Showing papers by "Carl V. Thompson published in 1990"
TL;DR: In this paper, the mechanisms and modes of grain growth in thin films are reviewed and the focus is on those factors that lead to the evolution of grain orientations as well as grain siamese expressions.
Abstract: in the average crystal orientation and can even result in epitaxial films. It is therefore not surprising that grain growth can profoundly affect the mechanical, electrical, and chemical properties of thin films. In this article the mechanisms and modes of grain growth in thin films will be reviewed. The focus will be on those factors that lead to the evolution of grain orientations as well as grain si zes. Spec ific attention will also be gi ven to those factors that allow control of microstructural evolution in thin films.
611 citations
TL;DR: In this article, the authors have studied initially continuous and patterned films of gold on fused silica substrates and two in situ techniques were used to monitor agglomeration: heating and video recording in a transmission electron microscope, and measurement of the intensity of laser light transmitted through a sample heated in a furnace.
Abstract: Very thin films, less than 100 nm-thick, are used in a variety of applications, including as catalysts and for thin film reactions to form patterned silicides in electronic devices. Because of their high surface to volume ratio, these very thin films are subject to cap-illary instability and can agglomerate well below their melting temperatures. In order to develop a general understanding of agglomeration in very thin films, we have studied initially continuous and patterned films of gold on fused silica substrates. Two in situ techniques were used to monitor agglomeration: 1) heating and video recording in a transmission electron microscope, and 2) measurement of the intensity of laser light transmitted through a sample heated in a furnace. Electron microscopy allowed inves-tigation of the role of the microstructure of the Au film and analysis of light transmis-sion during heating allowed determination of temperature-dependent and film-thick-ness-dependent agglomeration rates. These results will be described along with models for the agglomeration process.
304 citations
TL;DR: In this paper, it was shown that melting occurred in the explosive reactions of films with an atomic concentration ratio of 3Al:1Ni and that the propensity of multilayer films to undergo explosive reactions is dependent on the modulation length of the film as well as on the ambient temperature.
Abstract: Self‐propagating explosive reactions, with a reaction front speed of about 4 m/s, have been observed in free‐standing polycrystalline Al/Ni multilayer thin films. The resultant phases and microstructures are compared with those obtained by conventional thermal annealing. We show evidence which indicates that melting occurred in the explosive reactions of films with an atomic concentration ratio of 3Al:1Ni. It is also observed that the propensity of multilayer films to undergo explosive reactions is dependent on the modulation length of the film as well as on the ambient temperature. These observations are interpreted with a simple model based on the rate balance between the rates of heat generation and heat dissipation.
195 citations
TL;DR: In this article, the effects of grain-boundary grooving at the free surface of a thin film were modeled by introducing a stagnation condition on grainboundary migration, which resulted in a lognormal grain-size distribution.
Abstract: A computer simulation of grain growth in two dimensions has been used to model microstructural evolution in thin films. In particular, we have modelled the effects of grain-boundary grooving at the free surface of a film by introducing a stagnation condition on grain-boundary migration. This stagnation results in a lognormal grain-size distribution, which is similar to experimentally observed distributions.
153 citations
TL;DR: In this paper, a thin layer of amorphous nickel silicide formed between the nickel and polysilicon layers, and upon heating, this amorphus silicide thickened slightly, until crystalline Ni2Si formed at the nickel/amorphous-silicon interface.
Abstract: Isothermal and constant‐heating‐rate differential scanning calorimetry, cross‐sectional transmission electron microscopy, thin‐film x‐ray diffraction, and thermodynamic and kinetic analyses have been used to investigate silicide phase selection in nickel/amorphous‐silicon multilayer thin‐film reactions. The atomic concentration ratio of the films was two Ni atoms to one Si atom and the layer thickness ratio was one to one. During deposition, a thin layer of amorphous nickel silicide formed between the nickel and amorphous‐silicon layers. Upon heating, this amorphous nickel silicide thickened slightly, until crystalline Ni2Si formed at the nickel/amorphous‐nickel‐silicide interface. Further heating caused the simultaneous growth of both the amorphous nickel silicide and crystalline Ni2Si. Comparison of thermodynamic data to kinetic models for silicide formation and the analysis of calorimetry data suggests that nucleation barriers are responsible for the initial formation of the amorphous nickel silicide a...
109 citations
TL;DR: A theory for epitaxial grain growth is outlined and results given for experiments on Au, Al, Cu, and Ag films on vacuumcleaved NaCl, KBr, KCl, or mica.
Abstract: Epitaxial alignment has been obtained by means of grain growth in polycrystalline films deposited on single‐crystal substrates. A theory for epitaxial grain growth is outlined and results given for experiments on Au, Al, Cu, and Ag films on vacuum‐cleaved NaCl, KBr, KCl, or mica. Epitaxial grain growth provides a fundamentally different alternative to conventional epitaxy, and can lead to very thin films with improved continuity and crystalline perfection, as well as non‐lattice‐matched orientations.
