Haze is a kind of contamination on the surface of mask which observed in the wafer production clean room only on reticles exposed with 193nm or 248nm wavelength process. Analyses have been provided an approach with enhance reticle purging efficiency method for investigating the required purging flow of clean, dry gas to prevent the ingestion of external contaminants into the reticle.
In this study, we investigate the purging parameters theoretically by using natural convection with the purpose of avoiding rupturing the pellicle and expediting the overall purging process as shown in fig.1. Accordingly, a parametric analysis of important geometric variables including the size and number of purging holes is performed. Our study then process to identify the optimized parameters (number of holes, position of holes, purging flow rate) by using computational fluid dynamic (CFD) simulation. As indicated by our results, a parametric analysis investigating the effect of the pellicle variables shows that the purging time were sensitive to the number of purging or vent holes. As shown in fig.2 and fig.3, the total purging time can be reduced by increasing the number of purging or vent holes from 2 to 4. An increase in the number of purging holes from 2 to 4 help shorten the purging time by 20 to 40seconds. So the production throughput can be expected to rise while the consumption of gas can be reduced.