As semiconductor device dimensions continue to decrease, the main challenge in the area of junction formation involves decreasing the junction depth while simultaneously decreasing the sheet resistance. Laser annealing was being investigated as an alternative to rapid thermal annealing to repair the damage from ion implantation and to activate the dopants. With this technique, uniform, box-shaped profiles were obtained, with dopant concentrations that could exceed equilibrium solubility limits at normal processing temperatures. Unfortunately, these supersaturated dopant concentrations exist in a metastable state and deactivate upon further thermal processing. A comprehensive study was made of the deactivation kinetics of common dopants (P, B, Sb), for a range of concentrations and annealing conditions. For comparison, As deactivation data from the literature was also presented. P and As deactivate substantially at temperatures as low as 500C, while Sb at moderate concentrations and B remain fully active until 700 to 800C. It was proposed that As and P deactivate through the formation of small dopant-defect clusters while B deactivates through precipitation. The proximity to the surface was shown to be a second-order effect.

Thermal Stability of Dopants in Laser Annealed Si. Y.Takamura, S.H.Jain, P.B.Griffin, J.D.Plummer: Journal of Applied Physics, 2002, 92[1], 230-4. See also: Physical Processes Associated with the Deactivation of Dopants in Laser Annealed Silicon. Y.Takamura, P.B.Griffin, J.D.Plummer: Journal of Applied Physics, 2002, 92[1], 235-44