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The problem of the absorption of light by a nanoscale dielectric cone is discussed. A simplified solution based on the analytical Mie theory of scattering and absorption by cylindrical objects is proposed and supported by the experimental observation of sharply localized holes in conical silicon tips after high-fluence irradiation. This study reveals that light couples with tapered objects dominantly at specific locations, where the local radius corresponds to one of the resonant radii of a cylindrical object, as predicted by Mie theory.

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]

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 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]

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.

Abstract: This paper discusses the peculiar light coupling and absorption properties of a dielectric particle with a varying nanoscale radius and a high aspect ratio. To build progressive understanding, different levels of geometrical refinement with increasing complexity are proposed and compared. This study concludes that, in an elongated dielectric particle with a varying radius, light is coupled and absorbed only at optically resonant positions, i.e. where the radius allows for the constructive interference between the multiple internal reflections occurring inside the particle. The position, extension and magnitude of these resonance maxima, which vary according to the refinement level of the model, are discussed. [Copyright &y& Elsevier]

In order to minimize the considerable loss of Si material during the processing of a silicon photovoltaics (PV) substrate into a solar cell, the optimization of the saw damage (SD) removal is an important step. The PV cell process therefore requires a routine metrology solution suitable to probe the SD present in the substrate. Though cross-sectional Transmission Electron Microscopy is typically used for this purpose, this technique is not suited for in-line measurements. It is furthermore destructive, time-consuming and limited to very small sampling volumes. In this paper, we demonstrate the capabilities of the Photomodulated Optical Reflectance (PMOR) method for the in-line measurement of SD. PMOR is a laser-based pump-probe technique, wherein the probe laser measures the reflectance of the sample (DC reflectance) as well as the change in reflectance (AC reflectance) which the pump laser has induced by optically injecting excess carriers and heat. As PMOR is a local and nondestructive technique, it offers a very promising approach for the simultaneous characterization of roughness and SD. We demonstrate the versatility of this approach and the response of the DC and AC reflectances when studying wafers which have undergone successive etchings to remove the SD sequentially (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We discuss the selective epitaxial growth of InP on patterned Si (001) substrates with Shallow Trench Isolation using a thin Ge buffer to facilitate InP nucleation. The main focus is the defect formation during epitaxial growth and to develop solutions to reduce defect density so that device-quality III-V virtual substrates can be realized on large-scale Si substrates. We compare the InP growth on on-axis and off-axis Si substrates. In the case of off-axis wafers, the formation of stacking faults / twins cannot be avoided, at least not at one of the four side-walls of the Shallow Trench Isolation. The formation of antiphase domain boundaries is reduced (but not yet completely eliminated) by engineering the local Ge surface profile. Further, the high density of Ge surface steps promotes step-flow growth mode instead of 3D growth during the growth of the InP seed layer. Finally, high aspect ratios (>2) allow to confine threading dislocations in the bottom of the trench. [ABSTRACT FROM AUTHOR]

Electron beam induced etching (EBIE) with SF6 precursor molecules has been demonstrated as an approach to induce localized etching of Si with an etch yield of approximately 0.003 atoms/incoming electron. Further understanding of the EBIE mechanisms is presented through an analysis of the influence of the different electron beam parameters (beam energy and electron flux) and the effect of the sample bias on the EBIE rate. It is demonstrated that the etch rate increases with decreasing beam energy and with increasing electron flux to a saturation value. The latter is explained by a transition from an electron flux density limited process (at low current densities) to a gas supply limited process (at high current densities). The authors also demonstrate that a large etch rate enhancement is obtained by applying a positive sample bias. This is explained within the frame of a model outlining the role of the low secondary energy electrons in the electron stimulated etching process. [ABSTRACT FROM AUTHOR]

