Evaluation, reduction, and monitoring of progressive defects on 193-nm reticles for low-k1 process

Growing application of 193nm lithography for low-k1 process has increased the appearance of progressive defects on reticles often known as haze, precipitates or crystal growth. Although the industry has identified multiple potential sources of these progressive defects, a high contributor is a combination of pollutant reactions from reticle manufacturing process and wafer fab environment. This paper will address the analysis of progressive defects and the associated studies focusing on the sources from possible mechanism to prevention methods. In this evaluation, a split study was performed looking at mask cleaning recipes, pellicle types and also the resulting contaminant on the reticles. The reticles were then cycled through 193nm exposure and then inspected on KLA-Tenor's latest best known inspection strategy to capture and characterize the progressive defects. Finally, the mask specification for contamination level, inspection method and re-clean frequency to meet the wafer fab requirements was established. Under these controls, the impact of progressive defects on wafer yield can be minimized.