Stacking faults in silicon epitaxial layers

Abstract

A summary is given of a few specific causes responsible for the formation of stacking faults in silicon epitaxial layers grown on silicon substrates. From the technical point of view, these causes are associated with the treatment of the substrate before the growth process and with the prevention of penetration of foreign materials into the layer before and while it is growing. The location of the causes are: in the substrate (various defects and foreign materials which exist there before the growth process); in the epitaxial layer (mainly foreign materials which penetrate during the growth process); and in the interface region at and near the metallurgic junction of the substrate/layer. A brief review of the formation of stacking faults created during the layer growth process is given. In this connection, the subject of crystallographic planes and orientation of the stacking faults which determine its boundaries in respect to the rest of the epitaxial layer is touched upon. Also given is a practical summary of revealing the traces of the stacking faults on the layer surface by chemical etching. The major part of the paper is devoted to two subjects: the various causes responsible for the nucleation and formation of stacking faults and detailed examples of geometrical forms of the traces of the stacking faults on the layer surface. This is done by presenting photographs taken through an optical microscope on epitaxial layer surfaces grown during the research on the (111) silicon substrate. In such cases, the traces of the stacking faults on the layer surface appear as equilateral triangles, lines or various combinations of these. In each case, the connection between the experimental results of defect formation and their causes is given. The control possibilities on the formation, concentration and shape of stacking faults is reviewed. This is done by appropriate treatment of substrate surface both outside the reactor (mechanical and chemical polishing) and within the reactor (etching with H2 and HCl). Finally, a brief review of the utilization of stacking faults for measurement of the epitaxial layer thickness is summarised.