The Role Played in the Improvement of the SiO2/SiC Interface by a Thin SiO2 Film Thermally Grown Prior to Oxide Film Deposition

Abstract

To minimize electrical degradation from thermal oxidation of 4H-SiC, a thin and stoichiometric SiO 2 film was thermally grown, monitored by X-ray photoelectron spectroscopy. To obtain thicker films, SiO 2 was deposited by sputtering. Reduction in the flatband voltage was observed when compared to SiO 2 films thermally grown or deposited directly on 4H-SiC. Post-deposition annealing in Ar reduced the flatband voltage of the samples but induced an electrical degradation in the SiO 2 /4H-SiC interface. Nuclear reaction analyzes proved that the thin film thermally grown was not stable during the annealing, exchanging O atoms with the deposited film and with the gaseous ambient.

SiO2/SiC structures annealed in D218O: Compositional and electrical effects

“…At 600 C and 800 C, the SiO 2 film formed only by thermal oxidation presented slightly larger amounts of D incorporated due to annealing temperatures in water vapor, even though been thinner. These results are also in good agreement with the electrical properties observed for structures with dielectric films obtained by similar routes: 19 thermal oxidation in O 2 of SiC for a longer oxidation time induces higher negative effective charge in the SiO 2 /SiC interfacial region compared with the thermal growth of a thin SiO 2 film followed by the deposition by sputtering of additional SiO 2 film.…”

“…The sample with the smaller shift from the ideal curve is the one with a thin SiO 2 film thermally grown prior to the oxide film deposition, fact related to a reduced electrical degradation. 19 After the water vapor annealing, a significant reduction on the shift from the ideal curve can be observed for all samples, indicating reduction of the negative effective charge. One possible explanation for the origin of negative fixed charge in SiO 2 /SiC interfacial region is the presence of the O-lone pair state.…”

“…13,14 In order to improve the quality of the SiO 2 /SiC interface, different post-oxidation treatments have been employed, 3,15,16 as well as alternative routes to form SiO 2 films on SiC, aiming at minimizing the electrical degradation from thermal oxidation. [17][18][19] Concerning thermal oxidation conditions, it was observed that oxidations and/or reoxidations involving water vapor can lead to a higher dielectric strength, 20 lower values of D it , [20][21][22][23] and higher channel mobility 24 as compared to dry oxidations. For the Si-case, wet oxidation leads to a lower oxide breakdown voltage as compared to the dry one.…”

“…SiO 2 films were formed either by thermal oxidation, sputtering deposition, or by a short oxidation time prior to the oxide deposition. Since it was observed that these different routes lead to different electrical properties, 19 a relation between the electrical properties and water vapor interaction can be unrevealed. Oxygen profile and areal density of hydrogen, incorporated from water vapor during annealing, were obtained by nuclear reaction techniques.…”

Influence of thermal growth parameters on the SiO2/4H-SiC interfacial region

“…34,35 Thus, the electrical degradation seems to be controlled by the p × t parameter, i.e., an oxidation parameter that accelerates the SiO 2 film growth should lead to a larger electrical degradation. Therefore, alternative ways to obtain SiO 2 films on SiC such as thermal growing of a very thin and stoichiometric SiO 2 film in a minimal oxidation condition followed by the SiO 2 film deposition, 36 or the oxidation of a Si/SiC heterojunction produced by a layer-transfer process, 37 or even the direct deposition of the SiO 2 film on the SiC substrate, reducing the influence of the substrate in the thermal oxide formation 38 should be investigated in order to minimize the formation of electrical active defects in the SiO 2 /SiC structure.…”