Experiment with the SkyWater Open Source PDK

The Efabless Open MPW Shuttle Program provides fabrication for fully open-source projects using the SkyWater Open Source PDK announced by Google and SkyWater. The shuttle provides opportunities for designers to experiment and push the state-of-the-art without having to reconcile the risk associated with the cost of fabrication.

The shuttle program is open to anyone, provided that their project is fully open source and meets the other program requirements. The first shuttle run is planned for November of 2020, with more scheduled for 2021.

Project Submission Requirements
The following project requirements must be met in order to qualify for inclusion on the shuttle program:

  • The project must be targeted on the currently supported SkyWater Open PDK for the 130 nm process.
  • The project must be posted on a git-compatible repo and be publicly accessible.
  • The top-level of the project must include a LICENSE file matching the current Apache 2.0 license agreement. Third-party source code must be identified and source code must contain proper headers. See details here.
  • The repo must include project documentation and adhere to Google’s inclusive language guidelines. See details here.
  • The project must be fully open. The project must contain a GDSII layout, which must be reproducible from source contained in the project.
  • Projects must use a common test harness and padframe based on the Caravel repo. The projects must be implemented within the user space of the layout and meet all requirements for the Caravel.
  • Projects must successfully pass the Open MPW precheck tool, including LVS and DRC clean using the referenced versions of OpenLane flow.
  • Projects must meet a metal density specification to be supported on the shuttle. A metal density check will be implemented as part of the precheck process.


  • November 12, 2020: Project submission is open for first shuttle
  • November 30, 2020: Project submission is closed for first shuttle

Open Source MPW

Each shuttle will support up to 40 projects. If qualified project submissions exceed that number, they will be selected randomly for inclusion on the shuttle.

Each project will receive 50 packaged parts and 5 evaluation boards assemblies based on prefixed package and board designs.

You must have submitted a request through the Efabless platform, completed all requirements listed for submission including successfully passing a precheck on the platform. You must also have confirmed your submission in the ‘Define’ step of the request process prior to 11:59pm PST November 30, 2020.

Projects must only contain source code released under approved licenses. To make sure this is complied with, the following must be done:

  • All source files not under third_party directory must have correct license headers and SPDX identifiers.
  • The top level directory must have a LICENSE file which is correctly detected as one of the approved licenses.
  • All source code not developed directly by the group submitting must be under the third_party directory.
  • All code under the third_party directory must have LICENSE files which are correctly detected as one of the approved license files.

Repository should have a README file

All documentation should use inclusive language

Projects must have a complete JSON file containing project meta-data per the following format (TBD). The metadata will be used by the Efabless platform for creating entries into a public project showcase page for the shuttle program.

You can navigate to your project submission request from the Open MPW Shuttle Program landing page.

In a browser, navigate to and provide your email address. You will receive an invitation to join the community Slack channel.

All projects must use the Caravel test harness padframe. Customization of the pads on the padframe is not supported at this time.

The preferred license for all submissions is Apache 2.0 but other licenses are also possible. Please make sure not to submit repositories which include contents licensed under the explicitly prohibited list.

Some commonly used examples:

  • BSD-3-clause, BSD-2-clause, BSD Zero
  • MIT
  • ISC
  • GPL-2.0, GPL-3.0
  • LGPL-2.1, LGPL-3.0
  • CC0, CC-BY, CC-BY-SA
  • Unlicense

A full list of approved licenses can be found under these sections of the Google Open Source documentation:

A full list of explicitly prohibited licenses can be found under the Banned section of the Google Open Source documentation.

A full list of explicitly prohibited licenses can be found under the Banned section of the Google Open Source documentation.

Inclusion of any assets either in the repository or in third-party dependencies will cause your submission to be rejectedSome commonly used examples are:

While you are free to license your code under any license you choose, Apache 2.0 is Google’s preferred license.

For this initial MPW shuttle, Efabless will add fill to the layout to meet metal density requirements for the shuttle.

