Method irons out 2-D materials for computer chips

Two-dimensional electronic materials could be key ingredients in future energy-efficient computer chips—if engineers can learn to build devices with them. On Dec. 4 at the International Electron Devices Meeting in San Francisco, researchers from the Belgian semiconductor research company Imec presented a method for making and transferring smooth, high-quality sheets of tungsten disulfide and other 2-D materials. Devices with 2-D materials have been made in the lab but they tend to be one-offs. “We’re always limited by the precision of lab tools,” says Imec device physicist Iuliana Radu. Her team sought a way to transfer large sheets of 2-D materials from the surface on which they are grown, to the surface of a silicon wafer patterned with electronic circuits, without wrinkling the 2-D material or melting the underlying silicon devices. They grew a WS₂ film, 0.7 nm thick and 300 mm in diameter, on a silicon wafer. They attached the film to a glass carrier with proprietary adhesives and transferred it to the destination wafer, using lasers to melt the adhesives. The material can then be patterned to make large arrays of transistors whose performance is comparable to those made one at a time using more artisanal lab methods. These techniques work with other 2-D materials as well, Radu says.