Showing papers on "Nitride published in 1988"

Metal matrix composites

Abstract: A ceramic-reinforced aluminum matrix composite is formed by contacting a molten aluminum-magnesium alloy with a permeable mass of ceramic material in the presence of a gas comprising from about 10 to 100% nitrogen, by volume, balance non-oxidizing gas, e.g., hydrogen or argon. Under these conditions, the molten alloy spontaneously infiltrates the ceramic mass under normal atmospheric pressures. A solid body of the alloy can be placed adjacent a permeable bedding of ceramic material, and brought to the molten state, preferably to at least about 700° C., in order to form the aluminum matrix composite by infiltration. In addition to magnesium, auxiliary alloying elements may be employed with aluminum. The resulting composite products may contain a discontinuous aluminum nitride phase in the aluminum matrix and/or an aluminum nitride external surface layer.

Preparation and characterization of early transition metal carbides and nitrides

Abstract: Synthese a temperature programmee dans un courant de gaz reactif. Proprietes physicochimiques

Phase Relationships in the Silicon Carbide-Aluminum Nitride System

Abstract: Phase relationships in the SiC-AlN system were determined by analytical electron microscopy of local equilibria among adjacent phases in hot-pressed samples and in diffusion couples. At 2100° to 2300°C, a 4H–2H equilibrium exists, the 4H field extending from ∼2 mol% AlN to an upper limit of 11 to 14 mol% AlN. The wurtzite-type 2H (δ) solid solution extends from an impurity-sensitive lower limit of 17 to 24 mol% AlN up to 100 mol% AlN. Semiquantitative Auger electron spectroscopy and energy dispersive X-ray spectroscopy ultrathin-window detector measurements confirmed the assumption that the solid solutions have the general formula (SiC)1-x(AlN)x and belong to the SiC-AlN pseudobinary system. The existence of a miscibility gap below 1950°C was confirmed, but its limits were not determined accurately. A faulted metastable cubic phase, β′, exists below ∼2000°C and contains up to ∼4 mol% AlN. The transformations into the stable a structures occur through diffusion-controlled stacking rearrangements.

Aluminium nitride in steel

Abstract: Aluminium nitride (AlN) nucleates with difficulty in steel, unless precipitation is enhanced by thermal or mechanical treatments. This important characteristic determines the precipitation kinetics of AlN, and accounts for the wide variations in precipitate morphology achieved following different processing histories. The most significant effect of AlN in steel is on grain size control, which directly influences hardenability, hot ductility, texture development, and mechanical properties. In addition, the accompanying removal of nitrogen from solid solution affects the strain aging characteristics, weldability, mechanical properties, and creep performance. Aluminium nitride also exerts important second order effects through its influence on the precipitation of other alloy nitrides. The precipitation of AlN can cause embrittlement and cracking phenomena in castings, continuously cast products, ingots, and rolled or forged products, However, the basic mechanisms are well understood, and the occurre...

Manufacture of semiconductor device

Abstract: PURPOSE:To prevent the leakage current of the base-emitter junction by providing processes for selectively removing a nitride film, diffusing an impurity of a first conductivity type, and forming a shallow second region of the first conductivity type widely than a deep emitter region of the first conductivity type. CONSTITUTION:In an N-type semiconductor region 1 which is the collector of a bi-polar transistor, a P-type base region 2 is formed, an oxide film 5 is provided, the oxide film is removed in the portion in which a shallow second region 4 of a first conductivity type is to be formed, and a nitride film 6 having a film thickness of about 1-2mu is grown. Thereafter, the nitride film is etched by means of anisotropic dry etching to form such a structure that the nitride film 6 remains inside the oxide film 5, an N-type impurity is driven in by ion implantation, and a heat treatment is performed, forming a deep emitter region 3. Then, the nitride film 6 is selectively removed by not phosphoric acid or the like, and the N-type impurity is fiffused at a low temperature, forming the shallow second region of the first conductivity type. With this, crystal defects due to the ion implantation are isolated from the emitter-base junction of a bi-polar transistor, and thus the leakage current of the emitter-base junction can be prevented.

Ultraviolet light‐emitting diode of a cubic boron nitride pn junction made at high pressure

Abstract: Injection luminescence in the ultraviolet is observed from a cubic boron nitride pn junction diode made at high pressure. Microscopic observation and spectroscopic studies show that the light emission occurs near the junction region only in the forward‐bias condition. The spectra extend from ∼215 nm to the red, having a few peaks mainly in the ultraviolet.

