Detection of a charge built in the oxide layer of a metal-oxide-semiconductor field-effect transistor by lateral C-V measurement

The possibility of detecting the local charge in the SiO2 layer of a metal-oxide-semiconductor field-effect transistor (MOSFET) by the simple C-V measurement of the source-substrate junction (S-B junction) is analyzed. It develops a method for estimating the longitudinal linear size and distribution of the built-in charge along the channel near the Si-SiO2 interface by measuring the C-V dependence of the lateral source-substrate junction of the MOSFET. It is important to estimate the region of its spatial distribution during investigating such a localized charge. Change in the width of the space charge region of the S-B junction is detected from change in the capacitance of this junction. Irradiation with a positive bias on the source leads to the predominant localization of the built-in charge in the lateral outer region of the oxide layer for low exposition doses. The method can be used to read an information bit written in the form of a submicron local charge.