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

We evaluated the effect of NO annealing on hole trapping characteristic of SiC metal-oxide-semiconductor (MOS) capacitor by measuring flatband voltage (VFB) shifts during a constant negative gate voltage stress under UV illumination. Under low stress voltages, the VFB shift due to hole trapping was found to be suppressed by NO annealing. However, the VFB shift of the NO-annealed device increases significantly with stress time under high stress voltage conditions, while the device without NO annealing showed only a slight shift. This result implies that NO annealing enhances generation of hole traps, leading to the degradation of SiC-MOS devices in long-term reliability.

Impact of NO Annealing on Flatband Voltage Instability due to Charge Trapping in SiС MOS Devices

https://iopscience.iop.org/article/10.7567/APEX.11.091301/pdf

Passive–active oxidation boundary for thermal oxidation of 4H-SiC(0001) surface in O2/Ar gas mixture and its impact on SiO2/SiC interface quality

Metal-enhanced oxidation (MEO) using ultrathin Ba layers on 4H-SiC surfaces was investigated by physical and electrical characterizations. We found that while comparable oxidation rates were enhanced for Si- and C-face surfaces even at a low temperature, significant surface and interface roughness were induced by initial MEO termed the incubation period. Depth profiling revealed that although most Ba atoms aggregated on the oxide surface, a tiny amount (~1014 cm−2) remaining at the oxide interface was responsible for the following stable MEO reaction and the reduced interface state density with the drawbacks of degraded leakage current and breakdown characteristics of SiC-MOS devices.

https://iopscience.iop.org/article/10.7567/JJAP.55.120303/pdf

Insight into metal-enhanced oxidation using barium on 4H-SiC surfaces

We conducted a rapid water-quenching procedure with ultrahigh-temperature oxidation to avoid degradation of the high-quality SiO2/SiC interface formed by ultrahigh-temperature oxidation during the cooling process. A reduction in the interface state density was observed for the SiO2/4H-SiC(0001) interface formed by ultrahigh-temperature oxidation in dry O2 ambient using the water-quenching process, compared with other natural cooling processes. The oxidation temperature dependence of interface state density for the thermally grown SiO2/SiC structures formed using the water-quenching process revealed that degradation of the interface properties occurred not only during the cooling process but also during the continuous oxidation process at exceedingly high temperatures, above 1500 °C, in 100% dry O2 ambient at 1 atm.

https://iopscience.iop.org/article/10.7567/JJAP.56.04CR04/pdf

Yoshihito Katsu

Papers

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

Impact of NO Annealing on Flatband Voltage Instability due to Charge Trapping in SiС MOS Devices

Passive–active oxidation boundary for thermal oxidation of 4H-SiC(0001) surface in O2/Ar gas mixture and its impact on SiO2/SiC interface quality

Insight into metal-enhanced oxidation using barium on 4H-SiC surfaces

Impact of rapid cooling process in ultrahigh-temperature oxidation of 4H-SiC(0001)