Dielectric and interface properties of pyrolytic aluminum oxide films on silicon substrates

Aluminum oxide films have been deposited on silicon substrates by thermal decomposition of aluminum-isopropoxide. MOS capacitance and conductance measurements have been made on Al₂O₃-Si structures,and the influence of deposition parameters and silicon surface preparation on interface properties has been examined. The density of interface states varies from 10¹⁰ to 10¹¹ cm^?2(ev)^?1, and the flatband voltage (for ～1000Å oxide) can vary between zero and several volts positive depending upon the deposition parameters and silicon surface preparation. Postdeposition annealing in moist or dry-O₂ at 800°C decreases the flatband voltage. Infrared measurements indicate that this effect is accompanied by the growth of a thin interface SiO₂ film. Only a very thin interface SiO₂ film (～50Å) is required to produce zero flatband voltage. Biastemperature stress increases the flatband voltage value under negative gate bias. Excessive localized conduction and breakdown can be correlated with the occurrence of silicon surface defects. The radiation resistance of Al₂O₃-Si structures is strongly dependent upon the presence of a thin interface SiO₂ film.     

Structural properties of vapor deposited silicon nitride

Some of the chemical and physical properties of silicon nitride films have been studied to determine the effects of deposition process variables and wafer preparation prior to deposition. The boat temperature and the reaction gas mixture were changed to optimize the quality of the silicon nitride films. This resulted in amorphous films free of pinholes, cracks, and impurities, together with good electrical properties such as an effective barrier against sodium ions and a low fast and fixed surface state density. Most of the work has been done on silicon nitride deposited over silicon dioxide films or silicon dioxide steps on a siliconsubstrate. The silane-ammonia and the silicon tetrachloride-ammonia reactions resulted in silicon nitride of comparable physical and chemical properties. Cleaning procedures are most effective if they include an etching step to take off 50 to 100Å of the oxide prior to nitride deposition. The influence of subsequent heat treatments (up to 1200°C) on cracking and etch rates of the silicon nitride films has been studied. Films thicker than 2000Å deposited over oxide steps were found to crack after heat treatments above 1000°C. Films in the lower thickness range of 500 to 1000Å are most suitable because they have good resistance against cracking after heat treatments up to 1200°C, do not need excessively long etch times, and are still an excellent barrier against a heavy sodium contamination applied at 535°C.     

优钢连铸坯气泡成因分析及防范措施

在连铸生产实践中,皮下气泡是铸坯的一种主要缺陷,带有气泡的铸坯在轧制过程中容易产生裂纹,造成较多的轧制废品。因此防止连铸坯气泡的形成,对稳定连铸生产、提高产品质量具有重要意义。通过产品质量的提高,有利于提高莱钢产品的市场形象,扩大企业的影响力,提高优特钢产品的市场占有率。本文对优钢连铸坯中气泡的成因进行了分析,总结出连铸过程产生气泡（包括针孔）的主要原因有3类——脱氧不良、外来气体、水蒸气,并针对上述因素提出了预防措施。     

Effect of copper on the processes of impregnation of refractory metals with boron and silicon

Conclusions A study was made of the processes of diffusion impregnation of refractory metals in powder mixtures with 1–30 wt.% copper additions. It was found that the addition of up to 5 wt.% copper to the mixture accelerated the process of boronizing of refractory metals. The presence of more than 10 wt.% copper in the siliconizing mixture adversely affected the quality of the suicide coating. The addition of copper to the impregnating mixtures enabled good-quality diffusion coatings of considerable thickness to be obtained.Translated from Poroshkovaya Metallurgiya, No. 5(209), pp. 65–68, May, 1980.     

Reaction between silicon nitride and magnesium oxide during hot pressing

Conclusions Using the methods of microscopical examination, chemical and mass spectrometric analyses, electron probe microanalysis, and weight loss determination, astudy was made of the reaction between technical silicon nitride powder and magnesium oxide. It is shown that the reaction involves not only the formation of forsterite, enstatite, and variable-composition glasses but also diffusion of the main components, with a gradual fall in magnesium concentration over the whole length of the diffusion zone in a model system. In the temperature range 1600–1700°C magnesium atoms drive out of the silicon nitride lattice silicon atoms, which then react with oxygen from the magnesium oxide or air to form silicon monoxide ions in the gaseous phase. The evaporation of the silicon monoxide in the system results in loss of weight, which grows with rise in temperature. The processes of evaporation and dissociation of the starting components, which sharply increase in intensity at 1800°C, make a certain contribution to the loss of weight.Translated from Poroshkovaya Metallurgiya, No. 9(177), pp. 89–96, September, 1977.     

