Ab initio study of boron segregation and deactivation at Si/SiO2 interface

We perform first-principles density functional calculations to investigate the stability of various B-related defects near Si/SiO2 interface, and propose a mechanism for boron segregation to the interface. In Si, a substitutional B is energetically very stable and does not diffuse into the oxide in the absence of Si self-interstitials. Under nonequilibrium conditions, where self-interstitials are abundant, B dopants diffuse via the formation of a defect pair which consists of a B dopant and a self-interstitial. It is found that diffusing B dopants further segregate toward the oxide near the interface in form of positively charged interstitials, resulting in the suppression of activated dopants.

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