Abstract
The structural stability and electrical performance of SiO2 grown on SiC via direct plasma-assisted oxidation were investigated. To investigate the changes in the electronic structure and electrical characteristics caused by the interfacial reaction between the SiO2 film (thickness ~5 nm) and SiC, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), density functional theory (DFT) calculations, and electrical measurements were performed. The SiO2 films grown via direct plasma-assisted oxidation at room temperature for 300s exhibited significantly decreased concentrations of silicon oxycarbides (SiOxCy) in the transition layer compared to that of conventionally grown (i.e., thermally grown) SiO2 films. Moreover, the plasma-assisted SiO2 films exhibited enhanced electrical characteristics, such as reduced frequency dispersion, hysteresis, and interface trap density (Dit ≈ 1011 cm−2 · eV−1). In particular, stress induced leakage current (SILC) characteristics showed that the generation of defect states can be dramatically suppressed in metal oxide semiconductor (MOS) structures with plasma-assisted oxide layer due to the formation of stable Si-O bonds and the reduced concentrations of SiOxCy species defect states in the transition layer. That is, energetically stable interfacial states of high quality SiO2 on SiC can be obtained by the controlling the formation of SiOxCy through the highly reactive direct plasma-assisted oxidation process.
Highlights
Thermal oxidation is the standard method for growing high-quality SiO2 films
Because the growth of SiO2 on SiC substrates in a furnace is time consuming and requires high temperatures (800–1400 °C), a high thermal stress is inevitably induced during the oxidation process, which results in a thicker transition region and the generation of defects at the SiO2/SiC interface[15,18,19,20,21,22]
Zhu et al reported that the first layer of the transition layer contained SiOC3, which is formed through the reaction of O with the sub-surface Si atoms of the SiC substrate
Summary
Thermal oxidation is the standard method for growing high-quality SiO2 films. because the growth of SiO2 on SiC substrates in a furnace is time consuming (several minutes to hours) and requires high temperatures (800–1400 °C), a high thermal stress is inevitably induced during the oxidation process, which results in a thicker transition region (i.e., higher concentrations of SiOxCy species) and the generation of defects (e.g., excess C atoms and O vacancies) at the SiO2/SiC interface[15,18,19,20,21,22]. Several studies have reported that the bulk traps caused by the generation of defects during high-temperature oxidation are responsible for the low mobility of 4H-SiC-based MOSFETs. an excess of C atoms near the interface of the SiC substrate results in the formation of SiOxCy species via a reaction process involving O2 and di-interstitial C clusters [(Ci)2] that are formed through the pairing of interstitial C atoms, which is a major cause of the degraded performance of MOSFET devices with SiC substrates[24,25,26,27,28]. The results of this study indicate that the plasma-assisted oxidation method is very effective in improving the electrical characteristics of SiO2/SiC systems because of the reduced concentrations of SiOxCy species and the energetically stable interface states of such systems
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