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 SiO2 dielectric among other issues. Indeed, SiO2 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 SiO2 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 (ɛr ≈ 10) should be used to reduce the electrical field in the insulator. Among alternative dielectrics to silicon dioxide (SiO2), 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 (ɛr ≈ 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.

Microscopic cavities are known to be efficient gettering sites for metallic impurities in silicon. In the present study, they were formed in [111] silicon by 40 keV room temperature He+ implantation at doses of 5x10(16) and 10(17)/cm(2), followed by a heat treatment in an N-2 atmosphere using either rapid thermal annealing or conventional furnace annealing. Helium desorption and cavity evolution were studied by non-Rutherford elastic scattering of protons and Rutherford backscattering/channeling analysis. Cavities and residual defects were observed by transmission electron microscopy (TEM), The retained fraction of helium was shown to depend on the manner of annealing and was found to decrease with annealing time much more slowly than the first order gas release model. TEM observations show that {311} defects and dislocations are also present close to the cavities. Channeling analysis shows that {311} defects dissolve during the first minutes of annealing at 800 degrees C. It is assumed that the self-interstitials released from these defects are able to fill the smallest cavities, thus causing a rapid increase of the mean cavity radius. This variation, introduced in the desorption law, leads to reasonable agreement with the experimental results. For longer annealing time the total cavity surface decreases slowly with annealing duration. (C) 1999 Elsevier Science B.V. All rights reserved.