Test Structures for Ohmic Contact Characterization

Publisher SummaryFor an ohmic contact, the resistance of the linear part of the current-voltage characteristic is the parameter of interest. The ideal contact would have an impedence that is negligible as compared with that of the semiconductor device. This observation puts a stringent requirement on the metal-semiconductor contacts in modern very-large-scale integration (VLSI) circuits. When dealing with low-resistive ohmic contacts, the voltage drop across the metal-semiconductor interface is a small fraction of the total voltage. This situation is the opposite of when the voltage drop across the base of the rectifying contact could be considered as a secondary effect. To circumvent this problem, a number of test structures and procedures have evolved. The current flow pattern in these test structures is complicated. The current density is non-uniformly distributed across the contact area in the test structures as well as in the actual semiconductor devices.