Boron Diffusion and Silicon Self-Interstitial Recycling between SiGeC layers

Abstract

Substitutional carbon is known to locally reduce silicon self-interstitial concentrations and act as a barrier to self-interstitial migration through the carbon rich regions. A silicon spacer between two carbon rich SiGe layers is fabricated in this work to examine self-interstitial generation in a region that is isolated from self-interstitial formation at the surface or in the silicon bulk. Boron marker layers above, below and in between two SiGeC layers are used to monitor the self-interstitial concentration between the substitutional carbon. No evidence of selfinterstitial depletion in the silicon spacer is observed, despite annealing in conditions believed sufficient to allow the self-interstitials to reach and react with surrounding substitutional carbon. Simulations of the self-interstitial and carbon indicate that the silicon self interstitial concentration in the spacer layer can be sustained in part due to a silicon self-interstitial recycling process through a reverse "kick-out" reaction. EXPERIMENTSingle crystal, 25 nm thick boron marker layers located at 150, 440, 600, and 900 nm below the surface were grown by rapid thermal chemical vapor deposition at temperatures of 550-750°C on Czchokralski silicon substrates with or without two 25 nm Si 0.775 Ge 0.22 C 0.005 layers at depths of 300 and 750 nm. The samples were subsequently annealed in either nitrogen for 30, 120 or 240 minutes at 850°C, or oxygen for 30, 60 or 120 minutes at 850°C. Carbon, germanium and boron concentrations before and after annealing are measured by secondary ion mass spectrometry (SIMS) with 20% and 5% uncertainties in concentration and depth, respectively.Mat. Res. Soc. Symp. Proc. Vol. 810