103 citations
TL;DR: In this paper, the nucleation and growth kinetics of NiSi2 precipitation in amorphous silicon thin films ion implanted with nickel were investigated using scanning transmission electron microscopy, and it was shown that the growth rate could be approximately described by a delta function at time t = 0 when the films were annealed between 325 and 400 °C.
Abstract: The nucleation and growth kinetics of NiSi2 precipitation in amorphous silicon thin films ion implanted with nickel was investigated using scanning transmission electron microscopy. It was found that the nucleation rate could be approximately described by a delta function at time t = 0 when the films were annealed between 325 and 400 °C. The growth kinetics of the precipitates at these temperatures were described by r ∝ tn, where r was the average radius and n was about 1/3. This behavior is consistent with models for growth of three-dimensional particles in a two-dimensional diffusion field. It was also found that the implanted amorphous films displayed an enhanced rate of single crystal silicon formation, apparently catalyzed by migrating silicide precipitates.
98 citations
TL;DR: In this article, the effects of phosphorus, arsenic, and boron on surface energy-driven secondary grain growth (SEDSGG) in thin polycrystalline silicon films have been investigated.
Abstract: The effects of phosphorus, arsenic, and boron on surface‐energy‐driven secondary grain growth (SEDSGG) in thin polycrystalline silicon films have been investigated. At concentrations at or above 5×1020 cm−3, phosphorus and arsenic were found to markedly enhance SEDSGG while boron had little effect. However, codoping with phosphorous and boron or arsenic and boron lead to compensation (reduction or elimination) of the enhancement effect. The kinetics of SEDSGG were analyzed using transmission electron microscopy. In order to identify electronic as well as segregation effects of dopants on the kinetics of SEDSGG, electron concentrations in the Si films were determined from Hall measurements and dopant segregation was directly measured using scanning transmission electron microscopy and energy‐dispersive x‐ray analysis. Analogous to normal grain growth, dopant‐induced enhancement of SEDSGG can be explained in terms of an increased grain‐boundary atomic mobility due to changes in point‐defect concentrations r...
89 citations
TL;DR: In this paper, a combination of high speed photography, high speed temperature measurements, plan-view transmission electron microscopy, and thin film x-ray diffraction was used to investigate self-propagating explosive reactions in multilayer thin films.
Abstract: Self‐propagating explosive reactions can occur in multilayer thin films. Explosive silicidation in nickel/amorphous‐silicon multilayer thin films has been investigated using a combination of high‐speed photography, high‐speed temperature measurements, plan‐view transmission electron microscopy, and thin film x‐ray diffraction. The multilayer films had an atomic concentration ratio of 2 Ni atoms to 1 Si atom. The silicide phase formed by explosive silicidation was Ni2 Si. This was the same phase formed by conventional thermal annealing of the multilayer thin film. The temperature of the explosive reaction front was measured to be approximately 1565 K. The reaction‐front velocity was found to vary from 22 to 27 m/s and to be at most weakly dependent on the modulation period and the total film thickness. The resulting Ni2 Si grain structure formed by explosive silicidation is less defective than Ni2 Si formed by conventional thermal annealing. This was attributed to the higher reaction temperatures and the shorter reaction times of explosively formed Ni2 Si as compared to Ni2 Si formed via conventional annealing.
80 citations
TL;DR: In this paper, the authors investigated the deviation in the time to failure (DTTF) in lines with bimodal structures and found that lines with large grain structures have higher DTTF than lines with small grain structures.
Abstract: Interconnects containing bimodal grain size distributions are known to have lower me-dian times to electromigration-induced failure (MTTF). However, the deviation in the time to failure (DTTF) in such lines has not been well characterized. We find that Al-2%Cu-0.3%Cr interconnects with bimodally distributed grain sizes have MTTF’s which are more than an order of magnitude lower than lines with monomodally distributed small grain sizes. However, the DTTF’s for both types of lines are similar, and in fact slightly lower for lines with bimodal structures. An activation energy of 0.85 eV was obtained both for lines with monomodal large grain structures and bimodal grain struc-tures, suggesting that grain boundary diffusion is the controlling mechanism in both cases. A model based simply on microstructural characteristics,e.g. the distribution of the number of grain boundaries, can explain the lower MTTF’s and DTTF’s for lines with bimodal structures. The implications of bimodal grain size distributions on the reliability of large numbers of lines are discussed. Also, a new, convenient graphical tool for illustrating the failure rate of interconnects with lognormally distributed failure times is presented.
36 citations
TL;DR: Growth of amorphous-titanium-silicidc and crystalline C49 TiSi2 in titanium/amorphous-silicon multilayer films was investigated using a combination of differential scanning calorimetry (DSC), thin film x-ray diffraction, Auger depth profiling, and cross-sectional transmission electron microscopy.
