Characterization of silicon dioxide films on 4H-SiC Si (0001) face by cathodoluminescence spectroscopy and x-ray photoelectron spectroscopy

Abstract

We measured cathodoluminescence (CL) spectra of SiO2 films grown on 4H-SiC wafers and found that for an acceleration voltage of 5 kV, CL peaks at 460 and 490 nm, assigned to oxygen vacancy centers (OVCs), become weak by post-oxidation annealing in N2O ambient at 1300 °C whereas the CL peak around 580 nm, related to Si-N bonding structures, becomes intense. Furthermore, the peak assigned to N-Si3 configurations in x-ray photoelectron spectroscopy (XPS) spectra was observed in the SiO2/SiC interface in only samples annealed in N2O ambient. These results suggest that the interface trap densities decrease and the channel mobility in n-type MOS capacitors increases by the termination of dangling bonds by the N atom in the SiO2/SiC interface. CL spectroscopy and XPS provide us with extensive information on OVCs and dangling bonds in the SiO2/SiC interface on the 4H-SiC substrate.

Characterization of silicon dioxide films on 4H-SiC (0001) Si, (1-100) M, and (11-20) A faces by cathodoluminescence spectroscopy

“…We used a scanning electron microscope (SEM) with a Schottky-emission-type gun (HITACHI S-4300SE) as the excitation source for the CL measurements. 20 The CL signals were collected by an ellipsoidal mirror and optical fiber and detected using a Jobin Yvon HR-320 single monochromator equipped with a charge coupled device (CCD). We recorded the CL spectra at acceleration voltages of 3 and 5 kV at room temperature with a beam current of less than 5 nA.…”

“…The CL peaks from the optical fiber that was used for a detection of the CL spectra were not observed in our CL system. 19,20,22 Figure 1 shows the CL spectra of the SiO 2 films grown on the 4H-SiC (0001) Si, (1-100) M, and (11-20) A faces (we refer to these as samples Si, M, and A, respectively) measured at 3 kV. CL peaks were observed at 460, 490, and 640 nm for the SiO 2 films on the 4H-SiC substrates.…”

“…The CL peaks at 460 and 490 nm were attributed to OVCs, whereas the CL peak at 640 nm was attributed to NBOHCs. 20,22 The CL peaks at and 540 nm originate from a bound exciton and donor-acceptor pair by the 4H-SiC substrates, respectively. The weak CL peak at around 280 nm is considered to originate from OVCs.…”

“…The CL measurement of the cross section of a thermally grown SiO 2 film on a Si substrate indicated that the intensities of the these peaks in the SiO 2 /Si interface were stronger than that of the CL peak at 640 nm, which was attributed to non-bridging oxidation hole centers (NBOHCs). 19 We have also measured the CL spectra of SiO 2 films grown on 4H-SiC wafers 20 and found that for an acceleration voltage of 5 kV, the CL peaks at 460 and 490 nm assigned to OVCs become weak after POA in N 2 O ambient at 1300 C, whereas the CL peak around 580 nm related to Si-N bonding structures becomes intense. Furthermore, the peak assigned to N-Si 3 configurations in X-ray photoelectron spectroscopy (XPS) spectra was observed in the SiO 2 /SiC interface only in samples annealed in N 2 O ambient.…”

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

“…11 Besides, a non abrupt interface between SiO 2 films and SiC was revealed by nuclear reaction profiling (NRP) [12][13][14] differently from the case of silicon oxidation. 12,15 The probable causes for the presence of these interfacial regions can be: roughness, 13,16 oxygen vacancies, 17 or even excess of carbon. [7][8][9][10] Moreover, residual compounds on the SiC surface after the removal of the oxide film were observed.…”