Showing papers on "Silicon carbide published in 1996"

Status of silicon carbide (SiC) as a wide-bandgap semiconductor for high-temperature applications: A review

Abstract: Silicon carbide (SiC), a material long known with potential for high-temperature, high-power, high-frequency, and radiation hardened applications, has emerged as the most mature of the wide-bandgap (2.0 eV ≲ Eg ≲ 7.0 eV) semiconductors since the release of commercial 6HSiC bulk substrates in 1991 and 4HSiC substrates in 1994. Following a brief introduction to SiC material properties, the status of SiC in terms of bulk crystal growth, unit device fabrication processes, device performance, circuits and sensors is discussed. Emphasis is placed upon demonstrated high-temperature applications, such as power transistors and rectifiers, turbine engine combustion monitoring, temperature sensors, analog and digital circuitry, flame detectors, and accelerometers. While individual device performances have been impressive (e.g. 4HSiC MESFETs with fmax of 42 GHz and over 2.8 W mm−1 power density; 4HSiC static induction transistors with 225 W power output at 600 MHz, 47% power added efficiency (PAE), and 200 V forward blocking voltage), material defects in SiC, in particular micropipe defects, remain the primary impediment to wide-spread application in commercial markets. Micropipe defect densities have been reduced from near the 1000 cm−2 order of magnitude in 1992 to 3.5 cm−2 at the research level in 1995.

Carbide, nitride and boride materials synthesis and processing

Abstract: Part 1 Introduction: overview safety issues. Non-oxide materials - properties and applications engineering: introduction advanced ceramics - origin, current status, trends: origins of advanced ceramics recent status monolithic ceramics ceramics composites manufacturing applications engineering: the market wear components ceramic armour high temperature applications electrically conductive ceramics corrosion resistant applications automotive applications electronic substrates special applications. Critical powder characteristics: introduction Tungsten carbide: effects of Tungsten/carbon stoichiometry hard metal composition silicon carbide: effect of oxygen sintering developments effect of impurities effect of particle size and method of synthesis silicon nitride: sintering developments effect of particle size effect of impurities effect of synthesis method aluminum nitride: sintering developments effect of oxygen effect of impurities effect of synthesis method summary references. Part 2 Carbothermal reduction synthesis processes: overall process safety issues. Thermochemistry and kinetics: introduction thermochemistry kinetics importance of the gas phase synthesis of carbide and nitride powders references. Acheson process: introduction, history basic silicon carbide process description manufacturing cost factors summary references. Electric arc process: introduction boron carbide manufacturing other non-oxide ceramics references. Tube/pusher/moving bed furnace processes: introduction fundamental physio-chemical considerations system design considerations process scale-up considerations safety considerations conclusions acknowledges nomenclature references. Rotary tube reactor processes: introduction rotary furnace design configurations process considerations operating difficulties applications to non-oxide powder synthesis references. Fluidized bed reactor processes: background application to carbothermal reduction processes references. Part 3 Combustion synthesis processes: overall process safety issues. Thermochemistry and kinetics: principles of combustion synthesis thermodynamics and thermochemistry combustion front structure and stability analysis gasless combustion gas solid combustion synthesis of complex composites and solid solutions nomenclature references. Processes: introduction solid-solid reactions gas-solid reactions summary nomenclature references. Part 4 Gas phase synthesis processes: overall process safety issues references. (Part contents).

Silicon carbide high-power devices

Abstract: In recent years, silicon carbide has received increased attention because of its potential for high-power devices. The unique material properties of SiC, high electric breakdown field, high saturated electron drift velocity, and high thermal conductivity are what give this material its tremendous potential in the power device arena. 4H-SiC Schottky barrier diodes (1400 V) with forward current densities over 700 A/cm/sup 2/ at 2 V have been demonstrated. Packaged SITs have produced 57 W of output power at 500 MHz, SiC UMOSFETs (1200 V) are projected to have 15 times the current density of Si IGBTs (1200 V). Submicron gate length 4H-SiC MESFETs have achieved f/sub max/=32 GHz, f/sub T/=14.0 GHz, and power density=2.8 W/mm @ 1.8 GHz. The performances of a wide variety of SiC devices are compared to that of similar Si and GaAs devices and to theoretically expected results.

