Microstructure Observation of “Crystal-Originated Particles” on Silicon Wafers

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Abstract
Microstructure shape of “crystal-originated particles” (COP's) on mirror-polished silicon wafers (a) as received, (b) cleaned with NH4OH/H2O2/H2O solution (SC-1), and (c) annealed at high temperature (∼1150° C) in O2/N2 mixture or in H2, were observed using a scanning electron microscope (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM). Elemental analysis of the COP's was also made using TEM-energy dispersion X-ray spectroscope (EDX). The COP was a pyramidal pit with {111} sidewalls, or a vertical cave having some facets of {111}. In a part of the COP, oxygen was detected by TEM-EDX. It was suggested that the microstructure shape of the COP's has been determined until the mirror polishing is finished. The size of the COP becomes larger and the slopes of the COP become gentler after an anneal in 3% O2/N2 at 1150° C for 4 h and removal of the SiO2 layer by HF solution. The depth of the COP becomes shallower, its size larger and its corners rounder by annealing in H2 at 1100° C for 1 min. The COP's disappear by anealing in H2 at 1150° C for 4 h.