Open PDKs

CMOS (and variants):

Skywater 130 https://skywater-pdk.readthedocs.io/en/main/

Globalfoundries GF180 https://gf180mcu-pdk.readthedocs.io/en/latest/

IHP https://github.com/IHP-GmbH/IHP-Open-PDK

MinimalFab: https://www.minimalfab.com/update/news_en/226

SiEPIC Ebeam PDK: https://gdsfactory.github.io/ubc

VTT: https://github.com/gdsfactory/vtt

Libresilicon 1um https://libresilicon.com/#whitepaper

MEMS:

Science: https://science.xyz/docs/d/mems-tfe/process