Chemical states of piled-up phosphorus and arsenic atoms at the SiO2/Si interface

We have investigated the positions of the piled-up phosphorus atoms at the SiO2/Si interface using the extended X-ray absorption fine structure (EXAFS ) and S-ray photoelectron spectroscopy (XPS). The EXAFS and XPS data can be well explained on the assumption that the piled-up arsenic atoms exist at the tetrahedral sites. On the contrary, phosphorus atoms exist not at the t etrahedral sites but at the denser sites. The depth profile measurements of XPS have revealed that the piled-up arsenic and phosphorus atoms exist wit hin 20 Angstrom from the interface.