inductance of metal line in IC
One doesn't typically worry about or include the inductance in the design of the metal layers in IC's (with two notable exceptions).  In fact, if you look at the differential equations for signal propagation, if you include inductance they yield the wave equation, if you exclude inductance you get the diffusion equation.  In Chip design we use the diffusion equation, so just concern yourself with R's and C's.

THe two exceptions?
1) bond wires
2) when you've deliberately designed an inductor into the metal layers
    - typically only done for RF circuits that need tank circuits.