Abstract: Atom-probe (AP) analysis of silicon based samples frequently fail due to rupture of the tip. We have investigated the stability and failure mechanisms of silicon tips when prepared for AP analysis via Focused Ion Beam (FIB) milling. We observed four mechanisms that commonly lead to failure of the tips. These mechanisms are a deformation of the tips apex due to an interaction between the oxidized amorphous layer and induced mechanical vibrations, a rip off of an isolating oxide-layer, the rip off of a cap layer due to insufficient adhesion and a failure of the tip in the course of the analysis due to the rising voltage applied to the tip. In this paper we will discuss all four mechanisms show evidence of the causes of the breakdown and discuss options that allow avoiding tip failure. [Copyright &y& Elsevier]

Abstract: The use of an internal O18 implant to quantify the surface oxygen concentration, presented in Franzreb et al. [K. Franzreb, J. Lorincik, P. Williams, Surf. Sci. 573 (2) (2004) 291], is critically evaluated, in particular when applied for bombardment conditions leading to high depth resolution measurements. It is shown that this methodology gives no direct access to the surface composition, but only to the O/Si ratio in the total emission flux, ϕ O16/ϕ Si, which reflects the total amount of oxygen that passes through the surface. When applied under conditions relevant for high depth resolution studies (oxygen bombardment at low energies and small angles), extremely large ϕ O16/ϕ Si -ratios are observed (>50). These large values are interpreted in terms of the oxygen that leaves the surface by sputtering as well as by alternative processes such as by desorption. The latter is included in the total flux ratio ϕ O16/ϕ Si, but has little interaction with the sample surface and the departing Si-atoms. Therefore the use of these ϕ O16/ϕ Si ratios in ionization mechanism studies becomes inappropriate unless the desorbed oxygen fraction can be calculated quantitatively or is negligible. Based on the angular dependence of the useful ion yield of oxygen, we make a rough estimate of the desorbed oxygen fraction and show that this becomes a dominant fraction (up to 70%) in the emitted flux at low bombardment energies. [Copyright &y& Elsevier]

This paper investigates the effect of thickness, composition and anneal temperature in N2 on the band gap of the mixed oxide layer and the band offset with the Si substrate for layers grown by atomic layer deposition. For 1:1 (Al/Zr or Al/Hf) mixed oxides, the band gap reaches the bulk value for a thickness larger than 2 nm. In both cases (AlxZryOz and AlxHfyOz), the bulk values of the band gap show a linear dependence on the Al2O3 mol%, going from 5.6 (5) eV for pure ZrO2 (HfO2) to 6.7 eV for pure Al2O3. The effect of a post-deposition anneal on the band gap and the valence band alignment is also studied. Here, AlxHfyOz and AlxZryOz seem to act differently: while the annealing temperature does not have any influence on the band gap of AlxZryOz mixed oxide, the annealing in N2 at temperature from 900 °C generates an increase in the band gap value measured by XPS for AlxHfyOz. [Copyright &y& Elsevier]

To get an insight in the diffusion behavior of dopants such as arsenic and boron after annealing and in particular their segregation characteristics towards the interface in oxide structures on silicon, it is necessary to probe the dopant profile with very high accuracy and depth resolution. Sputter depth profiling as employed in secondary ion mass spectrometry (SIMS) is frequently used as the most suited tool for dopant profiling in view of its sensitivity and depth resolution. However in order to determine the segregated arsenic/boron peak, sub-nanometer depth resolution is required and artifacts such as beam induced broadening effects, potential ionization yield changes at interfaces, transient sputter yields need to be considered in detail. When reducing the primary beam energy the depth resolution can be improved and sub-nanometer depth sensitivity can be demonstrated. However comparisons with high resolution elastic recoil detection analysis demonstrate that it is at present impossible to obtain a reliable depth profile in the first nanometer near the surface nor even in the oxide part of the profile, where no ionization nor sputter yield transients are expected. Enhanced beam induced migration of boron during the initial phase of the bombardment needs to be invoked to explain the results. The latter appears to be enhanced under conditions (∼normal incidence) where full oxidation occurs. [Copyright &y& Elsevier]

Presents a study which measured boron and germanium (Ge) concentration profiles in rapid thermal and furnace annealed silicon (Si)-doped, epitaxial layers. Experimental procedure; Mathematical model for boron diffusion; Results and discussion; Conclusion.

