In order to detect a single particle of several tens of nanometers and to clarify the relationship between particle outbreak and the workings of wafer processing equipment, a scattered laser light measurement system has been produced experimentally. The system is composed of a high frequency pulse-laser oscillator, a two-dimensional charge-coupled device image processor, and a status-signal processor connected to the wafer process equipment. By using this system, in situ monitoring of a single particle of several tens of nanometers that flakes off films deposited on the upper ground electrode of the plasma etching chamber, and observation of its trajectory are successfully demonstrated for real tungsten etchback processing. Moreover, data from the system show that, after processing several hundred wafers, the outbreak of particles in the etching chamber had a correlation with specific workings of the etching equipment, such as turning off the rf power and the injection of purge gas to the chamber. The scattered light measurement system has demonstrated its ability to monitor particle outbreak, transport, and behavior.