Avoiding dislocations in ion-implanted

Damage from ion implantation in Si can lead to dislocation formation during subsequent thermal annealing. These dislocations may sharply degrade device performance, making it desireable to suppress their formation. In this paper the criterion for dislocation formation is reviewed. Knowing this criterion suggests several ways to avoid dislocation formation in high dose implants for device applications. 1. I N T R O D U C T I O N For future submicron devices one should be able to use high energy ion implantation for tailoring of doping profiles. It will then be necessary to anneal the ion implantation damage such that no dislocations or other secundary defects are present in the active areas of the device. Therefore secondary defect formation after ion implantation has become an issue again. In recent years various suggestions have been made to explain the formation of dislocations during annealing of primary damage, made by ion implantation below the critical dose for amorphization. It has been suggested that dislocation formation depends on: 1) the implanted ion species, 2) the number of excess atoms introduced during implantation, 3) a critical impurity dose, 4) a critical impurity concentration and 5) a critical peak concentration of displaced Si atoms. Below it will be shown that neither of these suggestions are consistent with the experimental findings. Instead, dislocation formation appears to depend critically on the total number of Si atoms displaced during implantation. Once the criterion for dislocation formation is known, it is also understood how dislocations may be avoided. This will be the message of our paper. 0167-9317/92/$05.00 © 1992 Elsevier Science Publishers B.V. All fights reserved. 358 F.W. Saris et al. / Avoiding dislocations in ion-implanted silicon iiii ii i l i i i ~ ̧ ........... i! !!!!~!̧!̧!!̧i̧~ . . . . . . ~ ~ ~ ~ ~+~,~i ................. ~iii~ iiiii iliiii~ ~ ! iiiiiiiiiiiiii ~ ̧ ~ ~'~"