Papers by Keyword: MOS

Abstract: Investigations were carried out to achieve high performance Silicon Carbide Metal-Oxide-Semiconductor device structures. 4H-SiC/SiO2 interface was prepared by growing amorphous SiO2 layers by an alternate low temperature atmospheric CVD technique using TEOS as source material and the interface properties were compared with the one prepared by conventional thermal oxidation technique. The low temperature CVD technique offered the improvement of the interface properties with reduced Dit in comparison with thermally oxidized interface. As a new attempt, an in situ post growth annealing technique in N2 atmosphere was carried out to reduce the Dit further. Both the CVD technique and the in situ annealing processes that were used in the present study have been identified to be potential approaches to improve the interface quality.

Abstract: A high temperature rapid thermal processing (HT-RTP) above 1400oC was investigated for use in the gate oxide formation of 4H-SiC by a cold-wall oxidation furnace. The gate oxide film of ~50nm can be formed for several minutes in the oxidizing atmospheres such as N2O and O2, where the oxidation rates were 8-10nm/min. After the initial oxide formation, the HT-RTPs in various ambient gases were conducted, and the dependences of their MOS interface properties on the gases were evaluated by a capacitance-voltage (CV) measurement. Based on the results, the process sequence of gate oxidation was determined as follows; the initial oxide was formed by the HT-RTO (oxidation) in N2O or in O2 with subsequent post annealing in Ar ambient, and then the HT-RTN (nitridation) in NO was conducted. The total process time becomes 20-50min. The interface trap density (Dit) of fabricated MOS capacitor shows 3-5x1011cm-2eV-1 at Ec-E~0.2eV. The field-effect channel mobility of fabricated 4H-SiC lateral MOSFETs was ~30cm2/Vs.

Abstract: In this work, we present results on the study of bonding and concentration of carbon in 4H-SiC MOS structure by x-ray photoelectron spectroscopy (XPS). The XPS spectra were fitted by several Gaussian lineshape functions. It is found that the so-called carbon clusters (C-C bonds) appear at the interface of SiO2/SiC, but are not seen in the oxide bulk. However, there are still some SiOxCy and Si-C bonds inside the oxide and the integrated area ratio of SiOxCy/Si-C bonds increases when further away from the SiO2/SiC interface. These observations can be interpreted in terms of the dynamic oxidation process that transforms Si-C bonds into SiOxCy bonds, which are then further oxidized to form SiO2 bonds.