'Hetero-print': A holistic approach to transfer-printing for heterogeneous integration in manufacturing

Lead Research Organisation: University of Glasgow
Department Name: School of Chemistry

Abstract

The rapidly developing technique of transfer printing on the micro and nanoscales allows the manufacture of high quality, high performance devices on a wide range of substrates in almost any location. This highly versatile capability features a high-precision mechanical pick-and-place assembly technique that utilises the adhesive properties of soft stamps, and the technology has only recently broken into the field of electronics and photonics. Placing this exciting and highly important development into context, in the 1990s Whitesides (Harvard University Chemistry Dept.), a pioneer in microfabrication and nanotechnology, established the ground-breaking concept of patterning self-assembled monolayers for lithographic, sensing, medical and pharmaceutical applications and termed this micro-contact printing. From this foundation, the technique has evolved into much higher levels of complexity in which micro-transfer printing has recently delivered micro- LED arrays that, for example, feature in flexible displays and provide inorganic analogues of flexible organic light-emitting diodes (OLEDs) - something that was previously thought to be extremely challenging if not impossible. In this programme, 'Hetero-print', we aim to rapidly push this exciting field further by establishing, for the first time and ahead of the international competition, new routes towards the manufacture of heterogeneous devices, consisting of integrated systems made from pure and/or hybrid inorganic/organic materials. The demand for these hybrid approaches is extremely high, because it opens up the prospect of multifunctional devices that organic materials can deliver in tandem with inorganic semiconductor technology. The ambition of Hetero-print is to deliver micro- and nano-transfer printing as the technology for the versatile and scalable manufacture of heterogeneous materials, structures and devices. In achieving this, we will introduce significant new capabilities for the manufacture of electronic, photonic, and other systems, which complement and are synergistic with those of established semiconductor mass-manufacturing methods including vacuum deposition and solution processing. In this respect, transfer printing is a highly scalable technique and perfectly suited to high volume manufacture, allowing >10,000 micro-sized integrated circuits to be processed in a single run. An issue with many photonic devices is cost, but micro-transfer printing can be economical with the number of print cycles from a single stamp running into the tens of thousands; the technique is also economical in terms of materials waste, providing a methodology to manufacture multiple-array devices in very high yield.

Planned Impact

Hetero-print addresses the urgent need for heterogeneous integration in many forms of advanced manufacturing. Although rooted in semiconductor industry techniques, new applications lie in the fields of flexible electronics, new forms of displays, silicon photonics, photonic integrated circuits, sensors for medicine and healthcare, novel quantum-based sensors, smart labels, and photovoltaics. These emerging fields are all of critical importance to the future UK economy, and many of the example applications mentioned will be implemented in mass market products and/or wearables, having significant societal impact. The enormous economic potential for end products is backed by authoritative forecasts, eg. IDTechEx predicts a market for organic and flexible electronics of over 73 billion USD by 2027.

The investigators bring a range of existing UK-based company collaborators spanning the range of relevant industries, from materials supply, through advanced printing technologies, to end-product integrated systems. These partners involve 12 companies and 4 Centres and Hubs (see letters of support). We expect early adoption of technologies developed from Hetero-print by the companies mentioned, plus others engaged through our workshops and the work of our 0.5 FTE Impact Champion. Where appropriate to apply external technical expertise or specialist equipment to manufacturability issues (e.g. yield optimisation and scale-up), we will arrange sub-contracts with organisations such as CPI. The investigators also have previous spin-out experience through the foundation of companies including mLED and Sci-Tron, and will have strong institutional support for launching similar new ventures if judged to be the appropriate mechanism to exploit research findings. There are a number of relevant translational organisations and consortia which include Fraunhofer UK, the Compound Semiconductor Applications and High Value Manufacturing Catapults, the CIM in Large Area Electronics, the National Hub in High-Value Photonic Manufacturing, and the Future Compound Semiconductor Manufacturing Hub. The investigators are well connected already to these various organisations, and recognise the importance of further developing collaborative links. We will work with selected partners on definition of a Technology Roadmap from the mid-point of the programme. In this exercise, we will benchmark Technology Readiness Levels of our various strands of activity, and also capture and prioritise opportunities for further exploitation.

