Contact resistivity of ECA bonded joints: How to extrapolate it?

Abstract

Ohmic contacts are of great importance in the quality and reliability of electronic circuits and also in the photovoltaic field. To characterize the electrical performance of such contacts, the contact resistivity is a well-known figure of merit applicable for such a task. However, its determination is still a difficult topic due to an observed dependence of the contact resistivity on the contact size for test structures in the nano-, micro-or millimeter scale, which should not be the case. The Transmission Line Method is the most prevalent and widely used method to determine the contact resistivity of planar devices, such as the joints based on conductive adhesives reviewed in this study. However, its reliability is questionable when the adhesive bulk is considerably more resistive than the contact itself, hence, the Contact End Resistance method is also reviewed. This method uses the same test structures but a different model of the contact, which improves the determination of the contact resistivity. According to our results, both methods still exhibit a dependence on contact area, but the contact end resistance method is less so, reducing the standard deviation in about 30 %. There is still room to increase the contact length for further studies without decreasing the contact end resistance and maintain accuracy. Current sensitivity studies on sample geometries are undergoing and further studies will be soon elsewhere published.