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Evaluating the thermal processes occurring inside an illuminated nanoscale semiconducting tip is of utmost importance for the physical understanding of laser assisted atom probe tomography (L-APT). In this paper, we present a methodology to evaluate the temperature at the apex of the tip using L-APT. The method is based on the known exponential dependence of the probability for field evaporation on the temperature and the electric field at the apex. We use this method to gain insights into the effect of tip shape, doping, and laser power on the peak temperature reached at the apex of an illuminated Si tip. [ABSTRACT FROM AUTHOR]

Research is presented concerning the development of a simulation of the passage of O+ and Si+ signals through a transient region before they attain a stationary state, as found in secondary ion mass spectrometry.

Research describing the effects of chromium and molybdenum on phase formation for metal oxide semiconductors is presented. The use of these materials as interlayers in comparison with titanium is investigated.

Self-annealing, a phenomenon responsible for room temperature changes in stress, microstructure and stress characteristics of electroplated copper, is shown to be closely linked to the composition of the plating bath and incorporation of organic additives in the copper layer. Self-annealing is also critically dependent on film thickness, a behavior that is explained as a result of very rapid primary crystallization just after deposition followed by a slower lateral recrystallization that produces big secondary grains.

The effect of thermal annealing on epitaxial GeSn (6.5% Sn) strained layers grown on Ge-buffered Si(100) wafers has been investigated using Rutherford backscattering spectrometry and X-ray diffraction to unambiguously determine the Sn substitutional content as well as the elastic strain in the layers. Vacuum annealing at temperatures below 400 °C for 20 min has no noticeable effect on the strain in the epitaxial layers. Once the temperature was raised above 400 °C, however, relaxation of the layer sets in and the GeSn layer has essentially completely relaxed following a 20 min anneal at 650 °C. Using Rutherford backscattering and channelling spectrometry to provide compositional information as a function of depth enables one to monitor the effect of the thermal anneal on the Sn distribution throughout the layer, and also to directly extract their substitutional fraction (i.e., their solubility in the lattice). The results obtained show that when the relaxation initially sets in both the Ge and the Sn remain firmly bound in substitutional lattice sites and it is only around 600 °C, and after substantial relaxation has taken place, that Sn is finally expelled from lattice sites and diffuses to the surface of the sample. [ABSTRACT FROM AUTHOR]

Strained Ge1-xSnx thin films have recently attracted a lot of attention as promising high mobility or light emitting materials for future micro- and optoelectronic devices. While they can be grown nowadays with high crystal quality, the mechanism by which strain energy is relieved upon thermal treatments remains speculative. To this end, we investigated the evolution (and the interplay) of composition, strain, and morphology of strained Ge0.94Sn0.06 films with temperature. We observed a diffusion-driven formation of Sn-enriched islands (and their self-organization) as well as surface depressions (pits), resulting in phase separation and (local) reduction in strain energy, respectively. Remarkably, these compositional and morphological instabilities were found to be the dominating mechanisms to relieve energy, implying that the relaxation via misfit generation and propagation is not intrinsic to compressively strained Ge0.94Sn0.06 films grown by molecular beam epitaxy. [ABSTRACT FROM AUTHOR]

Ge(1-x)Sn(x) has received a lot of interest for opto-electronic applications and for strain engineering in advanced complementary-metal-oxide-semiconductor technology, because it enables engineering of the band gap and inducing strain in the alloy. To target a reliable technology for mass application in microelectronic devices, the physical problem to be addressed is to unravel the complex relationship between strain relaxation (as induced by the growth of large layer thicknesses or a thermal anneal) and defect formation, and/or stable Sn-cluster formation. In this paper, we study the onset of Sn-cluster formation and its link to strain relaxation using Atom Probe Tomography (APT). To this end, we also propose a modification of the core-linkage [Stephenson et al., Microsc. Microanal. 13, 448 (2007)] cluster analysis method, to overcome the challenges of limited detection efficiency and lateral resolution of APT, and the quantitative assessment for very small clusters (<40 atoms) embedded in a random distribution of Sn-atoms. We concluded that the main relaxation mechanism for these layers is defect generation (misfit dislocations, threading dislocations, etc.), irrespective of the cause (thickness of layer or thermal anneal) of relaxation and is independent of the cluster formation. The low thermodynamic solubility limit of Sn in Ge seems to be the driving force for Sn-cluster formation. Finally, we also discuss the spatial distribution of Sn in clusters and relate them to the theoretically predicted stable Sn clusters [Ventura et al., Phys. Rev. B 79, 155202 (2009)]. [ABSTRACT FROM AUTHOR]

