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Journal of physics / Condensed matter 33, 105901 (2021). doi:10.1088/1361-648X/abcdb0, Diffraction and imaging using x-rays and neutrons are widely utilized in different fields ofengineering, biology, chemistry and/or materials science. The additional information gainedfrom the diffraction signal by x-ray diffraction and computed tomography (XRD-CT) can givethis method a distinct advantage in materials science applications compared to classicaltomography. Its active development over the last decade revealed structural details in anon-destructive way with unprecedented sensitivity. In the current contribution an attempt toadopt the well-established XRD-CT technique for neutron diffraction computed tomography(ND-CT) is reported. A specially designed ‘phantom’, an object displaying adaptable contrastsufficient for both XRD-CT and ND-CT, was used for method validation. The feasibility ofND-CT is demonstrated, and it is also shown that the ND-CT technique is capable to provide anon-destructive view into the interior of the ‘phantom’ delivering structural informationconsistent with a reference XRD-CT experiment., Published by IOP Publ., Bristol

The results of this work have shown that for microelectronic applications, gettering at dislocations is less important and oxygen precipitates are the main getter sink for Cu. Sufficient gettering of Cu in samples contaminated with low Cu concentration requires a higher density and larger oxygen precipitates compared to samples contaminated with high Cu concentration. It is demonstrated that the getter efficiency depends on the contamination level of the samples and getter test with low contamination level must be applied for microelectronic applications. Furthermore, a getter test for 3D chip stack technologies was developed. It was shown that although the wafers are thinned to a thickness of 50 μm their getter efficiency seems to be higher than for wafers of the original thickness. This is assumed to be due to the higher Cu concentration in the thinner wafers which can be gettered easier. It is also demonstrated that BMDs can getter Cu impurities even if the temperature does not exceed 300 °C. The getter efficiency tends to be higher if the samples are stored under day light and not in the dark.

The entire simulation process for long fiber reinforced thermoplastics is examined to determine the effective mechanical properties which are influenced by the microstructural fiber orientation state. Therefore, flow and fiber orientation simulations are conducted and the obtained fiber orientation tensors are used in two-scale structural simulations. The fiber orientation distributions as well as the mechanical properties are compared with micro-computed tomography data and results from threepoint bending tests performed by dynamical mechanical analysis (DMA), respectively. The validated results show that prediction of the essential mechanical properties is possible with the applied combinated methods and that the knowledge of the fiber orientation and its gradients is of crucial importance for the entire simulation process.

Amorphous/crystalline multilayer structures of Fe-P alloys were deposited electrochemically using the single bath technique. Hall-Petch behavior of microhardness with respect to sublayer thickness was observed down to a sublayer thickness of 15 nm. For thinner sublayers, a hardness plateau was obtained. The transition at a sublayer thickness of 15 nm coincides with the loss of the multilayer structure as observed in transmission electron microscopy. The transition is a possible result of a change in the amorphous to crystalline sublayer thickness ratio and the interface roughness development during the deposition process. Additionally, crack deflection at the interfaces was observed for the layered structures with small sublayer thickness in microbending experiments.

Two getter tests were carried out in order to study the getter efficiency of oxygen precipitates in silicon samples contaminated with low and high Cu concentration. The samples were pre-treated by RTA followed by annealing in the temperature range between 700 °C and 1000 °C for various times in order to establish different concentrations and different sizes of oxygen precipitates in the samples. From the analysis of the results of the normalized inner surface and the gettering efficiency, it was deduced that in highly contaminated samples Cu precipitates more easily at dislocations than at the surface of oxygen precipitates. Contrarily, in the samples contaminated with low Cu concentration the presence of dislocations does not improve the getter efficiency. Cu precipitates were found at the edge of a plate-like precipitate in a sample with low Cu concentration.

