Abstract: A conductivity cell for use in determining ionic concentrations in the gap between two semiconductor substrates or wafers. The wafer gap conductivity cell is composed of two flat electrodes separated by a fixed gap. The electrodes are fabricated from wafers of the same type and dimensions used as semiconductor device substrates. All or a portion of the surfaces of the wafer electrodes are coated with a conductive material. The wafer gap conductivity cell is placed in a wafer cassette or other suitable wafer holder, whose other slots are filled with wafers which are to be cleaned or subjected to another fabrication process. The cell can be used to characterize the processes used during the fabrication of semiconductor devices and assist in investigating the effect on the processes of different process vessel designs.