Preliminary study of a novel scanning charge-pumping method using extra gates for SOI wafer inspection

A novel scanning charge-pumping method using one or more extra contactless gates is proposed for silicon-on-insulator (SOI) wafer inspection. In the proposed method, a contactless; gate electrode is used as a measuring gate instead of the permanent gate electrode of normal metal-oxide-semiconductor transistors, allowing a wafer map of interface trap density to be obtained. A preliminary study is carried out using a sample device having two extra gate electrodes in the close vicinity of a measuring gate electrode, which are contacted on an oxidized SOI wafer. The results demonstrate that the proposed method is a promising technique for the characterization of interface trap density in SOI wafers.