Charge measurements in thin insulating layers of MIS and MIM structures by means of current–voltage characteristics and application to the MOS system

It is shown how it is possible to determine in a simple way the whole charge in the insulator and its charge centroid from the shifts of the current–voltage characteristics of an MIS or MIM structure with positive and negative biased metal, compared with theoretical or initial I–U curves. From measurements on the MOS system with Al as the gate metal follows: 1) virgin samples have a positive charge of 3.15 × 1012 e/cm2 at the gate metal and of 0.35 × 1012 e/cm2 at the semiconductor surface, 2) electrons injected from an avalanche breakdown at the semiconductor surface and trapped in the insulator have a charge centroid near the metal (xQ ≈ 0.73 d), 3) electric fields in the pre-breakdown range result in a change of the charges in the SiO2 (trapping of electrons, creation of positive charges), 4) the current flow in the pre-breakdown range creates a high number of surface states.