Showing papers on "Nitride published in 1992"

A new bulge test technique for the determination of Young's modulus and Poisson's ratio of thin films

Abstract: A new analysis of the deflection of square and rectangular membranes of varying aspect ratio under the influence of a uniform pressure is presented. The influence of residual stresses on the deflection of membranes is examined. Expressions have been developed that allow one to measure residual stresses and Young's moduli. By testing both square and rectangular membranes of the same film, it is possible to determine Poisson's ratio of the film. Using standard micromachining techniques, free-standing films of LPCVD silicon nitride were fabricated and tested as a model system. The deflection of the silicon nitride films as a function of film aspect ratio is very well predicted by the new analysis. Young's modulus of the silicon nitride films is 222 ± 3 GPa and Poisson's ratio is 0.28 ± 0.05. The residual stress varies between 120 and 150 MPa. Young's modulus and hardness of the films were also measured by means of nanoindentation, yielding values of 216 ± 10 GPa and 21.0 ± 0.9 GPa, respectively.

Phase control of cubic boron nitride thin films

Abstract: Ion beam assisted evaporation was used to deposit cubic and hexagonal boron nitride thin films. Boron was evaporated and bombardment was by argon and nitrogen ions. The effect of preparation conditions on the resulting phase was studied, and the relationship between the phase and the energy and momentum transferred into the film through ion bombardment was examined. It is shown that for a given temperature, the controlling factor in the resulting thin film phase is the momentum transferred into the film per depositing boron atom. At 300–400 °C a sharp threshold value of momentum‐per‐atom exists below which films are hexagonal and above which they are cubic. For 400 °C this threshold occurred at 200 (eV×amu)1/2 which is equal to 3.3×10−21 m kg s−1. Depositions performed using krypton and xenon instead of argon as the second bombarding gas confirmed this momentum‐per‐atom value. A second threshold was also observed, which was bombarding species dependent, above which either complete resputtering of the deposited material or reversion to the hexagonal phase occurred. Cubic boron nitride deposition was seen to occur in a window of momentum‐per‐atom values between these two thresholds. Using this information it was possible to grow cubic boron nitride using only nitrogen bombardment, although the window of momentum‐per‐atom values for nitrogen is very narrow. The effect of substrate temperature was studied, and it was found to be difficult to grow predominantly cubic phase films below 300–400 °C. The relationship between intrinsic stress and phase of the films is also discussed. A diagram is presented showing film phase as a function of bombardment, substrate temperature, and system chemistry. The parameter of momentum‐per‐atom is shown to combine into a single value the variables of ion beam assisted deposition: deposition rate, ion energy, ion flux, and ion species. It is suggested that, in general, for properties affected by ion bombardment the momentum‐per‐atom transferred into the film is the controlling factor. The results are shown to support momentum transfer as the dominant process in cubic boron nitride thin film formation.

Elastic constants of single‐crystal transition‐metal nitride films measured by line‐focus acoustic microscopy

Abstract: The elastic constants of single‐crystal NbN, VN, and TiN films were determined from surface acoustic wave (SAW) dispersion curves obtained by the use of an acoustic microscope with a line‐focus beam. Measurements were carried out for single‐crystal nitride films grown on the (001) plane of single‐crystal cubic‐symmetric MgO substrates. The phase velocities measured as functions of the angle of propagation display the expected anisotropy. Dispersion curves of SAWs propagating along the symmetry axes were obtained by measuring the wave velocities for various film thicknesses and frequencies. Using a modified simplex method, an inversion of the SAW dispersion data yielded the elastic constants of cubic symmetry, namely c11, c12, and c44. The Rayleigh surface wave velocities calculated from the determined elastic constants and known mass densities agree well with a result measured by Brillouin scattering spectroscopy reported elsewhere.

Crystal growth method for gallium nitride-based compound semiconductor

Abstract: Crystals of a gallium nitride-based compound semiconductor are grown on the surface of a buffer layer represented by formula Ga X Al 1-X N (0<×≦1). The crystallinity of the gallium nitride-based compound semiconductor grown on the surface of the buffer layer can be drastically improved.

Prospects for device implementation of wide band gap semiconductors

Abstract: Diamond, silicon carbide, gallium nitride, aluminum nitride, and boron nitride are currently under development for both electronic and optoelectronic semiconductor devices. Predictions based on their physical properties indicate that devices made from these materials should be far superior to currently available devices in high power, high frequency, and short wavelength applications. Yet actual device implementation requires that adequate materials processing technology exists. In this review, the current state of the art for producing semiconductor devices from these materials is evaluated, and recommendations for areas needing further research are outlined.