The aim of this contribution was to investigate the impact of nitrogen doping on oxygen precipitation in wafers obtained from ingots optimized with respect to voids by advanced pulling methods. Wafers cut from these ingots contain a central OSF region and an outer perfect vacancy region. The density of grown-in oxide precipitate nuclei in the wafers was distributed radially very inhomogeneous due to the variation of the vacancy supersaturation being proportional to v/G . Two step thermal treatments with a nucleation at 780 °C for 3 h or an oxygen out-diffusion anneal at 1100 °C for 2 h both followed by 1000 °C for 16 h have shown that nitrogen doping of ingots results in a homogeneous BMD density on the whole wafer. A nitrogen concentration of at least 3×10 13 cm −3 is required for the nitrogen enhanced oxygen precipitation indicating that diffusive nitrogen in the form of N 2 complexes is a prerequisite for the increase of the nucleation rate. Nitrogen is incorporated into the oxide precipitates increasing the density of the precipitating phase and thus reducing strain energy.

An internally gettering bulk defect zone and a defect denuded zone of at least 5 µm below the wafer surface were generated by out-diffusion of interstitial oxygen during annealing at temperatures in the range 1075-1100 °C in argon atmosphere. The CZ silicon material used was optimized with respect to voids and contained a central OSF region and an outer Pv region. Due to co-doping of at least 3×1013cm-3nitrogen, a laterally homogeneous bulk microdefect density was obtained which is independent of the temperature of the out-diffusion anneal. The internal getter created in this way efficiently getters nickel impurities as demonstrated in a getter test with 6.6×1011cm-3of intentional Ni contamination. In the central OSF region of the as-grown nitrogen co-doped wafers, the nuclei capable of generating OSFs also degrade the gate oxide integrity. Out-diffusion annealing at 1075-1100°C dissolves most of the defects capable of generating OSFs and it strongly improves the integrity of 5 nm gate oxides.

The influence of RTA pre-treatments on the morphology of oxygen precipitates in silicon wafers as deduced from haze getter tests was confirmed by FTIR and TEM investigations. Based on the results of the getter tests, the ratio between the density of plate-like and octahedral precipitates was calculated for RTA pre-treated silicon samples.

Nickel carbon nanotube composites with varying amounts of carbon nanotubes are deformed by high pressure torsion at different deformation temperatures to high strains, where no further refinement of the Nickel matrix microstructure is observed. Mean Nickel grain sizes increase with increasing HPT deformation temperature, while the size of the carbon nanotube agglomerates is significantly reduced. Additionally, the distribution of the agglomerates in the metal matrix becomes more homogenous. To investigate the mechanical performance of the HPT deformed composites, uniaxial tensile and compression tests are conducted. Depending on the HPT deformation temperature and the resulting microstructure, either brittle or ductile fracture occurs. Increased HPT deformation temperatures induce a decrease in the anisotropy of the mechanical properties, mainly caused by a shrinking of the carbon nanotube agglomerates. It is shown, that tuning the HPT deformation temperature is the key for optimizing both the microstructure and the mechanical performance.

Thermal treatments to enhance precipitation like RTA, ramp anneal and argon anneal were performed on low oxygen 300 mm wafers without vacancy or interstitial agglomerates (“so called” defect-free material). Best results were achieved using high temperature argon anneal leading to a homogenous BMD and denuded zone formation. Furthermore the getter efficiency was positively tested by intentional Ni-contamination. Concepts to overcome the slip danger like improved support geometries and nitrogen codoping were also evaluated and are seen to be beneficial.

In this paper, the key parameters of a rapid thermal annealing (RTA) nitriding step are discussed with respect to vacancy- and oxygen precipitate (BMD)-profile formation. These RTA key performance parameters are the maximum NH3 dissociation temperature (i), the temperature stability of the stored vacancy peak (ii), and the defect dissolution capability of self Si agglomerates at elevated temperatures (iii). This parameter study could be helpful for a future model of the vacancy in-diffusion process into the Si near surface region. Especially the gate oxide integrity (GOI) is an important parameter to establish long life cycles in current memory devices. After NH3 RTA processing, it was surprisingly found that the GOI defect level is still influenced by small-sized grown in particles. It is demonstrated that a complete restoration toward a high GOI signal can be achieved via a 1300 °C RTA step. The gate oxide integrity is afterwards as good as observed on a defect free polished CZ wafer.

