Nanoscale “direct-write” 3D printer earns student a prestigious IBM PhD Fellowship

Microscale electronics require creating intricate – and micron-thin – patterns of circuitry on a chip.

Creating these patterns using physical vapor deposition (PVD) or chemical vapor deposition (CVD) has meant coating the wafer substrate in a material, for example aluminum, then chemically carving away everything that isn’t wanted.

But a technique that recently earned UChicago Pritzker School of Molecular Engineering PhD candidate Xella Doi an IBM PhD Fellowship is working towards creating a “direct-write 3D printer” that would paint the intricate patterns themselves, with an ultimate target of a few billionths of a meter.

“In traditional lithography, you need to expose your substrate to a lot of different chemicals, which would damage delicate substrates, since you’re depositing a lot of material and then removing some to create your patterns,” Doi said. “Whereas for our system, we directly write the patterns with a nozzle like a 3D printer, so there's no secondary cleaning step or etch where you would damage a delicate substrate.”

As first author of a paper published in 2023, Doi and her team at the Guha Lab, demonstrated printed interconnects two orders of magnitude smaller than the current state of the art. She hopes to use the IBM PhD Fellowship to improve upon that technique, turning the nanoscale lines and dots the team demonstrated into the intricate circuitry needed for microelectronics.

“We’ve demonstrated some simple PVD depositions down to a two-micron resolution, but we're still exploring the ways to control it in a way that would result in reliable devices,” Doi said.

IBM selected Doi for the highly competitive fellowship, which dates back to 1951, out of a field of PhD candidates from universities across the globe. The program offers a stipend for research and partners each recipient with an IBM mentor.

Doi’s principal investigator, UChicago PME Prof. Supratik Guha, said Doi was the perfect candidate for the honor.

“We are very happy to hear that Xella was selected and we congratulate her,” Guha said. “And we are grateful to IBM for providing Xella this opportunity.”

A cooler way to print

Doi’s printing technique has been able to deposit aluminum at temperatures of 130 to 160 degrees Celsius. She hopes the IBM fellowship will help the team take that to the next level.

“We’re implementing a new system where we can do chemical vapor deposition (CVD) or atomic layer deposition (ALD), which allows us to deposit at low temperatures, relying on chemical reaction at the surface to deposit metals. We are also adapting deposition methods (CVD and ALD) that are widely used in semiconductor manufacturing for deposition over large areas” she said.

Although Doi envisioned the technique for building microelectronics, the technique the Guha Lab is pioneering will be applicable for many forms of research including areas such as quantum technologies.

“It’s basically a nanoscale 3D printer. Where 3D printers currently use inks or melted plastic, ours would be delivering the vaporized precursor for PVD and CVD,” Doi said. “The basic concept is to build these nanoscale nozzles that we can position and scan along a substrate surface, such as silicon or, really, any material, but especially the organic boards used to hold chips.”

• Learn more about how UChicago PME is advancing materials systems