AVS 49th International Symposium
    Applied Surface Science Wednesday Sessions
       Session AS-WeA

Paper AS-WeA6
Binding Energy Shifts in Soft X-ray Photoelectron Spectroscopy of HfO@sub 2@/SiO@sub 2@/Si High-k Gate-dielectric Structures

Wednesday, November 6, 2002, 3:40 pm, Room C-106

Session: High-k Dielectric Characterization
Presenter: M.D. Ulrich, North Carolina State University
Authors: M.D. Ulrich, North Carolina State University
J.G. Hong, North Carolina State University
J.E. Rowe, North Carolina State University
G. Lucovsky, North Carolina State University
T.E. Madey, Rutgers, The State University of New Jersey
Correspondent: Click to Email
We have observed binding energy shifts for thin films of (HfO@sub 2@)@sub x@(SiO@sub 2@)@sub 1-x@ on Si(111) substrates deposited as alternative high-k gate dielectrics in the film thickness range, 6-15 Å. Thin films of HfO@sub 2@ and (HfO@sub 2@)@sub x@(SiO@sub 2@)@sub 1-x@ on Si(111) substrates were prepared by remote plasma enhanced chemical vapor deposition (RPECVD). This process results in a 6-10 Å layer of SiO@sub 2@ between the deposited dielectric and substrate. Samples were analyzed using high-resolution soft X-ray photoelectron spectroscopy (SXPS) with synchrotron radiation. Photoemission measurements were performed at the National Synchrotron Light Source (NSLS) located at Brookhaven National Laboratories using beamline U4A which has a total instrumental resolution of better than 0.1 eV. The Si 2p@sub 3/2@ [SiO@sub 2@] binding energy from SiO@sub 2@ films on silicon substrates decreases with decreasing (5-30 Å) film thickness due to core hole screening. This shift is well described with an image charge model of core hole screening.@footnote 1@ According to this model, an overlayer above the SiO@sub 2@ layer should further increase Si 2p@sub 3/2@ [SiO@sub 2@] core hole screening causing an additional decrease in binding energy. For the HfO@sub 2@ samples, SiO@sub 2@ thickness was determined to be ~10 Å. The Si 2p@sub 3/2@ [SiO@sub 2@] binding energy was 0.3 eV lower than that of a SiO@sub 2@ film of similar thickness without the HfO@sub 2@ overlayer. The Si 2p@sub 3/2@ single-component SXPS spectra indicate that interfacial silicate exists between the SiO@sub 2@ and HfO@sub 2@ with a signal strength less than one third that of the SiO@sub 2@ peak. The result of the Si 2p@sub 3/2@ [SiO@sub 2@] binding energy matches the image charge model well. @FootnoteText@ @footnote 1@ J. W. Keister, J. E. Rowe, J. J. Kolodziej, H. Niimi, H.-S. Tao, T. E. Madey, and G. Lucovsky, J. Vac. Sci. Technol. A 17, 1250 (1999).