https://iopscience.iop.org/article/10.35848/1882-0786/abc787/pdf

Defect engineering in SiC technology for high-voltage power devices

The effects of nitridation on the density of traps at SiO2/SiC interfaces near the conduction band edge were qualitatively examined using a simple, newly developed characterization method that utilizes Hall effect measurements and split capacitance–voltage measurements. The results showed a significant reduction in the density of interface traps near the conduction band edge as a result of nitridation, but the interface traps were not completely eliminated by nitridation.

Characterization of Traps at Nitrided SiO 2 / SiC Interfaces near the Conduction Band Edge by using Hall Effect Measurements

Ultrahigh-temperature rapid thermal oxidation of 4H-SiC(0001) surfaces in dry O2 ambient was performed at temperatures up to 1700 °C. The temperature dependence of the reaction-limited linear growth rate of a thermal SiO2 layer revealed that not active but passive oxidation is dominant even at 1600 °C, and its activation energy was estimated to be 2.9 eV. We also found that high-temperature oxidation is beneficial in improving SiO2/SiC interface properties, but unintentional oxidation during the cooling down process causes interface degradation. By effectively suppressing the oxide growth during the cooling process, the lowest interface state density was obtained for the oxide formed at 1450 °C.

Ultrahigh-temperature rapid thermal oxidation of 4H-SiC(0001) surfaces and oxidation temperature dependence of SiO2/SiC interface properties

We report systematic first-principles calculations that reveal the atomic configurations, stability, and energy levels of carbon defects in SiC (0001)/SiO2 systems. We clarify the stable position (i.e., in SiC, SiO2, or at SiC/SiO2 interfaces) of defects depending on the oxidation environment (an oxygen-rich or -poor condition). At finite temperatures, the chemical potential of atomic species was corrected referring to thermochemical tables in order to obtain the temperature-dependent defect formation energies. Under an oxygen-rich condition, we found that the dicarbon antisite [(C2)Si] in SiC is one of the favorable defects at a typical oxidation temperature of 1600 K and it creates a localized level near the conduction band edge of SiC, being a critical defect for n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs). A variety of carbon-dimer defects at a SiC/SiO2 interface, such as Si—CO—CO2, Si—CO—CO—Si, and Si—(CO)—CO2, are stable under the oxygen-rich condition at 1600 K, and they create localized levels relatively close to the valence band edge of SiC, thus being critical defects for p-channel MOSFETs. In the viewpoint of static energetics, our results suggest that the oxidation of SiC under a high-temperature oxygen-poor condition is effective in suppressing the generation of carbon defects.

Structure and energetics of carbon defects in SiC (0001)/SiO2 systems at realistic temperatures: Defects in SiC, SiO2, and at their interface

https://iopscience.iop.org/article/10.35848/1882-0786/ababed/pdf

Design and formation of SiC (0001)/SiO2 interfaces via Si deposition followed by low-temperature oxidation and high-temperature nitridation

Surface morphology and electrical properties of silicon dioxide (SiO 2 ) on 4H-SiC substrates formed by metal-enhanced oxidation (MEO) using barium (Ba) atoms were systematically investigated. It was found that severe surface roughening caused by Ba-MEO can be suppressed by using SiO 2 capping prior to MEO. The Ba atoms at the SiO 2 /SiC interface were found to diffuse to the oxide surface through the deposited SiO 2 capping layer, and then the Ba density reduced to ∼1014 cm−2 before stable MEO. The resulting SiO 2 /SiC interface showed the reduced interface state density but the insulating property of the oxides was significantly degraded.

Structure and surface morphology of thermal SiO 2 grown on 4H-SiC by metal-enhanced oxidation using barium

An n-channel metal–oxide–semiconductor field-effect transistor (MOSFET) with high field-effect mobility (μFE) on 4H-SiC (0001) was fabricated using an ultrahigh-temperature gate-oxidation technique, and its improved channel mobility was demonstrated by employing a low-oxygen partial-pressure cooling procedure. The ideal flatband voltage for n-MOS and p-MOS capacitors and hysteresis-free drain current–gate voltage (I d–V g) characteristics were obtained through gate oxidation at 1450 °C in 100% O2 ambient at 1 atm followed by the low-oxygen partial-pressure (1%) rapid-cooling procedure. From the I d–V g characteristics, a μFE of 15.8 cm2 V−1 s−1 was obtained under the pure O2 gate-oxidation process.

https://iopscience.iop.org/article/10.7567/JJAP.57.120304/pdf

Yoshihito Katsu

Papers

Structure and surface morphology of thermal SiO 2 grown on 4H-SiC by metal-enhanced oxidation using barium

Improved channel mobility of 4H-SiC n-MOSFETs by ultrahigh-temperature gate oxidation with low-oxygen partial-pressure cooling