Incorporation of Cu Passivators in Post-CMP Cleaners

Simple first generation Cu post-CMP cleaners, such as oxalic acid solutions, promote corrosion of Cu due to removal of BTA and dissolution of cuperous oxide (Cu2O). The use of simple organic acid solutions imposed a short staging time before processing wafers to the next level due to corrosion of the exposed Cu. In some cases, a maximum holding time of less than one hour was needed to reduce device yield loss and reliability issues resulting from Cu corrsion. A way to significantly increase the post-clean wafer holding time was by incorporating a Cu passivator into the post-CMP cleaner. Four commonly used Cu passivators were evaluated in a commercially available, alkaline, post-CMP cleaner. Several unanticipated properties were observed when using 1,2,4-triazole, which will be discussed.