Comment

A chloride-based chemical-vapor-deposition (CVD) process has been successfully used to grow very high quality 3C-SiC epitaxial layers on on-axis α-SiC substrates. An accurate process parameters study was performed testing the effect of temperature, surface preparation, precursor ratios, nitrogen addition, and substrate polytype and polarity. The 3C layers deposited showed to be largely single-domain material of very high purity and of excellent electrical characteristics. A growth rate of up to 10 μm/h and a low background doping enable deposition of epitaxial layers suitable for MOSFET devices

Inappropriate Patient Confinement and Appropriate State Advocacy

A chloride-based CVD process has been studied in concentrated growth conditions. A systematic study of different carrier flows and pressures has been done in order to get good quality epilayers on 8 degrees off and on-axis substrates while using very low carrier flows. Hydrogen chloride (HCl) was added to the standard gas mixture to keep a high growth rate and to get homo-polytypic growth on on-axis substrates. The carrier flow was reduced down to one order of magnitude less than under typical growth condition. By lowering the process pressure it was possible to reduce precursor depletion along the susceptor which improved the thickness uniformity to below 2% variation (sigma/mean) over a 2 diameter wafer

Совершенствование сбытовой сети предприятия (на примере ОАО «Гомсельмаш»)

Atomization energies, enthalpies of formation, entropies as well as heat capacities of the SiHnXm and CHnXm systems, with X being F, Cl and Br, have been studied using quantum chemical calculations. The Gaussian-4 theory (G4) and Weizman-1 theory as modified by Barnes et al. 2009 (W1RO) have been applied in the calculations of the electronic, zero point and thermal energies. The effects of low-lying electronically excited states due to spin orbit coupling were included for all atoms and diatomic species by mean of the electronic partition functions derived from the experimental or computational energy splittings. The atomization energies, enthalpies of formation, entropies and heat capacities derived from both methods were observed to be reliable. The thermochemical properties in the temperature range of 298-2500 K are provided in the form of 7-coefficient NASA polynomials. (C) The Author(s) 2015. Published by ECS. All rights reserved.Funding Agencies|Swedish Foundation for Strategic Research</p

Концепт PRIVACY в англомовній картині світу

(uk) Стаття присвячена дослідженню концепту PRIVACY в аспектах лінгвокогнітології та лінгвокультурології в англійській мові.(en) The article is devoted to the investigation of the concept PRIVACY in the aspects of Cognitive and Cultural Linguistics in the English Language

Simulations of SiC CVD - Perspectives on the need for surface reaction model improvements

Simulations of SiC chemical vapor deposition is an excellent tool for understanding, improving and optimizing this complex process. However, models used up to date have often been validated for one particular set of process parameters, often in the silicon limited growth regime, in one particular growth equipment. With chlorinated precursors optimal growth condition is often found to take place at the border between carbon limited and silicon limited regimes. At those conditions the previous models fail to predict deposition rates properly. In this study we argue that molecules like C2H2, C2H4 and CH4, actually might react with the surface with much higher rates than suggested before. Comparisons are made between the previous model and our new model, as well as experiments. It is shown that higher reactivities of the hydrocarbon molecules will improve simulation results as compared to experimental findings, and help to better explain some of the trends for varying C/Si ratios

Effect of process parameters on dislocation density in thick 4H-SiC epitaxial layers grown by chloride-based CVD on 4 degrees off-axis substrates

The effect of process parameters such as growth temperature, C/Si ratio, etching time, and Si/H2 ratio on dislocation density was investigated by performing KOH etching on 100 mu m thick epitaxial layers grown on 4 degrees off axis 4H-SiC substrates at various growth conditions by a chemical vapor deposition (CVD) process using a chloride-based chemistry to achieve growth rates exceeding 100 mu m/h. We observe that the growth temperature and the growth rate have no significant influence on the dislocation density in the grown epitaxial layers. A low C/Si ratio increases the density of threading screw dislocations (TSD) markedly. The basal plane dislocation (BPD) density was reduced by using a proper in-situ etch prior to growth

Concentrated chloride-based epitaxial growth of 4H-SiC Concentrated chloride-based epitaxial growth of 4H-SiC

Abstract. A chloride-based CVD process has been studied in concentrated growth conditions. A systematic study of different carrier flows and pressures has been done in order to get good quality epilayers on 8° off and on-axis substrates while using very low carrier flows. Hydrogen chloride (HCl) was added to the standard gas mixture to keep a high growth rate and to get homo-polytypic growth on on-axis substrates. The carrier flow was reduced down to one order of magnitude less than under typical growth condition. By lowering the process pressure it was possible to reduce precursor depletion along the susceptor which improved the thickness uniformity to below 2% variation (σ/mean) over a 2&quot; diameter wafer

Simulation of Gas-Phase Chemistry for Selected Carbon Precursors in Epitaxial Growth of SiC Simulation of gas-phase chemistry for selected carbon precursors in epitaxial growth of SiC

Abstract. Numerical simulations are one way to obtain a better and more detailed understanding of the chemical vapor deposition process of silicon carbide. Although several attempts have been made in this area during the past ten years, there is still no general model valid for any range of process parameters and choice of precursors, that can be used to control the growth process, and to optimize growth equipment design. In this paper a first step towards such a model is taken. Here, mainly the hydrocarbon chemistry is studied by a detailed gas-phase reaction model, and comparison is made between C 3 H 8 and CH 4 as carbon precursor. The results indicate that experimental differences, which previous models have been unable to predict, may be explained by the new model

Ab Initio Study of Growth Mechanism of 4H-SiC: Adsorption and Surface Reaction of C2H2, C2H4, CH4, and CH3

Silicon carbide is a semiconductor material with ideal properties for high-temperature and high-power applications. The epitaxial layer fabrication Is usually performed using chemical vapor deposition (CVD) under a hydrogen rich atmosphere and high temperature. At such conditions the surface of the growing layer is expected to be passivatecl,by the abundantly present hydrogen. In this work, we use quantum chemical density functional theory (B3LYP and M06-2X) and transition state theory to study surface reactions related to the deposition of carbon on the (0001) surface of 4H-SiC. We show that it is unlikely for an adsorption to occur on a passivated, site unless the hydrogen termination is removed. We propose that unterminated sites can be effectively created during the CVD by an abstraction process. We provide details of the adsorption process of active carbon species, namely CH3, CH4, C2H2, and C2H4 gases, and their subsequent surface reactions such as desorption, abstraction of neighboring surface, hydrogens and dinner formation. The reaction rates and sticking coefficients are provided for the temperature range of 298-2500 K. Finally, entire reaction paths from adsorptions to stable surface products are presented and discussed.Funding Agencies|Swedish Foundation for Strategic Research; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials (AFM); Linkoping University</p

Neoliberalism, law and post communist reform : the evolving role of law in Russia’s transition to capitalism

EThOS - Electronic Theses Online ServiceGBUnited Kingdo