A new method for sampling low-volume AMCs in a front opening unified pod

Abstract

The Front Opening Unified Pod (FOUP) is widely utilized in advanced semiconductor production. However, the airborne molecular contaminants (AMCs) inside FOUPs are difficult to monitor by sampling because of the limited volume and the low concentrations of contaminants. To reduce cross contamination and to help identify the causes of product failures, high-throughput screening of FOUP AMC surveying is essential. In order to acquire an effective sample in a FOUP with a limited 30-liter volume, a rapid, simple, and reliable method of chelating and chilled impinger sampling is proposed. A chemical approach first produces AMC derivatives of gaseous reactions, and then heterogeneous over-saturation nucleation transforms the AMC derivatives into condensation nuclei so as to precipitate liquid phase droplets. Thus, the AMCs inside a purged FOUP can be captured rapidly as dissolved acid/alkaline crystalline salts. Experimental results have shown that the proposed technique is a promising method of surveying AMCs inside a purged FOUP that bypasses the constraints of the limited volume and low concentration conditions.