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

Process conditions to create ultra-shallow junctions for silicon devices ar e known to result in a transient enhanced diffusion (TED) of boron. The dif fusion of boron is due to its coupling with silicon self-interstitials. An anomalous behavior of these atoms is responsible for the boron TED. More pr ecisely, it has been experimentally evidenced that a great amount of excess Si interstitials is created after implantation and that a part of this sup ersaturation precipitates into extended defects during annealing. A modelis ation of this phenomenon is presented, aimed at enlarging the predictness o f the process simulations, such as in the simulator IMPACT-4, and at increa sing the understanding of boron TED. The continuous description of the nucl eation, '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 silico n 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. (C) 2000 Elsevier Science S.A. All rights reserved.