Ambient gas control in slot-to-slot space inside FOUP to suppress Cu-loss after dual damascene patterning

We investigated a Cu-loss problem after dual-damascene patterning during manufacturing; that is, more than a dozen wafers were stored in a FOUP. We found that a decreased yield due to the Cu-loss strongly depends on the wafer position in a FOUP and on the queue time between etching and wet cleaning. We developed a Cu-oxidation model to explain what happens during the queue time; that is, the F content, which catalyze Cu-oxidation, in the post-etch residue gradually evaporate into the slot-to-slot space. On the basis of our model, we applied ambient gas control in the slot-to-slot space to suppress the decrease in yield due to the Cu-loss.