Characterization of Crystal Quality by Crystal Originated Particle Delineation and the Impact on the Silicon Wafer Surface
Characterization of Si wafers by delineation of crystal originated particles (COP) provides insight into size and radial distribution of crystal related defects. A good correlation of the COP densities with gate oxide integrity and flow pattern defect densities is observed. The density and size distribution of COP in Czochralski Si ingots can be modified by the pulling rate and the cooling conditions of the crystal and is further influenced by high doping concentrations. The COP densities are comparable on wafers with (100) Si and (111) Si orientation as well as on p‐ and n‐type wafers with moderate doping level. No COP are found on float zone (FZ) and on epitaxially grown wafers. Crystal defects are also delineated by chemomechanical polishing and can be detected on the wafer surface as light point defects (LPD). LPD densities, however, do not necessarily correlate with the corresponding COP densities after SC1 treatment and do not reflect the quality of the crystals because polishing delineates only part of the larger crystal defects to a size which is above the detection limits of commercially available scanning surface inspection systems. High temperature annealing results in reduction of defect sizes and partial dissolution of COP. Investigations of FZ and oxygen doped float zone indicate that oxygen is participating in the formation of COP.
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