Characterization of High-k Ta[sub 2]Si Oxidized Films on 4H-SiC and Si Substrates as Gate Insulator

The main physical and electrical characteristics of the high- k insulator layer produced by the Ta 2 Si deposition and subsequent oxidation on SiC and Si substrates are investigated in this paper. The leakage current of these layers shows an asymmetric behavior with the polarity of the gate bias (gate + V or − V ), yielding a leakage current density as low as 10 − 8 A cm − 2 at 1 MV cm − 1 and 4.5 MV cm − 1 , respectively. To identify the conduction mechanisms, the experimental current-voltage curves have been fitted with a theoretical model accounting for a double hopping and tunnel/Poole-Frenkel conduction mechanism. The dielectric constant obtained for a 4H-SiC metal-insulator semiconductor (MIS) is ∼ 20 basically independent of the insulator thickness or the oxidation temperature. The dielectric constant obtained for Si MIS capacitors decreases with increasing oxidation temperature, and its value has been measured in the 10-7 range. 4H-SiC metal oxide semiconductor field effect transistors (MOSFETs) have been fabricated using oxidized Ta 2 Si as a gate insulator, demonstrating the feasibility of this insulator and reporting one of the first well-behaved MOSFETs on SiC with high- k gate dielectric. For the MOSFETs fabricated on a p-implanted and annealed region, a peak mobility up to 40 cm 2 ∕ Vs has been extracted, which is higher than mobilities commonly reported for thermal oxidized 4H-SiC MOSFETs.