For pre-amorphized B-implanted samples subjected to non-melt laser spike annealing, increasing the laser spike annealing temperature at below 1250C resulted in negligible sheet resistance changes due to the formation of inactive B-interstitial clusters. These clusters, which were seen as a kink in the B profile beyond the amorphous/crystalline interface, resulted chiefly from the inadequate removal of end-of-range defects. When the laser spike annealing temperature was increased beyond 1250C, sheet resistance improvement took place due to the increase in active B dose from the dissolution of the B-interstitial clusters at higher temperatures. Cluster dissolution also gave rise to a supersaturation of Si interstitials that deepened the junctions as a result of transient enhanced diffusion. With an additional post-laser spike annealing treatment, severe deactivation, especially at lower laser spike annealing temperatures, and further transient enhanced diffusion was observed. Two concurrent mechanisms: B clustering (which gave rise to deactivation and sheet resistance degradation) and dissolution of the B-interstitial clusters (which gave rise to transient enhanced diffusion) formed during the laser spike annealing step, were believed to take place during the post-laser spike annealing thermal budget. As the laser spike annealing temperature was increased, transient enhanced diffusion from the as-laser spike annealing profile upon rapid thermal annealing was significantly reduced as a result of an improved effectiveness of the end-of-range defect dissolution during the higher temperature laser spike annealing step. When C co-implantation was performed, deactivation and transient enhanced diffusion was successfully suppressed with the reduction in free Si interstitial concentration due to the formation of complexes of C and Si interstitials. The amount of deactivation upon rapid thermal annealing became independent of the laser spike annealing temperature for C-implanted samples, largely because B clustering became limited by the small concentration of free Si interstitials present instead of the laser spike annealing temperatures used.

 Suppression of Boron Deactivation and Diffusion in Preamorphized Silicon after Nonmelt Laser Annealing by Carbon Co-Implantation. C.H.Poon, A.See, Y.Tan, M.Zhou, D.Gui: Journal of Applied Physics, 2008, 103[8], 084906