DIY Silicon: Design Your Own Chips

Computers & Mobile Electronics Technology
DIY Silicon: Design Your Own Chips
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Matt Venn is a man on a mission: to make it possible for any maker anywhere to design their own chips, going from the core concepts of how the layers in a semiconductor interact all the way up to making a fully functional, application-specific integrated circuit (ASIC) of their own — and receiving the physical chip in the mail.

“Even though I’ve been using microcontrollers for 20 years, I never thought that someone [like me] could make them,” Venn recalls — this despite his history in working with field-programmable gate array (FPGA) chips, which allow you to customize their hardware internally. “It was so out of my idea of what was possible.”

One of Venn’s first chip designs turned a VGA monitor into a desk clock. Photo by Matt Venn

Open Source Chip Design

That is, until he attended an eye-opening Week of Open Source Hardware in Zürich, Switzerland. “Tim Edwards, who’s the head of analog at Efabless, did a presentation on an open source chip where everything was open, apart from the RAM,” Venn recalls. “He even had the board there running a little firmware printing out some messages onto an LCD, and it was using Claire Wolf’s PicoRV32. That talk blew my mind.”

He learned that Edwards was maintaining an open-source digital synthesis flow — a complete tool chain for creating digital circuits, from the logic behavior source code to the finished physical layouts for fabrication — called Qflow. “So when I got home, I tried it out on one of my FPGA designs, and I got some GDS [electronic design automation] files out, and I was like, ‘That’s cool!’” Venn continues. “Then I thought, ‘What about running a workshop where people could do this?’”

He looked into how much it cost to actually get a chip made — but the numbers were disappointing. “It’s about $10,000 to do a short run. I just thought, ‘It’s not going to work, people aren’t going to pay €1,000 [over $1,000] to take a course and get a chip.’”

But Venn wasn’t satisfied just creating chip designs. “Just doing a course where you end up with the files is not interesting enough,” he says. “I wanted to end up with a chip.”

Going to Silicon

Then in 2020 Tim Ansell announced that Google would offer chip designers a tapeout — the lithography photomask for etching chips — to get their open source designs manufactured together on a shared silicon wafer (aka shuttle), for free. “I was, like, ‘I’m in!’ I was just totally ready,” recalls Venn. “Luck favors the prepared.”

That Google-funded program, known as Open Multi-Project Wafer or OpenMPW, gave designers access to an open-source process design kit (PDK) for the 130nm manufacturing process at chip foundry SkyWater Technology. With a standardized shuttle layout for input and output, and access to the OpenLane toolchain on Efabless, suddenly chip production without major financial backing became possible.

What’s a PDK? “It’s got all the information you need to know to design a chip using a certain factory’s process,” Venn explains. “Having an open-source PDK where everything is public and you don’t have to sign an NDA [non-disclosure agreement] is a game changer.” In 2022 a second foundry, GlobalFoundries, opened their PDK for OpenMPW, giving makers access to a 180nm process as well.

Zero to ASIC Course

SkyWater’s open PDK was exactly the catalyst Venn needed to launch an educational course to bring chip design to a wider audience who, like Venn himself, had probably never considered that they could hold a self-designed chip in their hand.

“I did a talk about it for Hackaday Remoticon — this was in the pandemic,” Venn explains. He asked participants if they’d pay $500 to learn how to design chips and get them made, and 200 signed up. “So I was like, ‘Okay, I mean, let’s go!’ and then I spent one month solidly working and recording videos and writing up on my experience and launched the Zero to ASIC Course, and haven’t looked back.”
Backed by 6 hours of video content and 11 practical projects, Zero to ASIC Course is designed to take attendees from a basic background in electronics to creating their own physical chip on an MPW — delivered already mounted on a PCB for testing. At $650, plus $50 for the test board, it’s considerably cheaper than rival commercial training.

Tiny Tapeout

But Venn wanted to drop that barrier even lower with his next project, Tiny Tapeout. Like Zero to ASIC Course, Tiny Tapeout is designed to introduce newcomers to chip design — but its lessons are free, with attendees only paying if they want the payoff of a physical chip. This starts at just $100, dropping the cost dramatically through a simple approach: putting multiple small designs on a single die to create a multi-project chip. Jumpers on the test board let you select your IC design from the dozens of others included in the chip — or to flit around the other submissions, if you want.

Nowadays anyone can blink an LED on a microcontroller by copying a simple script from the internet into Arduino’s free IDE. “You can pretty much do that now for a custom chip, too,” Venn claims. “With Tiny Tapeout you can go to Wokwi, which is this in-browser circuit design and simulation tool, connect an AND gate between two inputs and one output, and then go to our GitHub template system, run the ASIC tools as part of an automated action, and then submit it to the next Tiny Tapeout run — and six months later receive a board with a chip on it where if you press two buttons then the output light turns on.
“Of course, there’s a whole world of stuff happening under the hood that is abstracted away, just like in the microcontroller example. You’re benefiting from all the work that’s been done to make it that easy. So, yes, it’s now that easy for a random maker to make a chip.”

For 100 bucks you get an IC about 100 by 160 microns, big enough to fit about 1,000 gates. What can you do with 1,000 gates? “Little blinkers, flashers, PWM servo drivers, motor drivers — people do whole CPUs.” And you can pay more for more chip space.

Venn hopes Tiny Tapeout will become the de facto choice for small-scale chip production. “I’m hoping it’s like the OSH Park of open-source silicon. Then if you want to learn Verilog, or you want to learn formal verification, or you want to end up doing a whole chip design, then you upgrade to the Zero to ASIC Course.”

SiliWiz

There’s a final string to Venn’s bow, and it’s there to help you get your head around what exactly is happening at the very lowest of levels. SiliWiz is an online interactive tool to learn how semiconductors work and how you build them using lithography. “We have visibility now all the way down to the electrons, basically, so we’ve got an unprecedented level of transparency on how chips really work,” Venn says. “And I think that’s one of the exciting things: you don’t need to know how it all works, but you could do if you wanted to.”

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Gareth Halfacree

Gareth Halfacree is the author of the Raspberry Pi User Guide and an expert in educational and embedded computing. A noted technology journalist and long-time tech author, Gareth also has an extensive background in computing education.

View more articles by Gareth Halfacree

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