Through-pellicle defect repair for advanced photomasks

A developing reality with advancing DUV femto-second pulsed laser repair of advanced photomasks after pelliclization is a significant operational cost savings. This economic advantage comes from the elimination of a previously critical inspection step before mounting the pellicle on the mask. The laser repair processes developed allow reduce the number of times masks are cycled through mask inspection tools and prevent recontamination of the mask surface due to handling during and after the inspection before pelliclization. The latter would require, without effective through-pellicle repair, removal of the pellicle, repair and/or reclean, then re-inspection and re-pelliclization of the mask (assuming success with the first cycle of repair and/or reclean). Meanwhile, the cost and lack of feasibility for this additional process both increase the investment in the mask while at the same time bringing it closer to being completely scrapped. Recently developed processes that allow for effective through-pellicle laser repair on advanced photomask technologies (sub 65 nm node) are reviewed, that have economic advantages and also make the repair of lower-end (and higher volume) photomasks significantly more profitable to the typical mask maker.