TSMC Collaboration Offers A New Path for ICs with Two-Dimensional Transistors

March 09, 2020 by Luke James

Scientists are constantly looking for new ways to extend Moore’s Law, and a recent project involving researchers from the U.S., China, and TSMC may have discovered a path towards creating integrated circuits that use two-dimensional transistors.

A researcher at Rice University in the U.S. and his colleagues in China and Taiwan have recently grown atom-thick sheets of hexagonal boron nitride (hBN) as two-inch diameter crystals over a wafer. 

The study, which was published in the journal Nature, reports how the researchers took advantage of the disorder among the meandering steps on a copper substrate to achieve the growth of this crystalline structure. 


Atoms of boron and nitride on copper substrate.

Atoms of boron and nitride on a copper substrate that make up a large-scale, ordered crystal of hexagonal boron nitride. Which could become a key insulator in future two-dimensional electronics. Image used courtesy of Tse-An Chen/TSMC.


Growing Perfectly Ordered hBN Crystals 

Previous attempts to grow perfectly ordered crystals of hBN, which is a wide bandgap semiconductor, have been futile. However, by utilising the aforementioned disorder and leveraging it to keep the hBN in line, the researchers were able to achieve their long-sought aim of producing it. 

When hBN is integrated into chips as a dielectric between nanoscale transistor layers, it is known to improve the dampening of electron scattering and trapping which restricts the efficiency of a built-in circuit. Although this has been known for quite some time, no attempt has been successful at ordering sufficiently large enough hBN crystals that would be useful until now. 

Taiwan Semiconductor Manufacturing Co (TSMC) was tasked with developing a proof-of-concept of the two-dimensional transistor for manufacturing purposes. 

TSMC produced this—a two-inch two-dimensional film—in partnership with experimentalists from Taiwan’s National Chiao Tung University. They then transferred the proof-of-concept hBN film to silicon and added on a layer of field-effect transistors (FETs) that were patterned onto 2D molybdenum disulfide over the hBN film. 

The main discovery in this work is that a monocrystal across a wafer can be achieved, and then they can move it. Then they can make devices said Boris Yakobson from the George R. Brown School of Engineering at Rice University. He added, “There is no existing method that can produce hBN monolayer dielectrics with extremely high reproducibility on a wafer, which is necessary for the electronics industry…”


Hexagonal boron nitride.

Wafer-sized, two-dimensional sheets of hexagonal boron nitride. Image used courtesy of TSMC and Rice University


Developing the ‘Successor’ to Moore’s Law

A few decades ago, Intel’s Gordon Moore said that the number of transistors found in an integrated circuit would double every couple of years. As the design of integrated circuits becomes smaller and smaller—today’s circuits measure only a few nanometers, after all—maintaining the rate of development needed to keep up with tech is becoming increasingly difficult. 

In theory, stacking two-dimensional layers, each with an unlimited number of transistors could resolve this problem if the layers are separated from each other. Thanks to its properties and wide bandgap, insulating hBN is a promising candidate as a successor to traditional silicon wafers.