Ultra-Pure Air (UPA) for AMC Control in Nano-processing Environment

As semiconductor processes advance to the nano-technology era (Chang, 2008), Airborne Molecular Contamination (AMC) becomes a major problem that severely affects production processes and yields. The damages caused by AMC in nanotechnology facilities have been found much worse than the contamination sourced from conventional airborne particulates. To address these AMC problems, an UltraPure Air (UPA) approach was explored and experimented, and a prototype system with a targeting level at 10-ppt capability has been developed. Although the prototype and experiments conducted to date have not demonstrated the ability to achieve a 10-ppt level AMC concentration, it is anticipated that through future process optimization and experimentation the 10-ppt level AMC concentration can be achieved. The UPA system is composed of three processing steps. In the first step, UV185+254nm are used to provide sufficient energy to break the molecular bonds of the contaminants. In this stage, aerosol droplets are introduced to react with these unstable compounds and form hydrophilic substances. After this 'immersing photochemical' oxidation process, secondly it involves contaminant flow through a compression and condensation module. In this stage, the nucleation, condensation and growth of the aerosols are applied to increase the collision probability between the contaminants and water droplets. Further on, a dehumidifying device removes the water droplets within the air, where the contaminants dissolved in the water are removed together during the dehumidification process. The third step is to remove the remaining contaminants, which cannot be treated in the previous steps, by selective molecular sieves and a final filtration device. This paper will begin with a brief review of AMC control schemes and UPA ideas followed by an introduction of AMC problems. And then, a model of contamination control and a prototype of UPA system will be proposed. Finally, a summary will be drawn with recommendation of future research.