The solid-state reaction and agglomeration of thin nickel-silicide films was investigated from sputter deposited nickel films (1–10 nm) on silicon-on-insulator (100) substrates. For typical anneals at a ramp rate of 3 °C/s, 5–10 nm Ni films react with silicon and form NiSi, which agglomerates at 550–650 °C, whereas films with a thickness of 3.7 nm of less were found to form an epitaxylike nickel-silicide layer. The resulting films show an increased thermal stability with a low electrical resistivity up to 800 °C. [ABSTRACT FROM AUTHOR]

We demonstrate the selective growth of high quality 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 trenches at high growth temperature as required for obtaining high quality layers was shown to be prohibited by Ge outdiffusion due to the high Ge chemical potential in such narrow channels. At low temperature, a hydride-terminated surface is maintained which counteracts the outdiffusion of the Ge adatoms and provides excellent trench filling. The resulting low crystalline quality can be restored by a selective Ge melt and epitaxial regrowth using a millisecond laser anneal. [ABSTRACT FROM AUTHOR]

The impact of Si interstitial (Sii) flux suppression on the formation of P junctions by rapid thermal annealing (RTA) is demonstrated. Here we investigate the role of amorphization coupled with C co-implantation on P diffusion and its activation. From experiments on C co-implants in a-Si versus c-Si, we conclude that only a small fraction of C interacts with Si interstitials (Sii). We have demonstrated that optimization of implants followed by spike RTA yields extensions suitable for gate lengths of 30 nm, with vertical depth Xj=20 nm (taken at 5×1018 at./cm3), abruptness of 3 nm/decade, and Rs=326 Ω/□. [ABSTRACT FROM AUTHOR]

Co-implantation schemes for sub-65 nm n-type extension formation have been explored. These included phosphorous (P) and arsenic (As) implants into crystalline Si as well as combinations using higher energy silicon pre-amorphization implant (PAI) steps together with low energy carbon (C) implantation. Dopant energies were varied between 500 eV and 1 keV, with C dose of1×1015 cm-2 and P and As doses of 7×1014 cm-2. The anneal step was a fast ramp-up and ramp-down spike at 1050 °C. Comparisons with dopant-only implants or with PAI and dopant only showed these two schemes to give deeper, more gradual and less well activated junctions than when combined with C. The best result was obtained using a 25 keV Si PAI, 6 keV C and 1 keV P, resulting in a junction depth of 20.5 nm at 1×1019 cm-3, and Rs=318 Ω/□ and a 3 nm/dec trailing slope. [ABSTRACT FROM AUTHOR]

We investigate the influence of the initial stage of the thermal treatment during solid-phase epitaxial regrowth (SPER) on the electrical activation level of arsenic in self-amorphized silicon, both with respect to heating ramp-up rates and the use of low-temperature preanneals. Enhancement of the electrically-active arsenic concentration by 14% is observed for activation with the fastest ramp-up rates (430 °C/s) compared to the slowest ones (36 °C/s). Around 50% of the 1015 at/cm2, arsenic implant at 5 keV is found to be nonsubstitutional and this fraction reaches even 99% for dose 3×1015 at/cm2. Arsenic clustering in silicon amorphous phase during SPER is recognized to play an important role in the decrease of the active dose. [ABSTRACT FROM AUTHOR]

Scanning spreading resistance microscopy is a two-dimensional carrier profiling technique now widely used for the characterization of silicon (Si) devices as well as other semiconductor materials. Whereas the state-of-the-art spatial resolution for this technique using commercial-diamond-coated silicon probes is limited to 10-20 nm, enhanced resolution is demonstrated through the use of full-diamond tips integrated in Si cantilevers. Sub-5-nm-spatial resolution is obtained on fully depleted silicon on isolator devices, putting the technique closer to the characterization requirements of the forthcoming semiconductor dimensions. Resistance and scanning electron microscope measurements clearly show that this enhanced resolution results from a smaller effective radius for full diamond tips as compared to the diamond-coated Si probes. [ABSTRACT FROM AUTHOR]

