The ability to deliver high end photomasks free of printable defects is key to the success of the photomask manufacturing process. Although investment in substrate purity, particulate control, and cleaning capability has increased dramatically, they have proven no match for the defects’ ability to destroy an otherwise ideal mask. It is, therefore, essential to continue to have the capability to repair defects in order to deliver high-end photomasks. The vast variety of potential defects, combined with the different mask substrates, has driven the repair capability to not only be very technically driven, but also versatile and quick.
Between the major defect categories of clear and opaque defects, opaque defects present the greatest challenge. Traditionally, this challenge lies in the reality that there is no perfect full height defect resulting in no one universal removal process. This is compounded with the fact that on any given photomask, these opaque defects can be greater than a micron, sub micron, very numerous, within tight geometries, or out in an isolated region of the photomask. Furthermore, defects identified as opaque defects have the possibility to be foreign material related, presenting a further challenge. They do not respond to repair in the same manner as the opaque defects. The multitude of issues, combined with the need to repair the defects with high throughput, has driven the need for an advanced opaque repair system.
This paper will look into the practical application of a laser-based advanced opaque repair tool. Repair tool capability will show repair performance including substrate damage, transmission effects, and edge placement repeatability. This paper will also present a view of the operations of the repair system including imaging capabilities, and process throughput. This practical review of the advanced opaque repair system will show that technical needs of opaque repair, as well as practical needs of throughput and ease of use, can be achieved within one repair process.