The effect of high field stress on the capacitance/voltage characteristics of buried insulators formed by oxygen implantation

In thin-film SOI (silicon-on-insulator) devices, where the body is fully depleted in normal device operation, the buried insulator has a pronounced effect on the transistor characteristics. In particular, the presence of fixed oxide charge and interface states at the body/insulator and the substrate/insulator interfaces influences the electrostatics in the body region. Consequently, it is necessary to have a simple method for determining the density of fixed charge at the interfaces. Moreover, from the viewpoint of long term device stability it is necessary to assess how the magnitude of the fixed charge varies under the influence of electric field stress. Previous work has demonstrated how the high-frequency capacitance/voltage plot can be used to determine the thickness of the body and buried oxide regions of SOI capacitors. The authors extend the technique to allow the determination of the fixed charge densities at both silicon/oxide interfaces, and they outline how the effects of high field stress can be interpreted