Lattice parameters of gallium nitride

Abstract: Lattice parameters of gallium nitride were measured using high‐resolution x‐ray diffraction. The following samples were examined: (i) single crystals grown at pressure of about 15 kbar, (ii) homoepitaxial layers, (iii) heteroepitaxial layers (wurtzite structure) on silicon carbide, on sapphire, and on gallium arsenide, (iv) cubic gallium nitride layers on gallium arsenide. The differences between the samples are discussed in terms of their concentrations of free electrons and structural defects.

Silicon carbide: Synthesis and processing

Abstract: Silicon carbide with its outstanding physical properties is a material of choice for special optoelectronic and electronic devices working under extreme conditions. Synthesis as well as processing are complicated compared to other materials. The present paper summarizes some aspects of crystal growth and processing and discusses arising problems.

Multi-layer susceptor for rapid thermal process reactors

Abstract: A multi layer RTP reactor susceptor includes a first layer which has a multiplicity of thin components that are preferably silicon carbide, graphite, or silicon carbide coated graphite with a thickness less than about 6 mm, with an emissivity such that the first layer radiates heat, and with thermal heat transfer characteristics such that the first layer facilitates maintaining a substrate or substrates supported by the susceptor at a uniform temperature, and facilitates maintaining uniform process gas characteristics over the substrates. A second layer of the susceptor is transparent to the heat source of the RTP reactor and provides a rigid, stable platform for the first layer.

Silicon carbide on insulator formation using the Smart Cut process

Abstract: The Smart Cut process has been applied for the first time to SiC, in order to form silicon carbide on insulator (SiCOI) structures. These structures have been formed on polycristalline SiC and on silicon substrates.

Determination of the active-to-passive transition in the oxidation of silicon carbide in standard and microwave-excited air

Abstract: The active-to-passive transition is determined on sintered silicon carbide for two atmospheres: standard air and air excited by microwaves, as a function of oxygen partial pressure and temperature. The experiments were done at low total pressure ranging from 103 to 25 × 103 Pa and at high temperature from 1385 to 1765 °C at a constant air flow rate. The results are compared with literature data and we try to explain why they are so many differences between all the experimental and theoretical results.

High temperature chemical vapor deposition of SiC

Abstract: A growth process has been investigated for the epitaxial growth of silicon carbide. The technique can simply be described as chemical vapor deposition (CVD) at high temperatures, hence the name high temperature CVD (HTCVD). The growth process however, differs greatly from that of the CVD process due to the significant sublimation and etch rates at the extreme growth temperatures (1800–2300°C). The grown rates obtained with the HTCVD are in the order of several tens of μm/h to 0.5 mm/h. The purity and crystallinity of the growth layers are outstanding showing strong free exciton related photoluminescence.

Process for reducing defects in oxide layers on silicon carbide

Abstract: A method is disclosed for obtaining improved oxide layers and resulting improved performance from oxide based devices. The method comprises exposing an oxide layer on a silicon carbide layer to an oxidizing source gas at a temperature below the temperature at which SiC would begin to oxidize at a significant rate, while high enough to enable the oxidizing source gas to diffuse into the oxide layer, and while avoiding any substantial additional oxidation of the silicon carbide, and for a time sufficient to densify the oxide layer and improve the interface between the oxide layer and the silicon carbide layer.

Elimination of SiC/SiO2 interface states by preoxidation ultraviolet‐ozone cleaning

Abstract: The preoxidation cleaning of silicon carbide surfaces (3C, 4H, 6H polytypes) by exposing them to ultraviolet radiation and oxygen is shown to produce a significant improvement in the electronic properties of SiC/SiO2 interfaces. It is found that this treatment results in a removal of defect species, otherwise present at the SiC surface after thermal oxidation of SiC. Carbon clusters are proposed as the attacked species responsible for a substantial part of the SiC/SiO2 interface states.

Particle/Matrix Interface and Its Role in Creep Inhibition in Alumina/Silicon Carbide Nanocomposites

Abstract: This study focuses on interfacial bonding between intergranular silicon carbide particles and an alumina matrix, to determine the creep inhibition mechanism of alumina/ silicon carbide nanocomposites. It is revealed that the silicon carbide/alumina interface possesses much stronger bonding than the alumina/alumina interface through three approaches: investigation of fracture toughness and fracture mode and consideration of internal thermal stresses acting at grain boundaries, estimation of equilibrium thickness of intergranular glassy films by force balance, and direct observation of grain boundaries by TEM. The rigid bonding of alumina/silicon carbide interfaces causes inhibition of vacancy nucleation and annihilation at the interfaces, causing remarkably improved creep resistance of the nanocomposite.

