Contactless device for the fast conductivity characterization of a large range semiconductors
Résumé
We report on the development and application of a brand-new contactless method based on eddy currents with a view to designing a generic apparatus for the characterization of some transport properties of a large range of semiconductors. The eddy current probe, constituted of a coil connected to a transmission line, interacts with the semiconductor wafer under inspection. The innovative approach of this work consists in measuring the impedance of the coil by reflectometry using a broadband multicarrier test signal, i.e. containing multiple frequencies. An electromagnetic model of the coil-wafer interaction is then used to estimate the conductivity of the wafer. This process results in a new contactless conductivity measurement system that exhibits a very wide conductivity measurement range and allows the characterization of a large variety of semiconductor materials. The device is also very fast potentially allowing the measurement of transport properties of semiconductors in fast transient conditions. As a practical example, the performance of our device is demonstrated by estimating the conductivity of a set of crystalline silicon wafers.
Mots clés
contactless conductivity measurement system
reflectometry
broadband multicarrier test signal
semiconductor wafer
transmission line
eddy current probe
transport properties
electromagnetic model
contactless method
generic apparatus
coil-wafer interaction
conductivity measurement range
semiconductor materials
fast transient conditions
crystalline silicon wafers