The spreading resistance probe (SRP) is a widely used measurement tool for electrical characterization of Si structures. From the measured spreading resistance depth profile, the underlying electrically active dopant profile can be extracted through the application of a series of specific software corrections. In this letter, it is shown that for sub-100 nm deep structures a new type of correction is needed in order to account for the impact of three-dimensional lateral current flow through the conductive surface sublayers located above the actual measurement depth. [ABSTRACT FROM AUTHOR]

Scanning spreading resistance microscopy (SSRM) is a powerful method for the characterization of Si semiconductor devices based on atomic force microscopy (AFM). It requires conductive probe tips made of doped diamond. Although various solid diamond probes have been fabricated, they could not satisfy the requirements for SSRM. Therefore, we have developed a SSRM probe composed of a pyramidal diamond tip attached to a Si cantilever. This letter describes the probe fabrication process briefly and presents excellent SSRM measurements obtained on Si calibration samples. Solid diamond tips integrated in Si cantilevers were used for SSRM showing a significantly higher dynamic range than the conductive probes known to date. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Epitaxial growth of phosphorus-doped silicon deposited at 250 °C from a radio-frequency glow discharge from SiH4 is demonstrated by high-resolution electron microscopy (HREM) and spreading resistance profile measurements. Thin epitaxial films are present at the interface between (100) Si substrates and hydrogenated amorphous silicon. After recrystallization at 700 °C, single-crystal layers are obtained, in which HREM reveals extensive twinning. The fact that epitaxial growth can take place at 250 °C in a system with a background pressure of only 5×10-6 mbar can be attributed to the presence of species in the SiH4 plasma that reduce the native oxide and the use of HF in the cleaning procedure. [ABSTRACT FROM AUTHOR]

Examines the growth of heavily P-doped silicon layers in a low temperature through radio frequency plasma chemical vapor deposition. Comparison of the films grown by vapor phase epitaxy (VPE) or solid phase epitaxy (SPE); Acquisition of steep doping profiles in VPE and fast P diffusion in SPE; Significance of the Hall of mobility of VPE.

The influence of trace metal impurities of low-temperature undoped amorphous silicon by homogeneous chemical vapor deposited a-Si:H has been explored for the first time. The metal impurities Ni, Cr, and Fe cause a shift of the transition temperature for the double-activated regime to a relatively low value. However, Ga and B impurities quench the photoluminescence intensity at a low temperature. Both of them cause weak photoemission of the films at room temperature. The shift of the transition temperature can be explained by the presence of non-radiative deep recombination centers. The quenching of the photoluminescence intensity is caused by the presence of nonradiative recombination centers. [ABSTRACT FROM AUTHOR]

Silicon crystallizes in the diamond-cubic phase and shows only a weak emission at 1.1 eV. Diamond-hexagonal silicon however has an indirect bandgap at 1.5 eV and has therefore potential for application in opto-electronic devices. Here we discuss a method based on advanced silicon device processing to form diamond-hexagonal silicon nano-ribbons. With an appropriate temperature anneal applied to densify the oxide fillings between silicon fins, the lateral outward stress exerted on fins sandwiched between wide and narrow oxide windows can result in a phase transition from diamond-cubic to diamond-hexagonal Si at the base of these fins. The diamond-hexagonal slabs are generally 5-8 nm thick and can extend over the full width and length of the fins, i.e. have a nano-ribbon shape along the fins. Although hexagonal silicon is a metastable phase, once formed it is found being stable during subsequent high temperature treatments even during process steps up to 1050 ºC. [ABSTRACT FROM AUTHOR]

