Precipitates Formed by High-Concentration Phosphorus Diffusion in Silicon

In high-concentration phosphorus diffusion (∼1020 atoms/cc) observations have been made of small (<200 Å) precipitate particles and dislocation loops in the region immediately adjacent to the surface. These particles occur in the high-concentration flattened portion of the concentration vs depth profile curves. Their presence is an assigned cause for the discrepancy between total and electrically active phosphorus. Electron microscopic techniques were used to identify the defects as ``interstitial.'' Contrast effects similar to those expected of a spherically symmetrical coherent precipitate were observed. Strains in the precipitates were found in the range ε=0.001→0.004 and seemed unaffected by low-temperature heat treatments (at 650°C).