A question about percentage of metal fill: am I wrong to assume it isn't possible to have a giant solid plane on metal layers? In magic, I can do something like

% box 0 0 2000 2000

Root cell box:

width x height  (   llx,  lly  ), (   urx,  ury  )  area (units^2)

microns:  100.000 x 100.000  ( 0.000,  0.000), ( 100.000,  100.000)  10000.000

lambda:   10000.00 x 10000.00  (  0.00,  0.00 ), ( 10000.00,  10000.00)  100000000.00

internal:  20000 x 20000   (     0,  0    ), ( 20000,  20000)  400000000

% paint m1

Loading DRC CIF style.

%

% drc find

There are no errors in (UNNAMED)

and DRC isn't complaining. Is this: • because I am, in fact, allowed to do this • because magic doesn't account for this; or • because the plane will automatically be swiss-cheesed during fabrication?

There are foundries which will automatically apply slot generation. I don't think SkyWater is one of those, although I have never been quite sure on that point. There are stress rules requiring that metal layers be less than 30um or else slotted; violating those rules carries some risk of metal delamination but is not a manufacturing issue so SkyWater doesn't reject designs that violate the stress rules. If you have so much metal that the density rule is violated, then SkyWater will reject it (and we do run density checks, although in magic, density checks are not part of the main DRC rule set and it is necessary to run a script to do the check. Usually we do those checks in klayout because we have a rule deck for them).

Ok, so my fat square there violated (m1.13) Max pattern density (PD) of met1 CU 0.77 (on https://skywater-pdk.readthedocs.io/en/main/rules/periphery.html ), but if I'd make slots in it to chop out 25% of it (somehow spread over the whole area) it'd be good.

I saw max width spec in the periphery rules but they were much less than 30u and I was wondering about that. ( like 4u for met1/2/3 and 10u for met4), and then they say slotting after that.