Boron activation and diffusion in silicon for varying initial process conditions during flash-assist rapid thermal annealing

Flash-assist Rapid Thermal Processing offers thermal budgets more than three orders of magnitude less than conventional annealing technologies. It therefore presents an opportunity for the continued scaling of complementary metal-oxide-semiconductor (CMOS) technologies, which demand highly doped, ultra shallow junctions for its source/drain extensions. These low thermal budgets are expected to limit dopant diffusion, while the extremely rapid ramp rates enable the attainment of anneal temperatures which were previously not possible. It is the goal of this work to gain a better understanding of the underlying mechanisms which are responsible for the dopant activation and diffusion in silicon material processed by Flash-assist Rapid Thermal Processing.; The extremely fast ramp rates, on the order of 1x106°Cs -1 and short processing times, which are typically less than 1 millisecond, offered by the Flash-assist Rapid Thermal Process, have enabled investigations into the early stages of the extended defect evolution. These studies of the End of Range defects associated with amorphous layers have revealed the existence of a highly unstable silicon interstitial defect structure, which was found to follow one of two evolutionary paths: evolution into the {lcub}311{rcub}-type defect or dissolution via the loss of interstitials. The silicon interstitial loss from this defect configuration was shown to be related to the anneal temperature through an Arrhenius relation, with an activation energy of 2.1eV, which differs from previously reported values of known defect structures.; The work herein also clearly established that higher boron activation levels can be achieved subsequent to amorphous layer re-crystallization, for sufficiently high anneal temperatures. This was determined to be a direct consequence of increased diffusion in the tail of the boron profile and activation in the profile peak. At such anneal temperatures the peak active boron concentration was independent of the amorphous layer re-crystallization temperature. The increase in active boron concentration subsequent to the re-crystallization process was also shown to be much larger than the reactivation of boron from the well researched boron interstitial cluster configuration. This fact strongly suggests the existence of boron in an alternative less stable configuration from which additional activation, subsequent to the re-crystallization process is possible.