Mechanism of Gold Diffusion into Silicon

Abstract

Gold was found to diffuse into silicon by a complex mechanism involving a vacancy-controlled interstitial-substitutional equilibrium. This led to very complex diffusion concentration profiles. In analyzing the problem, a new experimental value was found for the self-diffusion coefficient of silicon, 1.81×104 exp(−112±20 kcal/RT) cm2/sec, which compared very favorably with previous data on diffusion of bismuth, germanium, and tin in silicon. The interstitial gold-diffusion coefficient was found to be 2.4×10−4 exp(−8.9±2 kcal/RT), the substitutional gold-diffusion coefficient to be 2.75×10−3 exp(−47±10 kcal/RT), the equilibrium-interstitial gold solubility to be 5.95×1024 exp(−58±10 kcal/RT), and the equilibrium-substitutional gold solubility (Collin's data) below 1200°C to be 8.15×1022 exp(−40.6 kcal/RT).