Development and Microstructural Characterization of High‐Thermal‐Conductivity Aluminum Nitride Ceramics

Abstract: The effect of several additives, such as CaC2, CaO, Y2O3, and C, on thermal conductivity of hot-pressed AlN ceramics was investigated. The addition of CaC2 reductant was found to be useful for achieving high thermal conductivity of 180 W/(m·K) at room temperature. The characterization of AlN ceramics with CaC2 additive was performed by chemical analysis of Ca, C, and O and microstructural analysis using transmission electron microscopes equipped with an energy-dispersive X-ray analyzer and an electron energy loss spectrometer. The major influence on high thermal conductivity is the disappearance of a thermal barrier caused by oxygen impurities at the grain boundary.

Analysis of nonisothermal transformation kinetics; tempering of iron-carbon and iron-nitrogen martensites

Abstract: A powerful method for the analysis of solid-state transformation kinetics can be based on non-isothermal analysis where the temperature corresponding to a fixed stage of transformation is measured as a function of heating rate. Adoption of a specific kinetic model is not required for valid application of this method. This removes constraints imposed unnecessarily on so-called Kissinger-like procedures. The method was applied to study and to compare the tempering kinetics of iron-carbon martensite and iron-nitrogen martensite (about 1.1 wt pct interstitials). Dilatometry and differential scanning calorimetry were employed. This combination of experimental techniques allowed distinction between preprecipitation processes as segregation and clustering of interstitials. In contrast with iron-carbon martensite, no indications were obtained for clustering of interstitials in iron-nitrogen martensite. The preprecipitation stages have activation energies of 75 to 85 kJ/mole, which are ascribed to volume diffusion of interstitials. The precipitation of the transition carbide/ nitride (first stage of tempering) occurs with an activation energy of 110 to 125 kJ/mole, which is ascribed to pipe diffusion of iron. The precipitation of the equilibrium carbide/nitride (third stage of tempering) is associated with an activation energy of 195 to 205 kJ/mole which is ascribed to combined pipe and volume diffusion of iron.

Silicon nitride in electronics

Abstract: Introduction. 1. General Description of the Processes of Deposition of Silicon Nitride Films from a Gas Phase. Thermodynamic analysis of the silicon nitride CVD processes. Kinetic model of the deposition processes from a gas phase. References. 2. Methods of Synthesis. Direct nitridation of silicon. Deposition from the silane-containing gas phase. Deposition from the gas phase containing silicon tetrahalogens and silane halides. Synthesis of oxynitride silicon films. Synthesis of films by the methods of plasm- and photochemistry. References. 3. Modelling of Low-Pressure CVD Processes. General characteristics of the LPCVD. Thermal conditions of low-pressure reactors. Film thickness uniformity problem. Two groups of processes. Model of the processes with a limiting heterogeneous stage. Model of the processes with a limiting homogeneous stage. Summary. References. 4. Structure and Chemical Composition of Silicon Nitride. Structure of silicon nitride and oxynitride films. Chemical composition of silicon nitride. Chemical bond in silicon nitride. References. 5. Physical-Chemical Transformations in Silicon Nitride Films. Crystallization of silicon nitride and oxynitride films. Variation of the chemical composition of silicon nitride films under thermal treatment in different gaseous ambiences. Diffusion of impurities in silicon nitride films. Dissolution of silicon nitride films. References. 6. Electronic Structure and Optical Properties of Silicon Nitride. Silicon nitride structure of variable composition according to data of electron and vibrational spectroscopy. Electronic structure of a-Si 3 N 4 . Electronic structure of a-SiN x O y and SiN x . Optical properties of silicon nitride. Energy diagram of the MNS structure. Optical properties of a-SiN x O y and energy diagram of the Si-SiN x O y -Al structures. Red shift of the absorption edge in SiN x and irradiated Si 3 N 4 . Models of deep centres in a-Si 3 N 4 . References. 7. Electrophysical Properties. General description of electronic processes in amorphous silicon nitride. Polarization of silicon nitride layers. Depolarization of silicon nitride layers. Silicon nitride conduction. Recombination and diffusion of charge carriers in silicon nitride. Complex conductivity and noises of silicon nitride. Degradation of electrophysical properties of silicon nitride. Properties of nonstoichiometric silicon nitride. References. 8. Application of Silicon Nitride Films in Microelectronics. LOCOS process. Silicon nitride as a mask in diffusion. Silicon nitride films in electrically programmed read only memory (EPROM). Use of silicon nitride films for stabilization of MIS transistors. Ion-selective MNOS-transistors as indicators of pH of solutions and hydrogen impurities in gases. Films of silicon nitride and oxynitride as elements of the constructions of integrated optics. Optical MD on MNOS-structures. Increase of the radiative stability of MIS devices.

