Defects studies of semiconductor materials

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The nature and cause of defects in bulk and epitaxial semiconductor material are determined by combining the information obtained from several different techniques. Etch pit count, X-ray diffraction for measurement of precise cell parameter, X-ray topography, scanning electron microscopy (SEM), and electron microprobe analysis (EMA) are used to supplement each other. It is shown that more than one technique is necessary for a complete understanding of the defects. The approach is illustrated by three example: 1) The homogeneity study of GaAs wafers with equivalent doping but prepared under different conditions shows an excellent agreement between the amount of dislocations per sq cm obtained by the etch pit count, X-ray topography, and the degree of inhomogeneity as determined by variation ina 0 measurements. 2) The defects studies of the GaAsP epitaxial layer by X-ray topography, precise cell parameter measurements, SEM, and EMA indicate that the crystallographic defects are induced by misorientation during the growth process and by surface contamination of the substrate. 3) The examination of the surface defects of an etched silicon wafer by optical microscopy and X-ray topography indicates the presence of precipitates. Upon further studies using SEM and EMA it is shown that the defects are not precipitates but hillocks produced by surface contamination prior to the etching process.