Measuring particle deposition on witness surfaces using a silicon wafer scanner

Monitoring of cleanroom and spacecraft cleanliness during ground processing operations is essential in order to verify performance requirements for optical systems prior to launch. The objective is to replace manual particle counting with automated panicle counting in order to reduce the processing time for the witness places and to improve precision and accuracy of the measurements. A modified silicon wafer inspection instrument, using a HeNe Laser light source, was used to count and size particles deposited on wafers exposed in the cleanrooms. The previous paper discussed measuring particles on silicon wafer witness plates during operations cleanrooms and discussed analytical methods For calculating percent area coverage (PAC). This paper describes the optical performance of the ESTEK instrument and tests on the instrument.