Metrology to classify and deposit highly monodisperse nanoparticles of NIST-traceable sizes for surface scanner characterization

Abstract

Particulate contamination is one of the major sources of yield-loss in semiconductor manufacturing, especially as the feature size decreases. Surface inspection tools, like mask or wafer scanners, are widely used to detect contaminant particles on critical surfaces. Since the pellicle, which is a thin polymer film and transparent to the light source of lithography, has effectively worked in protecting the mask critical surface against particulate contamination, a lot of efforts were put predominantly on particulate contamination of wafers by evaluating the performance of wafer scanners using standard and process-related particles.1,2 Extreme Ultraviolet Lithography (EUVL) is considered as a promising candidate for the next generation lithography to manufacture semiconductors with feature sizes smaller than 32 nm. EUVL technology, however, suffers from particulate contamination, because the pellicles cannot be used to protect the mask due to high absorption of EUV beam by all known pellicle materials.3,4 In the process of EUVL, contaminant particles can be generated during any stages of integrated circuit (IC) manufacturing and may contaminate the critical surface of the mask having no pellicle protection on it. It is therefore important to carefully characterize the EUVL mask surface inspection tools. Since the mask or wafer scanners detect particles by measuring light intensity scattered by particles on masks or wafers, the performances of surface scanners are greatly affected by particle material and particle size.1,2 This makes the surface scanners need to be characterized with the particles commonly seen in semiconductor manufacturing. In the present study, a metrology to classify highly monodisperse nanoparticles of NIST-traceable sizes and then to deposit them on mask or wafer surfaces was developed, in order to characterize the surface scanners with known material, size and number of particles deposited on the mask or the wafer surface.