxidized Si-SiO 2 interface layers which contribute approximately 0.3-0.4 nm to the overall electrical oxide thickness have been integrated into devices with Si nitride, Si oxynitride, and Ta 2 O 5 alternative dielectrics. This article proposes an analogy between ͑i͒ microscopically inhomogeneous bulk glass alloys such as GeSe x with 1Ͻx Ͻ2, and ͑ii͒ interfaces included in these composite gate dielectric-semiconductor structures including, for examples, the Si-SiO 2 and internal dielectric SiO 2 -Si 3 N 4 interfaces. Scaling relationships for bond defect states applied initially to microscopically inhomogeneous glasses and thin films are applied here to interfaces in stacked gate dielectrics.

The dissociation dynamics of energy-selected 2-bromobutane ions has been investigated by photoelectron photoion coincidence (PEPICO). The data were collected with a conventional gas discharge light source at the University of North Carolina and at the SuperACO synchrotron storage ring of LURE in Orsay, France. The 2-bromobutane ion dissociates via Br and HBr loss within 0.3 eV of the ionization limit. The Br loss channel produces the sec-butyl ion C4H9 + via a simple bond cleavage and is found to proceed at a fast rate. At lower ion energies, the HBr loss channel produces the 2-butene ion via a concerted mechanism with rate constants in the microsecond range. A model that involves tunneling associated with the proton transfer is proposed. Asymmetric time-of-flight distributions and breakdown diagrams are fitted to the statistical RRKM theory with the aid of GAUSSIAN ab initio molecular orbital calculations at the MP2/6-31G* level. The fitting of the data was optimized for a barrier height of 0.438 eV and an imaginary frequency associated with the H atom transfer step of 1245 cm-1. This compares with the ab initio results of 0.796 eV and 1265 cm-1. Heats of formation at 0 K for 2-bromobutane cation (880.1 ± 2.7 kJ mol-1) and sec-butyl cation (794 ± 3 kJ mol-1) were derived from this work.