Copper has been widely used as the interconnect material for integrated circuits because of the good electrical conductivity and electron migration resistance. Copper dual damascene structure has been adapted due to the impossibility of etching the copper. For via first dual damascene (VFDD) integration, via is opened after trench etch. Generally, diluted HF cleaning after trench etch is used to remove both etch residues and carbon depletion layer of low-k material. In this study, we investigated the characteristics of copper dendritic formation occurred in post trench etch cleaning with single wafer spin tool (SWST).