MRS Spring Meeting 1999

Transient enhanced diffusion and dose loss of indium in silicon

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The dose loss and transient enhanced diffusion of indium in silicon were studied as a function of dose. Indium was implanted into silicon through a 90 A oxide at 50 keV for doses ranging from 3×1012 to 2×1014 cm-2. These conditions provide peak concentrations that approximately range from 1×1018-1×1020 cm-3. After an RTA anneal at 1000 °C for 5 s, indium exhibits substantial motion at both the tail and peak regions for high doses. The enhanced diffusion is mostly over within 5 s. There was not any observable enhanced diffusion in the tail region at the lowest dose although there was significant movement at the peak region. The dose loss correlates very well with the enhancement in the diffusivity. TEM images show that the amorphization dose lies between 3×1013 and 8×1013 cm-2. In spite of the amorphization, diffusion enhancement in the tail region still keeps increasing with dose, which is contrary to a model of `+1' interstitials and complete removal of interstitials in the regrown layer. The 550 °C 1 h anneals show that the dose loss can partially be attributed to the sweeping of the dopant by the growing a/c interface. Previously, the solubility of indium has been estimated to be around 1-2×1018 cm-3. At high doses, significant movement is observed at the peak of the indium profile although the peak concentration exceeds the solubility level by at least an order of magnitude. This shows that indium is not precipitating into an immobile phase like antimony or boron.