A strong reduction in the density of near-interface traps at the SiO2∕4H-SiC interface by sodium enhanced oxidation

Abstract

This paper demonstrates how sodium enhanced oxidation of Si face 4H-SiC results in removal of near-interface traps at the SiO2∕4H-SiC interface. These detrimental traps have energy levels close to the SiC conduction band edge and are responsible for low electron inversion channel mobilities (1–10cm2∕Vs) in Si face 4H-SiC metal-oxide-semiconductor field effect transistors. The presence of sodium during oxidation increases the oxidation rate and suppresses formation of these near-interface traps resulting in high inversion channel mobility of 150cm2∕Vs in such transistors. Sodium is incorporated by using carrier boats made of sintered alumina during oxidation or by deliberate sodium contamination of the oxide during the formation of the SiC∕SiO2 interface.

Electrical characterization of amorphous Al2O3 dielectric films on n-type 4H-SiC

“…We cannot distinguish between these two possibilities in this experiment but very similar behavior has been observed for thermal oxides on SiC containing sodium ions. 27 This experiment demonstrates two things. First, the net negative charge observed in the Al 2 O 3 layers is not a permanently fixed charge but rather electrons trapped within the oxide which can be released to the SiC using depletion bias and UV exposure.…”

Oxidation at Cs Pre-Adsorbed Si/6H-SiC(0001)-(3 × 3) Reconstructed Surfaces Studied Using Metastable-Induced Electron Spectroscopy

“…However, interface traps were generated at the SiO 2 /SiC interface, which is a disadvantage. The interface traps resulted in reduction of the channel mobility in the SiC metal-oxide-semiconductor field effect transistor (MOSFET) [2,3]. The Si-covered 6H-SiC(0001) surface was transformed from a Si-rich to C-rich one such as (3 × 3), (…”

“…† Corresponding author: t-ikari@ube-k.ac.jp on the Si surface with small amounts of oxygen exposure [8,9]. The reduction of the interface traps has been reported with Na-enhanced oxidation of a Si-face 4H-SiC surface [2].…”

Effect of boron incorporation on slow interface traps in SiO2/4H-SiC structures

“…Of these, NITs may play a dominant role because they are considered to create trap levels close to the conduction band edge of 4H-SiC at a high density [11][12][13][14]. It has been reported that NITs can be effectively removed by the incorporation of N [15], Na [16], K [17], and P [18] as revealed either by using low-temperature capacitance-voltage (C-V ) [15,18] or thermal dielectric relaxation current (TDRC) [16][17][18] measurements. It is interesting to note that improved field-effect mobilities can be obtained by utilizing oxides incorporating N [3,4], Na [5], and P [6], and thus we can assume that the NIT density is closely related to the field-effect mobility.…”