The metrics for measuring integration density used to be metal half-pitch and gate length. For a while they were about the same number. This number became known as the node or process number.
The half-pitch refers to half the minimum center-to-center distance spacing (or pitch) between Metal 1 lines.
By 1990s these numbers became uncoupled, and the 130nm node actually has 70nm gates. By 2000, the node number “had by then absolutely no meaning” (Paolo Gargini. IEEE article by Samuel K. Moore: The node is nonsense.)
It’s still used as a marketing tool, but it doesn’t really mean anything anymore.
The table above shows how the gate length and metal half width measurements have become uncoupled from the node number. The table came from this interesting video about the latest and smallest process sizes.
Finally, this chart shows how even though the 130nm process is quite old, it and larger/older sizes still account for about 50% of all ASICs made by EuroPractice.
Matt Venn's Zero To ASIC course is a real eye-opener to the possibilities of open source hardware. The course itself is a tour-de-force overview of almost all aspects of ASIC development from concept to GDSII. It's also great fun and regardless of your background or previous experience, you'll learn a lot and have a great deal of fun doing it. This course has inspired me to take the next step and submit my own design to efabless.