Controlling conductivity of deposited layers is crucial for many applications. In the case of thin films, the sheet-resistance, which can be measured by Eddy-currrent sensing, is the respective parameter for measuring conductivity. For materials such as transparent conductive oxides in solar cells or IR-blocking layers in architectural glass this parameter is of paramount importance. Also for metal layers or carbon fibers, intrinsic conductivity can be used to analyze process specifics and deviations in-line. For thin metal film deposition, grain sizes can affect the overall conductivity of the layer and if the thicknesses of metal is assumed as constant, the conductivity can reveal information about the grain size.

To achieve fast contactless in-line analysis of conductivity properties, the method of choice is the eddy current measurement. Its basic principle is the generation of circular (“Eddy”) currenty in a conductive layer by a magnetic field. As these currents generate a magnetic field themselves, this response can be detected by the system as a measure for the materials sheet-resistance, i.e. its conductivity. The eddy current technique operates on a kHz basis, uses no moving parts, and does not contact the sample like 4 point-probes. These properties make it ideal for fast in-line process control.

At LayTec, Eddy-Current-sensing is offered as an complimentary method in combination with methods such as reflectance, transmission or PL.