Silicon Carbide Power Devices Research Articles

Characterization of Polyimide Dielectric Layer for the Passivation of High Electric Field and High Temperature Silicon Carbide Power Devices

Silicon carbide (SiC) is a wide bandgap semiconductor suitable for high-voltage, highpower and high-temperature applications [1]. However, and among other issues, the production of advanced SiC power devices still remains limited due to some shortcomings of the dielectric properties of the passivation layer [2]. Due to their supposed high operating temperature and dielectric strength [3], spin coated polyimide materials appear as a possible candidates for SiC device passivation and insulation purposes. As a matter of fact, they are already used in current commercial SiC devices allowing a maximum junction temperature of 175 °C. The aim of this paper is to study the ability of polyimide (PI) coatings to be used for a Tjmax up to 300 °C. Therefore, the main electrical properties (dielectric permittivity, leakage current and breakdown field) at different temperatures of a high temperature commercially available polyimide material (from HD Microsystems) in both Metal-Insulator-Semiconductor (MIS) and Metal-Insulator-Metal (MIM) structures are presented and discussed.

MgO insulating films prepared by sol–gel route for SiC substrate

Silicon carbide (SiC) is a wide bandgap semiconductor suitable for high-voltage, high-power, and high-temperature devices from dc to microwave frequencies. However, the commercialization of advanced SiC power devices remains limited due to performance limitation of the SiO 2 dielectric among other issues. Indeed, SiO 2 has a dielectric constant 2.5 times lower than that of SiC, which means that at critical field for breakdown in SiC, the electric field in the adjoining SiO 2 becomes too high for reliable operation. This removes the main advantage of using SiC power devices if the ten times higher breakdown field for SiC in comparison to Si cannot be exploited. Therefore, alternative dielectrics having a dielectric constant higher than or of the same order as that of SiC ( ɛ r ≈ 10) should be used to reduce the electrical field in the insulator. Among alternative dielectrics to silicon dioxide (SiO 2), magnesium oxide (MgO) seems to be a good candidate regarding its bulk properties: large bandgap, high thermal conductivity and stability, and a suitable dielectric constant ( ɛ r ≈ 10). In order to evaluate such promising candidate, the sol–gel process appears to be a convenient route to elaborate this kind of coatings. By selecting appropriate precursor solution and optimizing the curing conditions of the films, MgO films could be obtained under various crystallization states: non-oriented and preferred 〈1 1 1〉 orientation. MIM structures have been used to investigate the insulating potentialities of the sol–gel MgO films. The dielectric strength of the films was found to be microstructure dependent, and reached 5–8 MV/cm at room temperature. Leakage currents were measured from 25 °C up to 250 °C.

Proposal of 98.5% High Efficiency Chopper Circuit QRAS for the Electric Vehicle and the Verification

A high-efficiency and high-power chopper based on a novel soft switching scheme QRAS (Quasi-resonant Regenerating Active Snubber) has been proposed in this paper. Operating efficiency of the proposed QRAS has been investigated by simulation and experiments. For the purposes of this study we fabricated a one-tenth prototype model and tested it under the rated load, light load, current discontinuous mode, and under operation out of the resonant stable operational region. The overall evaluation of these test results is provided and the possibility of implementation of an 80-kW practical model is demonstrated by these successful test results. In addition, as an approach to the next study, the feasibility of 8-kW SiC-QRAS is examined and a preliminary evaluation of the efficiency enhancement due to the use of silicon carbide (SiC) power devices is given based on successful experimental results. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 158(4): 68– 80, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20439

Compact models for silicon carbide power devices

Compact silicon carbide (SiC) power semiconductor device models for circuit simulation have been developed for power Schottky, merged-PiN-Schottky, PiN diodes, and MOSFETs. In these models, the static and dynamic performance of the power SiC devices requires specific attention to the low-doped, voltage blocking drift region; the channel transconductance in MOS devices; the relatively low-intrinsic carrier concentration; the incomplete ionization of dopants; and the temperature dependent material properties. The modeling techniques required to account for each of these characteristics are described.

