This paper demonstrates the increased light absorption efficiency of semiconducting atom probe tips resulting from focused-ion-beam (FIB) preparation. We use transmission electron microscopy to show that semiconducting tips prepared with FIB are surrounded with an amorphized shell. Photomodulated optical reflectance measurements then provide evidence that FIB-induced damage leads to an increase in both sub- and supra-bandgap light absorption efficiency. Using laser-assisted atom probe tomography (La-APT) measurements, we finally show that, for a nanoscale tip geometry, the laser-induced heating of a tip during La-APT is enhanced by the FIB preparation. We conclude that, upon supra-bandgap illumination, the presence of a FIB-amorphized surface dramatically increases the light-induced heat generation inside semiconducting tips during La-APT. Furthermore, we also deduce that, in the intriguing case of sub-bandgap illumination, the amorphization plays a crucial role in the unexpected light absorption.

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.

We present atom probe analysis of 40 nm wide SiGe fins embedded in SiO2 and discuss the root cause of artefacts observed in the reconstructed data. Additionally, we propose a simple data treatment routine, relying on complementary transmission electron microscopy analysis, to improve compositional analysis of the embedded SiGe fins. Using field evaporation simulations, we show that for high oxide to fin width ratios the difference in evaporation field thresholds between SiGe and SiO2 results in a non-hemispherical emitter shape with a negative curvature in the direction across, but not along the fin. This peculiar emitter shape leads to severe local variations in radius and hence in magnification across the emitter apex causing ion trajectory aberrations and crossings. As shown by our experiments and simulations, this translates into unrealistic variations in the detected atom densities and faulty dimensions in the reconstructed volume, with the width of the fin being up to six-fold compressed. Rectification of the faulty dimensions and density variations in the SiGe fin was demonstrated with our dedicated data treatment routine.

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)]. (c) 2015 AIP Publishing LLC.

In this work, we discuss the characteristics of particular island-type features with an amorphous core that are developed during the low temperature epitaxial growth of Ge and GeSn layers by means of chemical vapor deposition with Ge2H6. Although further investigations are needed to unambiguously identify the origin of these features, we suggest that they are originated by the formation of clusters of H and/or contaminants atoms during growth. These would initially cause the formation of pits with crystalline rough facets over them, resulting in ring-shaped islands. Then, when an excess surface energy is overcome, an amorphous phase would nucleate inside the pits and fill them. Reducing the pressure and/or increasing the growth temperature can be effective ways to prevent the formation of these features, likely due to a reduction of the surface passivation from H and/or contaminant atoms.

Ge(1-x)Sn(x) is receiving a growing interest in the scientific community, as it has important applications in opto-electronic devices, (as stressor) Source/Drain materials for Ge and SiGe MOSFETS. It is predicted that at 10% Sn concentration or even lower, unstrained Ge(1-x)Sn(x) will exhibit a direct band gap. Moreover, in strained Ge(1-x)Sn(x) the expected concentration of Sn for this cross-over is even lower.As the theoretical Sn incorporation in Ge(1-x)Sn(x) is less than 100, and Ge(1-x)Sn(x) is prone to relaxation, routes towards the growth of metastable strained films has been extensively explored. Although Ge(1-x)Sn(x) films (with x up to 10%) have been grown using various methods like molecular beam epitaxy, CVD growth etc. there remain issues with tendency of these layers to relax. Detailed studies on the relaxation mechanisms and effects on the Sn-atoms require suitable characterization techniques. Various techniques have been used to study the surface of the film, crystallography or concentration of Sn in the film but none of them provides information at the atomic scale as they average over many layers and atoms. Atom probe tomography (APT) analysis, on the other hand, is one such method that can provide atomic scale resolutions (similar to 0.3 nm) clue to its ability to perform atom by atom analysis.In this paper we explore the use of APT for characterizing Ge(1-x)Sn(x) layers. We comment on the difference of field evaporation values of Ge and Sn in Ge(1-x)Sn(x) layer by taking a closer look at the co-evaporation of the two elements and comment on the accuracy of depth reconstruction of APT for Ge(1-x)Sn(x) layer. Comparing the Sn-distributions and their local surroundings we saw a tendency for the Sn to locally enrich forming Sn clusters. Higher order clusters were observed for the relaxed sample. (C) 2013 Elsevier B.V. All rights reserved.

