Suppression of uphill diffusion caused by phosphorus deactivation using carbon implantation

Abstract

Ultrashallow junctions were analyzed using secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS) to investigate phosphorus redistribution at 500°C after laser activation. Evident pileup near the surface region due to uphill diffusion was observed during electrical deactivation of phosphorus. The uphill diffusion resulted from the profile gradient of interstitials which were generated during deactivation and recombined at the surface. The uphill diffusion of phosphorus was suppressed in samples implanted with carbon while the tail diffusion of carbon was enhanced simultaneously. This implies that excess interstitials were taken away via carbon diffusion. However, carbon did not affect phosphorus deactivation significantly. This suggests that the long-range diffusion mediated by interstitials was not the major mechanism governing the deactivation kinetics of phosphorus at 500°C.