Showing papers on "Silicon carbide published in 2001"

Silicon-Based Materials from Rice Husks and Their Applications

Abstract: Rice husk (RH) has now become a source for a number of silicon compounds, including silicon carbide, silica, silicon nitride, silicon tetrachloride, zeolite, and pure silicon. The applications of such materials derived from rice husks are very comprehensive. The methods of synthesizing these silicon-based materials from RHs and their applications are reviewed in this paper.

Method of forming vias in silicon carbide and resulting devices and circuits

Abstract: A method of fabricating an integrated circuit on a silicon carbide substrate is disclosed that eliminates wire bonding that can otherwise cause undesired inductance. The method includes fabricating a semiconductor device on a first surface of a silicon carbide substrate and with at least one metal contact for the device on the first surface of the substrate. The opposite, second surface of the substrate is then ground and polished until it is substantially transparent. The method then includes masking the polished second surface of the silicon carbide substrate to define a predetermined location for a via that is opposite the device metal contact on the first surface; etching the desired via through the desired masked location until the etch reaches the metal contact on the first surface; and metallizing the via to provide an electrical contact from the second surface of the substrate to the metal contact and to the device on the first surface of the substrate.

Silicon Carbide: A Novel Catalyst Support for Heterogeneous Catalysis

Abstract: Progress in developing a new class of support materials based on silicon carbide (SiC)is reviewed. Silicon carbide has superior mechanical and thermal properties which, coupled to chemical inertness,avoids several of the problems inherent in the use of commercial oxide and carbon based supports and catalysts. High surface area SiC can now be prepared easily in a commercially viable shape,with good mechanical properties,and at reasonable cost.I t can be shaped directly into monolith or honeycomb forms including some catalytically active material, rendering fabrication simple and cost effective. Furthermore, it can be modified for specific catalytic applications through the addition of metals. In many respects, it combines the best properties of oxide and carbon based supports without suffering many of their disadvantages.

Conversion of silicon carbide to crystalline diamond-structured carbon at ambient pressure

Abstract: Synthetic diamond is formed commercially using high-pressure1, chemical-vapour-deposition2 and shock-wave3 processes, but these approaches have serious limitations owing to low production volumes and high costs. Recently suggested alternative methods of diamond growth include plasma activation4, high pressures5, exotic precursors6,7 or explosive mixtures8, but they suffer from very low yield and are intrinsically limited to small volumes or thin films. Here we report the synthesis of nano- and micro-crystalline diamond-structured carbon, with cubic and hexagonal structure, by extracting silicon from silicon carbide in chlorine-containing gases at ambient pressure and temperatures not exceeding 1,000 °C. The presence of hydrogen in the gas mixture leads to a stable conversion of silicon carbide to diamond-structured carbon with an average crystallite size ranging from 5 to 10 nanometres. The linear reaction kinetics allows transformation to any depth, so that the whole silicon carbide sample can be converted to carbon. Nanocrystalline coatings of diamond-structured carbon produced by this route show promising mechanical properties, with hardness values in excess of 50 GPa and Young's moduli up to 800 GPa. Our approach should be applicable to large-scale production of crystalline diamond-structured carbon.

Dual frequency plasma enhanced chemical vapor deposition of silicon carbide layers

Abstract: A method for forming a silicon carbide layer for use in integrated circuit fabrication is disclosed. The silicon carbide layer is formed by reacting a gas mixture comprising a silicon source, a carbon source, and an inert gas in the presence of an electric field. The electric field is generated using mixed frequency radio frequency (RF) power. The silicon carbide layer is compatible with integrated circuit fabrication processes. In one integrated circuit fabrication process, the silicon carbide layer is used as a hardmask for fabricating integrated circuit structures such as, for example, a damascene structure. In another integrated circuit fabrication process, the silicon carbide layer is used as an anti-reflective coating (ARC) for DUV lithography.

Silicon carbide semiconductor device and manufacturing method thereof

Abstract: In a silicon carbide semiconductor device such as a trench gate type power MOSFET, the film thickness and the impurity concentration of a thin film silicon carbide semiconductor layer formed on a trench side face to constitute an accumulation-type channel-forming region and enable the device to operate with a low gate voltage, low on-resistance and low power loss are set so that on impression of a reverse bias voltage a pn junction between a P-type epitaxial layer and an n - -type epitaxial layer undergoes avalanche breakdown before the thin film silicon carbide semiconductor layer undergoes punch-through. By this means it is possible to obtain a target high source-drain withstand voltage.

