Korean researchers control where 2D semiconductor crystals start growing

The science ministry said Thursday that a Korean research team has developed a technique to control precisely where a two-dimensional semiconductor crystal begins to grow, a step toward stacking high-density, low-power AI chips.

The team, led by Kang Ki-bum of the Korea Advanced Institute of Science and Technology, with Kim Byung-jo of Ulsan National Institute of Science and Technology, Kim Woo-hee of Hanyang University and TDS Innovation, used oxygen released from oxide barriers such as hafnium oxide to suppress the formation of molybdenum disulfide crystal nuclei near the barrier edges while allowing a single nucleus to form at the center. The work was published in Nature on Oct. 8.

Two-dimensional semiconductor materials, which are only a few atoms thick, are seen as a way to build AI chips by stacking devices on top of existing logic circuits, cutting both power consumption and the time data takes to move between processing and memory. Making that work in a real chip requires uniform crystals at the exact positions a circuit design calls for.

In conventional selective growth, the area where a crystal may form is defined in advance, but the point inside that area where the nucleus appears is left to chance. Crystals that nucleate at different spots and grow into each other create boundaries that disrupt electron flow.

The team exploited a gradient in the suppressing effect of oxygen from the oxide barrier, which is strongest at the edges of the growth area and weaker toward the middle. That drew a single nucleus to the center of each pattern, producing single molybdenum disulfide crystals at the center in more than 99 percent of 400 experimental patterns.

"Through this research we have confirmed a new possibility for precisely controlling where a crystal starts in the growth of a two-dimensional semiconductor," Kang said. "Building on this underlying technology, we intend to apply two-dimensional semiconductors to actual manufacturing processes and ultimately develop next-generation AI semiconductor technology that stacks computing and memory vertically."

Kim Sung-soo, head of the Ministry of Science and ICT's research and development policy office, called the result a case in which basic research into how semiconductor materials form, combined with work to turn that understanding into core technology, has produced a new approach to semiconductor manufacturing.