Silicon carbide metal diffusion barrier layer

Abstract: Disclosed is the use of silicon carbide as a barrier layer to prevent the diffusion of metal atoms between adjacent conductors separated by a dielectric material. This advancement allows for the use of low resistivity metals and low dielectric constant dielectric layers in integrated circuits and wiring boards.

Liquid phase sintering of silicon carbide

Abstract: It is shown that the decomposition reactions during the sintering of liquid phase silicon carbide (SiC) can be described well by thermodynamics. This allows for an optimization of the sintering parameters. The use of carbon as a sintering additive, together with, for instance, yttria plus alumina, is of advantage. When C is used, SiO 2 will not occur in the liquid phase during sintering or in the amorphous and crystalline phases after sintering. The microstructure of sintered samples is described.

Type II Supernova Matter in a Silicon Carbide Grain from the Murchison Meteorite

Abstract: The circumstellar silicon carbide (SiC) grain X57 from the Murchison meteorite contains large amounts of radiogenic calcium-44 (20 times its solar system abundance) and has an anomalous silicon isotopic composition, different from other circumstellar SiC grains. Its inferred initial 44 Ti/Si and 44 Ti/ 48 Ti ratios are 1.6 × 10 −4 and 0.37. In addition, it contains radiogenic magnesium-26; the inferred initial 26 Al/ 27 Al ratio is 0.11. The isotopic and elemental data of X57 can be explained by selective mixing of matter from different zones of a typical type II supernova of 25 solar masses during its explosion. The high 44 Ti/Si ratio requires contributions from the innermost nickel zone of the supernova to the SiC condensation site, as similarly suggested by astronomical observations.

Fabrication of silicon carbide nanoceramics

Abstract: Ultrafine silicon carbide powder with an average particle size of 90 nm was densified by hot-processing with the addition of Al2O3, Y2O3, and CaO at 1750 °C. Silicon carbide nanoceramics with an average grain size of 110 nm were prepared by liquid phase sintering at low temperature. The materials showed superplastic deformation at a strain rate of 5.0 × 10-4/s at 1700 °C, which is the lowest temperature published. The microstructure and deformation behavior of materials from a submicrometer powder were also investigated as a reference.

Semiconductor ultraviolet detectors

Abstract: This paper presents an overview of semiconductor ultraviolet (UV) detectors that are currently available and associated technologies that are undergoing further development. At the beginning, the classification of UV detectors and general requirements imposed on these detectors are presented. Further consideration are restricted to modern semiconductor UV detectors, so the current state-of-the-art of different types of semiconductor UV detectors is presented. Hitherto, the semiconductor UV detectors have been mainly fabricated using Si. Industries such as the aerospace, automotive, petroleum, and others have continuously provided the impetus pushing the development of fringe technologies which are tolerant of increasingly high temperatures and hostile environments. As a result, the main effort are currently directed to a new generation of UV detectors fabricated from wide-band-gap semiconductors between them the most promising are diamond and AlGaN. The latest progress in development of AlGaN UV detectors is finally described in detail.

Effects of silicon carbide nano-phase on the wet erosive wear of polycrystalline alumina

Abstract: Wet erosive wear rates for alumina-silicon carbide nanocomposites have been measured and compared with those for pure polycrystalline aluminas of similar grain size. In pure materials for mean grain sizes >2 μm the dominant wear mechanism appears to be grain-boundary microfracture, leading to grain pullout; for finer grain sizes the worn surfaces are smooth. Within both grain size ranges significant reductions in wear rate are found for the nanocomposite materials, thus extending the span of established benefits obtained through the incorporation of silicon carbide nanoparticles into ceramic materials.

Method of forming silicon carbide trench mosfet with a schottky electrode

Abstract: A silicon carbide trench MOSFET is provided that includes a first conductivity type semiconductor substrate made of silicon carbide A first conductivity type drift layer and a second conductivity type base layer, both made of silicon carbide, are sequentially formed by epitaxial growth on the semiconductor substrate The first conductivity type drift layer has a lower impurity concentration than the semiconductor substrate A first conductivity type source region is formed in a part of a surface layer of the second conductivity type base layer A gate electrode is received through an insulating film, in a first trench extending from a surface of the first conductivity type source region to reach the first conductivity type drift layer A Schottky electrode disposed on an inner surface of a second trench having a greater depth than the first trench