Paramagnetic point defects in amorphous silicon dioxide and amorphous silicon nitride thin films

Abstract: In this paper the authors review paramagnetic point defects in amorphous silicon nitride thin films. We will discuss two intrinsic paramagnetic defects: a trivalent silicon center, named the K-center, and the recently observed nitrogen dangling-bond center. We examine the structural identification, and the electronic properties of the K-center, as well as consider why a SiN{sub x}:H is generally a very effective charge trapping dielectric. In addition, this paper compares and contrasts special features of the structure and electronic role of the paramagnetic point defects in both silicon dioxide and silicon nitride thin films; this may provide insight for further studies on the physics and chemistry of these dangling-bond centers in both materials.

Fabrication and Secondary‐Phase Crystallization of Rare‐Earth Disilicate–Silicon Nitride Ceramics

Abstract: The fabrication and intergranular-phase devitrification of silicon nitride densified with rare-earth (RE) oxide additives has been investigated. The additions of the oxides of Sm, Gd, Dy, Er, and Yb, having high melting points and behaving similarly to Y2O3, were compositionally controlled to tailor a microstructure with a crystalline secondary phase of RE2Si2O7. The lanthanide oxides were found to be as effective as Y2O3 in densifying Si3N4, resulting in identical microstructures and densities of 98–99% of theoretical density. The crystallization behavior of all six disilicates was similar, characterized by a limited nucleation and rapid growth mechanism resulting in large single crystals. Complete crystallization of the intergranular phase was obtained with the exception of a thin residual amorphous film which was observed at interfaces and believed to be rich in impurities, the cause of incomplete devitrification.

Nitride based semiconductor device and manufacture thereof

Abstract: A nitride based semiconductor device, wherein provided are a substrate (23), a first layer comprising an oriented polycrystalline nitride based semiconductor (24, 29, 32, 35, 39, 45, 46, 49) which is formed directly on the substrate (23) and has a thickness less than 5000 angstrom, operation layers (25, 26, 30, 31, 33, 34, 36, 37, 38, 40, 41, 42, 47, 48) made of single crystal nitride based semiconductors and formed directly on the first layer, and electrodes (27, 28, 43, 44) connected with predetermined places and at least one electrode (28, 44) of the electrodes (27, 28, 43, 44) are in connection with the first layer. The semiconductor device is manufactured by a crystal growth equipment by a molecular beam epitaxy method, wherein provided are a gas source (7) which feeds a compound containing nitrogen in the form of a gas, solid sources (2, 3, 4) which feed group III elements, and sources (5, 6) which feed n-type and p-type dopants. The first layer is created on the substrate (9) at a growth speed of 0.1-20 angstroms/sec by feeding the gas-like compound containing nitrogen and the group III elements onto the surface of the substrate (9) under the pressure less than 10⁻⁵ Torr and at a temperature of the substrate (9) of 300-1000 °C. The operation layer is created on the first layer at a growth speed of 0.1-10 angstroms/sec by feeding the gas-like compound containing nitrogen and the group III elements onto the surface of the first layer under the pressure less than 10⁻⁵ Torr and at the temperature of the substrate of 300-1000 °C.

Strength and Creep Behavior of Rare‐Earth Disilicate–Silicon Nitride Ceramics

Abstract: The flexural strength and creep behavior of RE2Si2O7–Si3N4 materials were examined. The retention in room-temperature strengths displayed by these ceramics at 1300°C was 80–91%, with no evidence of inelastic deformation preceding failure. The steady-state creep rates, at 1400°C in flexural mode, displayed by the most refractory materials are among the lowest reported for sintered Si3N4. The creep behavior was found to be strongly dependent on residual amorphous phase viscosity as well as on the oxidation behavior of these materials. All of the rare-earth oxide sintered materials, with the exception of Sm2Si2O7–Si3N4, had lower creep strains than the Y2Si2O7–Si3N4 material.

