Digital Lith

Project Acronym Digital Lith
Project Title Production Speed Digital Lithography
Project Start Date 1st May 2013
Project Duration 30 months
Partners’ names and countries Centre for Process Innovation, UK
Heidelberg Instruments Mikrotechnik GmbH, Germany

Project Coordinator:

Name: Dr Tom Harvey

Organization: Centre for Process Innovation


The aim of this project is to make and test a state of the art roll to roll digital photolithography machine suitable for use in the manufacture of organic thin film transistor arrays of the type used to make active matrix displays. The project partners are the Centre for Process Innovation in the UK and Heidelberg Instruments in Germany.

Making such transistors continuously onto a roll of plastic film is very challenging because 5 or 6 separate exposures are typically required in order to define the structure of the metal, dielectric and semiconductor layers in the transistor. Each of those layers has to be over-laid on top of each other to an accuracy of +/-1 micron, otherwise the transistors do not work very well. The plastic film carrier web changes size much more easily than traditional glass or silicon substrates due to heating, moisture content and the mechanical loading applied to tension the film web. Our machine therefore has a novel vision system which measures any distortions of the pattern on the film and compensates for them in real time before exposing the image. In order to ensure that the machine runs sufficiently fast, the optical exposure system has been designed to capable of exposing 0.1m2/min of film area, which is equivalent to 17cm2/s. In addition the system is able to accurately define down to 4 micron wide line and space so as to be able to resolve the smallest features of the transistor pattern.

We anticipate that the new machine will significantly reduce the cost of manufacture of O-TFT flexible display backplanes because photomask reticules, of which a significant number are required for each different display design, will no longer be required. This will also enable display developers to make more and varied designs with reduced design cycle time. In combination with other R2R tools, the new machine will significantly increase the speed of manufacturing of such flexible displays, enabling significantly larger volumes of displays to be produced at lower cost.