SiC power diodes provide breakthrough performance for a wide range of applications

Abstract: The electrical performance of silicon carbide (SiC) power diodes is evaluated and compared to that of commercially available silicon (Si) diodes in the voltage range from 600 V through 5000 V. The comparisons include the on-state characteristics, the reverse recovery characteristics, and power converter efficiency and electromagnetic interference (EMI). It is shown that a newly developed 1500-V SiC merged PiN Schottky (MPS) diode has significant performance advantages over Si diodes optimized for various voltages in the range of 600 V through 1500 V. It is also shown that a newly developed 5000 V SiC PiN diode has significant performance advantages over Si diodes optimized for various voltages in the range of 2000 V through 5000 V. In a test case power converter, replacing the best 600 V Si diodes available with the 1500 V SiC MPS diode results in an increase of power supply efficiency from 82% to 88% for switching at 186 kHz, and a reduction in EMI emissions.

Method of plasma etching of silicon carbide

Abstract: The invention provides a process for plasma etching silicon carbide with selectivity to an overlapping and/or underlying dielectric layer of material. The etching gas includes a hydrogen-containing fluorocarbon gas such as CH 3 F, an oxygen-containing gas such as O 2 and an optional carrier gas such as Ar. The dielectric material can comprise silicon dioxide, silicon nitride, silicon oxynitride or various low-k dielectric materials including organic low-k materials. In order to achieve a desired selectivity to such dielectric materials, the plasma etch gas chemistry is selected to achieve a desired etch rate of the silicon carbide while etching the dielectric material at a slower rate. The process can be used to selectively etch a hydrogenated silicon carbide etch stop layer or silicon carbide substrates.

Semi-insulating silicon carbide without vanadium domination

Abstract: A semi-insulating bulk single crystal of silicon carbide is disclosed that has a resistivity of at least 5000 Ω-cm at room temperature and a concentration of deep level trapping elements that is below the amounts that will affect the resistivity of the crystal, preferably below detectable levels. A method of forming the crystal is also disclosed, along with some resulting devices that take advantage of the microwave frequency capabilities of devices formed using substrates according to the invention.

Semiconductor processing equipment having improved particle performance

Abstract: A ceramic part having a surface exposed to the interior space, the surface having been shaped and plasma conditioned to reduce particles thereon by contacting the shaped surface with a high intensity plasma. The ceramic part can be made by sintering or machining a chemically deposited material. During processing of semiconductor substrates, particle contamination can be minimized by the ceramic part as a result of the plasma conditioning treatment. The ceramic part can be made of various materials such as alumina, silicon dioxide, quartz, carbon, silicon, silicon carbide, silicon nitride, boron nitride, boron carbide, aluminum nitride or titanium carbide. The ceramic part can be various parts of a vacuum processing chamber such as a liner within a sidewall of the processing chamber, a gas distribution plate supplying the process gas to the processing chamber, a baffle plate of a showerhead assembly, a wafer passage insert, a focus ring surrounding the substrate, an edge ring surrounding an electrode, a plasma screen and/or a window.

Silica films on silicon carbide: a review of electrical properties and device applications

Abstract: This paper reviews the present knowledge on silica films (SiO2) on silicon carbide (SiC). First, kinetic of thermal oxidation of SiC is described, and the effects of a great number of parameters (various SiC polytypes, substrate type, substrate orientation...) are discussed. Mainly, thermal oxides grown on SiC are close to stoichiometric silica and the oxidation rate depends on the terminal face of the SiC monocrystal. The next four sections discuss the electrical properties of the oxide, and of the oxide/SiC interface, and especially the effects of materials and technological process on the interface state density and the effective oxide charge (Section 5), and the origin of the interface states are discussed in detail (Section 6). Oxides grown on n-type SiC have electrical properties (in terms of dielectric strength, leakage currents, interface trap, and oxide charges) measured by means of metal-oxide-semiconductor (MOS) structures, similar to oxides grown on silicon. Until recently, p-type SiC MOS structures have had a large equivalent oxide charge and larger interface state densities in spite of many efforts, compared to silicon MOS structures. It seems nevertheless that recent studies have improved the SiO2/SiC interfacial quality. Aluminum, carbon and alkali species are ihs main suspected contaminants. Finally, Section 7 presents the applications of oxide films in SE-based devices: MOS capacitors and MOS field effect transistors (MOSFETs) for microelectronics, MOSFETs for power electronics, and some applications using silica layers as a passivation layer. In spite of a smaller than required carrier mobility in the inversion layer, MOS field effect transistors (MOSFETs) have been demonstrated to operate up to 650 degreesC and integrated circuits based on NMOS and PMOS technologies have been successfully operated up to 300 degreesC. Vertical power MOSFETs are also of importance but their performances are still limited by a specific on-resistance larger than device requirements. The effect of charges present in the oxide on the electrical properties of high voltage diodes is also briefly discussed.

