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Rapid thermal annealing (RTA) in silicon wafer processing is a technique used to control point defects, vacancies and silicon interstitials (1,2). The presence of these defects influences the nucleation and precipitation of supersaturated oxygen in Czochralski (CZ) silicon wafers. The precipitation of oxygen, which occurs during annealing of silicon wafers, is a very important phenomenon. This is because the oxygen precipitates provide a natural getter sink for unwanted metallic impurities which can get into the devices active region in the fabrication process. Vacancies are of high importance because they enhance oxygen precipitation. In CZ silicon vacancies are mainly bound with oxygen atoms forming so called VOn complexes where n is the number of oxygen atoms. The investigation of VOn complexes in silicon wafers is extremely difficult because of their low concentration, which is in the range of 1013 cm-3. So far, irradiation experiments are the main source of information about VOn complexes. The irradiation allows increasing their concentration to a much higher level compared to the level, which can be found in processed wafers. Akhmetov et al. (3) published the first detection of VOn complexes in non-irradiated but RTA pre-treated wafers. In order to be able to measure defects with very low concentration they used highly sensitive FTIR measurements at room temperature (RT). They found the absorption band at 985 cm-1 which they attributed to VO4. The estimated concentration of VO4 complexes was very close to calculated values from an ab initio model (4). In this work, we used a slightly modified method in order to investigate VOn complexes in RTA pre-treated wafers. The measurements were carried out at 6 K what allowed us to enhance the sensitivity. Moreover, the FWHM of the interstitial oxygen band is much smaller at 6 K compared to RT. This means that the range of wave numbers next to the Oi band typically covered by this band at RT can be investigated now. This range is very important because some absorption bands of VOn complexes with n > 4 are located there. In a previous study, in a wafer pre-treated by RTA at 1250 °C for 30 s in an Ar containing O2 atmosphere we found the absorption bands of VO4 at 985 cm-1 and 991 cm-1 in the measurements carried out at room temperature and at 6 K, respectively (5). In this wafer, we also detected an unknown band at 1030 cm-1 and the bands at 1096 cm-1 and 1099 cm-1, according to Murin et al. both assigned to VO5,6 (6). In order to better understand these complexes we performed additional experiments. The wafers were pre-treated by RTA in the range between 1250 °C and 1375 °C and the behavior of the detected bands was analyzed and correlated with simulations. The process of vacancy-oxygen complex formation after RTA was simulated using a rate equation model. It was found out that the most stable VOn complexes are the ones with n = 6, 5 and 4. In summary, the VOn complexes were investigated by FTIR spectroscopy at 6K in RTA pre-treated wafers. The process of vacancy-oxygen complex formation after RTA was modeled using a rate equation model. References R. Falster, M, Pagani, D. Gambaro, M. Cornara, M. Olmo, G. Ferrero, P. Pichler, M. Jacob, Solid State Phenom., 57-58, 129 (1997). M. Pagani, R. Falster, G. R. Fisher, G. C. Ferrero, M. Olmo, Appl. Phys. Lett., 70 (12), 1572 (1997). V. Akhmetov, G. Kissinger, and W. von Ammon, Appl. Phys. Lett., 94, 092105 (2009). G. Kissinger, J. Dabrowski, A. Sattler, C. Seuring, T. Müller, H. Richter, W. von Ammon, J. Electrochem. Soc., 154, H454 (2007). D. Kot, G. Kissinger, and A. Sattler, Semicond. Sci. Technol. 32, 104006 (2017). L.I. Murin, J. L. Lindström, B. G. Svensson, V. P. Markevich, A. R. Peaker, C. A. Londos, Solid State Phenomena, Vols. 108-109, pp. 267-272 (2005).