Preparation of c-Axis Oriented AlN Thin Films by Low-Temperature Reactive Sputtering

Abstract: C-axis oriented aluminum nitride (AlN) thin films on (110) silicon were prepared by reactive RF magnetron sputtering in argon and nitrogen atmosphere without substrate heating. We investigated the dependence of some properties for the AlN thin film on sputtering conditions, especially N2 concentration. It was found that c-axis orientation tended to improve gradually with decreasing N2 concentration. The full width of half the maximum intensity (FWHM) of the rocking curve for a (002) plane of hexagonal AlN was 1~2 degrees at a 10% N2 concentration. This was a suitable value for surface acoustic wave (SAW) device. IDT/AlN/(110)Si structure SAW resonators were fabricated. It was confirmed that the insertion loss was 14 dB and phase velocity was 4800 m/s, respectively.

Method for the formation of tin barrier layer with preferential (111) crystallographic orientation

Abstract: A process is described for forming, over a silicon surface, a titanium nitride barrier layer having a surface of (111) crystallographic orientation. The process comprises: depositing a first titanium layer over a silicon surface; sputtering a titanium nitride layer over the titanium layer; depositing a second titanium layer over the sputtered titanium nitride layer; and then annealing the structure in the presence of a nitrogen-bearing gas, and in the absence of an oxygen-bearing gas, to form the desired titanium nitride having a surface of (111) crystallographic orientation and a sufficient thickness to provide protection of the underlying silicon against spiking of the aluminum. When an aluminum layer is subsequently formed over the (111) oriented titanium nitride surface, the aluminum will then assume the same (111) crystallographic orientation, resulting in an aluminum layer having enhanced resistance to electromigration.

Selectivity for etching an oxide over a nitride

Abstract: A method of etching an oxide over a nitride with high selectivity comprising plasma etching the oxide with a carbon and fluorine-containing etchant gas in the presence of a scavenger for fluorine, thereby forming a carbon-rich polymer which passivates the nitride. This polymer is inert to the plasma etch gases and thus provides high selectivity to the etch process.

The Hessian biased force field for silicon nitride ceramics: Predictions of thermodynamic and mechanical properties for α‐ and β‐Si3N4

Abstract: A force field (MSXX) for molecular dynamics simulations of silicon nitride is derived using the Hessian biased technique from ab initio calculations on N(SiH3)3 and Si(NH2)4 clusters. This is used to model the nitrogen and silicon centers of the α and β forms of crystalline Si3N4 for prediction of crystal structures, lattice expansion parameters, elastic constants, phonon states, and thermodynamic properties. Experimental measurements on many of these important physical constants are lacking, so that these calculations provide the first reliable data on such fundamental properties of silicon nitride. This MSXX force field is expected to be useful for molecular dynamics simulations of dislocations and grain boundaries and for studying the reconstruction and energetics of clean, reduced, and oxidized surfaces.

LiMoN2: The First Metallic Layered Nitride

Abstract: : We report the first example of a layered ternary lithium nitride in which the lithium can be deintercalated and reintercalated. This ternary nitride, LiMoN2, has been synthesized by the reaction of two different precursors, Li2Mo(NtBu)4 and Li2MoO4, with ammonia gas. The structure was refined using a combination of X-ray and neutron powder diffraction data in the space group R3 and the lattice parameters are (A) a=2.8672(3) and c=15.813(3) which were obtained from the neutron data. The ideal structure consists of MoN2 layers with Mo in trigonal prismatic holes and Li in octahedral holes between the MoN2 layers. The diffraction studies indicate the presence of cation anti-site defects; the structure is best described as Solid State Nitrides Li batteries Crystal Structure Magnetic and Electrical Properties (Li0.84Mo0.16) oct(Mo0.84Li0.16)tpN2. LiMoN2 is metallic and Pauliparamagnetic with Xo = 0.59 x 10(6) emu g-1. We have employed a variety of different oxidizing agents for the deintercalation of the lithium from LiMoN2 and have been able to deintercalate up to 64% of the lithium. This deintercalated species can be reintercalated with n-butyllithium (in hexane) at room temperature. Electrochemical studies show a large hysteresis in charge-discharge cycles.

Ti/TiN/Ti contact metallization

Abstract: The present invention concerns a method for contact metallization on a semiconductor where a contact hole is formed in an interlevel dielectric layer down to a doped silicon region on the silicon substrate, and then the wafer is placed into a sputtering chamber where titanium is sputtered onto the wafer. A titanium nitride layer is sputtered on top of the titanium layer in the contact hole. This invention saves time and money, because the titanium nitride layer depositing and titanium layer forming steps can occur in the same chamber without forming the boro-phosphorous silicate glass layer in between. The titanium layer reacts with the silicon to form a silicide layer at the time of the sputtering in a hot deposition or in later steps that supply heat to the wafer for a period of time. Optionally, an additional titanium layer can be formed on top of the titanium nitride layer to clean off the titanium target used to sputter the titanium and titanium nitride layers on the wafer. A metal layer including aluminum is then formed on top of the titanium layer or the titanium nitride layer to form the contact metallization with the doped silicon region in the semiconductor.

