A Characterization Study of Collimated Particle Beam by Iris Type Lens

摘要

As pattern pitch of semiconductor circuit is smaller, nanoparticles generated in process are now considered as serious contamination sources which can reduce the yield of process. Therefore it is important to develop nanoparticle concentration monitoring system which can operate at the low pressure in real time. Particle beam mass spectrometer (PBMS) is a real time in-situ system which can be used to measure size distribution of nanoparticles (5 to 500 nm) at the 100 mtorr. PBMS needs collimated particle beams to measure number concentration distribution. Aerodynamic lenses system developed by Liu et al. (2005) have been widely used to obtain such collimated particle beam. It has good focusing characteristics at the designed conditions. However its focusing efficiency is greatly decreased in other conditions. Due to semiconductor manufacturing facility have limited space, PBMS having big volume should be multi process monitoring system. However previous aerodynamic lenses cannot be used in various conditions. Therefore we proposed and designed iris type aerodynamic lenses which can control the particle focusing efficiency by changing aperture size. The basic design of the iris type aerodynamic lens was perfor med based on theoretical analysis of particle trajector y using non-dimensional parameters including St, Re, Kn and Ma (Liu et al., 1995). At the previous study, we showed that iris type aerodynamic lenses can focus nano size particles in various conditions listed on ta ble 1 by numerically.