An Improved Cu-Decoration Technique for Characterizing Lattice Imperfections in Silicon Wafers

Abstract

An improved copper decoration technique is described. The technique eliminates such a disadvantage of the conventional techniques as the formation of alloyed surface layers. Silicon wafers are immersed in HF solution containing a small quantity of Cu²⁺ ions and are covered with copper layer, followed by annealing in dry O₂. The quantity of copper atoms in annealed silicon is proportional to the Cu²⁺ concentration of the HF solution. By selecting the solution with a proper Cu²⁺ concentration not to exceed the solubility limit for copper in silicon, the formation of alloyed surface layers is avoided. Thus the specimens can be immediately prepared for X-ray section topography to investigate both the surface and bulk of silicon wafers. The technique has been applied for studying swirl defects. It has allowed us to observe the gettering effect associated with swirl defects.