We are uniquely able to combine and tailor these varied technologies into optimized process flows for creating transistors, optical and microfluidics structures, opto-electrical devices, and more. This helps our industry partners to quickly realize applications in domains as diverse as displays, medical imaging and bioelectronics.
Spatial ALD
Spatial ALD is a novel variant of the familiar atomic layer deposition (ALD) technology. It offers the same precise control and uniformity of film composition and thickness as traditional ALD, but at much higher deposition rates – around 1 nm/s. Moreover, sALD is an atmospheric pressure process and does not require costly vacuum equipment.
Holst Centre has successfully upscaled sALD to large areas in sheet-to-sheet and roll-to-roll equipment, and can achieve highly uniform layers even for structures with an extreme aspect ratio. The technology is ready to be integrated into commercial production of e.g. thin-film solid-state batteries, optical stacks, thin-film photovoltaics and semiconductor and dielectric layer stacks for a host of large-area applications.
Schematic view of the roll-to-roll spatial ALD concept. A polymer foil is transported around a drum that houses injector slits (blue and red) for the reactive precursors, separated by inert gas (green). By moving both the web and the drum, a thin ALD-coating is applied on the polymer foil at high rate.
TFT technology
Holst Centre has long set the pace in the development of oxide and organic thin-film transistors (TFTs) for displays, imagers and many other applications. We continue to push TFT performance forward, for example by using sALD for semiconductor and dielectric layers. This allows high-mobility semiconductors to be created at process temperatures below 200°C – ideal for applications on low-cost PEN foils. We are also pioneering new materials such as p-type oxide semiconductors, which could pave the way towards CMOS-style TFT applications.
Encapsulation
Large-area electronics applications can be highly susceptible to environmental conditions such as humidity. This makes thin-film encapsulation essential for durable and robust flexible solutions.
With over a decade of experience in developing thin-film barrier layers, Holst Centre is a one-stop shop for encapsulation. We started out with the development of high-performance barriers for the most demanding applications, OLEDs, where we achieved lifespans equivalent to 25 years of normal use. We now use that expertise to create a variety of barrier options, tailored to the performance and cost requirements of specific applications. A bending radius down to 1 mm has been demonstrated for a full product. Our accelerated reliability testing helps speed up the qualification of new systems.
3D microstructures
Creating 3D structures within thin-film (2D-)stacks is essential for applications from lighting and batteries to bioelectronics and TFT backplanes. Holst Centre is exploring new ways of patterning thin films that can be deployed within roll-to-roll production. With a moving substrate, multi-level alignment is a huge challenge. Nano-imprint lithography solves the challenge by transferring the entire structure in one step: all alignment is done when creating the imprint master. This enables the reliable production of complicated structures with very high aspect ratios in high-volume manufacturing. In turn, this opens the door to integrating optical and microfluidic features directly on an active electronics backplane.