Investigation of Al/sub 2/O/sub 3/ and TiO/sub 2/ as gate insulators for 4H SiC pulsed power devices

Abstract

Achieving high quality and high electric breakdown of oxide on 4H-SiC substrates is still a major research challenge. 500 /spl Aring/ Al/sub 2/O/sub 3/ and TiO/sub 2/ were deposited on 4H-SiC by high vacuum and low-temperature e-beam evaporation. AFM (atomic force microscopy) results show that a surface mean height of 4-7 /spl Aring/ of Al/sub 2/O/sub 3/ was found on Si substrate and 74 /spl Aring/ of Al/sub 2/O/sub 3/ was found on SiC substrate. MIS capacitors were fabricated using one mask to evaluate the quality of these gate materials. C-V measurements at 10 kHz show that Al/sub 2/O/sub 3/ and TiO/sub 2/ have dielectric constants of more than 9 and 20, respectively. The leakage current of an Al/sub 2/O/sub 3/ MIS capacitor is about 10/sup -9/ A on a capacitor area of 150 /spl mu/m /spl times/ 150/spl mu/m at a gate voltage of /spl plusmn/10 V. An Al/sub 2/O/sub 3/ MIS capacitor has a lower leakage current than a TiO/sub 2/ MIS capacitor due to its large band gap offsets. Its breakdown electric field strength is more than 8 MV/cm. This research indicates that e-beam deposited Al/sub 2/O/sub 3/ may be a promising dielectric material for the pulsed power SiC devices.