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 correctio n schemes are, however, still based on the assumption of a single large pla nar circular contact. In this work, we present a new micro-contact correcti on factor scheme for spreading resistance measurements that is based on a c ombination of the homogeneous material micro-contact theory of Helm and the Schumann-Gardner multilayer approach traditionally used in SRP. The new mo del assumes that the measured resistance is composed of three terms: the se lf-resistance of the micro contacts, the interaction between these contacts , and a contact resistance related to the metal-silicon Schottky contact be ing used. The validity of the new model has been verified by three-dimensio nal device simulations for both conducting and insulating boundary conditio ns. For structures that are several micrometers thick, the new scheme agree s closely with presently used schemes (15%), provided appropriate radius an d barrier resistance calibration procedures are applied. For submicron prof iles, however, the new scheme solves a series of known artifacts in a consi stent and physically acceptable way (i.e., for example, much lower barrier resistance values are needed than before). Hence, the new scheme is recomme nded for submicron structures. Examples are discussed relating to lightly o n heavily doped epilayers and shallow implants in same type, highly doped s ubstrates. (C) 2000 American Vacuum Society. [S0734-211X(00)05701-2].