Manufacturing with Light 2: photochemical ALD to manufacture functional thin films

Lead Research Organisation: University of Liverpool
Department Name: Mech, Materials & Aerospace Engineering


The purpose of this project is to develop a novel photochemical atomic layer deposition (ALD) manufacturing technology to coat three - dimensional components and feedstock powders with ultrathin functional coatings. Conventional atomic layer deposition is already widely used in the displays and microelectronics industries. It is a thermo-chemical process where two precursor reagents are pulsed in cycles onto a heated work piece. The combination of the substrate temperature and the chemical reaction energy drive the process forward to deposit the thin film layer by layer. Because the process occurs on the surface, highly uniform and conformal layers can be deposited onto high-aspect ratio or porous materials with ultraprecise thickness control. The hypothesis for the proposed research is to use a photo-excitation process to activate one or both of the ALD chemical reagents so that they can react to deposit the thin film with a lower thermal input from a substrate heater.

We will adapt the existing Round 1 ALD reactor at Liverpool to incorporate a larger scale chamber capable of containing: (1) an array of 3D components; and (2) reactor furniture for a fluidised bed powder treatment system. The modified system will be built to accommodate ultraviolet sources for the processing of 3D components or the treatment of powder beds. We also propose to use new UV source lamps to target the wavelength of the output from a range of commercially available UV lamp modules to photo-chemically decompose the precursors to form the film. The replacement chamber will also be manufactured to enable access for in-situ monitoring of the deposition process using an existing fibre-optic cable based Raman probe and a quartz crystal microbalance. These will provide feedback on the start of deposition as a function of illumination, substrate temperature, flow rates etc. If achieved, these objectives represent a significant advancement of existing ALD technology and would open up new applications where ultrathin functional materials can be exploited, such as display electronics, biomedical devices and photovoltaics amongst others.

Planned Impact

This project will have direct impact on the world-wide research and development of ALD technology. The development of ALD manufacturing technology has been driven by advancements in the IC electronics sector over the last decade. The global ALD market is $0.5bn and is forecast to reach $1.8bn by 2016 [1]. This comprises 40% of materials and 60% of equipment sales. The current trend is now to diversify across other manufacturing sectors. The proposed project will
make a significant contribution to enabling ultrathin film manufacturing by enabling direct-write patterning and lower temperature processing.

The industry collaborators for the proposed program have clear and direct opportunities to exploit the arising research. One of our industrial collaborators Pegasus Chemicals has recently been established and specialises in the manufacturer of precursor materials for chemical vapour deposition and atomic layer deposition. The company has extensive experience in the design, selection and delivery of organometallic precursors and we will work with them to develop photochemically active sources for the research proposed here. The Liverpool University group has had a long-term collaboration with researchers in the company which will help us to accelerate the route to impact. The research has the potential to put the UK at the forefront of a crucial emerging area of new materials and precursors, which is likely to impact strategically on the UK and European economy. Nanoco is unique in the nanomaterials market as a company that manufacture large quantities of quantum dots to develop a wide variety of next-generation products, particularly in the fields of electronics, lighting, biomedical and PV solar cells. Renishaw is a global company with core manufacturing competences encompassing laser melting, vacuum casting and injection moulding technologies. Renishaw's laser melting process is an emerging manufacturing technology with a presence in the medical orthopaedics industry as well as the aerospace and high technology engineering and electronics sectors. Renishaw also sells a range of materials and consumables to support their vacuum casting, laser melting and low-volume production technologies. These included advanced powder materials of the type that we propose to develop further within this project.

[1] Annina Titoff, Editor in Chief "ALD Pulse" (2013)
Description The use of ultraviolet light has been used to lower the deposition temperature of thin film materials deposited by atomic layer deposition. Because light is used as the energy source, rather than only heat) to drive the thin film deposition forward, it is possible to pattern the thin films using a photomask. A new approach to constructing UV photomasks was developed using magnium fluoride as a UV window. Although the light-driven process has these advantages, the depsoition rate is limited by the light flux. The scale up the area and to increase the deposition rate, the research has established that much larger scale lamps would be required for industrial-scale processes. Such lamps exist in water treatment processing and this could be a way forward for higher level TRL research.

In addition to the deposition of flat (2D) films, the research went on to assess the treatment of powder feedstocks. Powders are used in ceramics, catalysts and additive manufacturing (AM 3D-printing), for exaample. Coating of these powders could be useful for changing the propoerties of the final products built from these powders. The project successfully demonstrated the coating of AM powders. However the light-driven process was slow in comparison with solution-based coating treatments. The research demonstrated the feasibility and that higher intensity lamps could be used to process industrial scale volumes of powders.
Exploitation Route The process may be application to the treatment of powder feed stocks for additive manufacturing. The feasiblity of the process was demonstrated to industrial partners in the IUK FLAC project (Functional Lattices for Automotive Components (FLAC)) including Renishaw, Hieta Technologies Ltd, Alcon Components Limited, Added Scientific Limited and Moog Controls Limited.
Sectors Chemicals,Manufacturing, including Industrial Biotechology

Description In the final pahse of Manufacturing with Light II, the project explored to treatment of metallic powders via photochemical ALD processes. This is being developed on the powder treatment rig that was provided to the project from Renishaw plc. The work has extended to copper treatments of aluminium based powders for additive manufacturing. The work has been taken further in an IUK project which targets the light-weighting of automotive parts. The "Functional Lattices for Automotive Components (FLAC)" project included an assessment of the lamp-assisted coating work, which focusd on the copper coating of AlSi10Mg, which is used in the automotive sector. The light-driven coating process was found to be too slow in its current form. However, scaling-up with larger light sources is a viable option.
First Year Of Impact 2019
Sector Manufacturing, including Industrial Biotechology
Impact Types Economic

Description EPSRC Impact Acceleration Account - Exploring the potential of atomic layer deposition as a route to manufacturing embedded microscopic field-emission tips for next generation solid-state diamond electron sources
Amount £14,651 (GBP)
Funding ID EP/R511729/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 11/2021 
End 02/2022
Description Knowledge Transfer Partnership
Amount £196,576 (GBP)
Funding ID KTP009766 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 08/2014 
End 04/2019
Description Manufacturing with Light 2: photochemical ALD to manufacture functional thin films
Amount £612,278 (GBP)
Funding ID EP/N017773/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 12/2015 
End 12/2018
Description Renishaw plc - coating of powders for additive manufacturing 
Organisation Renishaw PLC
Country United Kingdom 
Sector Private 
PI Contribution The research tested the feasibility of using photochemical or "light-assited" atomic layer deposition to coat powder feedstocks for additive manufacturing.
Collaborator Contribution Renishaw plc donated a power recirculation system to the project, which was adapted and developed as part of the EPSRC award. The company also sponsored a PhD student (Xabier Garmendia) through the DTC for Additive Manufacturing, to work on the powder recirculating system and the processing of powders via laser powder bed fusion (or "SLM"). Coated powders were processed at Renishaw by the PhD student and their facilities were used for characterisation.
Impact A powder recirculating system has been developed based on the original Renishaw design. This has been adpted to enable lamped assisted ALD coating of AM powder feedstocks.
Start Year 2015