Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - FlexCHIC (Flexible Complementary Hybrid Integrated Circuits)

Teaser

The research and development in the field of flexible electronics in recent years has shown that this technology could be a promising key enabler for future consumer applications due to several advantageous characteristics that are absent from any incumbent technology. These...

Summary

The research and development in the field of flexible electronics in recent years has shown that this technology could be a promising key enabler for future consumer applications due to several advantageous characteristics that are absent from any incumbent technology. These include; unique form factor that allows realisation of unconventional electronics such as bendable displays, as well as the inexpensive/high throughput processing that enables realisation of large-area devices such as sensor systems and/or low-cost disposable electronics e.g. medical diagnostics, identification systems. However, the realization of high-performance integrated circuits on flexible substrates for a low-cost/high-volume market still remains very challenging, primarily due to material and process related limitations. This project followed a unique approach in order to overcome these limitations through the use of solution-processable organic and inorganic semiconductors in combination with optical sintering methods for rapid material processing. The latter will allow the fabrication of hybrid complementary integrated circuits with performance characteristics beyond the current state of the art on arbitrary substrate materials including flexible temperature-sensitive substrates (e.g. plastic) within a fraction of time compared to conventionally used curing methods (e.g. thermal annealing). This multidisciplinary research work opens new insight into hybrid low-temperature additive transistor technologies and promises very valuable original results merging the broad understanding of the novel organic transistor technologies with novel solution-processable inorganic semiconductors in a complementary hybrid transistor integration process which will be beneficial for the further development of low-cost and large-area electronic systems of the future.

Work performed

In order to achieve high performance levels in a complementary electronic system which consists of electron transporting (n-type) and hole transporting (p-type) semiconductors the most effective way is to optimise the respective semiconducting materials separately in terms of performance and processability. We started working with n-type materials namely metal oxides such as zinc oxide (ZnO) or indium oxide (In2O3) which are processed from solution. Various structure configurations were fabricated on silicon and glass substrates using single and mixed multilayer architectures (heterostructures) of these semiconducting materials and analysed in regard to the use of different annealing temperatures ranging from 200 to 600 °C. After establishing an optimised layer system reaching the targeted performance levels set in the beginning of the project we developed a novel annealing technique (photonic curing) using high power xenon flash light to dry and anneal the solution-processed metal oxide films and thus replaced the conventional thermal annealing using temperatures beyond 200 °C accompanied with a significant saving of the processing time (18 seconds vs. 1 hour). Our studies revealed comparable performances of the photonically to the thermally annealed devices. Moreover, this approach allowed us to deposit semiconducting metal oxide films from solution on low-temperature substrate materials such as plastics which is a ground-breaking outcome of this project.
In a second step we started working on optimizing and improving the electronic properties of p-type semiconductors namely organic materials such as small molecules and/or polymers. Again, different architectures and material systems were analysed using maximum temperatures of 150 °C in combination with chemical doping techniques to tune the electronic properties resulting in performance levels close to those reached with the photonically annealed n-type metal oxides. These important findings finally build the cornerstone for the key target to fabricate high performing electronic devices and circuits on inexpensive, low-temperature substrates such as plastics.

The main findings from this project have been published and have been presented at an array of scientific meetings

K. Tetzner, I. Isakov, A. Regoutz, D. J. Payne and T. D. Anthopoulos, The impact of post-deposition annealing on the performance of solution-processed single layer In2O3 and isotype In2O3/ZnO heterojunction transistors, J. Mater. Chem. C, 2017, 5, 59.

S. Dellis, I. Isakov, N. Kalfagiannis, K. Tetzner, T. D. Anthopoulos and D. C. Koutsogeorgis, Rapid laser-induced photochemical conversion of sol–gel precursors to In2O3 layers and their application in thin-film transistors, J. Mater. Chem. C, 2017, 5, 3673.

K. Tetzner, Y.-H. Lin, A. Regoutz, A. Seitkhan, D. J. Payne and T. D. Anthopoulos, Sub-second photonic processing of solution-deposited single layer and heterojunction metal oxide thin-film transistors using a high-power xenon flash lamp, J. Mater. Chem. C, 2017.


K. Tetzner, H. Faber, T. D. Anthopoulos, Understanding the structure-property relationship in high-performance solution-processed bilayer metal oxide transistors, 13th International Conference on Nanosciences & Nanotechnologies (NN16), 5-8 July 2016, Thessaloniki, Greece.

K. Tetzner, Y.-H. Lin, T. D. Anthopoulos, Rapid fabrication of solution-processed metal oxide transistors via photonic processing at room temperature, Innovations in Large-Area Electronics Conference, 31 January - 1 February 2017, Wellcome Genome Campus Conference Centre, Hinxton, UK.

K. Tetzner, Y.-H. Lin, A. Regoutz, T. D. Anthopoulos, Photonic curing of solution-processed metal oxide semiconductors for the rapid fabrication of low-voltage thin-film transistor devices, European Materials Research Society Conference, 22-26 May 2017, Strasbourg, France.

K. Tetzner, Y.-H. Lin, A. Regoutz, A. Seitkhan, D. J. Payne, T. D. Anthopoulos, Sub-second photonic curing of

Final results

Up to now, the interest of industry in the solution-based fabrication of high-performance ICs for certain applications (flexible, large-area, low-cost) is existent but the processes, materials and technologies used so far could still not meet the requirements for the realisation of such applications due to several restrictions in the manufacturing process. The aim of this project was to overcome key technology bottlenecks that will in turn enable the development of high-performance complementary ICs on flexible plastic substrates using combination of innovative solution depositions techniques at low temperatures (<200 °C). The established flash sintering process (photonic curing) developed along the project might have a tremendous impact on future research activities in academia and industry as it allows the rapid fabrication of high performance solution-processed metal oxide transistors and circuits on plastic substrates. It is expected that the process developed and established during the project has a very high potential to pave the way for the rapid fabrication of electronic devices as it opens a completely novel approach in the manufacturing process.