Behavior of oxygen doped SiC thin films: An x-ray photoelectron spectroscopy study

Abstract: Thin silicon carbide films have been deposited by chemical vapor deposition on p-type (100) silicon substrates. The composition and bonds formed in these films have been analyzed by x-ray photoelectron spectroscopy (XPS) and infrared spectroscopy. The native surface oxide on the silicon carbide surface induced by air exposure has also been studied. Several phases are detected in the near-surface region: elemental Si, Si oxides (mainly SiO2), Si carbide (SiC) and Si oxicarbides (SiOxCy). Quantitative XPS analysis results indicate that, for atomic oxygen fractions <0.15, the Si–C phases are dominant in the films. Above this value no silicon oxicarbide is observed, but a multiphase material formed by elemental Si, Si oxides and Si carbides is observed. In spite of the film being a complex phase mixture, a simple relationship is found between the overall carbon and oxygen compositions. The carbon atomic fraction in the film decreases quasilinearly as the oxygen content increases, with a slope of about −1. An ...

Comparative study of high temperature composites

Abstract: Two classes of composite made using either ceramic matrix with high temperature fibers or carbon/carbon have been used for various applications that require high temperature resistance, over three decades. However, their use has been limited to special applications because of the high costs associated with fabrication. Typically the composites are cured at more than 1000°C, and in most instances the heating has also to be carried out in controlled environments. In addition, because of the high processing temperature, only certain type of expensive fibers can be used with the ceramic matrices. A recently developed inorganic matrix, called polysialate can be cured at temperatures less than 150°C, making it possible to use carbon and glass fibers. Composites made using carbon, glass and combinations of carbon and glass fibers have been tested in bending and tension. This paper presents the comparison of processing requirements and mechanical properties of carbon/carbon composites, ceramic matrix composites made with silicon carbide, silicon nitride and alumina fibers and carbon/polysialate composites. The results indicate that carbon/polysialate composite has mechanical properties comparable to both carbon/carbon and ceramic matrix composites at room and high temperatures. Since the polysialate composites are much less expensive, the authors believe that it has excellent potential for more applications in aerospace, automobile and naval structures.

High-temperature effects in the fracture mechanical behaviour of silicon carbide liquid-phase sintered with AlN–Y2O3 additives

Abstract: It has been shown that pressureless sintering of SiC to theoretical density is possible with sintering additives from the system AlN–Y2O3. While commonly a combination of oxides is used such as Al2O3–Y2O3 (–SiO2), the oxynitride additives offer the advantage that only a nitrogen atmosphere is required instead of a powder bed for thermochemical stabilisation at the sintering temperature. The thermal decomposition of AlN is suppressed quite effectively when a moderate nitrogen overpressure is applied, resulting in very small mass loss during densification which only depends on the oxygen content of the SiC starting powder. By varying the mass ratio of β-SiC to α-SiC and applying dedicated post-densification heat treatments, a platelet-strengthened microstructure is obtained which shows enhanced fracture toughness. The platelet formation is attributed to a solution / precipitation process with simultaneous phase transformation from β-SiC to α-SiC, followed by anisotropic grain growth of α-SiC. In the present work, recent progress in the mechanical properties of these materials is reported. By means of a simple surface treatment-annealing in air — it is possible to obtain four-point bending strengths in excess of 1 GPa in liquid phase sintered SiC. The strength retention at temperatures around 1200°C is significantly improved.

12-19 kV 4H-SiC pin diodes with low power loss

Abstract: 12-19 kV 4H-SiC UHV pin diodes have been developed for the first time. The developed UHV diodes have a low V/sub F/ of less than 1/4/sup th/ and short trr of less than 1/30/sup th/, as compared with those of commercialized 6 kV Si diodes. Therefore, they can drastically reduce both the conduction loss and the switching loss of electric power conversion equipment.