Abstract: Growth of amorphous-titanium-silicidc and crystalline C49 TiSi2 in titanium/amorphous-silicon multilayer films was investigated using a combination of differential scanning calorimetry (DSC), thin film x-ray diffraction, Auger depth profiling, and cross-sectional transmission electron microscopy. The multilayer films had an atomic concentration ratio of 1Ti to 2Si and a modulation period of 30 nm. In the as-deposited condition, a thin amorphous-titanium-silicide layer was found to exist between the titanium and silicon layers. Heating the multilayer film from room temperature to 700 K caused the release of an exothermic heat over a broad temperature range and an endothermic heat over a narrow range. The exothermic hump was attributed to thickening of the amorphous-titanium silicide layer, and the endothermic step was attributed to the homogenization and/or densification of the amorphous-silicon and amorphous-titanium-silicide layers. An interpretation of previously reported data for growth of amorphous-titanium-silicide indicates an activation energy of 1.0 ± 0.1 eV and a pre-exponential coefficient of 1.9 × 10−7 cm2/s. Annealing at high temperatures caused formation of C49 TiSi2 at the amorphous-titanium-silicide/amorphous-silicon interfaces with an activation energy of 3.1 ± 0.1 eV. This activation energy was attributed to both the nucleation and the early stages of growth of C49 TiSi2. The heat of formation of C49 TiSi2 from a reaction of amorphous-titanium-silicide and crystalline titanium was found to be –25.8 ± 8.8 kJ/mol and the heat of formation of amorphous-titanium-silicide was estimated to be –130.6 kJ/mol.
TL;DR: The first silicide phase to form at the vanadium/amorphous-silicon interface was amorphous-vanadium-silicide as mentioned in this paper, where the atomic concentration ratio was one V atom to two Si atoms and the modulation period was either 14 or 50 nm.
Abstract: Cross‐sectional transmission electron microscopy, isothermal and constant‐heating‐rate calorimetry, and thin film x‐ray diffraction have been used to investigate amorphous and crystalline silicide phase formation in vanadium/amorphous‐silicon multilayer thin films. The atomic concentration ratio of the films was one V atom to two Si atoms and the modulation period was either 14 or 50 nm. The first silicide phase to form at the vanadium/amorphous‐silicon interface was amorphous‐vanadium–silicide. Heating to temperatures above 750 K caused crystalline VSi2 to form at the amorphous‐vanadium–silicide/amorphous‐silicon interface. Analysis of cross‐sectional transmission electron microscopy and both isothermal and constant‐scan‐rate calorimetric data suggest that nucleation barriers control the formation of crystalline VSi2.
TL;DR: In this paper, the growth of an amorphous Ti-Si phase and subsequent formation of crystalline silicides during solid-state reactions in Ti/a-Si multilayer films have been studied using power-compensated differential scanning calorimetry, cross-sectional transmission electron microscopy, and thin-film x-ray diffraction.
Abstract: The growth of an amorphous Ti-Si phase and subsequent formation of crystalline silicides during solid-state reactions in Ti/a-Si multilayer films have been studied using power-compensated differential scanning calorimetry, cross-sectional transmission electron microscopy, and thin-film x-ray diffraction. By analyzing calorimetric data we have determined the activation energies for the formation of the various silicides (amorphous Ti-silicide, TiSi, C 49 -TiSi 2 , Ti 5 Si 3 ) as well as their heats of formation. An amorphous silicide is the first phase to form during heating and we have measured the composition profile of this amorphous layer using scanning transimission electron microscopy. Metastable phase equilibria in the Ti-Si system are discussed in light of the thermodynamic and compositional information obtained in our experiments.
TL;DR: In this paper, the authors suggest that pre-nucleation interdiffusion and nucleation itself are both key factors to consider in understanding phase selection in thin-ftlm reactions.
Abstract: Our experiments and analyses suggest the following sequence of events during reactions at Al/Ni interfaces: 1) Interdiffusion precedes Al3Ni nucleation, leading to the fonnation of metastable solid solutions. 2) Al3Ni nucleates in the interdiffused region at a fixed number of sites whose areal density changes as a function of the bilayer thickness, because of correlated changes in the population of grain boundary triple junctions. 3) Al3Ni coalesces into a continuous layer with a thickness of about 10 nm and the thickening of this layer is diffusion limited. These observations are consistent with the thermodynamic properties of the AI-Ni phases and suggest that pre-nucleation interdiffusion as well as nucleation itself are both key factors to consider in understanding phase selection in thin-ftlm reactions. The authors wish to thank Jerry Floro for depositing UHV samples, and mM for providing support for this project.
TL;DR: In this paper, the relative energies of various film orientations are measured by epitaxial grain growth, which selects the orientation having lowest total free energy, including the free energy of both the film-substrate interface and the free surface of the film.
Abstract: Conventional heteroepitaxial thin film growth may result in a film whose epitaxial orientation is metastable. One method of probing the relative energies of various film orientations is epitaxial grain growth. Epitaxial grain growth selects the orientation having lowest total free energy, including the free energy of both the film-substrate interface and the free surface of the film. Experimental examples of epitaxial grain growth in metal films on insulating substrates will be discussed.