High-resolution orthogonal patterning of organics

Lead Research Organisation: University of Cambridge
Department Name: Physics

Abstract

Organic electronics is a fast developing branch of modern science and technology that can complement conventional inorganic materials with lightweight, inexpensive, and mechanically flexible organic semiconductors. One of the key advantages of organic electronic materials lies in the low temperature, high-throughput device fabrication they enable. The solution-based fabrication of a variety of devices such as organic light emitting diodes (LEDs), field-effect transistors (FETs), solar cells, and sensors has been demonstrated using spin coating, ink-jet printing, and other wet printing techniques. While substantial improvements in materials synthesis, purification and deposition techniques over the past two decades enhanced film quality, uniformity, and environmental stability, the chemical processing of organic electronic materials remains one of the main challenges to be overcome. By chemical processing we mean any chemical treatment such as cleaning, depositing a second layer from solution to form multilayer devices, and depositing/developing resist layers for photolithographic patterning. The latter has, over the many decades of its development, grown into the dominant patterning technique in the semiconductor industry, for a number of important reasons. It offers an impressive combination of high resolution, precise registration, tight critical-dimension control, parallel throughput and the ability to cover large areas as demonstrated in the manufacture of LCD backplanes on glass sheets the size of a king bed. While cutting-edge photolithography equipment is very expensive, last generation technology is affordable and forecast to make an impact in organic electronics, especially given that alternative technologies such as inkjet printing are still largely unproven for large-scale manufacture.This project aims to leverage orthogonal lithography in order to create unique device architectures that will elucidate the fundamentals of organic electronic materials. Key research opportunities such as the ability to probe charge transport in a single crystalline domain of a conjugated polymer will be the focus of the proposed research. Orthogonal lithography, a breakthrough patterning process for organic electronic materials involves the use of resists soluble in fluorous solvents and resulted from a successful Materials World Network Project. Orthogonal lithography will be used to make complex, multilayer organic semiconductor devices not possible by other means. This will enable new fundamental studies to elucidate aspects of the physics of organic electronic devices which cannot be studies in more conventional structures.
 
Description This award led to the development of a photolithographic patterning technique for organic semiconductors that allows accurate micrometer resolution patterning of soluble organic semiconductors without leading to degradation in the materials' electronic and optoelectronic properties.
Exploitation Route The work has led to a patent application that has been licensed by an industrial partner.
Sectors Electronics
 
Description This project resulted in the development of novel approaches for patterning conjugated polymers by photolithography, which had previously been difficult because of problems with dissolution/swelling/degradation of the polymer to be patterned by the resist chemicals. The process has enabled new experimental structures for fundamental research and a novel patterning approach for large area polymer electronics. The IP filed has been licensed by an industrial partner, Plastic Logic. The project has also generated a new approach of making polymer heterojunctions without dissolution of underlying layers by inserting thin layers of conjugated polymers with fluorinated side chains. This approach is currently being refined by the PhD student on the project and will likely result in several additional publications in the couse of 2013. The project also resulted in a new synthetic route for copolymers comprising mainly electron deficient building blocks. Previously it had been difficult to achieve this using established routes, such as Suzuki polymerisation. Beneficiaries: Plastic Logic Ltd. as well as polymer electronics community in general
Sector Electronics
Impact Types Cultural
 
Title Patterning 
Description The present invention provides a method of patterning an electronic or photonic material on a substrate comprising: forming a film (polymer A) of said electronic or photonic material on said substrate; and using a fluoropolymer to protect regions of said electronic or photonic material during a patterning process. 
IP Reference WO2011004198 
Protection Patent application published
Year Protection Granted 2011
Licensed Yes
Impact The invention has resulted in a powerful experimental technique that we are continuing to use actively in our research programme.