Investigation of Ta2O5/SiO2/4H-SiC MIS capacitors

• Published in: Microelectronic engineering 2006, Vol.83 (1), p.58-60
• Main Authors: ZHAO, P, RUSLI, LOK, B. K, LAI, F. K, TIN, C. C, ZHAO, J. H, YAR, R. M
• Format: Article
• Language: English
• Subjects: Applied sciences; Compound structure devices; Dielectric, amorphous and glass solid devices; Electronics; Exact sciences and technology; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
• ISSN: 0167-9317; 1873-5568
• DOI: 10.1016/j.mee.2005.10.025

Tantalum pentoxide (Ta2O5) deposited by pulsed DC magnetron sputtering technique as the gate dielectric for 4H-SiC based metal-insulator-semiconductor (MIS) structure has been investigated. A rectifying current-voltage characteristic was observed, with the injection of current occurred when a positive DC bias was applied to the gate electrode with respect to the n type 4H-SiC substrate. This undesirable behavior is attributed to the relatively small band gap of Ta2O5 of around 4.3eV, resulting in a small band offset between the 4H-SiC and Ta2O5. To overcome this problem, a thin thermal silicon oxide layer was introduced between Ta2O5 and 4H-SiC. This has substantially reduced the leakage current through the MIS structure. Further improvement was obtained by annealing the Ta2O5 at 900 deg C in oxygen. The annealing has also reduced the effective charge in the dielectric film, as deduced from high frequency C-V measurements of the Ta2O5/SiO2/4H-SiC capacitors.