SiC devices for advanced power and high-temperature applications

Abstract: Silicon carbide (SiC) process technology has made rapid progress, resulting in the realization of very promising electronic devices and sensors, enabling advanced solutions in power industry and mobile systems. In particular, for electronics working under harsh environmental conditions, SiC devices reach unprecedented performance. Transfer to production has already started for some applications.

Boron carbide composite bodies, and methods for making same

Abstract: A composite body produced by a reactive infiltration process that possesses high mechanical strength, high hardness and high stiffness has applications in such diverse industries as precision equipment and ballistic armor. Specifically, the composite material features a boron carbide filler or reinforcement phase, and a silicon carbide matrix produced by the reactive infiltration of an infiltrant having a silicon component with a porous mass having a carbonaceous component. Potential deleterious reaction of the boron carbide with silicon during infiltration is suppressed by alloying or dissolving boron into the silicon prior to contact of the silicon infiltrant with the boron carbide. In a preferred embodiment of the invention related specifically to armor, good ballistic performance can be advanced by loading the porous mass or preform to be infiltrated to a high degree with one or more hard fillers such as boron carbide, and by limiting the size of the largest particles making up the mass. The instant reaction-bonded silicon carbide (RBSC) composite bodies surpass previous RBSC's as armor materials, and in this capacity approach the ballistic performance of current carbide armor ceramics but with potentially lower cost manufacturing methods, e.g., infiltration techniques.

Silicon carbide power metal-oxide semiconductor field effect transistors having a shorting channel and methods of fabricating silicon carbide metal-oxide semiconductor field effect transistors having a shorting channel

Abstract: Silicon carbide metal-oxide semiconductor field effect transistors (MOSFETs) and methods of fabricating silicon carbide MOSFETs are provided. The silicon carbide MOSFETs have an n-type silicon carbide drift layer, spaced apart p-type silicon carbide regions in the n-type silicon carbide drift layer and having n-type silicon carbide regions therein, and a nitrided oxide layer. The MOSFETs also have n-type shorting channels extending from respective ones of the n-type silicon carbide regions through the p-type silicon carbide regions to the n-type silicon carbide drift layer. In further embodiments, silicon carbide MOSFETs and methods of fabricating silicon carbide MOSFETs are provided that include a region that is configured to self-deplete the source region, between the n-type silicon carbide regions and the drift layer, adjacent the oxide layer, upon application of a zero gate bias.

Silicon carbide CMOS channel

Abstract: A method for fabricating a semiconducting device on a substrate, where the improvement includes forming a strained silicon carbide channel layer on the substrate. A silicon layer is formed on top of the strained silicon carbide channel layer. A gate insulation layer is formed on top of the silicon layer and strained silicon carbide channel layer, at a temperature that does not exceed about eight hundred centigrade. A gate electrode is formed on top of the gate insulation layer, and the gate electrode is patterned. A low dose drain dopant is impregnated into the substrate, and activated with a first laser anneal. A source drain dopant is impregnated into the substrate, and activated with a second laser anneal. After the step of activating the low dose drain dopant with the first laser anneal, an insulating layer is formed around the gate electrode, at a temperature that does not exceed about eight hundred centigrade, and a spacer is formed around the gate electrode. The spacer is formed of a material that is reflective to the second laser anneal. Thus, standard materials for the spacer, such as silicon oxide or silicon nitride are not preferred for this application, because they tend to be transparent to the laser beam emissions.

Interface reactions between silicon carbide and metals (Ni, Cr, Pd, Zr)

Abstract: The interface reactions between silicon carbide (SiC) and metals Cr, Zr, Ni and Pd have been studied in the temperature range of 700–1300°C by employing bulk diffusion couples. The reaction products have been identified by SEM/EDX and EPMA. It has been observed that interface reactions between SiC/Cr and SiC/Zr show layered structures and interface reactions between that of SiC/Ni and SiC/Pd show periodic bands in the reaction zone. The observed diffusion paths are related to the respective ternary isothermal phase diagrams. Based on the ternary solid state equilibria and diffusion paths, interpretations pertaining to the nature of reaction products and reaction morphology are discussed.

