It doesn't benefit from 22nm - analog blocks generally don't scale down at all, they have to be a particular size to achieve particular current handling, inductance etc. requirements. But we need the production line availability.
Does this even work longterm? I'd like to think transparent-by-design hardware manufacturing is not a pipe dream, but if that's the case, I would hate to give it too much thought.
From the 2025 Free Silicon Conference:
https://wiki.f-si.org/index.php?title=The_Transparent_Refere...
https://wiki.f-si.org/images/e/eb/OpenFab%40FSiC2025.pdf
The initiative started in Germany, where the research institute IHP already provides an open source 130nm PDK and associated foundry, but interest is spreading. Here's the abstract from that talk:
"The European Chips Act aims to double Europe’s share in global semiconductor manufacturing to 20% by 2030. However, most current investments focus on leading-edge nodes and pilot lines, which – while important – are not sufficient to achieve broad capacity scaling. At the same time, demand for mature nodes (≥65 nm) remains strong: over two-thirds of chips in automotive and industrial sectors still rely on nodes ≥90 nm, and this trend is expected to persist through 2030. This contribution introduces the concept of a Transparent Reference Fab – a fully open, scalable semiconductor fabrication model designed to serve as a blueprint for sovereign and trustworthy chip manufacturing in Europe. Unlike traditional pilot lines, the Transparent Reference Fab is production-ready and replicable. It includes open access to process design kits (PDKs), equipment configurations, process recipes, and operational know-how. The fab targets mature nodes, especially 65 nm CMOS, and is intended to be built on existing infrastructure to reduce time-to-market and technical risk. We argue that such a model can significantly multiply Europe’s production capacity by enabling private and public actors to replicate the reference fab across regions. This approach would not only strengthen Europe’s position in strategic semiconductor supply chains but also foster innovation, education, and security through transparency. The paper presents the strategic rationale, technical architecture, and implementation path, positioning the Transparent Reference Fab as a critical instrument for European resilience and competitiveness."
For example, I couldn't find anything about the costs necessary to bring up a fab?
We can save money during initial prototyping, by creating a small test structure as small as 1mmm^2, which reduces the cost of a prototype run to 5k$ - 10k$. Some services that provide this are MOSIS [0] in the US, and Europractice [1] in the EU. But when we go to a full production run, there's no way to get around creating a 'full reticle' design, as image sensors have a physical dimension determined by focal plan size requirement of imaging application. For example, in digital camera, if a sensor is 'full frame' then it obviously has to be 36mm x 24mm, regardless of if the process node would have let you shrink it. And if you make a serious mistake, then you need to do another production run, which means you pay the 300k$ - 1m$ once again.
In terms of the circuit functionality, image sensors require a mixture of analog and digital design, but in this area, even many of the digital circuits are custom designed, rather than relying on foundry-provided 'standard cells' and an automatic place-and-route flow.
Regarding node sizes for image sensors, TSMC built a 28nm fab recently for Sony exclusively to make their latest sensors. There was actually a HN post about that a couple years ago [1]. Also, it's important to note that in many applications, the image sensor layer is now actually stacked, with a layer of DRAM (in 45 nm, for example) between, and a ISP (image signal processor) chip on the bottom made in a smaller digital process. You can see an image of that stack up here [2].
[0] https://image-sensors-world.blogspot.com/2020/08/tsmc-report... [1] https://news.ycombinator.com/item?id=24321804 [2] https://fuse.wikichip.org/news/763/iedm-2017-sonys-3-layer-s...
