Contamination Control IN and OUT of the Cleanroom: Airborne Molecular Contamination, Part 2: Detecting AMC

摘要

"How do I know if I have AMC?" Hopefully, you are not suspicious of airborne molecular contamination because of poor yield or customer complaints. Last month, we discussed how AMC can be a "silent poisoner" of your process and product; and we discussed sources of AMC. Instead of suspecting that you might have AMC, be proactive - head it off at the pass. Detect AMC before it ruins the product; avoid damage to your bottom line. There are two basic approaches to monitoring (1) AMC on surfaces; (2) Contamination in the air. Many monitoring techniques have been proposed or commercially developed. We discuss a select sample of them. Thin film contamination can be detected on the product surface. Of course, by then you already have AMC; the secret is to detect it at a very low level. Periodically, a component can be removed from the build process and be analyzed for surface contamination. However, it may be easier and more cost effective to use witness samples. A witness sample is material that duplicates or emulates the surface of the product. If the product is metal, use a piece of the same metal; if plastic, use the same plastic so that the witness sample will have the same affinity for AMC.