Ab initio Study of Boron Pile-up at the Si(001)/SiO2 Interface

We studied the atomistic structure of boron atom at the Si(001)/SiO₂ interface using ab initio calculation method to investigate the mechanism of boron pile-up at the interface. We found that, if there is no defects, such as oxygen vacancy, at the interface, no stable sites of B would appear at Si/SiO₂ interface and SiO₂ layer, thus indicating that boron in silicon will only diffuse to the interface, but not segregate across the interface, unless additional defects or impurities exist. By introducing oxygen vacancy and H bonds, we found some stable configurations at Si/SiO₂ interface, which can support the mechanism of boron segregation at Si(001)/SiO₂ interface. Therefore, we assume that vacancy of O and H bonds may play a crucial role in segregation by opening additional trapping sites. Furthermore, we also found the largest energy difference between B at Si/SiO₂ interface and that in deep bulk Si is about 2.9eV, which is in agreement with experimental boron activation energy of emission from Si/SiO₂ value of 2.64eV