Nowadays, technological developments towards advanced nano scale devices such as FinFETs and TFETs require a fundamental understanding of three-dimensional doping incorporation, activation and diffusion, as these details directly impact decisive parameters such as gate overlap and doping conformality and thus the device performance. Whereas novel doping methods such as plasma doping are presently exploited to meet these goals, their application needs to be coupled with new metrology approaches such as atom probe tomography, which provides the 3D-dopant distribution with atomic resolution. In order to highlight the relevant processes in terms of dopant conformality, 3D-diffusion, dopant activation and dopant clustering, in this paper we report on 3D-doping and diffusion phenomena in silicon FinFET devices. Through the use of atom probe tomography we determine the dopant distribution in a fully completed device which has been doped using the concept of self-regulatory plasma doping (SRPD). We extract the dopant conformality and spatial extent of this doping process and demonstrate that after annealing the resulting 3D-doping profiles and gate overlap are dependent on the details of the plasma doping process. We also demonstrate that the concentration-dependent 3D-diffusion process leads to concentration gradients which are different for the vertical versus the lateral direction. Through a statistical analysis of the dopant atom distributions we can identify dopant clustering in high concentration regions and correlate this with details of the dopant activation and, eventually, the device performance.

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.

With the transition from planar to three-dimensional device architectures such as Fin field-effect-transistors (FinFETs), new metrology approaches are required to meet the needs of semiconductor technology. It is important to characterize the 3D-dopant distributions precisely as their extent, positioning relative to gate edges and absolute concentration determine the device performance in great detail. At present the atom probe has shown its ability to analyze dopant distributions in semiconductor and thin insulating materials with sub-nm 3D-resolution and good dopant sensitivity. However, so far most reports have dealt with planar devices or restricted the measurements to 2D test structures which represent only limited challenges in terms of localization and site specific sample preparation. In this paper we will discuss the methodology to extract the dopant distribution from real 3D-devices such as a 3D-FinFET device, requiring the sample preparation to be carried out at a site specific location with a positioning accuracy ∼50 nm.

Ge1-xSnx is receiving a growing interest in the semiconductor community as the material properties are interesting for both electrical and optical device applications. In this contribution we discuss the potential of Ge1-xSnx for future electrical device applications. Further, we will briefly review its fabrication by means of Chemical Vapor Deposition and discuss the structural material properties and its stability against thermal treatments.

Ge1-xSnx is receiving a growing interest in the semiconductor community as it is predicted that at similar to 10% Sn concentration, unstrained Ge1-xSnx will exhibit a direct band gap leading to potentially important Opto-electronic applications. In strained Ge1-xSnx the expected concentration of Sn for this crossover from an indirect towards a direct bandgap is even lower. Moreover Sn has a similar to 13% lattice mismatch with Ge opening up possibilities for strain engineering in high mobility CMOS devices based on Ge. Although Ge1-xSnx layers have been grown using various methods like molecular beam epitaxy, CVD growth etc. with Sn concentrations as high as 10%, one is faced with the problem of limited Sn-solubility in Ge and hence the corresponding limits beyond which the layer starts to relax. Understanding relaxation mechanisms and kinetics of these layers requires insight at the atomic scale of Sn-migration processes for which Atom Probe Tomography (APT) is a powerful tool. In this paper we use APT for characterizing Ge(1-x)Sn(x)layers and compare the Sn location and redistributions for fully strained and partially relaxed films. Comparing the Sn-distributions and their local surroundings we see a tendency for the Sn to locally cluster forming enriched regions, in the relaxed sample, while the majority of the enriched regions still remains embedded in the lattice planes. A small fraction of the Sn atoms is delocalized out of the lattice planes. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Interest in Sn-based semiconductors largely increased during the last decade (Fig. 1). If doubts remained in the early 2000's on the hypothetical use of (Si)GeSn epitaxial layers in advanced technologies (mainly due to the low Sn solubility in Si and Ge and the associated reduced thermal stability of those alloys), recent publications from various groups provide today a much better feeling on the potential of those materials. First of all, the growth of GeSn layers with high Sn content was demonstrated by different techniques overruling their apparent thermodynamics limitations. Next, and especially very recently, Sn-based devices are showing up: GeSn MOSCAP, GeSn pMOSFET or GeSn photodetectors for instance. This paper reviews the deposition techniques and different integration schemes to implement GeSn in various technologies and highlights the potential benefits in logic and photonics devices.