High resolution depth profiling of thin STO in high-k oxide material

High k-dielectrics have become an important material in the development of ultra shallow junctions. In addition, strontium titanium oxide (STO) has been used as an interposer material to grow GaAs on Si for MESFETs [RF devices implemented on GaAs on Si substrates using a SrTiO3 buffer layer, Motorola knowledge base, 14 September 2001]. Also, SrTiO3 has a potential to be used as insulating material between ferromagnetic electrodes in magnetic tunnel junctions for magnetic random access memory devices (M-RAM). In this study we have investigated a multilayer system of STO with lanthanum barium manganese oxide (LBMO). The layer thickness was down to 0.8 nm, corresponding to two unit cells of SrTiO3. With low energy Cs bombardment a depth resolution down to 2 nm per decade and a peak width of 2 nm FWHM was achieved. Since the erosion rates of STO and LBMO differ greatly, we will discuss a depth calibration procedure based on actual material composition. # 2004 Elsevier B.V. All rights reserved