A passive matrix addressed organic electroluminescent display using a stack of insulators as row separators

In order to use the impressive performances of organic light emitting diodes (OLEDs) in high-resolution flat-panel displays (FPDs), ways must be found to circumvent their incompatibility with standard microfabrication techniques. To integrate organic compounds in a passive matrix, one must be able to pattern the top electrode in rows without exposing them to any processing. We deposited a stack of three different insulators in one process in a commercial plasma-enhanced chemical vapor deposition (PECVD) tool, patterned it in a single lithography step and in a single wet etch step. The top insulator etches slowest, so the stack gets undercut. When organics and the top electrode are thermally evaporated on this pattern, they are physically discontinuous at the edges of the overhanging insulator. The lowest insulator etches slower than the middle one, so it tails out and prevents short circuits when the top electrode flows over the edge of the organic layers. This process combines simplicity and high resolution, two prerequisites for OLEDs to compete with existing FPD technologies.