A new dry cleaning methodology named laser shock cleaning and optical inspection
technique has been applied not only to remove the particles from the surfaces of image sensors but
also to inspect the surfaces automatically before or after the cleaning. In the packaging of CMOS
and CCD image sensing modules, the particles generated during the assembly process should be
removed from the surfaces of image sensors in order to ensure clear image as well as to enhance the
yield. The different kinds of particles were removed from the surfaces by the laser shock cleaning
technique which utilizes the airborne shock wave induced by intense laser pulse. For the
quantitative evaluation of cleaning performance, number, shape and size of the particles on the
surfaces of image sensors were measured by vision inspection technique before and after cleaning.
It was found that most particles on the surfaces were successfully removed after the treatment of
laser-induced shock waves. The average removal efficiency of the particles was over 95 %. It is
interestingly found that the remaining particles after the cleaning are based on organics, which are
probably attached during the bonding process.
About modulation transfer function of machine vision system based on CMOS and CCD image sensors