The precheck tool performs a series of checks to confirm the project meets the requirements for participating in the Open MPW Shuttle Program. The precheck tool addresses the following items:

  • Ensures the project has an Apache 2.0 LICENSE and all third-party IP is organized correctly with its own LICENSE file.
  • The project contains documentation including a populated info.yaml file. The tool checks for a minimal set of words that should not be used to comply with Google’s inclusive language policy.
  • The presence of a Makefile with the following targets: compress, uncompress, clean, verify.
  • The presence of netlists and GDSII files. The presence of Caravel modules within these and design complies with rules for Caravel in terms of pins and power routing.
  • The DRC check using Magic with OpenLane

The tool runs as a Linux container. It can be cloned and run offline prior to uploading the project to the Efabless platform. Further details can be found on the README file located in the git repository for the tool ( )

Efabless will confirm the deliverables provided by the submitter using both automated tools and manual review. This includes the following items:

  • User profile
  • Service agreement is accepted
  • Project repo is public and accessible
  • Licensing for the project and any third party components. Acceptable header files on all text and source files.
  • The project contains:
    • Source files to recreate the GDSII
    • Verification tests
    • Documentation
  • Expected netlist and GDSII files exist including expected module and instance name based on Caravel.
  • LVS and DRC checks.
  • Metal density check and fill to meet the density specification for the shuttle.

The git repo for the project should include the following items.

  • The project should include the Caravel test harness with the users design occupying the user space for the layout.
  • The GDSII in a compressed format.
  • A makefile with targets to compress, uncompress and clean the project.
  • All source required to generate the GDSII including any third-party components.
  • The makefile should also include verify target to executed a test verification suite for the design.
  • Documentation including a README file as well as a info.yaml file containing metadata for the project
  • LICENSE files for the top-level project as well as each of the third-party components used

The Open MPW Shuttle Program is sponsored by Google. All costs associated with fabrication, packaging, assembly into evaluation boards as well as shipping to world-wide locations are covered and the user bears no cost for these items.

The only item that a user may be responsible for is any import duty or taxes for shipping parts and boards to a location outside of the United States. The shipping cost will be included, but any additional costs for duty or tax are the responsibility of the recipient.

The Open MPW Shuttle Program supports a global community and will ship parts and boards to project owners worldwide.

The shipping cost will be included, but any additional costs for duty or tax are the responsibility of the recipient.

There are several options to get support.

  • After you have created a request, you can submit questions directly to Efabless through the Activity tab when viewing / managing your request.
  • You can post a question to the Open PDK community on slack. See the response to ‘How do I connect with the Open PDK community.’
  • You submit a help desk ticket using the pull-out menu on the lower right side of any web page on the Efabless site.

The list of steps is provided on the detail tab when viewing your request. They include:

  • Confirm the project is a public git repo with Apache v2.0 licensing.
  • Project successfully passes the Precheck tool executed on the Efabless platform.
  • Your profile includes your full name, email and physical address.
  • Shipping address provided above in the request is correct.
  • Review and accept the terms agreement from the landing page.

Once you have completed these steps, please select ‘change’ next to the ‘Submitted’ status indicator to update your request status to ‘CONFIRMED.’

Efabless will then review each of your deliverables and send any questions back to you using the message thread located on the Activity tab for the request.

Once everything has been confirmed, Efabless will update the status for ‘Provider’ to ‘CONFIRMED.’

Efabless will update the status of your request for ‘Provider’ to ‘CONFIRMED’ to indicate you have met all of the requirements for your project to be included on the shuttle.

If more than 40 projects are submitted, projects will be selected randomly to be included on the current shuttle. Project owners will be notified either way on the status of their project.

Bare dies are not provided to users as part of this program.

Caravel includes an electronic ID implemented in the metal layer for each project slot. You will be assigned an ID upon your project being accepted for the shuttle. You will be able to electronically read this ID through a register as part of the management function for Caravel. Please see the README for more detail. We are also targeting to have the packages laser marked for visual identification.

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Project submission opens November 15, 2020 and closes November 30, 2020.