Sol–gel MgO thin films for insulation on SiC

Silicon carbide (SiC) is a wide bandgap semiconductor suitable for high-voltage, high-power, and high-temperature devices from DC to microwave frequencies. However, the marketing of advanced SiC power devices remains limited due to performance limitation of the SiO 2 dielectric among other issues. Indeed, SiO 2 has a dielectric constant 2.5 times lower than SiC, which means that at critical field for breakdown in SiC, the electric field in the adjoining SiO 2 becomes too high for reliable operation. This suppresses the main advantage of using SiC power devices if the ten times higher breakdown field for SiC in comparison to Si cannot be exploited. Therefore, alternative dielectrics having a dielectric constant higher or in the same order as SiC ( ε r ≈ 10 ) should be used to reduce the electrical field in the insulator. Among alternative dielectrics to silicon dioxide (SiO 2), magnesium oxide (MgO) seems to be a good candidate regarding its bulk properties: large bandgap, high thermal conductivity and stability, and a suitable dielectric constant ( ε r ≈ 10 ). In order to evaluate such a promising candidate, the sol–gel process appears to be a convenient route to elaborate this kind of coatings. By selecting an appropriate precursor solution and optimizing the curing conditions of the films, MgO films could be obtained under various crystallization states: non-oriented or preferred [1 1 1] orientation. MIM structures have been used to investigate the insulating properties of the sol–gel MgO films. The dielectric strength of the films was found to be microstructure–dependent, and reached 3 to 8 MV/cm at room temperature. Leakage currents were measured from 150 up to 250 °C, with values less than 10 −5 A/cm 2 at 1 MV/cm.

Characterization of SiC Schottky diodes at different temperatures

The emergence of silicon carbide (SiC) based power semiconductor switches, with their superior features compared with silicon (Si) based switches, has resulted in substantial improvement in the performance of power electronics converter systems. These systems with SiC power devices have the qualities of being more compact, lighter, and more efficient; thus, they are ideal for high-voltage power electronics applications. In this study, commercial Si pn and SiC Schottky diodes are tested and characterized, their behavioral static and loss models are derived at different temperatures, and they are compared with respect to each other.

Silicon Carbide Power Devices and Processing

AbstractAn overview of silicon carbide (SiC) power device technology is given with an emphasis on processing issues and commercial applications. Schottky Barrier Diodes (SBDs) were the first to be made commercially available in 2001, with power switch and RF amplifiers soon to follow. This paper discusses the performance of current available rectifiers and published power switch development and identifies key issues in processing and device structures which have influenced past and will impact future SiC product development.

SiC power-switching devices-the second electronics revolution?

Silicon carbide (SiC) offers significant advantages for power-switching devices because the critical field for avalanche breakdown is about ten times higher than in silicon. SiC power devices have made remarkable progress in the past five years, demonstrating currents in excess of 100 A and blocking voltages in excess of 19000 V. In this paper we describe the latest progress in three classes of SiC devices: diodes (p-i-n and Schottky), transistors (junction field-effect transistor, metal-oxide-semiconductor field-effect transistor, and bipolar junction transistor), and thyristors (gate turn-off).

In situ boron incorporation and activation in silicon carbide using excimer laser recrystallization

In situ incorporation and activation of boron into silicon carbide is demonstrated using excimer laser recrystallization in a boron trifluoride ambient. Rutherford backscattering spectroscopy and x-ray analysis demonstrate that there is no crystalline damage during recrystallization at laser fluences below ∼1.4 J/cm2. Point-contact current–voltage measurements confirm dopant activation, and the formation of shallow (∼90 nm) pn junctions in silicon carbide. This technique may be applied to the fabrication of shallow junctions and low resistance contacts in silicon carbide power devices without ion implantation and furnace annealing.

Overview of SiC power electronics

Abstract This paper reviews the status of silicon carbide power electronics. Results on SiC high voltage rectifiers and thyristors are summarized. Current issues in silicon carbide power devices are discussed, including the small device area and high base region resistance of the devices. It is shown that micropipes are not the defects that limit SiC device area. It is some other defects which cause a premature breakdown. To overcome these problems, liquid phase epitaxial growth for high power SiC devices is proposed.

Recent progress of silicon carbide power devices

Recent progress of silicon carbide power devices

Performance limiting micropipe defects in silicon carbide wafers

Reports on the characteristics of a major defect in mass-produced silicon carbide wafers which severely limits the performance of silicon carbide power devices. Micropipe defects originating in 4H- and 6H-SiC substrates were found to cause pre-avalanche reverse-bias point failures in most epitaxially-grown pn junction devices of 1 mm/sup 2/ or larger in area. Until such defects are significantly reduced from their present density (on the order of 100's of micropipes/cm/sup 2/), silicon carbide power device ratings will be restricted to around several amps or less.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>