The wet etching of thin metallic films has been developed to one of the key methods in micro system technology. The advantage of this technique – high selectivity, high reaction rates and low costs - is the reason for its use in microelectronics, and very different types of sensors and actuators. This paper gives an overview of the specific problems of the microlithography in thin metal films and stacks of it. The wet etching processes are regarded as open-circuit electrochemical processes. The dissolution, the activation and the passivation can be described by simple model considerations based on an open-circuit electrochemistry under conditions of a complex mixed potential formation. Topological aspects are included regarding specific transport processes and the dimensions of micro patterns. Experimental examples of dissolution rate dependences on chemical conditions, galvanic and topological effects as well as examples of the influence on spontaneous passivation processes in thin film stacks are given and quantitatively explained. It is shown that the coupling between electrochemical processes far from equilibrium, diffusion and convection influences strongly the technical micropatterning. Open-circuit oscillations during the dissolution of sputtered copper films are described as an example of spontaneous formation of micropatterns. These phenomena can be explained by a qualitative model, which allows the interpretation of oscillation, bifurcation and chaos on the one hand and the spontaneous formation of a micropattern on the other hand.
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