We present an extended X-ray absorption fine structure investigation of the local environment of Sn atoms in strained and relaxed Ge1-xSnx layers with different compositions. We show that the preferred configuration for the incorporation of Sn atoms in these Ge1-xSnx layers is that of a a-Sn defect, with each Sn atom covalently bonded to four Ge atoms in a classic tetrahedral configuration. Sn interstitials, Sn-split vacancy complexes, or Sn dimers, if present at all, are not expected to involve more than 2.5% of the total Sn atoms. This finding, along with a relative increase of Sn atoms in the second atomic shell around a central Sn atom in Ge1-xSnx layers with increasing Sn concentrations, suggests that the investigated materials are homogeneous random substitutional alloys. Within the accuracy of the measurements, the degree of strain relaxation of the Ge1-xSnx layers does not have a significant impact on the local atomic surrounding of the Sn atoms. Finally, the calculated topological rigidity parameter a**=0.69±0.29 indicates that the strain due to alloying in Ge1-xSnx is accommodated via bond stretching and bond bending, with a slight predominance of the latter, in agreement with ab initio calculations reported in literature. [ABSTRACT FROM AUTHOR]

This study relates to the heteroepitaxy of InP on patterned Si substrates using the defect trapping technique. We carefully investigated the growth mechanism in shallow trench isolation trenches to optimize the nucleation layer. By comparing different recess engineering options: rounded-Ge versus V-grooved, we could show a strong enhancement of the crystalline quality and growth uniformity of the InP semiconductor. The demonstration of III-V heteroepitaxy at scaled dimensions opens the possibility for new applications integrated on Silicon. [ABSTRACT FROM AUTHOR]

The evolution of (001) and (111) facets for the epitaxial growth inside submicron trenches is systematically studied in this report. The analysis with the method of "Lagrange multiplier" indicates the equilibrium crystal shape. In the case of non-equilibrium without external fluxes, we employed the "weighted mean curvature" method to mathematically model the inter-facet migration rate for two extreme kinetic cases: "surface diffusion limited" and "surface attachment/detachment limited." Coupled with external supply of atoms, the self-limited behavior of facet size is theoretically predicted. Moreover, we find that the self-limited stable facet size in trenches of different widths has a specific relationship determined by the surface energy ratio, kinetic rate ratio, and isolated growth rate difference. The two limited cases could be discriminated according to the mathematical fitting of one exponent in this relationship based on the stable facet size in trenches of different widths. [ABSTRACT FROM AUTHOR]

During the solid phase reaction of a Ni(Pd) alloy with Si(100), phase separation of binary Ni- and Pd-silicides occurs. The PdSi monosilicide nucleates at temperatures significantly below the widely accepted nucleation temperature of the binary system. The decrease in nucleation temperature originates from the presence of the isomorphous NiSi, lowering the interface energy for PdSi nucleation. Despite the mutual solubility of NiSi and PdSi, the two binaries coexist in a temperature window of 100 °C. Only above 700 °C a Ni1-xPdxSi solid solution is formed, which in turn postpones the NiSi2 formation to a higher temperature due to entropy of mixing. Our findings highlight the overall importance of the interface energy for nucleation in ternary systems. [ABSTRACT FROM AUTHOR]

It is shown by SEM imaging of the tip and by observing the emission pattern of the evaporated atoms that laser assisted evaporation in an atom probe can lead to nonhemispherical tip shapes and time-dependent nonuniform emission. We have investigated this nonuniformity by observing the change in field of view when using laser wavelengths of 515 nm and 343 nm on silicon. The change is monitored in situ by 0.5 nm thick silicon oxide. We demonstrate that the field of view can easily be changed by more than 10 nm and that the apparent oxide layer thickness can deviate substantially from its correct value. The dependence of the tip shape deformations and the reconstruction artifacts on the laser wavelength are explained through simulations of the laser-tip interaction and nonhomogeneous heating effects. [ABSTRACT FROM AUTHOR]

