Reduction of extra pattern defects in immersion layer reworks by cleans recipe optimization: CFM: Contamination free manufacturing

In order to remove the photoresist during the rework process, a dry rework is primarily used to ash the photoresist followed by a wet cleans process to remove the remaining organic residues. An effective process with very high particle removal efficiency (PRE) is desired at this surface cleaning step. A cleans process with lower PRE leaves particles on the wafer surface which create extra pattern defects during the immersion lithography. The kill ratio of extra pattern defects being very close to 1, almost a die is affected for presence of a single defect. A 2x reduction in the extra pattern defects with the application of the new cleaning approach has been observed in this work.