Galvanic effects in the wet-chemical etching of metal films

The problem of etch rate changes caused by galvanic effects, when etching a metal in contact with another metal, is examined. Areas covered include the electrochemistry of the galvanic element formation during etching and a description of undercutting in electrochemical terms and how the effect can be prevented by using a suitable etchant. The influence of the galvanic effect in producing beveled edges is also considered, showing how the desired beveling angle can be obtained by an appropriate choice of top metallic layer and etchant.