An integrated shadow-mask based on a stack of inorganic insulators for high-resolution OLEDs using evaporated or spun-on materials

While organic materials show impressive performances as electroluminescent diodes, their integration in a passive matrix to form a high-resolution dis play is a challenge. The anode call easily be patterned in columns prior to the deposition of organic materials, but conventional microfabrication tec hniques cannot be used to etch the cathode on top because organics are affe cted by treatments applied to photosensitive resins. We microfabricated an integrated shadow-mask with openings in rows orthogonal to the columns of t he anode. The mask has an overhanging edge so that the cathode evaporated o n top is discontinuous at its edges, thereby separating the diodes along ro ws. The mask is composed of a stack of inorganic insulators all deposited i n a commercial plasma-enhanced chemical vapor deposition tool, and whose di fferent etching rates in hydrofluoridric acid enable to obtain the overhang in one lithographic step. The process is very simple, as high resolution a s microfabrication can provide, and the resulting device is less prone to s hort-circuits than when a lift-off photoresist is used. Pixellation is repo rted both from evaporated small molecules and spun-on polymers. (C) 2001 El sevier Science B.V. All rights reserved.