Knack for reticle cleaning

Cleaning is one of the most important processes in mask making, because it decides final quality. In cleaning process, it is necessary for reticle cleanliness to not only remove particles from reticle but also prevent adsorption and re-deposition onto reticle. There is the knack for reticle cleaning, and we introduce three keys in this paper. The first key is the rinse after chemical treatment. By the rinse sequence modification, the cleaner was refined and the particle removal ability was improved. The second key is quality control to grasp the situation of cleaner. By the daily check, cleaner's abnormal condition is found at an early stage, quick action is taken, and then stable cleaning quality is kept every day. And the third key is proper choice of cleaners. We have adopted pre-cleaning process and selected the adequate cleaner for each cleaning level and improved cleaning yield and quality.