We report the Ge thermal instability against surface diffusion in extremely narrow channels isolated by SiO2 and demonstrate the selective growth of strain-relaxed Ge epitaxial layers in channels as narrow as 10 nm on patterned Si (001) substrates by a combination of low temperature growth and selective recrystallization using Ge melt and regrowth during a millisecond laser anneal. Filling narrow channels at high growth temperatures is prohibited by Ge outdiffusion due to the high Ge chemical potential in such narrow channels. The Ge thermal instability depends on the channel width and a critical channel width of 50 nm is extracted from our calculation and experimental results. The Ge surface diffusion rate is dominated by the surface diffusion activation energy barrier that is significantly enhanced by the adsorbed surface hydrides. At a low temperature below 450 °C, a hydride-terminated surface is maintained which increases the Ge surface diffusion barrier and retards the outdiffusion of the Ge adatoms, providing excellent channel filling. The resulting low crystalline quality can be restored with a millisecond laser melt and regrowth. [ABSTRACT FROM AUTHOR]

The effect of oxygen flooding during ultralow energy SIMS depth profiling of silicon with Cs+ primary ions is presented. New experimental data show the effective sputtering yield of silicon in the presence of oxygen, as well as the energy distribution of the secondary Si- ions. It is found that the component sputtering yield of Si is very sensitive to minute amounts of oxygen in the proximity of the sputtered surface. At these very low flooding pressures (in the 10-9–10-8 mbar range), one cannot account for a full oxidation in the time frame of a typical measurement; it is concluded that in this particular case, which is technologically very relevant, small traces of oxygen will change the desorption characteristics of cesium as well as silicon. It shows that oxygen that is adsorbed to the silicon surface provides an attachment site for impinging cesium ions and thereby increases the retention capacity of cesium tremendously. Also, oxygen changes the secondary ion yield and can even promote the desorption of Si from the analysis surface. [ABSTRACT FROM AUTHOR]

Local electrical stress in gate dielectrics using conductive atomic force microscopy (C-AFM) induces structural damage in these layers. To allow C-AFM to become a mature technique to study oxide degradation, the impact of this structural damage, i.e., protrusions and holes, on the electrical behavior must be well understood. The physical nature and growth mechanism of protrusions due to a negative substrate voltage (Vs<0) is, however, debated in literature. In this work, we have studied the chemical composition of the surface protrusions using various analysis techniques (atomic force microscopy, transmission electron microscopy, and electron energy loss spectroscopy) showing that it consists of oxidized Si. A mechanism is proposed to explain the correlation between the observed surface damage and the measured current during constant voltage stress. [ABSTRACT FROM AUTHOR]

The growth of tungsten nitride carbide (WNxCy) films obtained by atomic layer deposition using triethylboron, tungsten hexafluoride, and ammonia precursors is determined by the density and type of reactive sites. The film properties change as a function of thickness. On silicon dioxide and silicon carbide, growth is initially nonlinear such that the transient regimes are characterized by island formation, as evidenced by a parabolic tungsten growth curve extending to film thicknesses of up to 5 nm. Such films have low densities of ∼4–6 g cm-3 corresponding to only ∼30%–45% of the bulk density of ∼13.1 g cm-3 determined for a WN0.45C0.55 composition. X-ray reflectivity, thermal desorption, and elastic recoil detection spectroscopies reveal surface roughening and compositional and density differences close to the substrate surface. The offset from linear growth in the case of WNxCy films deposited on silicon dioxide is induced by the initial reaction of silanol and siloxane groups with triethylborane resulting in passivating ethylsilyl groups on the surface. A transient regime is not observed for WNxCy growth on hydrogen-terminated silicon with the initial growth being dominated by the reduction of tungsten hexafluoride to tungsten. On silicon nitride a short transient regime is observed relative to the carbide and oxide surfaces attributed to the enhanced binding of the triethylboron precursor. [ABSTRACT FROM AUTHOR]

Hydrogen passivated, HF-last-cleaned Si(100) layers are experimentally investigated to determine their reactivity toward aqueous HF HX and HX, where X is a halogen. The Si surface is not affected by the HCl and HBr solution. HI oxidizes the Si surface. HF HCl and HF HBr solutions have no effect on the surface while the HF HI solution induces a reoxidation process which results in enhanced microfaceting of the Si(100) surface.