With the introduction of the Czochralski method for growing of silicon single crystals oxygen in silicon became an issue with positive and negative impact on silicon devices. On the one hand the oxygen strengthens the wafers against slip dislocation formation, on the other hand precipitating oxygen in the device active area can degrade the device performance. However, oxygen precipitates in the bulk are beneficial because they act as gettering sinks for metallic impurities and thus can improve the device performance. Therefore, oxygen is a major issue in silicon defect engineering. Extensive research on oxygen precipitation started in the seventies of the 20th century and it is still ongoing because new tools become available which offer new possibilities of characterization, higher resolution and lower detection limits. In the field of modeling, the tremendous advances of computer technique and software during the last decades made it possible for a much broader community to run larger models and to make predictions being much more sophisticated. The challenges of defect engineering in silicon device technology changed over the years. In the eighties, two or three step heat treatments were applied to out-diffuse the interstitial oxygen from the device active area followed by nucleation and growth of oxygen precipitates. This procedure is very time consuming. In the nineties, a new RTA based method was discovered. Vacancy profiles, which controlled the spatial distribution of oxygen precipitation in the wafers, were generated by high temperature RTA treatment. During this method, the oxygen does not diffuse out. Because intrinsic point defects are very fast diffusors, a good adjustment to the following device process has to be made. Today, one of the major requirements of high end silicon device technology is void-free silicon because with ongoing decreasing feature size voids became a major yield decreasing problem. There are several solutions to this issue like the growth of void-free silicon crystals and void dissolution in silicon wafers by heat treatment at very high temperature. Both methods are strongly connected with oxygen precipitation. Growth of nearly void-free silicon often leads to radial inhomogeneities of the concentrations of intrinsic point defects [1, 2]. The challenge of defect engineering is to create a radially homogeneous concentration of oxygen precipitates. The ongoing increase of wafer diameter imposes additional problems to oxygen precipitation. If the density of oxide precipitates becomes too high, overlay problems in mask alignment occur [3]. This requires new adjustments of oxygen precipitation. The low feature size in addition to the large wafer diameter asks for low thermal budget processing. A new problem arises because the oxygen precipitates need a certain surface and density to be able to getter enough metallic impurities. Examples from our own recently published results about ab initio calculation for understanding of the initial stages of oxygen precipitation [4], EELS investigation of the stoichiometry of oxygen precipitates [5], the gettering mechanism of Cu at oxygen precipitates [6], and N-doping for the homogeneous oxygen precipitation during high temperature annealing in wafers optimized with respect to voids [1, 2] will be presented. In summary, it can be said that oxygen in silicon remains an ongoing issue. Control of oxygen precipitation becomes more and more demanding for high end device technologies. Oxygen precipitation is not yet fully understood but the current developments of diagnostic methods allow new insights. [1] G. Kissinger, G. Raming, R. Wahlich, T. Müller, 300 mm Czochralski silicon wafers optimized with respect to voids with laterally homogeneous oxygen precipitation, Physica B 407, 2993 (2012). [2] G. Kissinger, G. Raming, R. Wahlich, T. Müller, Nitrogen doped 300mm Czochralski silicon wafers optimized with respect to voids with laterally homogeneous internal getter capabilities, Mat. Sci. Forum 725, 221 (2012). [3] K. Izunome, Advanced silicon wafers for leading-edge semiconductor devices, Proceedings of the 6th Int. Symposium on Advanced Science and Technology of Silicon Materials (JSPS Symposium), Nov. 19-23, 2012, Kona, Hawaii, USA, pp. 9-13. [4] G. Kissinger, J. Dabrowski, T. Sinno, Y. Yang, D. Kot, A. Sattler, Ab initio calculations and rate equation simulations for vacancy and vacancy-oxygen clustering in silicon, J. Cryst. Growth 468, 424 (2017). [5] G. Kissinger, M. A. Schubert, D. Kot, T. Grabolla, Investigation of the composition of the Si/SiO2 interface in oxide precipitates and oxide layers on silicon by STEM/EELS, ECS J. of Solid State Sci. and Technol. 6, N54 (2017). [6] G. Kissinger, D. Kot, M. Klingsporn, M. A. Schubert, A. Sattler, T. Müller, Investigation of the copper gettering mechanism of oxide precipitates in silicon, ECS J. of Solid State Sci. and Technol. 4, N124 (2015).

