A Study of the Deactivation of High Concentration, Laser Annealed Dopant Profiles in Silicon

Abstract

ABSTRACTAs semiconductor device dimensions continue to decrease, the main challenge in the area of junction formation involves decreasing the junction depth while simultaneously increasing the active dopant concentration. Laser annealing is being investigated as an alternative to rapid thermal annealing (RTA) to repair the damage from ion implantation and to activate the dopants. With this technique, uniform, box-shaped profiles are obtained, with dopant concentrations that can exceed equilibrium solubility limits. Unfortunately, these super-saturated dopant concentrations exist in a metastable state and deactivate upon further thermal processing. In this work, a comprehensive study of the deactivation kinetics of common dopants (P, B, and Sb) was performed across a range of annealing conditions. For comparison, As deactivation data from the work of Rousseau et al.1 is also presented. Each dopant exhibits different deactivation behavior, however, As and P can be classified as unstable species while B and Sb are stable against deactivation until higher temperatures of 700-800°C. In addition, a means of maintaining these metastably doped layers is being investigated with the goal of meeting the International Technology Roadmap for Semiconductors (ITRS) requirements for ultrashallow junctions.