GDSII/GDS2 is a binary file format that represents the layers needed to produce an ASIC.

In the LibreLane flow, Magic is used to ‘stream’ the final GDSII files.

All shapes are assigned to a given GDSII layer, and each layer ends up being used to create a mask, although often this may involve the combination of one or more GDSII layers to form one mask, and the shapes are often grown, or shrunk, or merged and thus what ends up on the mask may not be the same as what was drawn by the designer. Each mask is then used in a photolithographic step to produce the chip.

We can use other programs or even software libraries to generate valid GDSII files. Here I’ve used gdspy to convert the Hackaday logo into GDSII.

You can check the very simple program out here

The Skywater PDK defines all the layers that we can use in the GDSII files.

Course feedback

The Zero To ASIC course took me on a fantastic journey from drawing and simulating a MOSFET, formal verification leading up to implementing a custom design with an open PDK and completely open source tools. The course is crammed full of interesting material with great pacing and support from Matt, and it's been a fantastic opportunity to meet other folks with shared interests and different backgrounds. The course has left me excited with opportunities for new projects and optimism for some working silicon!

Jamie Iles (digital course)