Morphology of etch hillock defects created during anisotropic etching of silicon

Abstract

Etch hillocks are defects created during anisotropic etching of (100) silicon. From direct measurements of defect micrographs, we have determined the structure of etch hillocks to be pyramids bounded by (567) planes. The defects planes are different from those which are observed to emerge as anisotropic etch facets, such as (111), (211), (212), (133) and (411). We also describe the process by which defects are annihilated in high-concentration etchant. The relative stability of various defect edges is in agreement with calculations of the degree of backbonding of Si atoms along hillock edges. Our results suggest that the mechanisms responsible for hillock formation are distinct from those causing faceting during undercutting of convex corner masks.