4,826 research outputs found
Mathematical model for a radioactive marker in silicide formation
A mathematical model is constructed to interpret the profiles of radioactive (^31)Si tracers in a
computer simulation proposed by R. Pretorius and A. P. Botha [Thin Solid Films 91, 99 (1982)].
This model assumes that only Si moves in the silicide, that the Si moves interstitially and
convectively, and that the moving Si can exchange sites with the stationary Si in the silicide lattice.
An analytical solution of this model is given and confirms the published computer simulation
data. However, it is shown that the model is physically inadequate. Solutions of another model
which assumes that metal, instead of Si, is the moving species for silicide formation (either
interstitially, or substitutionally, or both), with self-diffusion of (^31)Si in the silicide during silicide
formation. Almost all the experimental data can be fitted by solutions of both models. These
examples demonstrate that radioactive tracer experiments alone are insufficient to determine the
moving species when a solid binary compound film forms by reaction of adjacent elemental layers.
Both inert marker and tracer data are needed to identify the moving species and the mechanisms
Improvement of thermally formed nickel silicide by ion irradiation
A significant improvement of the lateral uniformity of thermally formed Ni_(2)Si layers has been observed after low‐dose (10^(13)~3 × 10^(14) ion/cm^2) Xe irradiation of an As‐deposited Ni film. Measurements have also been made on samples that contained a thin impurity layer formed intentionally between the silicon substrate and the evaporated nickel film. The impurity layer was thick enough to prevent thermal silicide formation in unirradiated samples, but in irradiated samples, the silicide formation was not prevented. Similar results were obtained for As implantations. We attribute this effect to ion mixing of the interfacial layer. These results demonstrate that a low‐dose irradiation can render the process of silicide formation by thermal annealing more tolerant to interfacial impurities. The concept is of potential significance to VLSI technology
Thermal stability and nitrogen redistribution in the〈Si〉/Ti/W–N/Al metallization scheme
Backscattering spectrometry, Auger electron spectroscopy, and x‐ray diffraction have been used to monitor the thin‐film reactions and nitrogen redistribution in the 〈Si〉/Ti/W–N/Al metallization system. It is found that nitrogen in the W–N layer redistributes into Ti after annealing at temperatures above 500 °C. As a consequence of this redistribution of nitrogen, a significant amount of interdiffusion between Al and the underlayers is observed after annealing at 550 °C. This result contrasts markedly with that for the 〈Si〉/W–N/Al system, where no interdiffusion can be detected after the same thermal treatment. We attribute this redistribution of nitrogen to the stronger affinity of Ti for nitrogen than W. If the Ti layer is replaced by a sputtered TiSi_(2.3) film, no redistribution of nitrogen or reactions can be detected after annealing at 550 °C for 30 min
Model Checking Classes of Metric LTL Properties of Object-Oriented Real-Time Maude Specifications
This paper presents a transformational approach for model checking two
important classes of metric temporal logic (MTL) properties, namely, bounded
response and minimum separation, for nonhierarchical object-oriented Real-Time
Maude specifications. We prove the correctness of our model checking
algorithms, which terminate under reasonable non-Zeno-ness assumptions when the
reachable state space is finite. These new model checking features have been
integrated into Real-Time Maude, and are used to analyze a network of medical
devices and a 4-way traffic intersection system.Comment: In Proceedings RTRTS 2010, arXiv:1009.398
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