Vacancy dependent nucleation curves were measured. They exhibit four maxima which all increase with increasing vacancy concentration. Even at 1000 {degree sign}C considerable nucleation takes place for high vacancy concentrations. The analysis of nucleation based on classical nucleation theory has shown that nucleation of oxide precipitates takes place at heterogeneous nucleation sites. These sites contain oxygen atoms and vacancies and it is assumed that these sites are VOn complexes with 2

The coherent agglomeration of interstitial oxygen into single-plane and double-plane plates can explain the two peaks in the M-shaped nucleation curves in Czochralski silicon. The density of nucleation sites for the double-plane plates corresponds to the VO2 concentration. Ab initio calculations have shown that the agglomeration of oxygen atoms in single-plane and doubleplane plates is energetically favorable. These plates are under compressive strain. VO2 agglomeration plays only a minor role for modeling the M-shaped nucleation curves because of prior homogenization treatments. It is of much higher impact if as-grown wafers are subjected to nucleation anneals because of the higher vacancy concentration which was frozen in during crystal cooling. This results in higher nucleation rates at higher temperatures. Because the oxygen diffusivity below 700 °C is important for the nucleation rate and many controversial results about the diffusivity in this temperature range were published, we have analyzed the data from literature. We have demonstrated that the effective diffusivity of oxygen at temperatures below 700 °C which corresponds to the quasi equilibrium dimer concentration is very similar to the extrapolation from oxygen diffusivity at high temperature. The high effective diffusivities from out-diffusion and precipitation experiments, and the somewhat lower effective diffusivities from dislocation locking experiments are the result of an ongoing formation of fast diffusing dimers because the equilibrium is disturbed as the result of the strongly increasing difference in the diffusion length between interstitial oxygen and the fast diffusing dimer with decreasing temperature.

We have investigated the impact of RTA induced vacancy supersaturation on oxide precipitation based on as much as possible experimental and theoretical values. Oxygen precipitation after RTA processing was found to be controlled by the initial concentration of interstitial oxygen in a sixth power dependency and frozen vacancies just in a cubic dependency. The formation of tensile strained nVO2 clusters seems to be the favored process for coherent nucleation of oxide precipitates. The reduction of interstitial oxygen can be accurately modeled for the temperature range from 1150 {degree sign}C to 1250 {degree sign}C using Ham's theory for precipitate growth and an empirical relation based on nucleation of oxide precipitates by agglomeration of VO2 complexes. During RTA treatments at temperatures {greater than or equal to} 1300 {degree sign}C vacancies seem to be consumed by other processes. Below RTA temperatures of 1150 {degree sign}C, oxide precipitation is dominated by shrunken as-grown precipitate nuclei because as-grown nuclei can be dissolved only at RTA temperatures {greater than or equal to} 1150 {degree sign}C.

This paper presents a multidisciplinary approach to a problem of soil–wheel interaction during the landing of an airplane on a grass airfield, with terramechanical analysis of the forces acting between a wheel and the surface. The experiment on stress and deformation state in soil under a wheel on touchdown was performed in the field. The soil stress state (major stress S1, minor stresses S2 and S3, stress invariant in an octahedral system, MNS and OCTSS) was determined with the use of an SST (stress state transducer), which was installed at 15 cm depth. Soil deformation was determined with an inertial measuring system, integrated with the SST. These soil data were captured exactly at the moment touchdown. In the experiment, a four-passenger, STOL multirole airplane was used and pilots performed two landing patterns: normal landing and emergency landing (without propeller thrust).

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.

A new method for determination of soil stress-strain relationships under traffic in field experiments is described. Tire or track sinkage as well as vertical movements of a point in soil volume can be quantified using an optoelectronic method. In soil stress measurements, a standard stress state transducer (SST) with six strain gage type pressure transducers was used. Detailed descriptions of technical solutions are described and presented on illustrations. The measuring system is capable of collecting simultaneously soil stress and deformation data. Results from a preliminary experiment with the use of a tracked armoured vehicle are presented and analysed. Soil stress and deformation data measured simultaneously are used for the evaluation of soil stress–strain relationship, which may become a mechanical characteristic of the investigated soil.