The interface of zirconium oxide thin films on silicon is analyzed in detail for their potential applications in the microelectronics. The formation of an interfacial layer of ZrSi[SUBx]O[SUBy] with graded Zr concentration is observed by the x-ray photoelectron spectroscopy and secondary ion mass spectrometry analysis. The as-deposited ZrO[SUB2]/ZrSi[SUBx]O[SUBy]/Si sample is thermally stable up to 880 °C, but is less stable compared to the ZrO[SUB2]/SiO[SUB2]/Si samples. Post-deposition annealing in oxygen or ammonia improved the thermal stability of as-deposited ZrO[SUB2]/ZrSi[SUBx]O[SUBy]/Si to 925 °C, likely due to the oxidation/nitridation of the interface. The as-deposited film had an equivalent oxide thickness of ∼1.3 nm with a dielectric constant of ∼21 and a leakage current of 3.2&time;10[SUP-3]A/cm[SUP2] at -1.5 V. Upon oxygen or ammonia annealing, the formation of SiO[SUBx] and SiH[SUBx]N[SUBy]O[SUBz] at the interface reduced the overall dielectric constants. [ABSTRACT FROM AUTHOR]

A study was undertaken to determine the efficacy of various underlayers for the nucleation and growth of atomic layer deposited HfO[sub 2] films. These were compared to films grown on hydrogen terminated Si. The use of a chemical oxide underlayer results in almost no barrier to film nucleation, enables linear and predictable growth at constant film density, and the most two-dimensionally continuous HfO[sub 2] films. The ease of nucleation is due to the large concentration of OH groups in the hydrous, chemical oxide. HfO[sub 2] grows on chemical oxide at a coverage rate of about 14% of a monolayer per cycle, and films are about 90% of the theoretical density of crystalline HfO[sub 2]. Growth on hydrogen terminated Si is characterized by a large barrier to nucleation and growth, resulting in three-dimensional, rough, and nonlinear growth. Thermal oxide/oxynitride underlayers result in a small nucleation barrier, and nonlinear growth at low HfO[sub 2] coverages. The use of chemical oxide underlayers clearly results in the best HfO[sub 2] layers. Further, the potential to minimize the chemical oxide thickness provides an important research opportunity for high-κ gate dielectric scaling below 1.0 nm effective oxide thickness. [ABSTRACT FROM AUTHOR]

In atomic layer deposition (ALD), film thickness control by counting the number of deposition sequences is poor in the initial, nonlinear growth region. We studied the growth of TiN films formed by sequentially controlled reaction of TiCl[sub 4] and NH[sub 3] on thermal SiO[sub 2] during the transient, nonlinear period. Using low-energy ion scattering and Rutherford backscattering spectroscopy analysis, we have found that a three-dimensional growth of islands characterizes the ALD TiN growth on SiO[sub 2]. Growth at different temperatures (350°C and 400°C) affects the extent of the transient region and the rapid closure of the film. At 400°C, a reduced growth inhibition and an earlier start of three-dimensional growth of islands results in film closure at about 100 cycles, corresponding to a TiN thickness of 24 ± 3 Å. At 350°C the minimum thickness at which the TiN layer becomes continuous is 34 ± 3 Å, deposited with 150 cycles. [ABSTRACT FROM AUTHOR]

