Relationship between electrical properties and interface structures of SiO2/4H-SiC prepared by dry and wet oxidation

Abstract

We have investigated the relationship between the electrical properties and interfacial atomic structure of SiO2/4H-SiC interfaces, prepared by dry and wet thermal oxidation procedures with 4H-SiC (0001) and 4H-SiC (000-1) substrates, using extended x-ray absorption fine structure (EXAFS) spectroscopy and electrical methods. From the current–voltage (I–V) and capacitance–voltage (C–V) measurements, the gate leakage current onset and density of interface states were shown to depend on the thermal oxidation procedure used for creating SiO2/4H-SiC (000-1) interfaces. This dependence was not observed for SiO2/4H-SiC (0001) interfaces. From EXAFS oscillations, we found that C and Si vacancies formed at the SiC side of SiO2/4H-SiC (0001) and SiO2/4H-SiC (000-1) interfaces, respectively. Compressive stress at the SiC sides of SiO2/4H-SiC (0001) and SiO2/4H-SiC (000-1) interfaces prepared with the dry thermal oxidation procedure caused decreases in bond lengths. Stress at the interface was smaller in the case of wet oxidation. Wet oxidation released the interface stress more effectively for 4H-SiC (000-1) substrates than for 4H-SiC (0001) substrates. A high gate leakage current onset related to a high interface charge, while a high density of interface states related to a high interface stress and a high interface roughness.

Carrier Trap Density Reduction at SiO2/4H-Silicon Carbide Interface with Annealing Processes in Phosphoryl Chloride and Nitride Oxide Atmospheres

“…The kinetics of oxidation suggest that wet oxidation is preferable due to the much shorter time required to form gate oxide [ 44 ]. Some results suggest that this process can result in lower interface state densities than conventional dry oxidation [ 45 , 46 ]. Recently, it has been shown that, during oxidation, the wet oxidation process generates lower interface stresses [ 45 , 47 ].…”

Influence of Hydrogen-Nitrogen Hybrid Passivation on the Gate Oxide Film of n-Type 4H-SiC MOS Capacitors

“…The work reported by Hirai et al showed that wet H 2 O oxidation treatment significantly reduced the intrinsic strain of gate oxide near the interface, compared to dry O 2 oxidation [17], which may be due to the ability of H 2 O to remove the carbon-related byproducts of oxidation from the interface more efficiently than O 2 [16]. However, it is worth noting that the previous research on 4H-SiC wet oxidation was mostly performed at an environment temperature less than or equal to 1200 • C [12][13][14][15][16][17][18], which may be limited by the maximum operating temperature of the quartz furnace. Although the former researchers have reported the influence of wet oxidation on the channel mobility of 4H-SiC MOSFETs [12][13][14], the information about the effect of high-temperature wet oxidation on the integrity of gate oxide is not sufficient.…”

“…On the other hand, it has been reported that thermal oxidation in wet ambience with H 2 O gas results in the improvement of 4H-SiC MOS interface quality [12][13][14][15][16][17][18]. Several previous works showed that the channel mobility of 4H-SiC MOSFETs on a-face, C-face, and Si-face can be significantly enhanced by wet oxidation [12][13][14].…”

Ozone oxidation of 4H-SiC and flat-band voltage stability of SiC MOS capacitors

“…[8][9][10] These defects can be eliminated by POA and improved oxidation processes; [5,[11][12][13] the latter can suppress the generation of these defects fundamentally by increasing the oxidant concentration near the SiC/silicon dioxide (SiO 2 ) interface. [14][15][16] Improved oxidation processes include wet oxidation, [17] NO oxidation, [6] plasma oxidation, [18,19] and ozone (O 3 ) oxidation. [20] Although these methods can reduce the interface trap density (D it ) of SiC MOS devices to some extent, wet oxygen, NO, and plasma oxidation may lead to V th /V fb instability, [21,22] the introduction of fast traps, [23] and sample damage due to highly energetic particle bombardment, [24] respectively.…”