  Several issues concerning the applicability of the temperature coefficient of
the resistivity (TCR) method to scaled interconnect lines are discussed. The
central approximation of the TCR method, the substitution of the interconnect
wire TCR by the bulk TCR becomes doubtful when the resistivity of the conductor
metal is strongly increased by finite size effects. Semiclassical calculations
for thin films show that the TCR deviates from bulk values when the surface
roughness scattering contribution to the total resistivity becomes significant
with respect to grain boundary scattering, an effect that might become even
more important in nanowires due to their larger surface-to-volume ration. In
addition, the TCR method is redeveloped to account for line width roughness. It
is shown that for rough wires, the TCR method yields the harmonic average of
the cross-sectional area as well as, to first order, the accurate value of the
resistivity at the extracted area. Finally, the effect of a conductive barrier
or liner layer on the TCR method is discussed. It is shown that the liner or
barrier parallel conductance can only be neglected when it is lower than about
5 to 10% of the total conductance. It is furthermore shown that neglecting the
liner/barrier parallel conductance leads mainly to an overestimation of the
cross-sectional area of the center conductor whereas its resistivity is less
affected.
