Abstract: An apparatus for measuring charge in an oxide layer overlying a silicon substrate containing very high density product chips characterized by thick oxides and high substrate doping levels in the field regions. A specially designed extremely thin conductive probe is pressed against the oxide layer whose charge is to be measured. A bias is applied to the probe for biasing the underlying silicon surface into accumulation or inversion. An intensity modulated light beam is focussed at the point of probe contact. The resulting amplitude modulated photovoltage is detected and applied to a computer to derive the value of the oxide charge therefrom.

Abstract: An apparatus for measuring and quantitatively determining the number of surface states at or near the insulator-semiconductor interface in a metal-insulator-semiconductor (MIS) structure by injecting a controlled amount of charge into the insulator to induce a change in the surface state occupancy and measuring simultaneously and directly the amount of charge injected into the insulator, the charge so induced in the semiconductor and in the surface states and the corresponding change in the surface potential of the semiconductor induced by the injected charge.BACKGROUND OF THE INVENTION1. Field of the InventionThis invention relates generally to an apparatus and a method for measuring the surface state charges in a metal-insulator-semiconductor structure by measuring simultaneously and directly the amount of charge injected into the insulator, the net change in the semiconductor body and its surface and the change in the surface potential of the semiconductor body.2.