High-temperature compatibility of refractory metals with scandium oxide

Conclusions Chemical reaction between Sc₂O₃ and Ta, Mo, and W is not observed when they are heated to 2100°C in a protective medium for 4 h. The depth of diffusion of the metal into the oxide is less than the resolving power of the microscope (1). It is, therefore, theoretically possible to use scandium oxide as a dispersion-strengthening phase for metal artifacts of Ta, Mo, and W, for coating these artifacts with Sc₂O₃, etc.Translated from Poroshkovaya Metallurgiya, No, 1, pp. 83–87, January, 1968.     

Deoxidation with silicon and the control of oxide inclusions in electrical steels

The oxygen solubility in Fe-Si melts in equilibrium with SiO₂ at 1873 K has been determined in a concentration range of 0.1–70 wt % Si. Model alloys are melted in quartz crucibles in an argon atmosphere. The oxygen content in analytical samples is determined by the inert-gas reducing-fusion method after careful sample preparation. The results obtained have been processed using a thermodynamic model that can calculate the oxygen activity and solubility in Fe-Si melts up to 100 wt % Si. The effects of the heating rate and the silicon content on the carbon concentration in carbonyl iron and Fe-Si alloys are studied using the inert-gas reducing-fusion method in the temperature range 1673–2373 K. Oriented electrical steels are investigated using fractional gas analysis. The main forms of oxygen in these steels are found to be silicates, Al₂O₃, and MgAl₂O₄.     

Preparation and properties of oxide films of the rare earth metals

The properties of films of rare earth metal oxides obtained by evaporation of the metal in an oxygen atmosphere are given. The deposits were highly dispersed and crystallized with a cubic type-Mn₂O₃ structure. The data obtained include: width of the forbidden band (4–6 eV), refractive index (1.89–2.05), specific electrical resistance (10¹⁴–10¹⁵ ω·cm), breakdown voltage (10⁶–10⁷ V/cm), etc. It is shown that films of REM oxides are promising as passive elements of microcircuits, transparent coatings, temperature and heat-flow sensors. These examples by far do not exhaust the possibilities for use of such films. Materials Science Institute. Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2, pp. 107–111, January–February, 1998.     

低碳低硅钢中氧化物夹杂的控制

重庆钢铁股份有限公司新区炼钢厂结合低碳低硅钢的生产实践,为改善钢水可浇性、避免因中间包水口堵塞而停浇的事故发生,对转炉后搅、顶渣脱氧和RH碳脱氧工艺进行了优化。工艺改进后,转炉终点钢水w(O)降低了127×10-6,渣中w(FeO+MnO)<5%,钢水中铝的加入量减少了0.38～0.43 kg/t,有效降低了钢中氧化物夹杂含量,钢中w(T.O)控制在(14～25)×10-6内。生产实践表明:采用"BOF→RH→CC"工艺路线生产低碳低硅钢,提高了钢水洁净度、单中包连浇炉数达18炉。     

Selective reduction of metals in the lattice of a complex oxide

The results of our experiments on the carbon reduction of metals from iron-containing rich and lean monometallic ores and complex ores in which iron is present along with other metal oxides in a common crystal lattice are analyzed. It is concluded that reduction should be considered as an electrochemical process consisting in the supply of electrons to the cations to be reduced. The source of electrons in the experiments is a chemical reaction on the surface of interaction between a reducer and oxides. Electron transport deep into ore lumps is performed by anion vacancies. Vacancies draw cations with a high electron affinity and neutral atoms, which ensures selective metal reduction. A continuous metallic shell does not form on the surface of lean and complex ores, and oxide layers, along which vacancies move into an ore lump, are retained. As a result, the entire ore lump undergoes reduction. Therefore, lean and complex ores can easily be reduced as compared to rich ores.     

Crystal structure of compounds and phase equilibria in ternary systems of two transition metals and silicon

Summary Phase equilibria in ternary systems of two transition metals and silicon have been investigated.In systems containing iron, cobalt or nickel, ternary phases with closest packing of atoms have been found; in some systems, there are continuous solid solutions of isostructural binary compounds, or there is limited solubility in binary suicides.