# sky130

Harald Pretl

02/03/2022, 2:07 PM
Hi everyone, I am looking for the spec of the max. allowed current density of the metal layers (and potentially the resistors)? Please send a pointer to the respective document, thanks!
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Tim Edwards

02/03/2022, 2:32 PM
There were no such numbers in SkyWater documentation, but I worked out some likely numbers, as it's just aluminum so should be possible to get the values knowing the material and dimensions. If @User has a copy of the numbers I calculated, he could post them. Otherwise I need to look up where I wrote them down, which I can do in a few hours from now.

Weston Braun

02/03/2022, 5:38 PM
I lost those numbers. Sorry. I think the PDK info page has current density for the resistors though

Boris Murmann

02/03/2022, 10:10 PM
1mA/um should be reasonably safe (I assume the thickness is a good fraction of a micron).
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Tim Edwards

02/19/2022, 9:39 PM
I just happened to come across my notes on the calculations that Weston and I did. For good measure, I put them in a public document here: (sheet labeled "Layer Resistances and Capacitances") The numbers are based on rules from other processes pro-rated to the specific thicknesses of the metal layers in the SkyWater process. I don't have any relevant information about electromigration in Titanium Nitride, so I don't have a number for local interconnect. But for the other metal layers, the values are: Metals 1 and 2: 0.65 mA/um Metals 3 and 4: 1.50 mA/um Metal 5: 2.30 mA/um