Interactions of B dopant atoms and Si interstitials with SiO_2 films during annealing for ultra-shallow junction formation

摘要

In this work we present an investigation of the effect of oxide thickness on annealed B diffusion profiles. Experiments were specifically designed to determine the effect of varying oxide thickness on the B diffusion profile after annealing. Boron was implanted through a 50 A screen oxide. Implant oxide was etched to varying degrees on different samples resulting in screen oxide thickness from 0 to 50 A. On samples where the screen oxide was completely etched away, cap oxide was deposited with thickness varying from 0 to 50 A. The implanted wafers were then spike annealed at 1050℃. We found that the thicker the oxide during annealing, the deeper the B diffusion profile. A model of the Si-SiO_2 system based on the interactions of B dopant atoms and silicon interstitials with SiO_2 films is proposed to explain the experimental observations. The model takes into account the segregation of Si interstitials at the Si/SiO_2 interface and the diffusion of that Si in the oxide.