SkyWater130 PDK for Electric VLSI Design System is now available

[Adam Megacz Joseph]

Western Semiconductor Corporation has produced a SkyWater130 PDK for
the Electric VLSI Design System [1] and released it under the Apache
license. You can find it here:

https://gitlab.com/westernsemico/com.westernsemico.vlsi

Electric uses the term "technology description" for what most people
would call a PDK. The technology description is packaged as an XML file
containing all of the data you'd usually find in a foundry PDK, but in
machine-readable form: the layer list, critical dimensions, DRC
rules, GDS mappings, LVS device recognition tables, sheet resistances,
and interlayer capacitances.

All of the SkyWater130-specific parameters are in a single file, here:

https://gitlab.com/westernsemico/com.westernsemico.vlsi/-/blob/master/src/com/westernsemico/vlsi/tech/SkyWater130.java

When you run this Java program it spits out the XML file. The Java
code is generally easier to read since you can write loops and
subroutines instead of cutting and pasting.

The Electric SkyWater130 technology is still somewhat incomplete, but
there's enough there to be able to do DRC+LVS on FET circuits, and to
dump out a SPICE deck for simulation.

I had to deduce most of the design rules from the English text of the
DRC error messages in errors.csv. I have a bunch of questions about
that which I will post in a follow-up message. I suppose Mentor is
still claiming that they own every SVRF file written by anybody
anywhere on the planet, including people who aren't Mentor employees.
At least that's what they were claiming last time I checked a few
years ago. It looks like you guys had to do a lot of work to release as
much as possible without butting heads with them; thank you for doing
all that work, and more generally for putting together a basically
complete PDK with no NDA requirement! Western Semiconductor has made
Electric technologies for eight other processes from five other
foundries, and the SkyWater130 technology is the only one that can be
released as open source. Thank you for making this possible!

There is some discussion about SkyWater130 on the Electric mailing list
in these threads:

https://groups.google.com/forum/#!topic/electricvlsi/gDjs51hNrc4
https://groups.google.com/forum/#!topic/electricvlsi/qRX1YJ0rHT8
https://groups.google.com/forum/#!topic/electricvlsi/p1tZwlLYdzs

- a

[1] https://staticfreesoft.com/

[song jin]

hello, I have successfully imported pdk into Electric. However, when I imported a GDS, Electric reported 6 errors indicating some layers cannot be recognized correctl such as GDS layer 236, type 0 unknown. Moreover, ERC check reported that No nwell contact in this area. Would you please tell me how to fix this problem? Thank you very much!

[ad...@westernsemico.com]

Hello Song Jin!

Quoting song jin (2023-01-30 07:35:06)

> hello, I have successfully imported pdk into Electric.

That is great! I'm glad to hear that it worked for you.

> However, when I imported a GDS, Electric reported 6 errors indicating some
> layers cannot be recognized correctl such as GDS layer 236, type 0 unknown.

Hrm, skywater-pdk (git commit 49d3c73c2cd8ea42cdae5056440baef0f72e7e42)
docs/rules/gds_layers.csv doesn't list 236/0 as being a valid GDS layer.

The only mention I can find of 236/0 is an entry in the klayout colorization
file from open_pdks (1.0.389, git 1cf0d5ddec191db3c878823ed0ded912319da9c6).
Curiously, the klayout file doesn't have a descriptive name (like
"via3.blockage") for this layer. It is still not clear to me what the purpose
of this layer is.

Could you tell me where the GDS you are trying to import came from? Did you get
it from the foundry, or was it the result of some foundry-specific tool (like a
fill generator)? You might be seeing non-designer layers. Note: I will have
very limited Internet access from tomorrow until 2023-Feb-10; I might not be
able to read any replies until then.

> Moreover, ERC check reported that No nwell contact in this area.

Ah, I did not implement the ERC (Electrical Rule Check), so unfortunately you
can't use Electric's ERC tool for Skywater130 yet.

Regarding the future of the Electric PDK: this has been on the back burner for
me while waiting for eFabless to allow self-paid GDS-handoff customers to use
their own circuitry instead of the Caravel Management Engine. I'm still not
sure if that has happened yet.

- a

[rtedwards8]

Layer 236:0 is a boundary layer that is unmentioned in the SkyWater documentation.  I had to divine its use from the SkyWater GDS files.  In the tech file for Magic, I refer to it as "outline".  It is not a physical mask layer.

---Tim