Graphene Mass Production, Roll to Roll

Graphene, the lightest and thinnest compound known to man at one atom thick, has several amazing and unique properties that make it a very interesting candidate for many futuristic applications. However, its use is presently limited due to a bottleneck in its synthesis and mass production, which are still at an infant stage and expensive.

A European research project, GRAFOL, is aiming to change that by spearheading the roll-to-roll mass roduction of graphene films on silicon wafers. Companies like Philips, Intel and specialized manufacturer Graphenea feature on the applications side of the project, with a goal to apply project results to advanced graphene electronic devices.

The project, which is being funded with 10.5 million euros over four years, aims to develop the first roll-based chemical vapour deposition (CVD) machine for the mass production of few-layer graphene for transparent electrodes for LED and display applications, and adapts the process conditions of a wafer-scale carbon nanotube growth system to provide a low-cost batch process for graphene growth on silicon. The project focuses on applications such as transparent electrodes for OLEDs and GaN LEDs, optical switches, plasmonic waveguides, VLSI interconnects, and RF NEMs.

Due to its high carrier mobility, long ballistic mean free path, a high frequency photoconductivity, and a large thermal conductivity, graphene is being considered as a component in next-generation electronic, optoelectronics and microsystems. Production of graphene is possible by four main methods, and prototype devices based on graphene (eg. field effect transistors, photo-transistors and detectors, and transparent electrodes for touch screens,) have been demonstrated with very promising results. GRAFOL aims to turn an emerging technology, the on-substrate synthesis of graphene, into a large-scale production technology available to industry as shown conceptually in the figure.

It is important to realize that the advancement of microelectronics today is not only due to the shrinking of device dimensions, which nano-materials allow, but also to the enlargement of wafer size (the unit of measure for production). The increase of wafer diameter from 50mm in 1970’s to 300mm in early 2000’s, corresponding to a 36 fold increase in area, has made it much more cost effective to manufacture microelectronics, quite simply because more chips are made simultaneously. It is quoted by semiconductor companies, that for graphene to be seriously considered for microelectronics, it must be on at least the 300mm wafer scale, on Si and attain a life cycle production cost (taking into account source materials, running costs, equipment depreciation) of $1 per square inch of deposited area on a substrate. Such a competitive cost can only be achieved if the area of graphene deposited is increased per run, that is, scaling the production to at least a 300mm wafer scale (another wafer size transition to 450mm is expected towards the end of this decade).

Taking it one step further, for certain applications such as transparent electrodes graphene should be produced in even larger scale than that required for microelectronics. This truly large-scale production of graphene would become possible with a successful development of roll-based technology.

Despite its attractive properties, graphene will not yet be used in mainstream electronic applications due to two technological obstacles, namely (1) mass production and (2) device integration. Device integration deals with aspects such as physical integration and process integration (material compatibility, thermal budget). Mass production must use the route of chemical vapour deposition (CVD) onto metal surfaces. To tackle mass production, equipment must be developed which addresses economical manufacturing (yield, throughput, equipment reliability and maintainability) as well as quality assurance (process qualification, material consistency /standard characteristics, monitoring). These obstacles are dealt with in this project.

The value-added / high tech applications developed here have been carefully selected to require graphene on surfaces, and to be those which truly benefit from not only the high specifications but also cost effective production of graphene when deposited on the wafer-scale or by a roll-based method.

GRAFOL started in October 2011, and will run for 4 years. The coordinator is the University of Cambridge, led by professor John Robertson. Professor Robertson leads a team of 14 partners, consisting of both academic research labs as well as businesses like ours. The project benefits from expertise of the likes of Aixtron (one of the world's largest manufacturers of CVD machines, based in Aachen, Germany), Philips, Thales, and Intel. Financing comes from the European Union's FP7 research framework, under the research theme "Nanosciences, nanotechnologies, materials and new production technologies", which focuses on projects with a strong industrial impact. -- Graphenea