Electrical characterization of Si_3N_4/SiO_2 double layers on P-type 6H-SiC

摘要

MNOS, MNS and MOS devices have been fabricated on p-type 6H-SiC substrates without epitaxial layers. They have been characterized using high frequency CV, GV, and IV measurements. The high frequency CV characteristics of p-type 6H-SiC MNOS structures indicate a very similar interface quality to p-type 6H-SiC MOS devices. A lower effective fixed insulator charge Q_I is found in MNOS devices with a higher oxide thickness x_ox. An x_ox of 10 nm is effective in avoiding charge instability. The effective fixed insulator charge Q_I can be modified in the 10 nm oxide SiC MNOS devices by injecting carriers into the nitride. Similar leakage current characteristics compred to p-type 6H-SiC MNS structures have been found for p-type 6H-SiC MNOS devices, but the SiO_2/Si_3N_4 insulator current is lower, particularly for positive electric fields. At the oxide breakdown limit (-10 MV/cm). Poole-Frenkel conduction is observed in the nitride for negative electric fields due to direct tunneling of holes into the nitride.