Precipitation Effects in Diffused Transistor Structures

Abstract

Transmission x‐ray diffraction microscopy was used to detect precipitation effects in phosphorus‐diffused silicon—especially after subsequent gold diffusion. The precipitate (after gold diffusion) appears to be a complex—formed by gold combining with excess phosphorus in the silicon lattice. This complex formation is responsible for the apparent high solubility of gold in phosphorus‐diffused areas, and it has a potentially detrimental effect upon diode reverse characteristics. Furthermore, this phenomenon provides a sink for gold atoms that would otherwise fill silicon lattice sites. This effect has important consequences on the fabrication of fast switching devices, since it tends to rob the crystal lattice of gold recombination centers.