Composition and electrical properties of ultra-thin SiOxNy layers formed by rf plasma nitrogen implantation/plasma oxidation processes, Journal of Telecommunications and Information Technology, 2007, nr 3

Experiments presented in this work are a summary of the study that examines the possibility of fabrication of oxynitride layers for Si structures by nitrogen implantation from rf plasma only or nitrogen implantation from rf plasma followed immediately by plasma oxidation process. The obtained layers were characterized by means of: ellipsometry, XPS and ULE-SIMS. The results of electrical characterization of NMOS Al-gate test structures fabricated with the investigated layers used as gate dielectric, are also discussed

Comparison of composition of ultra-thin silicon oxynitride layers’ fabricated by PECVD and ultrashallow rf plasma ion implantation, Journal of Telecommunications and Information Technology, 2007, nr 3

In this paper differences in chemical composition of ultra-thin silicon oxynitride layers fabricated in planar rf plasma reactor are studied. The ultra-thin dielectric layers were obtained in the same reactor by two different methods: ultrashallow nitrogen implantation followed by plasma oxidation and plasma enhanced chemical vapour deposition (PECVD). Chemical composition of silicon oxynitride layers was investigated by means of X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The spectroscopic ellipsometry was used to determine both the thickness and refractive index of the obtained layers. The XPS measurements show considerable differences between the composition of the fabricated layers using each of the above mentioned methods. The SIMS analysis confirms XPS results and indicates differences in nitrogen distribution

The influence of annealing (900◦C) of ultra-thin PECVD silicon oxynitride layers, Journal of Telecommunications and Information Technology, 2007, nr 3

This work reports on changes in the properties of ultra-thin PECVD silicon oxynitride layers after high- temperature treatment. Possible changes in the structure, composition and electrophysical properties were investigated by means of spectroscopic ellipsometry, XPS, SIMS and electrical characterization methods (C-V, I-V and charge- pumping). The XPS measurements show that SiOxNy is the dominant phase in the ultra-thin layer and high-temperature annealing results in further increase of the oxynitride phase up to 70% of the whole layer. Despite comparable thickness, SIMS measurement indicates a densification of the annealed layer, because sputtering time is increased. It suggests complex changes of physical and chemical properties of the investigated layers taking place during high-temperature annealing. The C-V curves of annealed layers exhibit less frequency dispersion, their leakage and charge-pumping currents are lower when compared to those of as-deposited layers, proving improvement in the gate structure trapping properties due to the annealing process

Ionicity of ZnO —A key system for transparent conductive oxides

The electronic structure of ZnO is dominated by coexisting electron and ionic states/bonds caused by charge polarization and self-trapping phenomena of the valence charges. Their interplay manifests itself in intrinsic electronic defects which have different degree of spatial localization and electronic correlation. The relative abundance of intrinsic defects can be determined by the ionicity factor $f_{\mathrm{i}}$ and its value can be derived from three independent experimental procedures in a consistent way. This approach also explains the complex satellite features in the XPS and XAS data. Ionicity and satellite formation are two experimental findings which can be explained consistently in the same context of mixed-atomic valence states and intrinsic electronic defects

Depth profiles of Ta2O5/SiO2/Si structures : a combined X-ray photoemission, Auger electron, and secondary ion mass spectroscopic study

We prepared thin films of tantalum oxide on SiO2/Si substrates by thermal oxidation of tantalum. The different oxide layers and their interfaces were characterized by SIMS, AES, and XPS. Characteristic structures were obtained after different oxidation procedures. The comparative discussion of AES and SIMS depth profiles makes possible an unequivocal characterization of the reactive interfaces between the oxides of Ta and Si. The Ta2O5/SiO2 interface in particular shows non-stoichiometries which depend on the oxidation procedures and which determine the performance characteristics of pH-sensitive Ta2O5 field-effect transistors

Ta2O5-gates of ph-sensitive devices : comparative spectroscopic and electrical studies

Thin films of tantalum pentoxide (Ta2O5) were prepared on Si/SiO2 substrates by thermal oxidation of tantalum. In systematic oxidation studies we followed the growth of the Ta2O5/SiO2 interface. The oxide layers and their interfaces were characterized by SIMS, SAM, XPS, by comparative C-V measurements and by pH-(ISFET) sensitivities. Depending on the oxidation procedure, we find non-ideal stoichiometries of the Ta2O5/SiO2 interface, whose widths vary as a function of the oxidation time of the previously evaporated metallic tantalum. Specific annealing procedures lead to unexpectedly high leakage currents, which correlate with the formation of voids in the oxide layers. Even in the absence of voids, non-ideal interfaces provide high concentrations of electrically-active states in gate oxides of ISFETS, which in turn determine the results of C-V measurements and ISFET characteristics. For ideal stoichiometric and atomically abrupt interfaces, we observe long-term stability and ideal Nernstian behaviour in the pH-(ISFET) sensitivities

The stability of C60 and its derivatives upon handling in microsystems technologies

We investigate C60, C60(OH)24, C60(F3)12, C60Cl2 and analyse the stability of these derivatives upon processing in sol-gel, spin-coating, spraying, dropping and evaporating procedures to obtain thin films for possible microsystems application. We use X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Near Edge X-ray Absorption Fine Structure Spectroscopy (NEXAFS) to analyse the fullerene species within the films. We find fullerene molecules stable in evaporation procedure but not stable in films obtained by using fullerenes dissolved in toluene, chlorobenzene and cyclohexane. Most stable are the evaporated films of pure C60, while the soluble derivatives are less stable. The fluorine derivatives are most stable when processed by spray coating with ethanol as a solvent. Fullerol was dissolved in H2O and films are obtained by spray coating