The study was undertaken to establish the pharmacological basis of the stimulatory activity of galantide (M15) and galanin(1-14)-(a-aminobutyric acid8-[Abu8])scyliorhinin-I [Scy-I] in gastric smooth muscle.Isotonic contractions of the isolated, longitudinal rat gastric fundus strips were recorded.Galanin, galanin(1-15)-NH2, M15 and galanin(1-14)-[Abu8]Scy-I elicited concentration-dependent contractions. Their EC50s equaled 12.95, 174, 70.06 and 187 nM respectively. Hill's coefficients for galanin and galanin(1-15)-NH2 were not different from unity, indicating an interaction of one peptide molecule with one receptor according to the principles of classical receptor theory. Hill's coefficients were 0.73 and 1.56 for M15 and galanin (1-14)-[Abu8]Scy-I, respectively, a value significantly different from unity. Cold-storage denervation, tetrodotoxin-TTX (1 mM), spantide (100 mM) and NK1-3 receptor antagonists SR140333, 48968, 142801 (up to 10 mM) notably diminished M15, galanin(1-14)-[Abu8]Scy-I, SP(5-11) and [Abu8]-Scy-I evoked contractions without affecting activities of galanin and galanin(1-15)-NH2. Additionally, cross-desensitization experiments attenuated activity of M15 and galanin(1-14)-[Abu8]Scy-I without any noticeable action on galanin or galanin(1-15)-NH2.The action of chimeric peptides on the smooth muscle of the rat gastrointestinal tract depended not only on the myogenic interaction of those peptides with galanin binding sites, but also on the activation of tachykinin receptors or the release of endogenous mediators from the presynaptic terminals.

We have investigated the impact of rapid thermal annealing (RTA) induced vacancy supersaturation on oxide precipitation based as much as possible on experimental and theoretical values. Oxygen precipitation after RTA processing was found to be controlled by the initial concentration of interstitial oxygen in a sixth power dependency and frozen vacancies just in a cubic dependency. The formation of tensile strained nVO 2 clusters seems to be the favored process for coherent nucleation of oxide precipitates. The reduction of interstitial oxygen can be accurately modeled for the temperature range from 1150 to 1250°C using Ham's theory for precipitate growth and an empirical relation based on nucleation of oxide precipitates by agglomeration of VO 2 complexes. During RTA treatments at temperatures ≥ 1300°C vacancies seem to be consumed by other processes. Below RTA temperatures of 1150°C, oxide precipitation is dominated by shrunken as-grown precipitate nuclei because as-grown nuclei can be dissolved only at RTA temperatures ≥ 1150°C.

The surface‐stress tensor is an important quantity entering the elastic theory of interaction between atomic steps on solid surfaces. For the clean Si(001) surface the difference between its diagonal elements, the surface stress anisotropy Δσ, comes out by about a factor of two smaller in experiment than compared to the value obtained from previous first‐principles calculations. This discrepancy was usually assigned to the presence of surface defects; as other plausible causes one could quote unrealistic atomic surface structures used for the calculations or even a failure of the local‐density approximation (LDA) on which the calculations were based. This constituted a serious deficiency in the understanding of the Si(001) surface. We demonstrate that, when first‐principles LDA calculations are carried out for the perfect Si(001) surface with the correct character of reconstruction, the calculated and measured Δσ agree within the experimental and numerical uncertainties. We conclude that standard LDA calc...

We discuss calculations from first-principles (using the local-density approximation for exchange and correlation) of defect total energies, vibrational modes, internal energies and entropies. Results are presented for the defect-induced distortion field of an arsenic impurity in silicon and for the vibrational entropy of a silicon vacancy. We also discuss the important role of electron and atom chemical potentials, presenting results for the Ga vacancy in the GaAs bulk and at the (111) surface.

We performed parameter-free, self-consistent calculations of the electronic structures, total energies, and forces of the As antisite, of an As-interstitial-Ga-vacancy defect pair, and of various configurations between these limits. The total-energy surface exhibits an interesting metastability. The theoretical results can explain all established properties of the so-called $\mathrm{EL}2$ defect.

We report parameter-free, self-consistent calculations of the electronic structures, total energies, and forces of the ${\mathrm{As}}_{\mathrm{Ga}}$ antisite, of an As-interstitial--Ga-vacancy defect pair, and of various configurations between these limits. The corresponding total-energy surface exhibits an interesting metastability. The results are discussed with respect to photoquenching, thermal stability, optical, electronic, and magnetic properties of EL2. This comparison shows that the behavior of EL2 may be understood in terms of the isolated arsenic antisite, which exhibits via the mentioned metastability (${\mathrm{As}}_{\mathrm{Ga}\mathrm{?}}$${\mathrm{As}}_{\mathrm{i}}$) and the dissociation and/or association (As?${\mathrm{VGaAs}}_{\mathrm{i}}$) a variety of different properties. It is pointed out that this new mechanism of metastability may be significant for other point defects in semiconductors as well.