Papers by Keyword: Fixed Oxide Charge

Abstract: The influences of positive fixed oxide charges and donor-like interface traps on breakdown voltages of SiC devices with FGR and JTE terminations were studied. The breakdown voltages of devices with both FGR and JTE terminations were found to degrade when the level of fixed oxide charges overs 1×10¹² cm^-2 due to enhancement of junction curvature by fixed oxide charges. The introduction of donor-like interface traps at the interface shows similar behaviors as fixed positive charges, suggested that both fixed oxide charges and interface traps should be taken into account when one optimizes device designs and processes.

Abstract: The fundamental aspects of thermal oxidation and oxide interface grown on 4H-SiC(0001) Si-face and (000-1) C-face substrates were investigated by means of high-resolution x-ray photoelectron spectroscopy (XPS) using synchrotron radiation together with electrical measurements of SiC-MOS capacitors. We found that, for both cases, there existed no distinct C-rich transition layer despite the literature. In contrast, atomic scale roughness causing degradation of SiC-MOS devices, such as negative fixed charge and electrical defects just at the oxide interface, was found to be introduced as thermal oxidation progressed, especially for the (000-1) C-face substrate.

Abstract: We performed high-pressure H2O vapor annealing on 4H-SiC n-MOS capacitors to control SiO2/4H-SiC interface properties. High-pressure H2O annealing was performed at 270～ 420oC at a pressure of 1.31～1.67MPa. Effective negative fixed oxide charge decreased with increasing anneal temperature in the case annealed with Al gate electrodes. However, it increased with increasing anneal temperature in the case annealed without Al gate electrodes. The effect of annealing was much larger on the C-face than that of Si-face. Interface state densities near the conduction band edge was decreased at 420oC under 1.67MPa compared to other samples, especially on the C-face n-MOS capacitors.

Abstract: The structure and electrical properties of ZrO2 dielectric thin films deposited by rf magnetron sputtering were investigated. The fixed oxide charge and interface trap density at the ZrO2/Si interface is substantially decreased by annealing at 500 C. Annealing treatment also enhances the quality of the film by reducing leakage current. The carrier transport mechanism in the ZrO2 film is dominated by thermionic emission.

Abstract: Different SiC thermal oxide passivation techniques were characterized using UV-induced hysteresis to estimate the fixed charge, Qf, and interface-trapped charge, Qit. Steam-grown oxides have a fixed charge density of Qf=-1x1012 cm-2, and a net interface-trapped charge density of Qit=4x1011cm-2. Addition of a thin low-pressure chemical-vapor deposited (LPCVD) silicon nitride layer decreased these parameters to Qf=-2x1011 cm-2 and Qit=4x1010 cm-2. Dry oxide shows a fixed charge density, Qf=-3x1012 cm-2 and interface-trapped charge density, Qit=4x1011 cm-2 which changes to Qf=+7x1010 cm-2 and Qit=1x1010 cm-2 with the addition of a LPCVD silicon nitride cap. Dry thermal oxide with a silicon nitride cap was used to passivate SiC MESFETs to achieve a power-added efficiency of 60% in pulsed operation at 3 GHz in Class AB bias conditions.