Direct measurements of interfacial contact resistance, end contact resistance, and interfacial contact layer uniformity

A four-terminal microelectronic test structure and test method are described for electrically determining the degree of uniformity of the interfacial layer in metal-semiconductor contacts and for directly measuring the interfacial contact resistance. A two-dimensional resistor network model is used to obtain the relationship between the specific contact resistance and the measured interfacial contact resistance for contacts with a uniform interfacial layer. A new six-terminal test structure is used for the direct measurement of end contact resistance and the subsequent determination of front contact resistance. A methodology is described for reducing the effects of both contact-window mask misalignment and parasitic resistance associated with these measurements. Measurement results are given for 98.5-percent Al/1.5- percent Si and 100-percent Al contacts on n-type silicon.