The outcomes of Hetero-print will be very suitable for exhibiting either as actual hardware demonstrators, which particularly is the case with Workpackage 4 (Interconnects and Systems Demonstrations'), or through videos of manufacturing processes or systems in operation. The Strathclyde IoP team, for example, has extensive and very positive recent experience of such demonstrations both through events targeted at professional audiences, and aligned with EPSRC projects (eg. UP-VLC project Open Day, Quantum Showcases), and in wider public engagement activity (e.g. Glasgow Explorathon). Within Hetero-print, the two workshops will provide a natural focus for preparation of demonstrators illustrating the breadth of achievement. These particular events will be targeted at professional audiences, addressing fellow academics, industrialists, trade association members, and government and funding body representatives. Once available, the same demonstrators will be suitable for public outreach events and/or permanent installations, and the Hetero-print Impact Champion will co-ordinate this important strand of activity.

Consistent with their past achievements, the investigator team will continue to prioritise publication in the highest impact academic journals, and dissemination through UK and international conferences.

Publications

10 25 50
 
Description Ongoing collaboration with Plessey Semiconductors with the potential for exploitation of IP.
First Year Of Impact 2018
Sector Electronics,Manufacturing, including Industrial Biotechology
 
Title Effect of end group functionalisation of small molecules featuring the fluorene-thiophene-benzothiadiazole motif as emitters in solution-processed red and orange organic light-emitting diodes 
Description A series of red fluorescent materials (compounds 1-4), which each contain the symmetric fluorene-thiophene-BT-thiophene-fluorene core, is presented along with their performance in solution-processed OLED devices. Extending the molecular conjugation through end-capping with additional fluorene units (compound 2), or through incorporation of donor functionalities (compounds 3 and 4) improves OLED performance relative to the parent compound 1. Notably, incorporating triphenylamine donor groups in compound 3 led to solution-processed OLED devices operating with a peak luminance of 2888 cd m-2 and a low turn-on voltage (3.6 V). 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Title Supporting data for "Direct integration of micro-LEDs and a SPAD detector on a silicon CMOS chip for data communications and time-of-flight ranging", published in Optics Express 2020 
Description This paper reports on the direct integration of micro-LEDs and a SPAD detector on a silicon CMOS chip for data communications and time-of-flight ranging. The dataset is an origin file organised as followed: 1) folder Fig2 - Current density-voltage-optical power and current density-bandwidth; 2) folder Fig3 - Distribution of forward diode voltages and optical power density at 60 A/cm2; 3) folder Fig4 - BER as a function of received power by the ultrafast camera in the OCC demonstration; 4) folder Fig6 - BER as a fuction of incident power on the SPAD for the 500 kbps and 1 Mbps VLC links, ToF arrival time histogram, and ToF ranging results. 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
Impact This database will allow any interested party to inspect raw data presented in figures in the final publication. 
 
Title Tetrathiafulvalene-oligofluorene star-shaped systems: new semiconductor materials for fluorescent moisture indicators 
Description  
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
 
Description Cambridge Centre for Gallium Nitride Outreach Apps 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Two android apps which provide an interactive way for users to learn about light emitting diodes.
Year(s) Of Engagement Activity 2018,2019,2020
URL https://www.gan.msm.cam.ac.uk/resources/our-apps
 
Description Cheltenham Science Festival 2019: Communication using Liht 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Three separate school groups attended a workshop on light-based communications, covering fibre optics, LiFi and single photon sources.
Year(s) Of Engagement Activity 2019
 
Description Inside an LED - Harrow School 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact A lecture at Harrow school, to which multiple other local schools were also invited. Teachers from across the Rugby Group of public schools also attended.
Year(s) Of Engagement Activity 2018
 
Description Lots and Lots of Light Bulbs (Grove School) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact An EYFS workshop on light and energy delivered to two classes at the Grove School.
Year(s) Of Engagement Activity 2018