The sidewall resistor—A novel test structure to reliably extract specific contact resistivity

Conventional contact resistance extraction structures suffer inaccuracies when measuring small values of contact resistivity which are sensitive to small perturbations in device fabrication. This is because two-dimensional current crowding around the periphery of the contact window introduces parasitic resistance components which are not accounted for by the one-dimensional model and which can be much larger than the contact resistance component for low values of specific contact resistivity ρ
c
. Unfortunately, there is no direct method to isolate these parasitics, which makes the extraction of ρ
c
using the conventional test structures difficult. In this paper, a novel test device, the sidewall resistor, which utilizes the vertical sidewall dimensions, is demonstrated to circumvent these difficulties. The proposed structure has the advantage that a simple one-dimensional (1-D) extraction technique can still be used. The specific contact resistivity between pure Al and N+ polycrystalline Si is accurately extracted with the value of 7.4 × 10
^-8
Ω.cm
²
. The sidewall resistor is then used to extract the contact resistivity between pure Al and WSi
2
which turns out to be less than 5 × 10
^-9
Ω.cm
²
.