R‐Curve Behavior and Strength for In‐Situ Reinforced Silicon Nitrides with Different Microstructures

Abstract: R-curves for two in-situ reinforced silicon nitrides A and B of nominally the same composition are characterized using the Griffith equation and indentation fracture mechanics. These R-curves are calibrated against fine-grained silicon nitrides which have a known chevron-notch (long-crack) toughness and with a nearly flat R-curve behavior. Silicon nitride A, with its coarser microstructure and higher chevron-notch toughness, shows lower resitance to crack growth than silicon nitride B if the crack size is less than ∼200 μm. These results are consistent with the indentation–Strength measurements which show a crossover of strength between the two materials at an indentation load between 49 and 98 N, and below the crossover A has a lower strength. The toughening behavior is explained using an elastic-bridging model for the short crack, and a pullout model for the long crack. The effects of R-curve properties on design are discussed.

Synthesis of Advanced Ceramics in the Systems Si-B-N and Si-B-N-C Employing Novel Precursor Compounds

Abstract: The reaction of Cl3Si-NH-Si(CH3)3 with BCl3 yields the novel compounds Cl3Si-NH-BCl2 and (Cl3SiNH)2-BCl. The ammonolysis of these monomeric precursors in liquid ammonia gives rise to highly crosslinked borosilicon imides. Pyrolysis of the polymeric imides in a stream of ammonia at 1250°C yields amorphous borosilicon nitrides with formal compositions of Si3B3N7 and Si6B3Nu respectively. MAS-NMR, DTA/TG, SEM and TEM investigations reveal that the resulting materials are single phase. p]The reaction of the novel precursors with primary amines yields meltable and soluble polymers suitable for producing fibers or coatings. Subsequent pyrolysis in NH3 leads also to amorphous borosilicon nitride. The physical and chemical properties of the new materials will be discussed.

Exaggerated Texture and Grain Growth in a Supperplastic SiAlON

Abstract: This paper reports on a fine-grained superplastic [beta]-silicon nitride solid solution (SiAlON) which was found to develop elongated grains and a pronounced texture during tensile deformation at 1550[degrees] C. The texture development is well-described by a geometrical model of grain rotation in accordance with the strain field. Once aligned, grains can then grow with little constraint due to impingement and often coalesce into each other. With the above microstructural development, the stress-strain curve displayed unusually strong strain hardening characteristics due to a fiber-reinforcement effect of the aligned silicon nitride grains on the glass-containing matrix. By extending the rheological model of Chen and Yoon and considering these microstructural evolutions, the authors are able to simulate the deformation behavior.

High performance induction plasma torch with a water-cooled ceramic confinement tube

Abstract: A high performance induction plasma torch (1) comprises a cylindrical torch body (2) made of cast ceramic or composite polymer, a coaxial cylindrical plasma confinement tube (9) located inside the torch body (2), a gas distributor head (11) secured to one end of the torch body (2) to supply the confinement tube (9) with gaseous substances, a cylindrical and coaxial induction coil (3) completely embedded in the ceramic or polymer material of the torch body (2), and a thin annular chamber (25) separating the coaxial torch body (2) and confinement tube (9). This confinement tube can be made of pure or composite ceramic materials based on sintered or reaction bonded silicon nitride, boron nitride, aluminum nitride or alumina, or any combinations of them with varying additives and fillers. The annular chamber (25) is about 1 mm thick and high velocity cooling water flows therein to efficiently cool the plasma confinement tube (9).

Crack healing behavior of hot pressed silicon nitride due to oxidation

Abstract: It is shown that limited oxidation of an MgO-containing, hot-pressed silicon nitride ceramic at 800 deg C and above results in increased strength due to crack healing. Slight oxidation of the surface produces enstatite and cristobalite which fills in cracks. More extensive oxidation leads to strength degradation due to the formation of new flaws by the evolution of N2 gas at the surface. The apparent fracture toughness also increased at 800 deg C and above due to oxidation. Bonds formed between the two surfaces of the crack during oxidation leads to a reduction in stress intensity at the crack tip, suggesting that valid high-temperature toughness values cannot be obtained in an air environment. The increase in strength due to crack healing by oxidation can be achieved without compromising the fatigue properties of the silicon nitride ceramic.

