Improved contact resistivity and intra-die variation in organic thin film transistors

Abstract

We studied the processing-related influence on contact resistivity of organic thin-film transistors in top gate architecture which are placed and oriented differently over flexible substrates. Appropriate plasma treatment reduces degradation of the source and drain contacts, increases effective contact surface for self-assembled monolayer treatment, and thus better injection. Increasing the semiconductor film thickness reduces the contact resistivity until a certain critical thickness. By these means, the contact resistivity has been reduced by two orders of magnitude. We did a mass characterisation of 366 solution-processed transistors on six samples that lead to a modified transfer line method in which we permutated the transistors to extract the contact resistivities. Thus, the intra-die dependency of the contact resistivity on the distance from the centre of the sample, the orientation of the transistor, its width, the pre-processing of the samples and on the semiconductor layer thickness has been analysed. These results serve as an evaluation of appropriate processes for printed organic transistors.