New MIT method uses 2D materials to "catch up" with Moore's Law

2D materials could allow manufacturers to "catch up" with Moore's Law

The team of MIT researchers developed a method that could one day allow manufacturers to develop increasingly small transistors — beyond the limits of Moore's Law — using 2D materials.

In a test, the team used the new method, called "nonepitaxial, single-crystalline growth", to grow 2D materials onto industrial silicon wafers. They reported that the resulting 2D materials were defect-free.

"We expect our technology could enable the development of 2D semiconductor-based, high-performance, next-generation electronic devices," explained Jeehwan Kim, associate professor of mechanical engineering at MIT. "We've unlocked a way to catch up to Moore’s Law using 2D materials."

Specifically, the team developed a functional transistor from a 2D material called transition-metal dichalcogenides, or TMDs. Research has shown that these conduct electricity better than silicon on the nanometer scale. Kim and his colleagues outlined their method in a new paper in Nature.

A novel method for manufacturing next-gen transistors

Scientists have previously attempted to develop transistors on silicon wafers using 2D materials. The problem is that these silicon wafers lack a supporting scaffold of other materials that would be utilized with 2D materials at such a small scale. So attempts to grow 2D materials on silicon have typically yielded a messy patchwork of crystals. These form grain boundaries that greatly reduce conductivity.

"It’s considered almost impossible to grow single-crystalline 2D materials on silicon," Kim said. "Now we show you can. And our trick is to prevent the formation of grain boundaries."

The new "nonepitaxial, single-crystalline growth" method uses conventional vapor deposition methods to pump atoms across a silicon wafer. These atoms eventually settle and nucleate, allowing them to grow into two-dimensional crystal orientations. If left alone, these "nuclei" would grow in random directions across the wafer.

The key to the MIT team's method, however, is that they found a way to direct the nuclei, or growing crystals, to create single crystalline regions across the wafer. They used a "masking" method where they coated the silicon wafer with a pattern of tiny pockets of silicon dioxide. Each of these pockets was designed to capture the nuclei, or crystal seeds, to form a 2D material.

In their tests, the researchers showed that they could use this method to develop a simple TMD transistor with an equal electrical performance as a pure flake of the same material used.

"Until now, there has been no way of making 2D materials in a single-crystalline form on silicon wafers, thus the whole community has almost given up on pursuing 2D materials for next-generation processors," Kim explained. "Now we have completely solved this problem, with a way to make devices smaller than a few nanometers. This will change the paradigm of Moore's Law."