Characterization of contact interface, film sheet resistance and 1/f noise with circular contacts

The resistance and noise of films prepared with poor contacts are dominated by the contact interface and for perfect contacts holds that resistance and noise stem from outside the contact interface region. The proposed test pattern to study the different contributions uses one mask. It permits two- and four-point measurements enabling the detection of a weak contribution from outside the contact interface on top of a strong interface contribution. The resistance and noise for poor and perfect contacts are calculated between pairs of circular top electrodes of equal diameters 2r at distances L with L/2r = 10. The dependences of resistance and noise on the contact diameter are quite different for perfect and poor contacts. 1/f noise of films taken from literature are compared in the noise figure of merit K = Cus [cm2]/Rsh[O]. K is the ratio of 1/f noise normalized for bias, frequency and unit surface to sheet resistance. Materials can be classified based on K-values. Very high K-values point to inhomogeneous electric fields on a microscopic scale (percolation conduction). The contact interface 1/f noise and specific contact resistance are characterized by Cust [cm2] and ¿ct [O cm2]. Reviews of K for films and Cust for interfaces show that 1/f noise is a more sensitive tool than merely the resistance parameters Rsh and ¿ct.