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Distribution and segregation of arsenic at the SiO2/Si interface

The segregation and pile-up of arsenic atoms at the Si/SiO2 interface in steady state was investigated in detail by a combination of gracing incidence x-ray fluorescence spectroscopy (GI-XRF) measurements, electrical measurements, etching on the nanometer scale, and measurements of the step heights...

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Bibliographic Details
Published in:Journal of applied physics 2008-07, Vol.104 (2)
Main Authors: Steen, C., Martinez-Limia, A., Pichler, P., Ryssel, H., Paul, S., Lerch, W., Pei, L., Duscher, G., Severac, F., Cristiano, F., Windl, W.
Format: Article
Language:English
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Summary:The segregation and pile-up of arsenic atoms at the Si/SiO2 interface in steady state was investigated in detail by a combination of gracing incidence x-ray fluorescence spectroscopy (GI-XRF) measurements, electrical measurements, etching on the nanometer scale, and measurements of the step heights by interferometry. Using GI-XRF measurements and removal of the highly doped segregation layer by a sensitive etching process it was possible to distinguish clearly between the piled-up atoms and the arsenic atoms in the bulk over a large range of implantation doses, from 3×1012 to 1×1016 cm−2. The samples were annealed at different temperatures from 900 °C to 1200 °C for time periods long enough to make sure that the segregation reflects an equilibrium state. With additional step height measurements at line-space structures, the thickness of the layer with the piled-up arsenic and the shape of the segregation profile was determined. Electrical measurements indicated that the segregated arsenic atoms are deep donors with an electrical activity that increases eventually to full electrical activation for high sheet concentrations of the segregated atoms. The measured data can be modeled as a steady state of neutral arsenic atoms in the segregation layer with positively charged substitutional arsenic atoms and free electrons. For the highest concentration, a saturation of the sheet concentration of segregated arsenic atoms was observed that correlates with the increase in electrical activation. For the use in process simulation programs, a three-phase segregation model was adapted and calibrated.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.2956700