High-resolution depth profiling of ultrathin gate oxides using medium-energy ion scattering

Medium-energy ion scattering (MEIS) has been used to characterize the compo sition of ultrathin gate dielectrics. Examples covering investigations on s ilicon-oxides and oxynitrides as well as high-dielectric constant (high-K) films on silicon substrates are discussed. with special emphasis on underst anding film growth. In the MEIS spectra obtained from ultrathin films. the signals from different oxygen and nitrogen isotopes are well separated. By analyzing samples that have undergone different thermal processing steps in gases of different isotopes, both growth mechanisms and also atomic exchan ge effects can therefore be monitored directly. For various high-it dielect ric films, we found that oxygenisotope exchange is significant even at temp eratures below 500 degreesC. This may point to a serious Limitation for the application of such materials as gate dielectrics in semiconductor devices . (C) 2001 Elsevier Science B.V. All rights reserved.