AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
DMA Characterization of Sub-50nm Silica Nanoparticle Size Standards and Comparison with PSL Size Standards
ZEESHAN SYEDAIN, Benjamin Hunt, William Dick, MSP Corporation
Abstract Number: 308 Working Group: Nanoparticles and Materials Synthesis
Abstract Advanced manufacturing of semiconductor devices at technology nodes below 30nm requires new defect review and inspection tooling to maintain device yield. Historically, wafer inspection tools, photomask inspection tools, and other defect review tools have been calibrated with polystyrene latex (PSL) spheres, which are relatively uniform in size and shape. New inspection tools utilize deep ultraviolet (DUV) or extreme ultraviolet (EUV) radiation of high intensity to detect and measure defects smaller than 20nm. Repeated exposure to intense UV sources can cause degradation of the PSL. In addition size distribution of commercially available PSL spheres becomes broader with decreasing particle size, which limits their applicability as size standards. Silica nanoparticles provide a suitable alternative to PSL, as they can be synthesized with amorphous and uniform quasi-spherical structure and high thermal stability. In this study, thermal stability and monodispersity of 18-50nm silica nanoparticle size standards were compared to commercial PSL size standards. For measuring size distribution, the nanoparticles were suspended in buffer solution and generated as airborne particles using electrospray (TSI model 3480) and classified with a DMA. At 30nm, the silica size standard had a peak diameter of 29.5±0.7nm and relative full-width half maximum (RFWHM) value of 11%, while the PSL size standard had a peak diameter of 30±1 nm with RFWHM of 60%. The distribution differences between silica and PSL particles were comparable at 20nm and 50nm sizes. Silica particles deposited on silicon wafers tolerated high thermal treatment without any change in size, further demonstrating their suitability for sub-50nm calibration of defect inspection tools.