Scanning spreading resistance microscopy (SSRM) is an analytical technique originally developed for measuring two-dimensional carrier distribution in Si device structures with high spatial resolution. It is in essence an atomic force microscope equipped with a conducting tip that is biased relative to the sample. The spreading resistance value derived from the measured electrical current is a function of the local carrier concentration at the surface region surrounding the probe’s tip. In this letter, we report the successful application of SSRM to the analysis of InP semiconductor device structures. We imaged a multilayer epitest structure, and a cross section of a three-dimensional structure in which we observed lateral Zn-dopant diffusion. Comparison of the SSRM profiles with one-dimensional secondary ion mass spectrometry depth profiles shows good qualitative agreement. SSRM analysis of InP-based device structures was found to be much simpler than that of Si structures: there is no need for surface preparation of the cleaved surface, a lower tip force is required, and metal tips, rather than doped diamond can be used. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: Ultra thin Si cap growth by Reduced Pressure Chemical Vapor Deposition on relaxed Ge substrates is detailed in this paper for Ge pMOSFET (Metal Oxide Semiconductor Field Effect Transistors) passivation purposes. A cross calibration of different measurement techniques is first proposed to perfectly monitor Si monolayers thickness deposited on Ge substrates. Different characteristics, impacting Ge pMOSFETs device performances, are next detailed for various Si cap growth processes using different Si precursors: DiChloroSilane (DCS), silane and trisilane. The critical Si thickness of plastic relaxation has been determined at 12 monolayers. Presence of point defects has been identified for very low growth temperature as 350°C. Ge–Si intermixing, caused by a Ge segregation mechanism, is strongly reduced by the use of trisilane as Si precursor at low temperatures. [Copyright &y& Elsevier]

Abstract: Single and polycrystalline Si1−x Ge x samples have been bombarded using low energy oxygen ions to study the change in their surface morphologies and ripple formation. Both strained, relaxed and polycrystalline Si1−x Ge x samples grown on Si(001) were used to study the effect of crystallinity on ripple formation. Bombardment by 1keV oxygen ions shows completely different morphologies for the different samples under identical experimental conditions. Ripples on Si1−x Ge x samples appear much earlier than in Si. Moreover, the nature of the ripples for the polycrystalline sample is markedly different from those of the single crystals. The ripples on relaxed samples are greatly influenced by the location of the dislocation lines on the sample surface. The observations clearly show that rippling is affected not only by the layer constituents but also by its crystallinity and presence of regular structures that favour rippling in a specific direction. [Copyright &y& Elsevier]

Abstract: Nowadays, fundamental SIMS physics limits the quantitative compositional analysis of new semiconductor structures with high depth resolution and high spatial resolution. Therefore, a new concept (Zero-energy SIMS) is introduced which is based on electron beam inducted etching (EBIE) of the substrate surface and subsequent post-ionization of the volatile species by short high-power laser pulses. Silicon electron beam induced etching with SF6 as precursor species with an etching yield of 0.003 Si atoms/electron is demonstrated. Zero-energy SIMS experiments in a magnetic sector instrument with SF6 in positive mode show both electron-induced processes (ESD of fluorine) and collision-induced removal of Si atoms. These sputter events are caused by the impact of accelerated SF6 fragment anions which are formed by an electron-attachment process in the gas phase. In negative mode, a large contribution of cluster ions is observed due to the high flux of incoming polyatomic cations, formed by electron-impact ionization of SF6 molecules in the gas phase. The kinetic energy distributions of these particles are in agreement with the recombination model for cluster emission. [Copyright &y& Elsevier]

Abstract: To understand negative ion formation under Cs+ bombardment, we have studied the steady-state Cs depth distribution in Si and Ge with a focus on high-resolution analysis conditions i.e. Cs+ energies between 500eV and 5keV and impact angles from 0° to 60°. The in situ internal Cs depth profiles have been measured with a low energy O2 + beam (0.5–1keV) similar to the work of Yoshikawa [S. Yoshikawa, H. Morita, et al., Appl. Surf. Sci. 203–204 (2003) 252–255]. To minimize the distortions on Cs profiles, a non-oxidizing condition (at impact angle 60°) was chosen instead of an oxidizing condition. The internal Cs profiles in Si have a flat saturation region near the surface, with an intensity independent from the bombardment conditions. Only the profile width scales with impact angles and energies. Whereas in the Ge-case, a Gaussian profile is always obtained. Based on the internal Cs profiles, a possible near surface altered layer formation in Si and Ge under Cs bombardment is suggested. [Copyright &y& Elsevier]