Titanium nitride film in contact hole with large aspect ratio

Abstract: A semiconductor device includes a titanium nitride film as a barrier which is formed in a hole. The width or diameter of the hole is smaller than 1 μm, and the aspect ratio thereof is larger than 0.7. The sidewall of the hole is substantially perpendicular to the surface of a semiconductor substrate. By the low pressure CVD method with a cold wall type CVD apparatus, it becomes possible to form the titanium nitride film having excellent characteristics with a good step coverage in a considerably fine hole having a large aspect ratio.

Passivation coating for flexible substrate mirrors

Abstract: A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity The silicon nitride layer can be deposited on the substrate before metal deposition thereon to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors Also, the silver or other reflective metal layer on mirrors comprising thin, lightweight, flexible substrates of metal or polymer sheets coated with glassy layers can be protected with silicon nitride according to this invention

A superconducting thin film and a method for preparing the same

Abstract: An outer surface of a superconducting thin film of compound oxide such as YBa2Cu3O7-.delta. is protected with a protective layer which is composed of any one of (i) oxide of metal such as SiO2 and TiO2, (ii) carbide such as SiC, (iii) nitride such as BN or (iv) the same material as the substrate such as SrTiO3.

Frequency effects and properties of plasma deposited fluorinated silicon nitride

Abstract: The properties of low‐hydrogen, fluorinated plasma‐enhanced chemical vapor deposition (PECVD) silicon nitride films grown using NF3/SiH4/N2 feed mixtures in 200 kHz and 14 MHz discharges were compared. High‐energy ion bombardment at 200 kHz is expected to enhance surface diffusion and chemical reconstruction. Compared to fluorinated silicon nitride deposited at 14 MHz under otherwise comparable conditions, the 200 kHz films had a lower Si–H bond concentration (≲1×1021 cm−3), lower total hydrogen content (5–8×1021 cm−3), better resistance to oxidation, lower compressive stress (−0.7 to −1.5 Gdyne/cm), and higher density (3.1 g/cm3). The dielectric constant of better low‐frequency Class I films was constant to 500 MHz, while that of high‐frequency films fell up to 15% between 100 Hz and 10 MHz. The absorption edges of low‐frequency PECVD fluorinated silicon nitride films were between 5.0 and 6.1 eV, which compare with 4.4 to 5.6 eV for the high‐excitation frequency fluorinated material and 3 to 4 eV for con...

Effect of Boron Nitride Coating on Fiber-Matrix Interactions

Abstract: Coatings can modify fiber-matrix reactions and, hence, interfacial bond strengths. Commercial mullite, SiC, and carbon fibers or fabrics were coated, with boron nitride via low-pressure chemical vapor deposition, and incorporated into a mullite matrix by hot-pressing. The influence of fiber-matrix interactions for uncoated and BN-coated fibers on fracture morphologies was studied. These observations were related to the measured values of interfacial shear strengths.

Nature of the dominant deep trap in amorphous silicon nitride.

Abstract: We observe a strong correlation between changes in the density of paramagnetic silicon-``dangling-bond'' centers and changes in the space-charge density in amorphous silicon nitride films subjected alternately to positive and negative charge injection and optical illumination. Our results provide, for the first time, direct experimental evidence associating a specific point defect with the trapping phenomena in amorphous silicon nitride. We also demonstrate both directly and for the first time the amphoteric nature of the silicon nitride silicon-dangling-bond center.

Passivation of GaAs FET's with PECVD silicon nitride films of different stress states

Abstract: The passivation of GaAs MESFETs with plasma-enhanced chemical-vapor-deposited (PECVD) silicon nitride films of both compressive and tensile stress is reported. Elastic stresses included in GaAs following nitride passivation can produce piezoelectric charge density, which results in a shift of MESFET characteristics. The shift of MESFET parameters due to passivation was found to be dependent on gate orientation. The experiments show that nitride of tensile stress is preferable for MESFETS with (011-bar) oriented gates. The shifts in V/sub TH/,I/sub DSS/, and G/sub M/ of the devices before and after nitride passivation are less than 5% if the nitride of appropriate stress states are used for passivation. The breakdown voltage of the MESFETs after nitride deposition was also studied. It is found that the process with higher hydrogen incorporation tends to reduce the surface oxide and increase the breakdown voltage after nitride deposition. In addition, the passivation of double-channel HEMTs is reported for the first time. >

