Modelisation of extended defects to simulate the transient enhanced diffusion of boron

Process conditions to create ultra-shallow junctions for silicon devices are known to result in a transient enhanced diffusion (TED) of boron. The diffusion of boron is due to its coupling with silicon self-interstitials. An anomalous behavior of these atoms is responsible for the boron TED. More precisely, it has been experimentally evidenced that a great amount of excess Si interstitials is created after implantation and that a part of this supersaturation precipitates into extended defects during annealing. A modelisation of this phenomenon is presented, aimed at enlarging the predictness of the process simulations, such as in the simulator IMPACT-4, and at increasing the understanding of boron TED. The continuous description of the nucleation, ‘pure growth’ and Ostwald ripening of one kind of extended defects, dislocation loops, is exposed. The comparison of the calculated sizes and densities of dislocation loops with their experimental values validates the modelisation. It was demonstrated that the concomitant evolution of silicon free interstitials results in the right amount of boron diffusion. TED is correctly simulated throughout the annealing thanks to this enhancement of the physical basis of IMPACT-4.