Direct observation of electrically harmful surface defects of Si wafer immersed in slightly Cu-contaminated water

Images of defects generated by immersing silicon wafer in slightly Cu-contaminated water of 500 ppt level were observed for the first time by using a highly sensitive defect detection system and coordinate linked atomic force microscopy. There are three types of surface defects: a protrusion-type defect 100-200 nm wide and 2-10 nm high, a shallow pit 100-200 nm wide and 5-10 nm deep, and a larger shallow pit 1 mu m wide and 2-8 nm deep. They are detected as laser beam scatters with sizes smaller than 90 nm-diam in spherical polystyrene-latex standard particle equivalence. From oxide breakdown characteristics of the wafer, these extremely small or shallow defects are believed to be potential origins which can deteriorate gate oxide integrity. (C) 2000 Elsevier Science B.V. All rights reserved.