Sputtering of Aluminum Cathodes on OLEDs Using Linear Facing Target Sputtering with Ladder-Type Magnet Arrays

Abstract

A facing target sputtering (FTS) system with a configuration of vertically parallel facing Al targets and a substrate holder perpendicular to the Al target plane was designed for direct sputtering of Al cathode on organic layers at a low substrate temperature. The linear FTS system has a linear twin target gun with ladder-type magnet arrays for more effective and uniform confinement of high-density plasma. Due to more effective confinement of high-density plasma and a perpendicularly placed substrate position, we were able to deposit an Al cathode layer directly on an organic layer at a low temperature of without an additional substrate cooling system. It was found that organic light-emitting diodes (OLEDs) with linear FTS-grown Al cathodes have a lower leakage current density than that of OLEDs with dc-sputtered Al cathodes. The leakage current of OLEDs with linear FTS-grown Al cathodes is similar to reference OLEDs with Al cathodes grown by thermal evaporation. The low leakage current density at reverse and forward bias demonstrates that there is no plasma damage effect caused by the bombardment of energetic particles. This indicates that the FTS system with ladder-type magnet array could be effective in direct Al cathode sputtering on OLEDs or organic photovoltaics.