Need to incorporate the real micro-contact distribution in spreading resistance correction schemes

It has been known since the early start of the spreading resistance probe (SRP) technique that the metal-silicon probe contact consists typically of a series of small micro contacts. All of the currently applied SRP correction schemes are, however, still based on the assumption of a single large planar circular contact. In this work, we present a new micro-contact correction factor scheme for spreading resistance measurements that is based on a combination of the homogeneous material micro-contact theory of Helm and the Schumann-Gardner multilayer approach traditionally used in SRP. The new model assumes that the measured resistance is composed of three terms: the self-resistance of the micro contacts, the interaction between these contacts, and a contact resistance related to the metal-silicon Schottky contact being used. The validity of the new model has been verified by three-dimensional device simulations for both conducting and insulating boundary conditions. For structures that are several micrometers thick, the new scheme agrees closely with presently used schemes (15%), provided appropriate radius and barrier resistance calibration procedures are applied. For submicron profiles, however, the new scheme solves a series of known artifacts in a consistent and physically acceptable way (i.e., for example, much lower barrier resistance values are needed than before). Hence, the new scheme is recommended for submicron structures. Examples are discussed relating to lightly on heavily doped epilayers and shallow implants in same type, highly doped substrates. (C) 2000 American Vacuum Society. [S0734-211X(00)05701-2].