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ITRS Error in reported metal capacitance?

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ITRS Error in reported metal capacitance

The 2010 ITRS metal "capacitance per unit length for intermediate wires (pF/cm)" are report to be ~2. Assuming a metal pitch of 0.14um, dielectric thickness of 0.29um, and epsilonr of 2.9, the ITRS are off by one order of magnitude. My calculated values are also of the same order as values reported in tsmc's documentation. Can anyone confirm whether there is an error in the ITRS reported values?
 
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The ITRS value accounts not only for a single area-to-area cap/length but for a full-around-the-wire cap/length value, this means Ctot/length = Cup/down + Cleft/right + Cfringe,corners -- and thus states a worst-worst case.

With metal_width = metal_pitch/2 and an appropriate value for metal_height = 150nm we can calculate:

Cup/down + Cleft/right = 2 * ε0εr * (70/290 + 150/70) = 1.22 pF/cm , which makes 61% of the ITRS value. The leftovers are easily covered by the fringe cap, which just can be estimated -- or calculated by a 2-dimensional field solver.

For the review of your question I got help from an Intel guy -- thanks a lot, Alfred!
 
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