Former Purdue University mechanical engineering students Alex Bauer, from left, Mark Ragei, and Dylan Balter make a presentation during the spring 2022 Malott Innovation Awards. (Image: Purdue University/Jared Pike)

Purdue University engineers have developed a patent-pending tool to make the manufacture of ultrathin semiconductors more consistent, controllable, and repeatable than traditional methods.

A research team led by Thomas Beechem, an associate professor of mechanical engineering in the College of Engineering, has created a tool that uses a dry-transfer process to move graphene and other ultrathin, 2D materials from the growth substrate where they are synthesized to a device substrate.

“Everyone wants their electronics to be smaller, faster, quicker, and more powerful. So, transistors keep getting smaller and smaller, which means the semiconductor industry is looking beyond silicon,” Beechem said. “Manufacturers are thinking about materials that are only atoms thick, like graphene and molybdenum disulfide (MoS2), but the substrates that they grow on best aren’t the best for making devices.

‘The challenge is moving the material from the growth substrate to a platform good for making devices. Right now, this transfer is an artisanal process completed in a one-off manner — but workers can’t do that at scale.”

Beechem said their tool provides users with more control and degrees of freedom, including creating their own recipes for a scalable process. Using a dry-transfer process, the tool also removes the need to etch materials that easily contaminate the ultrathin layers.

“The tool allows us to control several aspects of peeling samples from a substrate: How much force is used to grab the sample? How fast do we peel? What angle do we contact the 2D material with the stamp?” Beechem said.

“The goal is opening up the parametric space to develop fab recipes for 2D materials in the same way we do for all processes taking place in a semiconductor clean room. Users can try different degrees of freedom — not just up and down, but rotation as well — to find the best recipe for their particular growth substrate and device platform.”

The next step is to develop the tool for commercialization by connecting with industrial partners that are pursuing ways to standardize 2D-device fabrication.

“Two-dimensional materials have been darlings in the lab for over a decade now,” Beechem said. “To get them off the lab bench and into the real world, tools must be developed that allow their scalable integration into commercial fabs. Our tool steps in that direction in an attempt to make an iffy process in the lab into something more automatic.”