Reclamation of waste mixture of sulfuric acid and hydrogen peroxide used to clean semiconductor wafers

The mixture of sulfuric acid and hydrogen peroxide, or the so-called piranha, used to clean semiconductor wafers generally requires considerable water and chemicals to allow it to be discharged as wastewater and sludge. We have developed a new method of converting the waste mixture into concentrated sulfuric acid, decomposing the hydrogen peroxide in the waste mixture and adding a trace of nitric acid. This method allows the waste mixture to be reused and the amount of water and chemicals required for treating the waste to be reduced.