VQ technology is, broadly speaking, a non-contact alternative to traditional CV technology, with some additional capabilities. In CV, one determines depletion depth by measuring the capacitance of the series combination of an oxide layer and the depletion region, while varying the depletion depth by changing the voltage between the substrate and an electrode at the surface of the oxide.
VQ involves depositing corona charge on a wafer and computing various paramters from measurement of the surface potential, V, and the charge applied, Q. VQ measures the depletion depth via the capacitance ΔQ/ΔV, where Q is known from measuring the current drawn by applying the corona charge and V is measured via a Kelvin probe.
