Haze Prevention and Phase/Transmission Preservation through Cleaning Process Optimization

摘要

Several haze studies were conducted in a test environment where UV lamps and test chambers were used to simulate a wafer fab environment. This study was designed to investigate reticles experiencing different cleaning processes in a real wafer production environment. A split test was carried out to benchmark two different fabs: an 8" R & D fab and an 8" memory production fab. Reticles cleaned with UV treatment and hot DI water were exposed on ArF scanners for up to 80 hours over a period of two months. Starlight inspection before and after laser exposure confirmed no significant defect count increase after exposure. Ion chromatography (IC) results from masks cleaned on a new Steag MaskTrack cleaner suggest that hydrogenated water (H_3-H_2O) and ozonated water (O_3-H_2O) processes can further reduce the sulfate and ammonium ion residual count by 40%. UV + hot water cleaning also shows advantages in phase and transmission preservation where less than a 0.2 degree phase angle loss per clean can be achieved.