The 22-year-old is building chips in his parents’ garage

Zeloof spun hand-cut half-inch polysilicon squares, each to become a separate chip, on a small home turntable at 4,000 rpm to cover them with the photosensitive material needed to transfer its design to the surface. Then his home photolithograph shines on his design: a network of 12 circuits, each with 100 transistors (and a dancing bear), a total of 1,200 transistors.

Zeloof’s first chip, the Z1, was made in 2018, when it was still in high school and has six transistors.

Photo: Sam Kang

Its second chip, the Z2, was completed in August 2021 and has 1,200 transistors.

Photo: Sam Kang

Zeloof is running on the Z3, a chip that will be able to add 1 + 1 as a step towards a full microprocessor.

Photo: Sam Kang

Each chip is then engraved with acid and cooked in an oven at about 1000 degrees Celsius to bake in phosphorus atoms to regulate its conductivity. Three more rounds under the photolithograph – separated by steps, including time in a vacuum chamber filled with glowing purple polysilicon etching plasma – completed each chip. Today’s commercial factories produce chips in a similar way, using a sequence of steps to gradually add and remove material in different parts of the design. These chips are much more complex, with billions of much smaller transistors stacked tightly together, and the steps are performed by machines, not by hand. The transistors of Zeloof’s second-generation chips were about 10 times faster than those of his first and had characteristics smaller than 10 microns, not much larger than red blood cells.

In August, Zeloof tested the Z2 by connecting it to a square beige semiconductor analyzer released by Hewlett Packard about two decades before its birth. A series of steadily rising voltage curves on its glowing green screen signaled success. “This curve was amazing to look at,” says Ziloof, “the first sign of life after spending an entire day immersing this little piece of crystal in a glass of chemical.”

How to celebrate when your home chip works? “Twitter it!“Says Ziloof. His project has won followers on Twitter and millions of views on YouTube, as well as some helpful tips from veterans of the semiconductor industry since the 1970s.

Ziloof says he doesn’t know for sure what he wants to do after this spring, but he’s thought about the place that DIY chips could have in today’s technology ecosystem. In many ways, DIY experimentation has never been more powerful: robotics equipment and 3D printers are easy to buy, and hacker-friendly hardware such as the Arduino and Raspberry Pi microcontrollers are well established. “But the chips are still made somewhere in a big factory,” says Ziloof. “There has been little progress in making it more accessible.”

Ellsworth, whose home-made transistors inspired Zelloff, says he could benefit from the ability to produce high-quality, practical chips. “The tools we have today could put this in the scope of small-scale operations, and I think it makes a lot of sense for certain problems,” she said. Ellsworth says chip technology, considered obsolete by leading factories, could still be useful to engineers.

Zeloff recently upgraded his photolithography machine to print details measuring about 0.3 microns or 300 nanometers – roughly on par with the commercial chip industry in the mid-1990s. Now he’s thinking about features that he could incorporate into a chip on the scale of Intel’s historic 4004. “I want to push garage silicone even harder and open people’s minds to the possibility that we can do some of these things at home,” he says.

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