DEPTH PROFILE OF TRAPPED CHARGES IN OXIDE LAYER OF 6H-SIC METAL-OXIDE-SEMICONDUCTOR STRUCTURES

Oxide layers etched at an angle were fabricated on a 6H-SiC substrate by varying etching time in diluted hydrofluoric acid, and 6H-SiC metal -oxide-semiconductor structures with various oxide thicknesses were fo rmed. High-frequency capacitance-voltage measurements were carried out for determining the change in gate voltages corresponding to the midg ap condition as a function of the thickness of the oxide layer, and th e depth profile of trapped charge density in the oxide was estimated f rom the result. It is found that negative charges build up near the 6H -SiC/SiO2 interface, and that positive charges accumulate in the regio n at 40 nm from the interface. No significant difference is observed i n the depth profiles of the trapped charge density between the oxide l ayers on the carbon and silicon faces. The origin of these trapped cha rges is discussed in conjunction with the carbon-related compounds in the oxide layers. (C) 1996 American Institute of Physics.