Reducing the rework in the photo-lithography process of wafer-bump assembly with quality management

The rework rate following the PDCA-based metrology and the cause-and-effect diagram indeed obtained the significant improvement during the four-month record. The root causes in abnormal PR coating inducing the rework can be cardinally classified as three types: harmful familiarity for the staff, the staff not following the SOP and the defects coming from the previous sputtering process. During these distinguishing and improving efforts, the rework ratio in abnormal PR coating contribution was reduced from 0.29% to 0.19%. The entire weekly rework rate was decreased from 1.71 to 0.51.