Carbon coatings produced by high temperature chlorination of silicon carbide ceramics

Abstract: Carbon coatings are widely used to modify surfaces of materials and improve their tribological properties. In this work, carbon layers were formed on various types of sintered and CVD silicon carbide (SiC) using a novel technique involving a reaction with chlorine and chlorine-hydrogen gas mixtures at 1000 °C. Following the work done on powders and fibers, this method successfully produced adherent coatings on SiC ceramics, which could be grown to thickness above 200 µm. Highly disordered carbon with contributions from nanocrystalline graphite was identified by Raman spectroscopy, x-ray diffraction, and energy dispersive spectroscopy. The kinetics of the chlorination reaction at 1000 °C for different gas mixtures fit to a linear reaction rate equation. Coatings produced in pure Cl2 are graphitic and demonstrate a low hardness (1.8 GPa), Young’s modulus (18 GPa), low wear rate, and a friction coefficient of ∼0.1, which is almost constant for any testing conditions in dry or humid air. Coatings produced in Cl2/H2 mixtures have microhardness up to 50 GPa and Young’s modulus up to 800 GPa. Although the presence of hydrogen had little effect on the Raman spectrum of the carbon layers, its presence changed the structure and permeability of the carbon film.

Effects of silicon carbide (SiC) power devices on HEV PWM inverter losses

Abstract: The emergence of silicon carbide (SiC) based power semiconductor switches with their superior features compared with silicon (Si) based switches has resulted in substantial improvements in the performance of power electronics converter systems. These systems with SiC power devices are more compact, lighter, and more efficient, so they are ideal for high-voltage power electronics applications, including hybrid electric vehicle (HEV) traction drives. In this paper, the effect of SiC-based power devices on HEV traction drive losses are investigated. Reductions in heat sink size and device losses with the increase in the efficiency will be analyzed using an averaging model of a three-phase PWM inverter (TPPWMI). For more accurate results, device physics is taken into consideration to find the loss equations for the controllable switches.

Design rules for field plate edge termination in SiC Schottky diodes

Abstract: Practical design of silicon carbide (SiC) Schottky diodes incorporating a field plate necessitates an understanding of how the addition of the field plate affects the performance parameters and the relationship between the diode structure and diode performance. In this paper, design rules are presented for SiC Schottky diodes that incorporate field plate edge termination. The use of an appropriate field plate edge termination can improve the reverse breakdown voltage of a SiC Schottky diode by a factor of two. Reverse breakdown voltage values can be obtained that are up to 88% of the theoretical maximums.

Method for manufacturing silicon carbide semiconductor device

Abstract: A manufacturing method of a silicon carbide semiconductor device includes the steps of: preparing a semiconductor substrate including a silicon carbide substrate, a drift layer and a first semiconductor layer; forming a plurality of first trenches in a cell portion; forming a gate layer on an inner wall of each first trench by an epitaxial growth method; forming a first insulation film on the surface of the semiconductor substrate; forming a gate electrode on the first insulation film for connecting to the gate layer electrically; forming a source electrode on the first insulation film for connecting to the first semiconductor layer in the cell portion; and forming a drain electrode connected to the silicon carbide substrate electrically.

Low temperature formation of backside ohmic contacts for vertical devices

Abstract: A method for forming an ohmic contact to silicon carbide for a semiconductor device comprises implanting impurity atoms into a surface of a silicon carbide substrate thereby forming a layer on the silicon carbide substrate having an increased concentration of impurity atoms, annealing the implanted silicon carbide substrate, and depositing a layer of metal on the implanted surface of the silicon carbide. The metal forms an ohmic contact “as deposited” on the silicon carbide substrate without the need for a post-deposition anneal step.

SiC Based Field Effect Gas Sensors for Industrial Applications

Abstract: The development and field-testing of high-temperature sensors based on silicon carbide devices have shown promising results in several application areas. Silicon carbide based field-effect sensors can be operated over a large temperature range, 100-600 °C, and since silicon carbide is a chemically very inert material these sensors can be used in environments like exhaust gases and flue gases from boilers. The sensors respond to reducing gases like hydrogen, hydrocarbons and carbon monoxide. The use of different temperatures, different catalytic metals and different structures of the gate metal gives selectivity to different gases and arrays of sensors can be used to identify and monitor several components in gas mixtures. MOSFET sensors based on SiC combine the advantage of simple circuitry with a thicker insulator, which increases the long term stability of the devices. In this paper we describe silicon carbide MOSFET sensors and their performance and give examples of industrial applications such as monitoring of car exhausts and flue gases. Chemometric methods have been used for the evaluation of the data.