In the advanced technology photomask manufacturing industry, it is challenging to produce defect-free photomasks, especially for the increasingly smaller critical dimension current days . Since the 193nm immersion scanner numerical aperture (1.35) has remained the same as in previous nodes, more mult i-patterning and aggressive source mask optimizat ion illumination sources are being used to print smaller feature crit ical dimensions (CDs) and pitches. To accommodate such specialized sources, more model -based mask OPC and ILT are being used, making mask designs very complicated. This in turn makes mask manufacturing very challenging , especially for the defect inspection, repair, and metrology processes that are used to guarantee defect-free masks. So, it is necessary to develop an application for handling mask defects. In this paper, we introduce a new application called LPR (Lithography Printability Review) to verify any outlier defects or repairs before the mask ships to the wafer fab. The paper details how LPR works in the mask-making flow and how the LPR module is set up. This application has been tightly integrated with KLA’s server and inspectors. The paper concludes with showing the benefits realized in mask making cycle time as a result of implementing LPR into a high volume advanced photomask production line.
OMOG (opaque MoSi on glass) blank is widely used in advanced masks because of its advantage in high resolution and 3D effect1-2. And the manufacture flow is simple compared to phase shift mask. But the repair of this type mask is a challenge. The OMOG material is sensitive to the etching gas thus the etching rate is much higher than PSM. This article presents a problem, the poor edge roughness after repair in OMOG mask, is also related to the high etching rate. The CD (critical dimension) of advanced masks is very small. If there is some distortion in the features’ edge, the AIMS result is easy out of spec. The poor edge roughness we met usually gets poor AIMS result. To find the reason, we checked the manufacture flow and then focused on three steps: repair process, plasma treated process and short clean. Finally we found the plasma treated process was the main reason, and the clean process also contributed to it. Plasma process makes the mask surface oxidization and the oxide layer is high clean durability. The etching rate of oxide is slower than pure OMOG material, and the oxide layer’s uniformity is not good. The two characteristics lead to different etching ratio in the defect area. This is the reason of the poor edge roughness. If the oxide layer is uniform in the defect area, the problem won’t happen. That’s why not all the masks we repaired met the problem. We also found the removal of the oxide layer by clean process could solve this problem. This is an indirect evidence for explaining the reason.