Effects of dilute HCl wafer cleaning solutions on borophosphosilicate glass films

Dilute HCl mixtures are frequently used in wafer cleaning processes where removal of metal contamination is part of the overall goal of the cleaning process. Caution must be used when the processing sequence simultaneously includes steps with both dilute HCl mixtures and thin films with heavy phosphorous concentrations such as borophosphosilicate glass (BPSG). An interaction between the chlorine in the HCl containing bath and the phosphorous in the BPSG film caused the initiation of visual defects on the surface of the interlevel dielectric layer. These visual defects can be eliminated by optimizing the dilution of the HCl mixture, while maintaining effective metals and particulate removal.