Etching of copper in deionized water rinse

A new yield loss mechanism is described that is related to the etching of Cu in deionized water. Water that contains high concentrations of dissolved oxygen can etch Cu at the bottom of vias during pre-metallization wet cleans. The etching creates voids in the Cu which remain after metallization, resulting in high resistance and functional fails in the affected array circuits. The dissolved oxygen concentration in the deionized water must be minimized to prevent etching of Cu.