ARSENIC DEACTIVATION ENHANCED DIFFUSION - A TIME, TEMPERATURE, AND CONCENTRATION STUDY

The electrical deactivation of arsenic in silicon has been studied wit h regard to its effect on enhanced diffusion. Experimental structures consist of a buried boron layer as an interstitial detector, and a ful ly activated arsenic doped laser annealed surface layer. As these stru ctures are annealed at temperatures between 500 and 750 degrees C, ars enic in the surface layer deactivates and we observe enhanced diffusio n of the buried boron layer. A study with time reveals that the enhanc ed diffusion transient and the deactivation transient are similar, ind icating a strong correlation between both phenomena. The dependence on concentration shows a maximum enhanced diffusion for concentrations b etween 3 and 4 x 10(20) cm(-3) of initially active arsenic. Above thes e concentrations, the large supersaturation of interstitials nucleates dislocation loops and lowers the overall enhancement measured in the buried boron layer. Temperature data show that even for temperatures a s low as 500 degrees C, enhanced diffusion is observed. These data are convincing evidence that the enhanced diffusion observed is due to th e deactivation of arsenic and provides important insights into the mec hanisms of deactivation. We propose that arsenic deactivation forms sm all clusters of various sizes around a vacancy with the injection of a n associated interstitial into the bulk. (C) 1998 American Institute o f Physics. [S0021-8979(98)04219-4].