Cross-posting this question here: https://skywater-pdk.slack.com/archives/C016YSAP6TZ/p1646674339442299

The minimum diffusion contact width is 420 nm, isn't it? At least, it is for the poly contact.

Ah, dog bone transistors.

I don't think so. Maybe it is a Magic DRC limitation. Maybe it doesn't allow a dog bone transistors. It should pass a commercial tool DRC check.

@User I think this is a bug in the DRC deck.

Exactly what are you referring to that you think is a bug in the DRC deck?

You cannot draw an NMOS that is 0.36um width which is a valid size.

That's not a bug in the DRC deck. It is an intentional limitation of the parameterized device generator. Strictly speaking, SkyWater states that a MOSFET has a minimum width of 0.42um. That's their DRC rule. Narrower transistors are only allowed in SkyWater-approved standard cell libraries. I have bent the rules a bit by allowing any cell to be given an

<http://areaid.sc|areaid.sc>

layer.

Ahhh, I see.

Note that there is a "machine-rule" ("MR") deck made for klayout which matches the SkyWater machine-rule deck for Calibre and specifies all the rules that will cause SkyWater to reject our reticle (or else we have to go through a long process of confirming and waiving each such violation with SkyWater). Ultimately, you can do anything on your chip that does not violate a manufacturing rule, and that includes making transistors down to width of 0.15um. The non-MR rules are basically yield- or performance-related, and so when violating those rules, it's incumbent upon the designer to accept the risk. Ideally, I would at some time like to split the magic DRC deck into MR and non-MR rules, so that you can get a clean result when intentionally violating non-MR rules. As it stands now, only klayout will give you such a result.

I see. I have students designing "user rule" memory cells, so this size is important.

I mentioned one way in your cross-post, which is to paint, for example, the

scnmos

device type. That automatically forces the cell to be covered with

<http://areaid.sc|areaid.sc>

.

@User I'm not clear how to do that. If I paint scnmos, it doesn't actually change any of the layers and still gives the DRC error...

The device types that are sort of "SkyWater-reserved" are locked to prevent casual use by unwary designers. Use

tech unlock *

, and then you can draw them.

@User It looks like 0.36 is wide enough for contacts without the dog bone

@User Then it should be the best width possible considering area for extremely small digital cells. And 0.36/0.15 size is still in the bin.csv file.