A scalable method for large-area integration of 2D products

Double-sided (2D) materials have great potential to provide devices with much smaller size and expanded capabilities in terms of what can be achieved with today’s silicon technologies. But to take advantage of this potential we need to be able to integrate 2D products into semi-automated manufacturing lines – a very difficult step. A team of Swedish Graphene researchers in Sweden and Germany is now reporting on a new way to do this work.

The approach, just published in Nature Communication with researchers from Graphene flagship partners RWTH Aachen University, Universität der Bundeswehr München and AMO GmbH, Germany, Graphene KTH Logo Partner Member of the Royal Institute of Technology, Sweden, in collaboration with Protemics GmbH.

Integrating 2D materials with silicon or with a substrate with integrated electronics presents several challenges. “There is always this critical stage of moving from a specific growth substrate to the final substrate on which you build sensors or components,” says Arne Quellmalz, a researcher at Graphene Linked Ball Flagship KTH and lead author of the paper. “You may want to combine a graphene photodetector for on-chip optical communication with silicon reading electronics, but the growth temperature of these materials is too high, so you can’t do this directly on the device’s substrate.”

To date, most of the experimental methods for transferring 2D materials from their growth substrate to the required electronics are either incompatible with high-volume manufacturing or lead to severe contamination. of its 2D material and electronic properties. The beauty of the solution suggested by Quellmalz and colleagues is that it lies in the existing mechanical resources in semiconductor manufacturing: to use a standard dielectric material called bisbenzocyclobutene (BCB), along with equipment normal wafer connection.

“We basically glaze both wafers together with resin made of BCB,” Quellmalz explained. “We heat the resin, until it grows slowly, like honey, and press the 2D material against it.” At room temperature, the resin hardens and forms a stable bond between the 2D stuff and the wafer, he says. “To stack materials, we repeat the steps of heating and pressing. The resin becomes slow again and behaves like a cone, or water bed, which supports the cover stack and transforms it. to the surface of the new 2D material. ”

The researchers demonstrated the transfer of graphene and molybdenum disulfide (MoS2), as a representative for transition metal dichalcogenides, and graphene stacked with hexagonal boron nitride (hBN) and MoS2 to heterostructures. The extruded layers and heterostructures were reported to be of high quality, that is, they showed a uniform coating over up to 100-millimeter silicon chips and showed little weight in the 2D materials. which was moved.

“Our method of movement is in principle applicable to any 2D material, independent of the size and type of growth substrate,” says Dr. Max Lemme, from Graphene AMO GmbH flagship partners and RWTH Aachen University. “And, because it relies on devices and methods that are already common in the semiconductor industry, it could significantly accelerate the emergence of a new generation of devices where 2D products are integrated. in addition to standard integrated or microsystem cycles. work is an important step towards this goal and, while many other challenges remain, the range of potential applications is vast: from photonics, to sensing, to neuromorphic computing. The integration of 2D products could be a real game changer for the European high. -tech industry. ”

The European Commission recently launched a € 20 million project to bridge the gap between laboratory-scale manufacturing and mass production of electronic devices based on two-dimensional materials, the 2D Graphene Flagship (2D-EPL) Experimental Pilot Line . “This paper is a great example of the work we will be doing in the 2D-EPL project,” said Cedric Huyghebaert, program manager for imaging materials and model integration at imec and technical director of the 2D-EPL project. “This is one of our current urgent actions to develop tools and design books for manufacturing devices based on 2D materials that are compliant with semiconductor industry standards,” Huyghebaert said. “The next step is to demonstrate the potential of these processes for the delivery of innovative sensors and optoelectronic devices on a pilot line.”

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