Open PDKs

Automatic setup of PDKs for open-source tools from foundry sources.

Open PDKs currently has support for building the sky130 and gf180mcu PDK families for the SkyWater SKY130 and GlobalFoundries GF180MCU process. Sources for the foundry process data are cloned automatically from repository services (primarily github).

Other non-free processes (such as X-Fab XH035 or XH018) can be obtained as "plug-ins" for Open PDKs. Sources for non-free foundry process data must be obtained separately.

An important consideration for anyone wishing to obtain one of the open source PDKs is that Open PDKs is a PDK builder, and running it is like running a compiler to build a complex software application. Doing so can be difficult, time consuming, and resource-intensive. The software world came up with the idea of a "package manager" application that handles pre-built software. Likewise, there is a "PDK package manager" for handling pre-built PDKs, called Ciel (formerly called Volare).

Table of Contents:

• Open PDKs Format
• Build Instructions
• Example Usage
• Licenses

Open PDKs Format

PDK Naming Conventions

For a given PDK, Open PDKs expects a single PDK family with one or more PDK variants. PDK variants differ from one another, for example, by using a different metal stack or other process options.

PDK family	PDK variant
sky130	sky130A, sky130B
gf180mcu	gf180mcuA, gf180mcuB, gf180mcuD, gf180mcuD
...	...

The PDK variant is an extension of the PDK family name.

The PDK family and PDK variants can consist of letters (a-z and A-Z), digits (0-9) and underscores (_). Please do not use hyphens (-), periods (.), commas (,), colons (:) or any other special punctuation (@, #, ! etc.).

The PDK_ROOT environment variable points to a directory in which each the PDK variant has a subdirectory. The PDK environment variable contains the name of the PDK variant.

Therefore, the path $PDK_ROOT/$PDK/ points to the PDK file structure of the specified PDK variant.

IP Naming Conventions

IP libraries are named according to the following structure:

<pdk-family>_<tag>_[pr|sc|io|sram|...]

For example, sky130_fd_sc_hd is the foundry-provided high-density standard cell library for sky130.

The tag is chosen by the entity providing the IP. The fd tag is used when the IP library is foundry-provided. If you supply your own IP library, you can choose your own tag (that is not yet used). For example, ef was used by Efabless.

IPs extend this structure after two underscores by their name:

<pdk-family>_<tag>_[pr|sc_<scl-name>|io|sram|...]__<ip-name>

For example gf180mcu_fd_sc_mcu7t5v0__and2_1 is a two-input and gate with a buffer strength of one from the gf180mcu_fd_sc_mcu7t5v0 standard cell library.

Structuring the PDK

The general file structure of a PDK variant is as follows:

<pdk-variant>
├── libs.doc
├── libs.qa
├── libs.ref
└── libs.tech   

Within libs.ref/ you can find the IP libraries:

libs.ref
├── <pdk-family>_fd_io              Foundry I/O cells
├── <pdk-family>_fd_pr              Foundry primitives (devices)
├── <pdk-family>_fd_sc_<scl-name>   Foundry standard cell library
...

Within an IP library you can find folders for the different views:

<pdk-family>_fd_io
├── cdl             CDL files
├── gds             FDS layout
├── lef             LEF files
├── lib             Liberty files
├── mag             Magic layout files
├── maglef          Magic LEF files
├── spice           Spice netlists
├── verilog         Verilog files
├── xschem          Xschem schematics
...

Within libs.tech/ you can find the EDA tool setups:

libs.tech
├── klayout                     KLayout technolog files
├── librelane                   LibreLane setup
├── magic                       Magic setup and device generators
├── netgen                      Netgen setup 
...

Directories are typically named after the tools that use the files they contain. Symbolic links are permitted within the PDK file structure to enable the sharing of common files and directories between PDK variants.

Build Instructions

Read the README file in subdirectory sky130/ for instructions on building the SkyWater sky130A PDK, or in the directory gf180mcu/ for instructions on building the GlobalFoundries gf180MCU PDK.

Instructions:

git clone https://github.com/RTimothyEdwards/open_pdks.git
cd open_pdks
./configure [options]
make
[sudo] make install

where the configure [options] are specific to each foundry PDK supported by Open PDKs and can be queried using

./configure --help

At a minimum you will want to pass a configure option to declare the PDK that you want to build. It is possible to build multiple PDKs at once, but not recommended due to the large memory and disk space overhead required by each one.

./configure --enable-[PDK_name]-pdk

The Open PDKs version of the PDK can be built locally within Open PDKs without the need to declare an install target or run "make install". However, it is highly recommended to declare a target location and install there, using

./configure --prefix=[path] --enable-[PDK_name]-pdk

followed by "make" and "make install". The default install location is /usr/local/share/pdk ([path] above is /usr/local). The install location should be a read-only filesystem area for regular users, since the PDK contents should not be altered.

Also see the website at http://opencircuitdesign.com/open_pdks/. The "Install" page has full instructions for configuring and installing Open PDKs.

Example Usage

SkyWater sky130 PDK:

./configure --prefix=/usr --enable-sky130-pdk --enable-sram-sky130 \
	--enable-sram-space-sky130 --enable-reram-sky130
make
sudo make install

GlobalFoundries GF180MCU PDK:

./configure --prefix=/usr --enable-gf180mcu-pdk
make
sudo make install

Both of these examples install into the directory /usr/share/pdk/. The first one builds PDKs sky130A (standard) and sky130B (with the ReRAM option). The second one builds PDKs gf180mcuA (3 metal stack), gf180mcuB (4 metal stack), gf180mcuC (5 metal stack with 0.9um thick top metal), and gf180mcuD (5 metal stack with 1.1um thick top metal).

Existing shuttle services as of this writing (September 2025) use sky130A, sky130B (Cadence, Chip Foundry), and gf180mcuD (Wafer.Space).

Given the configurations above with prefix "/usr", most open source tools will expect

export PDK_ROOT=/usr/share/pdk		(sh, bash)
or
setenv PDK_ROOT /usr/share/pdk		(csh, tcsh)

Licenses

Open PDKs is open-source software distributed under the Apache-2.0 license. See file LICENSE for the complete license text.