Recyclable anisotropic etchant for advanced flip chip manufacturing (Green)

The demand for ever finer circuitry especially for IC-substrate manufacture has lead the way away from the traditional subtractive circuit formation to additive, semi-additive, and (advanced) modified semi-additive technology. These technologies provide many challenges to conquer during production. Except for the fully additive process, which remains a niche technology, a copper seed layer is required in order to be able to pattern plate the desired circuitry. This seed layer has to be removed through etching to finalize the circuit formation. This process step is commonly described as flash etching or differential etching. This paper describes the newly developed ferric sulfate based etchant for flash/differential etching. The focus will be on the etch performance in comparison to hydrogen peroxide etchants. In addition regeneration equipment designed for this application will be illustrated and discussed, especially under economical and ecological aspects.