Modeling of ultrashallow spreading resistance probe calibration curves

Accurate determination of resistivity and carrier density from spreading resistance (SR) data depends heavily on the quality of the SR probes. This quality can be assessed by the shape of the calibration curve, which primarily depends on the properties and behavior of the point contact diodes. In this article, we demonstrate that the SR calibration curve can be simulated using an accurate representation of the SR equivalent circuit. This simulation includes physical models for the point contact diodes, the traditional geometric spreading resistance, and all parasitic resistances. Modeling of the point contact diode is emphasized based on measurements and analysis of the full current/voltage relationships for bulk p-type material.