Selective oxidation and chemical state of Al and Ti in (Ti, Al)n coatings

Abstract: (Ti, Al)N hard coatings are a promising alternative to TiN owing to an improved resistance to oxidation. In order to study the oxidation process in more detail, (Ti, Al)N coatings reactively sputter-deposited on high speed steel substrates from a target composed of Ti:Al = 50:50 (at%) were annealed in air and in vacuum at temperatures between 500 and 800 °C. Auger electron spectroscopy (AES) sputter depth profiling as well as X-ray photoelectron spectroscopy (XPS) studies indicate a high stability of the Ti-N bond, whereas Al has considerable mobility in the mixed nitride. The chemical shift of the Al 2p XPS and LVV AES peaks allow a distinction between oxide, nitride and metallic states of Al. Preferential sputterin during depth profiling with 3 keV Ar+ ions resulted in a relative depletion of Al in the surface layer. It is concluded, that the Al in (Ti, Al)N is only weakly bonded to nitrogen as compared to Ti.

Selective Carbide Oxidation and Internal Nitridation of the Ni-Base Superalloys IN 738 LC and IN 939 in Air

Abstract: Ni-base superalloys contain beside other phases relatively large blocky MC carbides of the type (Ta, Nb, Ti, W)C, which oxidize much faster than the γ/γ′ matrix. The large volume increase during oxidation and the oxide formation at the carbide-oxide interface shift the corrosion products outward. High shear stresses between the Cr2O3 scale and the carbide oxidation products lead to scale cracking favoring internal corrosion processes in this area. The formation of Al2O3 in the subscale is accompanied by a volume increase and tensile stresses in the outer Cr2O3 scale. This causes scale cracking and gives nitrogen a chance to enter the metal and form the most stable nitride, TiN beneath the Al2O3 subscale.

Conduction and charge trapping in polysilicon-silicon nitride-oxide-silicon structures under positive gate bias

Abstract: Carrier conduction and trapping in silicon-nitride-oxide-silicon SNOS structures has been studied under positive gate bias using current-field (I vs. E) characteristics and flat-band voltage shift-fluence ( Delta V/sub FB/ vs. F) for structures with a thick bottom oxide (>100 AA). Under these conditions evidence is found of electrons tunneling from the Si through the bottom oxide, and holes injected from the gate moving through the nitride with recombination occurring in the nitride layer. Trapping of both electrons and holes is significant and the saturation value of the flat-band voltage shift is shown to depend parabolically on the thickness of the nitride layer. A simple two-carrier conduction model is proposed to explain the observed conduction and trapping characteristics. It is also shown that holes are the dominant conduction carriers in polysilicon-silicon nitride-silicon (SNS) structures under both positive and negative gate-bias conditions. >

Ammonolysis Products of the Dialkylamides of Titanium, Zirconium, and Niobium as Precursors to Metal Nitrides

Abstract: The dialkylamides of titanium(IV), zirconium(IV), and niobium(V) react with liquid ammonia to produce solid products of high metal content. Infrared spectroscopy and elemental analysis indicate that these ammonolysis products are nitridoor imido-bridged polymers. Based on metal content, pyrolysis at <800°C converts these materials quantitatively to the corresponding nitride or carbonitride. The only products trapped following vacuum pyrolysis are ammonia and dialkylamine. Temperature-programmed pyrolysis with analysis of the evolved gases by mass spectroscopy shows that the composition of the gaseous products depends on whether helium or hydrogen is used as the carrier gas. The presence of a hydrogen atmosphere compared to a helium environment or a dynamic vacuum results in a lower carbon content of the titanium and niobium products. A general reaction scheme for conversion of the precursor compounds to refractory materials is formulated from the results of the various pyrolytic experiments.

Method of forming a salicided self-aligned metal oxide semiconductor device using a disposable silicon nitride spacer

Abstract: A method of fabricating a SALICIDED self aligned metal oxide semiconductor device using a disposable silicon nitride spacer, metal silicide and a single implant step for the source, drain and gate regions is disclosed. The fabrication of the device is accomplished in seven major steps: First, on a substrate having an oxide layer, an undoped polysilicon layer defining the gate region is deposited. Second, an oxide layer is grown and then a silicon nitride layer is deposited. Third, the oxide and the silicon nitride layers are selectively etched, leaving the oxide and the nitride layers on the walls of the polysilicon gate region. Fourth, a cobalt layer is deposited on the wafer and processed to form cobalt silicide, after which the cobalt that did not come in contact with the silicon or the polysilicon gate region is removed. Fifth, the nitride layer on the walls of the gate region is removed. Sixth, a single ion implant step is used to form the N-channel Transistors of the device. Seventh, a single ion implant step is used to form the P-channel transistor of the device.

