Detection of low-level copper-contamination on silicon surfaces by drop nucleation

摘要

Nucleation and growth of liquid drops from the vapor can be used to locate efficiently surface inhomogeneties such as topological defects, oxide patches, metallic impurities, organic contamination, and particles. In this study, nucleation of water drops was used to investigate the surfaces of copper-contaminated silicon substrates. Hydrogen-terminated siicon (111) substrates wer dipped into copper-contaminated ultranpure water and exposed to suppersaturated water vapor. The amount of copper deposited was varied by changing the strength of the solution. Nucleation occurred at vapor pressures close to saturation. Higher densities of nucleated drops appeared on areas with greater concentrations of copper. Using this technique, itwas possible to detect copper concentrations as low as 6x10~(11) atom/cm~2. Below this concentration, treated and untreated substrates coulb not be distinguished. The extreme sensitivity of the technique to background nucleants shows its potential for efficient screening of surfaces for a large range of inhomogeneities.