Ultra-pure air (UPA) for AMC control in nano-processing environment

Abstract

As semiconductor processes advance into the nano-technology era, airborne molecular contamination (AMC) has become a major problem that severely affects production processes and yields. The damage caused by AMC in nano-scale technology production has been found to be much worse than contamination related to conventional airborne particulates. To address these AMC problems, an ultra-pure air (UPA) approach has been explored and its prototype pre-treatment system has been experimented with. The schematic of a UPA system is composed of three processing steps. In the first step, UV 185þ254 nm is 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 the 'immersing photochemical' oxidation process, the second step involves contaminants flowing through a compression and condensation module. In this concentrating module, nucleation, condensation, and growth of the aerosols are facilitated to increase the collision probability between the contaminants and water droplets. Further on, a dehumidifying device removes the water droplets within the air, so the contaminants dissolved in the water are removed together with the water during the dehumidification process. The third step is to remove the remaining contaminants, which cannot be completely treated away in the previous steps, through specifically selective molecular sieves and other corresponding filtration devices. Xylene was used to exemplify a prototype system framed with a target level of 10 ppt capability. The purpose of this article is twofold. One is to introduce the UPA system and its theoretical rationales. The other is to experimentally demonstrate the effectiveness of using immersed UV for mitigating AMC problems.

Review—Airborne Molecular Contamination: Recent Developments in the Understanding and Minimization for Advanced Semiconductor Device Manufacturing

“…In recent years, another school of thought has emerged, proposing separating air supply to ballroom type environment from mini-environment, whose intake air can be directly treated to ultrapure level without moving through the makeup-air unit (MAU), HVAC, and air filtration processes. 46 The ultrapure air (UPA) is produced via mainly advanced oxidation processes. For example, the immersing UV technology (iUV) developed by Chuang and Chang (2013) 47 requires the conversion of insoluble air contaminants into hydrophilic substances for iUV to function properly.…”