Role of fringing field on the electrical characteristics of metal-oxide-semiconductor capacitors with co-planar and edge-removed oxides

Abstract

Due to the simplicity of the fabrication process, the ultra-thin oxide metal-oxide-semiconductor capacitors (MOSCAPs) can be a promising device for sensing, memory, and transconductance applications. The investigation of the fundamental electrical characteristics of ultra-thin oxide MOSCAPs is still of importance. In this work, the influence of the removal of the surrounded gate oxide was studied to know the role of fringing field. For edge-removed oxide, the tunneling saturation current shows no oxide thickness dependency and exhibits a low current level of 9.4×10−11 at 2V (dox=2.3 nm). Also, its deep depletion occurs earlier when biasing. In contrast, for the device without oxide removing, i.e., co-planar oxide, the saturation current is strongly related to the oxide thickness and exhibits a high current level of 3.5×10−6 at 2V (dox=2.3 nm) due to regular oxide voltage drop modulation effect on effective Schottky barrier height. For the thick oxide of 4.2 nm the inversion capacitances are frequency dependant for CP-OX but are independent for ER-OX MOSCAPs. These characteristics are mainly caused by the different fringing fields and the defect densities at device edge between two structures.