The determination of the oxygen concentration at the surface is the critical parameter in all models [Surf. Sci. 112 (1981) 168; Nucl. Instrum. Meth. Phys. Res. B 14 (1986) 403; in: A. Benninghoven, B. Hagenhoff, H.W. Werner (Eds.), SIMS, Vol. X, Wiley, New York, 1997, 203 pp.; Phys. Rev. B 50 (1994) 15015; in: A. Benninghoven, P. Bertrand, H.N. Migeon, H.W. Werner (Eds.), SIMS, Vol. XII, Elsevier, Amsterdam, 2000, 151 pp.; J. Appl. Phys. 90 (2001) 4456] that study the large enhancement of the ionisation probability of positive ions by the presence of oxygen at the surface. Different analysis techniques (low energy ion scattering, Rutherford back scattering spectrometry and secondary ion mass spectrometry) are combined in order to clarify the oxygen dependence of the ionisation probability of Si+, αSi+, during O2+ bombardment. A ratio of ion signals is correlated with the surface oxygen content, determined by LEIS, allowing us to study the enhancement of the ionisation probability of Si by oxygen at the surface for energies between 1 and 5 keV per O2+ ion. For a wide range of oxidation conditions the oxygen enhancement can be described by a power law dependence on the oxygen content αSi+∝(CO/CSi)3.24, whereby the power shows no significant energy dependence for the studied energy range. The steep enhancement of the ionisation probability at high oxygen content, which is energy dependent, can be correlated to a change in the surface structure: enhanced shadowing of silicon by oxygen, observed by LEIS. [Copyright &y& Elsevier]

To study the oxygen dependence of ionisation processes during O2+ bombardment, low-energy ion scattering was used as a surface analysis technique since it has very high surface sensitivity. An LEIS instrument was reconfigured to collect secondary ions simultaneously with the compositional analysis based on LEIS. The gradual conversion of the Si surface into an oxidised surface under oxygen bombardment has been studied. A correlation between the Si+ intensity and the oxygen concentration could be established, i.e. I(Si+)∝(CO/CSi)2.9. It was observed that, at the stage where the oxygen concentration no longer increases, the amount of visible (for LEIS) Si atoms decreases further, implying a further structural change. This change coincides with the steep increase in the Si+ ion intensity near complete oxidation and can be interpreted as the main cause for this change in ionisation probability. [Copyright &y& Elsevier]

Retrieving molecular information by sputtering of organic systems has been concretized in the last years due to the introduction of sputtering by large gas clusters which drastically eliminated the compound degradation during the analysis and has led to strong improvements in depth resolution. Rapidly however, a limitation was observed for heterogeneous systems where inorganic layers or structures needed to be profiled concurrently. As opposed to organic material, erosion of the inorganic layer appears very difficult and prone to many artefacts. To shed some light on these problems we investigated a simple system consisting of aluminum delta layer(s) buried in a silicon matrix in order to define the most favorable beam conditions for practical analysis. We show that counterintuitive to the small energy/atom used and unlike monoatomic ion sputtering, the information depth obtained with large cluster ions is typically very large (∼10 nm) and that this can be caused both by a large roughness development at early stages of the sputtering process and by a large mixing zone. As a consequence, a large deformation of the Al intensity profile is observed. Using sample rotation during profiling significantly improves the depth resolution while sample temperature has no significant effect. The determining parameter for high depth resolution still remains the total energy of the cluster instead of the energy per atom in the cluster. [ABSTRACT FROM AUTHOR]

Abstract: Rutherford backscattering and channeling spectrometry (RBS/C) as well as transmission electron microscopy (TEM) are used to characterize the crystalline structure of a GaN layer grown on a Si (111) substrate. The channeling measurements are performed along the off-normal axis in the plane of the GaN layer. The threading edge dislocation defect density obtained from RBS/C is quantitatively compared to the results obtained from TEM. The strain is found not to be completely relaxed, e T ≠0, in spite of the large thickness of the GaN layer (3.0μm), and in spite of the incorporation of various buffer layers. [Copyright &y& Elsevier]

