Study of Nano/Micro Aerosol Particles Measurement for the UHV Slit Valves

In response to the nano-scale miniaturization trend of IC devices, advanced semiconductor processes require more stringent cleanliness. This study sets up a UHV measurement system for particles detection within a highly cleanliness testing chamber with a UHV slit valve to be test, and an experimental procedure is proposed and examined to investigate particle generation while this slit valve is in operations. Cycle numbers of 10,000, 20,000 and 40,000, respectively, are set for slit valve testing. A series of experiments are conducted to gather particles generation information and to clarify the possible causes and sources of dust particles and its concentrations and the particle sizes. The condensation particle counter (CPC) is used to measure the particle concentration and the differential mobility analyzer (DMA) is for particle sizes measurement. Besides, scanning electron microscopy (SEM) and atomic force microscope (AFM) are used to investigate the condensation behaviors on a witness wafer and the energy dispersive x-ray spectroscopy (EDS) is used to the surface characterizations of the slit valve O-ring. In atmosphere experiments, the particle sizes and size distributions are measured by CPC and SMPS instruments and the gathered results are compared to the measured particle sizes by SEM and AFM and are used to evaluate the assumptions of particle generating sources and mechanisms. Experimental results show that the particle sizes and particle concentrations increase as the cycle numbers increases. To examine the particle generations in vacuum, the particle sizes of the deposited particles on wafer are measured by SEM and AFM. The results are compared with the SMPS measurement.