Etching of AC thin film electroluminescent devices

Realization of high definition ac thin film electroluminescent (ACTFEL) devices require fine control of geometric definition. Suitable etching processes need to be defined to address the requirements of both isotropic and anisotropic etching profiles, with good etching rates and high selectivity to underlying Si features. Three different etching processes are analyzed and compared with reference to these parameters. Wet chemical processing provides high etch rates and high selectivities for the ACTFEL materials. Using phosphoric acid leads to an infinite selectivity to all ACTFEL materials. Unfortunately, wet chemical etching has poor control for step profiles. Ion beam etching and sputter etching, however can produce both isotropic and anisotropic patterns, but are comparatively slow and suffer from poor selectivity to the Si based materials. Although individually no method is ideal, for full ZnS:Mn ACTFEL device fabrication these results show that a combination of two of these etching processes will provide the necessary geometry's for very high definition structures.