A method is presented for the calculation of the oxygen surface concentration in steady state when sputtering silicon and silicon oxides with oxygen ions. The case of sputtering with 5 keV oxygen atoms as a function of incidence angle has been studied. Measurements of erosion rates under the mentioned sputtering conditions, including oxygen and noble gases as primary ions, with and without oxygen flooding, are the input data. The dependence of the component sputtering yield of silicon on the oxygen surface concentration is also obtained, as well as the preferential sputtering ratio. These quantities, from the point of view of the calculation work frame, depend on the degree of oxygen supersaturation (oxygen atomic fraction >2/3) at the surface in normal incidence. The possibility of supersaturation is a result of our assumptions and its level can be estimated within a narrow range. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The Si[sup +] and O[sup +] signals, as obtained in secondary ion mass spectrometry (SIMS) analysis of silicon when using oxygen as the primary species, pass through an initial transient region before reaching the stationary state. We simulate this transient zone to check a phenomenological model for the secondary ionization of sputtered atoms. The simulation is split into two parts: the sputtering of neutrals obtained from implantation, sputtering, relocation/replacement, and diffusion, simulations and their subsequent ionization. The ionization phenomena are also described by some ad hoc fitting functions with which the SIMS measurements are better approached than with the model. The fitting functions and the model outputs are verified with experimental secondary ionization data. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Secondary ion mass spectrometry has become the preferred tool for impurity profiling primarily due to its excellent depth resolution and high detection sensitivity. Prerequisite in obtaining high detection sensitivity for positive secondary ions is the use of oxygen as primary ions. This leads to a high degree of oxidation of the sample surface, which is essential for a high secondary ion ionization efficiency. Unfortunately, this oxygen bombardment not only leads to the transformation of the original target surface into an oxidized layer but, as the latter requires a certain fluence before stationary state is reached, inherently causes some nonlinearities and transients in the secondary ion signal and the fluence-eroded depth relation. In this work a computer code implantation, sputtering, replacement/relocation, and diffusion (ISRD) has been optimized to predict the compositional changes of the sample surface (or altered layer formation), the sputter yields and the surface regression as a result of the interaction of oxygen beams with Si-targets. This article describes a careful reevaluation of the previously used version of ISRD (and the parameters contained in the program) in order to obtain a systematic agreement with experimental data on sputter yields, altered layer formation, and surface recession, and with other theoretical predictions. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The influence of Cr and Mo on phase formation and preferential orientation of CoSi[sub 2] is reported. Three different regimes are distinguished, depending on the thickness of the interlayer. For a thin interlayer or a capping layer, CoSi forms first, as in the standard Co/Si reaction. The remaining Cr or Mo can be considered as a contaminant that is present in the CoSi layer, causing a delay in CoSi[sub 2] nucleation and inducing preferential (220) and (400) nucleation. For interlayers with intermediate thickness, epitaxially (400) oriented CoSi[sub 2] is formed. For a thick interlayer, a polycrystalline layer of CrSi[sub 2] (or MoSi[sub 2]) is formed first, followed by CoSi formation on top of the CrSi[sub 2]. At higher temperatures, the CoSi layer is transformed into a polycrystalline, continuous layer of CoSi[sub 2] on top of the CrSi[sub 2] or MoSi[sub 2] layer, while some grains of CoSi[sub 2] are formed underneath the CrSi[sub 2]. A similar behavior for Ti interlayers is observed, although a much thicker Ti layer is needed before the third regime is reached. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The article studies the influence of oxygen flooding during ultralow energy SIMS depth profiling of silicon with cesium ions. Findings reveal that oxygen that is adsorbed to the silicon surface offer an attachment site for impinging cesium ions.

The impact of the phosphorus concentration [P] on the solid-phase epitaxial regrowth rate of preamorphized p-type germanium is analyzed by using Rutherford backscattering, secondary ion mass spectrometry and transmission electron microscopy. The regrowth retardation is associated with segregation across the crystalline/amorphous boundary and snow plow of P in excess of the metastable solid solubility in the recrystallized material.

The growth of tungsten nitride carbide W[N.sub.x][C.sub.y] films obtained from layer deposition using triethylboron, tungsten hexafluoride, and ammonia precursors is determined by the density and type of reactive sites. A transient regime is not observed for W[N.sub.x][C.sub.y] growth on hydrogen-terminated silicon with the initial growth being dominated by the reduction of tungsten hexafluoride to tungsten.

Focuses on a study which examined the oxidation of GaAs and Al[subx]Ga[1-x]As targets by oxygen irradiation. Background on secondary ion mass spectrometry; Experimental procedures; Results.

Presents a study that examined the influence of oxygen on the analysis of a platinum/silicon structure with secondary ion mass spectrometry. Experimental details; Results of the study; Conclusions.

Presents a study that examined oxygen content in zone melting recrystallization silicon-on-insulator layers. Analysis of the secondary-ion-mass spectrometry profile of the samples; Relation between peak oxygen concentration and silicon layer thickness; Evaluation of the oxygen distribution in the substrate of the samples.

Research describing the growth kinetics of germanium deposited on silicon is presented. In particular the characteristics of germanium island density and morphology are investigated.