(460b) Quantifying the Effects of near-Surface Diffusion and Electrical Activation of Boron in Silicon
Defect behavior in silicon can be controlled by manipulating the chemical state of nearby surfaces and solid-solid interfaces, with important implications for transistor fabrication by ion implantation and annealing. Silicon interstitials formed during the ion implantation step are responsible for unwanted transient enhanced diffusion (TED) of dopants, and affect the degree of dopant activation as well. Earlier work in our laboratory has shown that certain chemical treatments of surfaces and interfaces changes its ability to act as sinks for interstitials. The fundamental kinetic quantity describing ?sink? behavior can be described by an annihilation probability (S). Yet surfaces and interfaces also support electrically charged defects, which create local strong electric fields that influence the local motion of interstitials that are charged. The degree of charge buildup can be quantified by an electric potential (Vi). The combined effects of S and Vi not only influence the annihilation of interstitials, but lead under some conditions to the pile up of electrically active dopants near the surface or interface. However, up to now, the precise nature of the interplay, including the most relevant time scales during annealing, has never been quantified. Through continuum modeling on the nanometer length scale, the present work provides such quantification. Differential equations describing the diffusion and reaction of silicon and boron interstitials are solved to yield the time evolution of boron profiles that are compared in important cases to experiment.