Abstract: We describe the use of binary thin films on Si to calibrate the yields in proton-induced X-ray emission (PIXE) measurements. Besides of the element to be calibrated, the standards also contain a common reference element. The incorporation of a common reference element allows one to eliminate errors in the accumulated beam charge during the calibration of the PIXE set-up. The binary calibration standards allow us to determine the response function with an accuracy close to 1%. As an example, we will perform the calibration for Fe and Co, and we will determine the Co concentration in Fe1 − x Co x thin films. [Copyright &y& Elsevier]

Abstract: A mathematical model was developed to examine the growth rate of III–V compounds inside sub-micron trenches by MOVPE. Based on this model, we theoretically analyzed the possible dependence of the growth rate on the trench width primarily from two aspects, i.e. Knudson diffusion and enhanced equilibrium vapor pressure due to the shrinking trench size. Then, associated with the experimental data from the growth of both InAlAs and InAs, we found that the average growth rate inside submicron trenches is primarily influenced by trench diffusion type under typical growth conditions. [Copyright &y& Elsevier]

Abstract: Laser-assisted atom probe tomography is a material analysis method based on field evaporating ions from a tip-shaped sample by a combination of a standing electric field and a short (pico- or femtosecond) laser pulse. The laser-pulse thereby acts as a starting signal for a time-of-flight mass analysis of the ions whereby the thermal energy deposited in the tip by the laser pulse temporarily enables the evaporation of ions from the surface of the tip. Here we will use simulations of the laser absorption on a silicon tip to find the optimal position of the laser spot in order to maximize the mass resolution achieved during the experiments. We will confirm our simulations by showing that the experimentally observed mass resolution indeed changes as predicted by the simulations. [Copyright &y& Elsevier]

The fabrication of nanoscale semiconductordevices for use in future electronics, energy, and health is amongothers based on the precise placement of dopant atoms into the crystallattice of semiconductors and their concurrent or subsequent electricalactivation. Dopants are built into the lattice by fabrication processeslike ion implantation, plasma-based doping, and thermal annealing.Throughout the fabrication processes fundamental phenomena like dopantdiffusion, activation, and clustering occur concurrently with damagingand subsequently recovering the crystal lattice. These processes aredescribed by atomic-scale mechanisms of ion–host atom interactionand have an immense impact on the electrical performance of the resultingdevices. Insight in their fundamental nature is of utmost importancefor optimizing the performance of nanoscale technologies. In thispaper, we demonstrate direct three-dimensional imaging of boron clustersand atoms in crystal defects using field ion microscopy. Our approachallows for the first time the complete characterization of the sizeand crystallographic orientation of boron-decorated crystal defects.This new method opens a path to image a wide variety of dopant-clusterforms and hence to study the formation and dissolution of boron clustersin silicon on the atomic scale. [ABSTRACT FROM AUTHOR]

Abstract: Pre-amorphized silicon wafers are implanted with 30keV and 0.5keV C+ ions at room temperature with fluences about 2×1015 atoms/cm2. The depth profiles of implanted carbon are measured using high-resolution Rutherford backscattering spectroscopy. The observed average depth of C for the implantation is 6.1nm while that for the C+ implantation is 4.0nm, showing a large cluster effect on the projected range. [Copyright &y& Elsevier]

Abstract: To further boost the CMOS device performance, Ge has been successfully integrated on shallow trench isolated Si substrates for pMOSFET fabrication. However, the high threading dislocation densities (TDDs) in epitaxial Ge layers on Si cause mobility degradation and increase in junction leakage. In this work, we studied the fabrication of Ge virtual substrates with low TDDs by Ge selective growth and high temperature anneal followed by chemical mechanical polishing (CMP). With this approach, the TDDs in both submicron and wider trenches were simultaneously reduced below 1×107 cm−2 for 300nm thick Ge layers. The resulting surface root-mean-square (RMS) roughness is about 0.15nm. This fabrication scheme provides high quality Ge virtual substrates for pMOSFET devices as well as for III–V selective epitaxial growth in nMOSFET areas. A confined dislocation network was observed at about 50nm above the Ge/Si interface. This dislocation network was generated as a result of effective threading dislocation glide and annihilation. The separation between the confined threading dislocations was found in the order of 100nm. [Copyright &y& Elsevier]