Statistical modeling of transmission line model test structures. I. The effect of inhomogeneities on the extracted contact parameters

Extraction of electrical contact parameters by transmission line model (TLM) test structures is based on the assumption that the electrical and geometrical parameters of the contacts within a structure are identical. Statistical modeling is presented to show that the usual extraction procedure can lead to large errors in the extracted contact parameters in the case of nonideal TLM structures, even if there is no error in the measured electrical and geometrical parameters. Errors in the extracted parameters as functions of the nominal contact parameters are presented graphically. These graphs can be used to assess the accuracy of the TLM measurements and to optimize TLM test structure design. In the parameter intervals examined, the TLM method works best (yields the fewest errors in all extracted parameters) when the geometrical length of a contact is equal to about two times the electrical transfer length