Dielectric function and reflectivity of 3C–silicon carbide and the component perpendicular to the c axis of 6H–silicon carbide in the energy region 1.5–9.5 eV

Abstract: The optical properties of commercially available 3C‐ and 6H‐SiC single crystals were studied in the energy region 1.5–9.5 eV with conventional and synchrotron‐radiation spectroscopic ellipsometry. The surface perfection of the materials was investigated by transmission electron and atomic force microscopies. The calculated values for the effective and static dielectric functions were higher than those found in the literature. This is consistent with the fine structure and absolute values of the corresponding reflectance spectra, which were higher than those reported in other studies. The dispersion of the refractive indices in the energy region below and above the indirect gap is determined and can be used as reference and for the design and analysis of semiconductor structures and devices.

Silicon carbide composite article particularly useful for plasma reactors

Abstract: A composite silicon carbide article and its method of making in which a surface layer or film of silicon carbide is deposited, for example by chemical vapor deposition (CVD), over a free standing silicon carbide substrate, as is formed by bulk methods such as sintering and hot pressing. The article is advantageously used in a plasma reactor, especially an oxide etcher for semiconductor fabrication, and may be any of several parts including the chamber wall, chamber roof, or collar around the wafer. The bulk SiC provides an inexpensive and strong support structure of perhaps a complex shape while the CVD SiC film has advantages for plasma processing and may be tailored to particular uses. The composite SiC structure is particularly useful in that the electrical conductivities of the bulk SiC and film SiC may be separately controlled so as to provide, among many possibilities, a grounding plane, a window for RF electromagnetic radiation, or both. The ultra-high purity achieved in CVD silicon carbide also benefits the control of micro-contamination inside the reactor chamber, a key factor for increased device yield.

Tribological Performance of Diamond and Diamondlike Carbon Films at Elevated Temperatures

Abstract: In this study, the authors investigated the tribological performance of diamond and diamondlike carbon (DLC) films as a function of temperature. Both films were deposited on silicon carbide (SiC) by microwave plasma chemical vapor deposition and ion-beam deposition processes. Tribological tests were performed on a reciprocating wear machine in open air (20 to 30% relative humidity) and under a 10 N load using SiC pins. For the test conditions explored, the steady-state friction coefficients of test pairs without a diamond or DLC film were 0.7 to 0.9 and the average wear rates of pins were 10−5 to 10−7 mm3/N·m, depending on ambient temperature. DLC films reduced the steady-slate friction coefficients of the test pairs by factors of three to five and the wear rates of pins by two to three orders of magnitude. Low friction coefficients were also obtained with the diamond films, but wear rates of the counterface pins were high due to the very abrasive nature of these films. The wear of SiC disks coated with e...

Silicon carbide MOSFET technology

Abstract: The research and development activities carried out to demonstrate the status of MOS planar technology for the manufacture of high temperature SiC ICs will be described. These activities resulted in the design, fabrication and demonstration of the world's first SiC analog IC—a monolithic MOSFET operational amplifier. Research tasks required for the development of a planar SiC MOSFET IC technology included: characterization of the SiCSiO2 interface using thermally grown oxides; high temperature (350°C) reliability studies of thermally grown oxides; ion implantation studies of donor (N) and acceptor (B) dopants to form junction diodes; epitaxial layer characterization; device isolation methods; and finally integrated circuit design, fabrication and testing of the world's first monolithic SiC operational amplifier IC. High temperature circuit drift instabilities at 350°C were characterized. These studies defined an SiC depletion model MOSFET IC technology and outlined tasks required to improve all types of SiC devices.

Silicon carbide CMOS devices

Abstract: A monollithic CMOS integrated device formed in silicon carbide and method of fabricating same. The CMOS integrated device includes a layer of silicon carbide of a first conductivity type with a well region of a second conductivity type formed in the layer of silicon carbide. A MOS field effect transistor is formed in the well region and a complementary MOS field effect transistor is formed in the silicon carbide layer. The method of fabrication of CMOS silicon carbide includes formation of an opposite conductivity well region in a silicon carbide layer by ion implantation. Source and drain contacts are also formed by selective ion implantation in the silicon carbide layer and the well region. A gate dielectric layer is formed by deposition and reoxidation. A gate electrode is formed on the gate dielectric such that a channel region is formed between the source and the drain when a bias is applied to the gate electrode. Source drain and body contacts are preferably formed of the same material in a single fabrication step.