A feasibility test for real-time fine particle measurements in vacuum semiconductor processing equipment has been conducted. The approach in monitoring particles in process equipment is an installation of a sensor at a critical location inside the process equipment (hence the term ‘in-situ’) to track free particle levels in real-time. Common method for particle detection in a process chamber today is a use of test wafer with a laser wafer scanner. However, this method does not give a real time information of the particle status in the process chamber. In this paper, a new method has been developed to detect particles in real time in vacuum system for particles smaller than an optical method can detect. The system consists of a particle charging region and a particle detection region in a vacuum system. Particles with 50nm are successfully detected at about 10 torr region.