Nondestructive measurement of subsurface structural defects in polished single-crystal silicon

A correlation has been found between scattering levels measured by a new photon backscattering technique and lattice damage revealed by etching polished and ion-implanted silicon wafers. The surfaces of the wafers appeared featureless when observed by Nomarski microscopy and no roughness differences could be measured by diamond stylus profilometry before etching. Photon backscattering thus appears to provide a nondestructive method for inspecting for subsurface damage in silicon wafers. A byproduct of the study was the finding that etched, ion-implanted silicon wafers which clearly showed the imprint of the mask used for the ion implantation did not have steps or height differences between ion-implanted and untreated areas. This result indicates that the etch rate was the same for ion-implanted and untreated areas, but that the optical constants of the material appear to have changed in the implanted regions.

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