Improved Characteristics of 4H-SiC MISFET with AlON/Nitrided SiO₂ Stacked Gate Dielectrics

Abstract

We investigated the impact of a combination treatment of nitrogen plasma exposure and forming gas annealing (FGA) for a thermally grown SiO2 layer on channel electron mobility in 4H-SiC metal-insulator-semiconductor field-effect-transistors (MISFETs) with and without deposited aluminum oxynitride (AlON) overlayers. This treatment was effective for improving the interface properties of nitrided SiO2/SiC structures formed by thermal oxidation in NOx ambient as well as pure SiO2/SiC structures. A channel mobility enhancement was perfectly consistent with a reduction in interface state density depending on the process conditions of the combination treatment, and a peak mobility of 26.9 cm2/Vs was achieved for the MISFETs with the nitrided SiO2 single dielectric layer. Comparable channel mobility was obtained with a gate insulator consisting of the AlON stacked on a thin nitrided SiO2 interlayer, indicating that both the combination treatment and the AlON/SiO2 stacked dielectrics can be integrated into the SiC MISFET fabrication processes.

Effect of nitrogen incorporation into Al-based gate insulators in AlON/AlGaN/GaN metal–oxide–semiconductor structures

“…In the current study, to evaluate the validity of AlON insulators for GaN-based HEMTs, we investigated AlON=AlGaN=GaN MOS structures using the reactive sputtering method. Contrary to our previous research on SiC MOS devices consisting of SiO 2 underlayers beneath the deposited AlON films (AlON=SiO 2 =SiC stacks), [16][17][18] an excellent MOS interface quality, together with suppressed charge injection into the insulators, was successfully achieved even with the direct sputter deposition of AlON films on AlGaN=GaN substrates. On the basis of physical characterizations, the impact of nitrogen incorporation into the Al-based oxides was studied in detail.…”

“…Then, postdeposition annealing (PDA) was conducted in N 2 ambient at 800 °C for 3 min to improve the electrical properties of the Al-based oxides by referring to the optimized PDA conditions in our previous study on SiC MOS devices. 16,17) No significant change in film thickness was observed for both AlON and Al 2 O 3 films after the PDA. The nitrogen atomic concentration in the AlON films determined by conventional X-ray photoelectron spectroscopy (XPS) analysis using Ar ion sputtering was about 18% (atomic concentrations for total Al, O, and N were 38, 44, and 18%, respectively).…”

“…15) We have also implemented AlON gate dielectrics stacked with thin SiO 2 underlayers (AlON=SiO 2 structures) into silicon carbide (SiC) power MOSFETs. [16][17][18] Consequently, a significant reduction in carrier injection into the gate stacks and an improved reliability of SiC MOSFETs were demonstrated using sputter deposition 16,17) and CVD 18) methods. In the current study, to evaluate the validity of AlON insulators for GaN-based HEMTs, we investigated AlON=AlGaN=GaN MOS structures using the reactive sputtering method.…”

Fundamental Aspects of Silicon Carbide Oxidation

“…This enlarged band offset for the thick MOS devices is preferable from the viewpoint of reducing gate leakage, but electrical defects should negatively impact on the device performance and reliability. Therefore, fundamental tactics, such as applying deposited gate oxides and band engineering by utilizing stacked structures, are indispensable to take advantage of C-face SiC-MOS devices [25][26][27][28]. We also evaluated the modulation of energy band alignment of SiO 2 /4H-SiC(0001) structures due to the interface defect passivation [29].…”

Structural and Insulating Behaviour of High-Permittivity Binary Oxide Thin Films for Silicon Carbide and Gallium Nitride Electronic Devices

“…It has to be mentioned that ternary insulators have also been investigated for MOSFET application in 4H-SiC. In particular, AlON films provided interesting and reliable results both in MOS and MOSFET applications [114][115][116]. However, ternary elements are not the focus of this review.…”