Experimental and simulation study of the flash lamp annealing for boron ultra-shallow junction formation and its stability

The application of advanced annealing techniques has emerged as an essential dopant activation step for the formation of ultra-shallow junction in forthcoming complimentary metal-oxide-semiconductor (CMOS) technology. Recent works demonstrated that flash lamp annealing (FLA) is able to provide junctions that are highly activated and ultra-shallow. However, it is found that the thermal budget from the FLA is not enough to fully dissolve the extended defects induced by the pre-amorphizing implant. This affects the junction stability upon post-FLA thermal annealing cycle. In this work, the junction stability is investigated through the de/re-activation behavior of B in the flash-annealed junctions subjected to subsequent isochronal RTA annealing. The experimental results show that a single pulse FLA leads to significant dopant deactivation. It is also found that the deactivation level can be reduced by the additional of flash pulses or eliminated by a spike RTA prior to the FLA. To understand the physics underlying the FLA junction formation and deactivation, junction profiles and activation data are simulated using an atomistic kinetic Monte Carlo (kMC) simulator. The simulated distributions of the defects for various flash conditions are used to study their evolution as well as interaction with dopants. Detailed analyses reveal that large amount of extended defects remains after a single pulse flash annealing. Thus, upon post-FLA thermal annealing, the defects at EOR region emit interstitials toward the surface which deactivate the B through the formation of dopant-defect clusters. For the case of prior RTA schemes, the simulated results show distinct variations in the amount of extended defects and it can be correlated to the different extent of junction stability.