Synthesis of polycrystalline cubic boron nitride

Abstract: A sintered polycrystalline compact of cubic boron nitride is made by forming a mixture of about 45 to 65 percent by weight cubic boron nitride (cBN), from about 30 to 45 percent by weight hexagonal boron nitride (hBN), and from about 2 to 7 percent by weight an aluminum containing material, preferably aluminum nitride, and cobalt aluminide having a melting temperature lower than the melting temperature of cobalt phase. The mixture of cBN crystals, hBN and adjuvant materials is compacted into preforms and subjected to heat treatment in a non-oxidizing atmosphere. The preforms are placed onto a cemented tungsten carbide substrate containing cobalt and subjected to elevated pressure and temperature conditions at which the boron nitride is thermodynamically stable. The elevated pressure and temperature conditions are maintained for a time sufficient to permit the infiltration of a cobalt phase into the cBN matrix and sinter the compact. Typically, the cobalt phase is infiltrated from a tungsten carbide substrate cemented with cobalt phase. The compact is characterized by substantial intercrystalline cBN to cBN bonding, and has superior abrasive wear resistance, chemical resistance, impact resistance, thermal conductivity and stability. Further, the technique produces a sintered cBN compact that can be machined more efficiently by EDM.

Manufacture of semiconductor device

Abstract: PURPOSE:To facilitate selection and control within a range, in which ions are not implanted, by equalizing the width of a sidewall film and the film thickness of a coated film when a stepped section is generated in the coated film deposited by the stepped section of a gate electrode section, the coated film is etched in an anisotropic manner and the sidewall film is formed. CONSTITUTION:Boron ions are implanted using a gate electrode 5 as a mask, and a P region 13 is formed in a polycrystalline silicon film 3 and an oxide film 10 of specified thickness is deposited. An oxide film pattern 11 is formed at a place, where the estimated maximum misalignment (a) is taken into consideration, and the oxide film pattern 11 is etched in an anisotropic manner while employing a nitride film 9 as a stopper from the state, thus shaping a sidewall film 12. The nitride film 9 is removed through etching, boron ions are implanted for forming source-drain diffusion layers in a P diffusion layer region, thus forming a P diffusion layer. The quantity of the offset of a TFT can be formed at a constant value regardless of the misalignment of a photoresist and the accuracy of finishing, thus allowing the inhibition of the variation of characteristics, thus stable performance characteristics are achieved.

Internal stress compensation and scaling in ultrasensitive silicon pressure sensors

Abstract: The pressure sensitivity of boron-doped silicon membranes has been characterized as a function of diaphragm dimensions and internal membrane stress. Using an electrostatic technique based on silicon microbridges, the internal stress for p/sup ++/ silicon (on glass), LPCVD silicon dioxide, and LPCVD silicon nitride was measured; typical values are 40, -300, and 950 MPa, respectively. Silicon membranes with several different edge lengths and deposited oxide and/or nitride coatings were characterized for sensitivity. While the pressure sensitivity can be reduced by more than a factor of twenty in the membranes due to boron-induced internal stress, the use of stress-compensating dielectrics can improve this sensitivity by a factor of six or more. Based on this theory and the measured material parameters, scaled experimental devices show typical sensitivities within 10-20% of the theoretical design targets. Pressure sensitivities as high as 2900 ppm/Pa have been achieved. >

Laser‐induced interaction of ammonia with GaAs(100). I. Dissociation and nitridation

Abstract: UV laser irradiation of ammonia adsorbed on GaAs(100) leads to molecular desorption and dissociation. A nitride passivation layer can be formed on the GaAs surface at 100 K by simultaneous exposure to ammonia and uv photons in a UHV environment. The nitride layer consists of a mixture of Ga and As nitrides. While the dominating GaN surface species is thermally stable, AsN desorbs below 800 K. Surface NH2 is identified as an intermediate. The implication of this study for selective area passivation and GaN growth is discussed.

First-principles total-energy calculation of gallium nitride.

Abstract: A first-principles total-energy calculation is performed on gallium nitride (GaN). The equilibrium lattice parameters, the bulk modulus, and the cohesive energy of GaN in the wurtzite structure is calculated and compared with experimental values. In our calculation, the ground state of GaN is a zinc-blende structure, and the difference between these two phases is around 1.4 mRy.