A method for the measurement of the turn-on condition in MOS transistors

Metal-oxide-silicon (MOS) integrated circuits usually consist of MOS transistors and interconnections. Both, interconnections and MOS transistors are built up of diffused regions in the bulk substrate and conductive strips (metal or polycrystalline silicon) on top of the oxide. For proper electrical operation the interconnection paths should not exhibit MOS transistor effects, i.e. should not induce inversion layers at the silicon-silicon dioxide interface. Furthermore from a designer's point of view it will be desired that some transistors operate in the saturated mode and others in the non-saturated mode. This implies that a method for the determination of the turn-on of channel conduction is highly desirable for designers of MOS integrated circuits. Using a straightforward definition of turn-on, a fast and simple measurement method will be presented for the determination of the relation between gate voltage and diffused region voltage for MOST structures in the turn-on condition.