TITANIUM SILICIDE AS A DIFFUSION SOURCE FOR PHOSPHORUS - PRECIPITATION AND ACTIVATION

The diffusion into a p-type silicon substrate of phosphorus ions implanted in TiSi2 layers has been investigated for several thermal treatments in the 950-1150-degrees-C temperature range. The drive-in was performed using either a rapid thermal annealing system or a traditional furnace. Shallow junctions, lower than 100 nm, were obtained with high dopant concentration at the silicide/silicon interface. The amount of diffused active phosphorus increases linearly with the square root of the annealing time, as measured by Hall technique in a layer-by-layer removal procedure. Precipitate particles are observed by transmission electron microscopy. The agglomeration and precipitation of impurities might be associated to the high tensile stress induced by the silicide layer on the surface silicon region and to its influence on the solid solubility and clustering of phosphorus atoms. Precipitates are easily dissolved after thermal annealing in absence of the TiSi2 layer.