A fluid ejection device comprises a substrate having a first surface; a fluid ejector formed over the first surface; and a cover layer defining a firing chamber formed about the fluid injector, and defining a nozzle over the firing chamber. The cover layer is formed by at least two SU8 layers....http://www.google.de/patents/US7226149?utm_source=gb-gplus-sharePatent US7226149 - Plurality of barrier layers
