High-precision resistivity measurement of silicon wafer under unstable lift-off distance using inductive and laser sensors-integrated probe

Abstract

This article proposes a novel contactless method to measure the resistivity of silicon (Si) wafer. In this method, the probe is designed and integrated with an inductive sensor and a laser sensor. The inductive sensor measures the resistivity of Si wafer, and at the same time, the laser sensor detects the lift-off distance (LOD) between the coil of inductive sensor and the wafer surface. The measured resistivity of Si wafer by using the inductive sensor is corrected based on the LOD value. The proposed method can effectively avoid the influence of the LOD changes during the measurement, and thus it improves the accuracy of resistivity measurement. In the experiment, the Si wafers where the resistivity ranges from 0.001 to 1 Ω cm are measured by using the inductive sensor only and the proposed method, respectively. Experimental results show that comparing with only using the inductive sensor, the measurement stability and measurement accuracy of the wafer resistivity by the proposed method are significantly improved.