Spatially Resolved Resistivity Measurements in Semiconductor Wafers using Microwave Techniques

In this paper we present a 35 Ghz microwave reflection system which we have used for measuring the resistivity of semiconductor wafers. By using a tapered parallel plate antenna for directing the microwave radiation on to the wafer there is no need for placing the sample inside a waveguide. The system can measure resistivity in the range of 0.5 Ω-cm to 50 μ-cm with a spatial resolution of 0.040" × 0.040" which is similar to what can be achieved using standard four point probes.