Fast growing protrusions from epitaxial semiconductor surfaces

Abstract

Epitaxially deposited germanium and silicon layers often exhibit large (typically 20 μ high) dome-shaped surface defects. These protrusions greatly hinder subsequent device fabrication procedures-especially that of masking. Observation by optical and scanning electron microscopy shows that these dome-shaped defects may extend to a height of some twenty times the epitaxial layer thickness and are characterized by geodesic faceting. Cross sectioning experiments on germanium wafers show that they appear not to originate within the substrate but probably nucleate at the site of some surface contamination. Impurity concentrations in the defects were too low to allow positive identification of the species using spark source mass spectrometry or the electron microprobe. However, such defects could be artificially promoted by contaminating the surface with any of a number of materials. Copper was particularly effective in this respect. Mechanisms for this enhanced growth are proposed. © 1970 The Metallurgical Society of American Institute of Mining, Metallurgical and Petroleum Engineers, Inc., and American Society for Metals.