In order to elucidate the influence of stress and in-diffused nitrogen on oxide precipitation after rapid thermal annealing (RTA), we carried out experiments with one-side and double-sided nitride layers accompanied by simulation models which help to understand the behavior of intrinsic point defects, nitrogen, and strain. We found that the presence of a nitride layer of any thickness, within the rage which we investigated, in direct contact with the silicon surface is sufficient to markedly change the precipitation behavior of interstitial oxygen after RTA at 1175 and 1250 °C. The presence of the nitride layer during the stabilization and growth of the oxide precipitates is not of any influence on the precipitation behavior. Therefore, the RTA of wafers covered with silicon nitride is the crucial step controlling the bulk microdefect (BMD) depth profiles. A 10 nm oxide between silicon substrate and nitride layer prevents any change of the BMD depth profile. Only in a direct contact with the nitride layers the vacancy supersaturation, which enhanced the oxide precipitation compared to wafers without nitride layers, was generated. Nitrogen peaks below the silicon surface generated by in-diffusion of nitrogen during RTA lead to an enhanced oxygen precipitation only for RTA at 1250 °C and not for RTA at 1175 °C. We propose a model based on very tiny coherent α-Si3N4 precipitates generated at nitrogen-vacancy (NV) complexes which can act as nucleation sites for oxygen precipitation. Because the stability of NV seems limited to temperatures above 1200 °C, it would not be effective for RTA at 1175 °C. RTA treatment of silicon wafers with one-sided nitride layers at 1250 °C leads to very sharp and small defect denuded zones in subsequent annealing and would be suitable for proximity gettering. The depth of the denuded zone is nearly independent of the thickness of the nitride layer.

6H-SiC-crystals have been grown using the modified Lely method. The growth rate was investigated for dependence on the growth time, the source composition and the system pressure. It was shown that the growth rate is strongly influenced by the deviation from the stoichiometry and the system pressure. The influence of the composition of the vapour phase is dominant compared with the system pressure in the first stages of the growth process. The average growth rate decreases with increasing growth duration.

Secondary ion mass spectroscopy (SIMS) and inductively coupled plasma spectroscopy (ICP-OES and ICP-MS) have been used to study the impurity concentration within different stages of the SiC crystal growth technology. The pure constituents silicon and carbon, the synthesized SiC powder as well as sublimation grown crystals of 6H polytype were investigated. It was found that the main impurities are iron, aluminium, tungsten, vanadium, nickel and copper. Although high purity silicon and carbon were used as starting materials the impurity level increases due to the preparation technique. However, in comparison to the SiC source powder the crystals show a reduction in the impurity concentration by one order of magnitude.

After storage of silicon wafers in polymer boxes, an increase in the number of localized light scatters (LLS) may be observed. This phenomenon, caused by chemical processes on the surface, is called time dependent haze (TDH). Intentionally generated TDH was investigated. An increase of LLS could be observed after the storage of contaminated wafers. Preparations with inorganic compounds exhibit crystallites formed on the surface. A high vapor pressure and a good solubility in water of organic compounds favored the generation of organic TDH. In both experiments, copper promoted the formation of TDH. Preparations with mixtures of contaminants revealed the interaction of chemical compounds on the surface. Ammonium sulfate had a strong impact on the formation of TDH. Pulsed force mode-atomic-force microscopy measurements, a new mode in atomic force microscopy, was used to differentiate chemical species constituting TDH by adhesion force mapping. © 2003 The Electrochemical Society. All rights reserved.