Etch back detection

Abstract: An improved method for the etch-back planarization of interlevel dielectric layers provides for cessation of the etch-back upon exposure of an indicator layer. the indicator layer, usually a metal, metal nitride, or silicon nitride is formed either within the dielectric or over an underlying metallization layer prior to patterning by conventional photolithographic techniques. A sacrificial layer, typically an organic photoresist, is then formed over the dielectric layer. Because of the presence of both relatively narrow and relatively broad features in the metallization, the thickness of the sacrificial layer will vary over features having different widths. As etch back planarization proceeds, the indicator layer which is first encountered releases detectable species into the planarization reactor. Detection of these species indicates that removal of the overlying dielectric layers to a predetermined depth is achieved. By placing the detectable layer over only those regions which are expected to be exposed last, the method can be utilized to indicate the end point of etch back planarization of the interlevel dielectric.

Film stress‐related vacancy supersaturation in silicon under low‐pressure chemical vapor deposited silicon nitride films

Abstract: The effect of stress in silicon nitride films, deposited by the low‐pressure chemical vapor deposition process, on the point defect concentrations in silicon has been studied. The stress level in the nitride film is varied by controlling the ratio of flow rates of reactant gases R=fSiH2Cl2/fNH3, from 1/6 to 6. The stress in the nitride film is tensile and its magnitude increases with decreasing R. During anneals at 1100 °C in Ar with a high stress in the nitride, phosphorus diffusion in silicon is retarded, antimony diffusion is enhanced, and extrinsic stacking faults shrink faster than with a low stress. These results suggest that a vacancy supersaturation and a self‐interstitial undersaturation exist under the nitride and that the deviation from the equilibrium point defect concentrations are closely related to the stress level in the silicon nitride film. From the phosphorus junction profiles with varying shape width, an effective vacancy diffusivity of 3×10−10 cm2/s has been obtained.

Deposition and characterization of ternary nitrides

Abstract: Hard coatings of titanium nitride, titanium carbide, and aluminum oxide are the materials most widely used for improved performance and productivity on high‐speed steel and cemented carbide tools. However, very little effort has been focused on the deposition of ternary nitrides. This paper presents the deposition and characterization of ternary nitrides of (Ti, Zr) and (Ti, Al) using cathodic arc plasma deposition process. The films were analyzed in terms of surface topography, composition, and mechanical properties. These coatings were also evaluated for wear applications and decorative properties. The results are also compared with TiN and (Ti–6Al–4V)N films obtained by the same process.

Refractory electrical device

Abstract: The present invention is an electrical device made up of a mixture of silicon carbide and molybdenum disilicide, and may include silicon nitride or aluminum nitride or boron nitride. An electrical device is also disclosed which is particularly suited for use as an igniter in liquid and gas fuel burning systems. The device is made up of a sintered, preferably hot-pressed, mixture of fine powders of aluminum nitride or silicon nitride, silicon carbide and molybdenum disilicide where, when all three are present, they are present in substantial quantities.

Thin film single crystal substrate

Abstract: A thin film single crystal substrate useful in the production of a semiconductor, comprising a base substrate made of single crystal diamond and at least one thin film of a single crystal of a material selected from the group consisting of silicon carbide, silicon, boron nitride, gallium nitride, indium nitride, aluminum nitride, boron phosphide, cadmium selenide, germanium, gallium arsenide, gallium phosphide, indium phosphide, gallium antimonide, indium arsenide, indium antimonide, aluminum phosphide, aluminum arsenide, aluminum antimonide, cadmium telluride, mercury sulfide, zinc oxide, zinc sulfide, zinc selenide and zinc telluride, and optionally an intermediate layer between the base substrate and the thin film of single crystal, which optionally comprises an intermediate layer between the base substrate and the thin film of single crystal.

Method of making a high performance MOS device having both P- and N-LDD regions using single photoresist mask

Abstract: A method for making an integrated circuit structure having both PMOS and NMOS devices with lightly doped (LDD) source and drain regions is disclosed utilizing a single photoresist mask in which a substrate is implanted with a low concentration dopant of a first conductivity type through a silicon nitride shielding layer. Spacers are then formed against the sidewalls of oxide and nitride coated polysilicon gate electrodes by RIE etching of a polysilicon layer formed over the nitride shielding layer subsequent to the first implantation. A separate photoresist mask layer is then formed over a portion of the structure and the remaining exposed portions of the shielding nitride layer are then etched, resulting in the formation of first el-shaped shielding members against the sides of the gate electrodes. The exposed polysilicon spacers are then removed and the substrate is implanted with a high concentration dopant of a second conductivity type at an energy level insufficient to penetrate through the el-shaped nitride spacer to form conventional source/drain regions in the substrate.