As technical advances continue, the pattern size of semiconductor circuit has been shrunk. Defect control becomes tighter due to decrease in defect size that affects the image printed on the wafer. It is critical to the photomask which contained considerably shrunk circuit and ultra high density pattern for sub – 14 nm tech devices. Therefore particle source from all processes should be controlled extremely. Most of defects generated in mask fabrication processes have been mainly created during each unit process. In this paper, we introduce a study of airborne molecular contamination to Cr etching process. The impact of mask front-end handling system to defect generated in Cr etching process even in very lower concentration environment airborne molecular contamination. By the experiment results we will bring forward the possible defect generation mechanism. Based on this understanding, appropriate solution to mitigate defects caused by airborne molecular contamination to Cr etching process will be proposed.