Selected Publications - 2005:
1) Structure and strain relaxation mechanisms of ultrathin epitaxial Pr2O3 films on Si(111)
T. Schroeder, T.-L. Lee*, L. Libralesso*, I. Joumard*, J. Zegenhagen*, P. Zaumseil, Ch. Wenger, G. Lupina, G. Lippert, J. Dabrowski and H.-J. Müssig
IHP Microelectronics, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
* E.S.R.F., 6, Rue Jules Horowitz, 38043 Grenoble, France
Journal of Applied Physics 97(7), 074906 (2005).
The structure of ultrathin epitaxial Pr2O3 films on Si(111) was studied by Synchrotron Radiation-Grazing Incidence X-Ray Diffraction. The oxide film grows as hexagonal Pr2O3 phase with its (0001) plane attached to the Si(111) substrate. The hexagonal (0001) Pr2O3 plane matches the in-plane symmetry of the hexagonal Si(111) surface unit cell by aligning the <1010> Pr2O3 along the <112> Si directions. The small lattice mismatch of 0.5 % results in the growth of pseudomorphic oxide films of high crystalline quality with an average domain size of about 50 nm. The critical thickness tc for pseudomorphic growth amounts to 3.0±0.5 nm. The relaxation of the oxide film from pseudomorphism to bulk behaviour beyond tc causes the introduction of misfit dislocations, the formation of an in-plane small angle mosaicity structure and the occurence of a phase transition towards a (111) oriented cubic Pr2O3 film structure. The observed phase transition highlights the influence of the epitaxial interface energy on the stability of Pr2O3 phases on Si(111). A mechanism is proposed which transforms the hexagonal (0001) into the cubic (111) Pr2O3 epilayer structure by rearranging the oxygen network but leaving the Pr sublattice almost unmodified.
PDF published by AIP Journals (http://journals.aip.org)
2) Structure, twinning behavior and interface composition of epitaxial Si(111) films on Pr2O3 (0001)/ Si(111) support systems
T. Schroeder, G. Lupina, Ch. Wenger, A. Mane, G. Lippert, H.-J. Müssig, and P. Storck*
IHP Microelectronics, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
* SILTRONIC AG, PSF 1140, 84479 Burghausen, Germany
Journal of Applied Physics 98, 125313 (2005)
The structure of epitaxial Si overlayers on a hexagonal Pr2O3(0001) / Si(111) substrate system was investigated by a combination of X-ray reflectivity, specular X-ray diffraction, off-specular grazing incidence X-ray diffraction and transmission electron microscopy. The Pr2O3 film grows on the Si(111) substrate in the (0001) oriented hexagonal phase matching the in-plane symmetry by aligning the [1010] oxide along the bulk [011] Si direction. The hexagonal Pr2O3(0001) surface induces the growth of an [111] oriented cubic Si epilayer exhibiting a microstructure which is composed of two types of domains. The ABC-stacked domains preserve the crystal orientation of the substrate while the CBA-stacked domains are rotated by 180°. A depth profile of the chemical composition of the epi-Si / Pr2O3 / Si(111) materials stack was recorded by combining ion beam sputtering techniques with X-ray photoelectron spectroscopy.
PDF published by AIP Journals (http://journals.aip.org)
3) A complex X-ray characterization of epitaxially grown high-k gate dielectrics
P. Zaumseil and T. Schroeder
IHP Microelectronics, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
J. Phys. D: Applied Physics Letters 38 (2005) 1-5
Different X-ray techniques are used to characterize Pr2O3 layers epitaxially grown on Si substrates. X-ray reflectometry (XRR) is the preferred technique to determine the layer thickness and to detect and characterize possible interface layers. With standard X-ray diffraction (XRD) we found for Si (100) substrates that Pr2O3 grows in its cubic phase with the [110] direction perpendicular to the surface, while the hexagonal phase in (0001) orientation is preferred for Si(111). In the thickness range of microelectronic applications, Pr2O3 layers can be considered as well-ordered heteroepitaxial structures. The relaxation of the oxide layer from pseudomorphism to bulk behaviour was studied in the techno
logical important thickness range (1 – 10 nm) by synchrotron radiation grazing incidence XRD.
PDF published by Journal of Physics D: Applied Physics (http://www.iop.org/EJ/journal/0022-3727)
4) Si Segregation into Pr2O3 and La2O3 high-k gate oxides
G. Lippert, J. Dabrowski, V. Melnik, R. Sorge, Ch. Wenger, P. Zaumseil, and
H.-J. Müssig
IHP Microelectronics, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
Applied Physics Letters 86, 042902 (2005)
Pr and La oxide thin films were investigated in the context of their application as high-k dielectrics in Complementary Metal Oxide (CMOS) technology. The films were deposited by Molecular Beam Epitaxy (MBE) on bare and TiN-covered Si(001). The influence of growth and post-deposition annealing on the composition and electrical parameters was studied. We observed Si penetration from bare Si(001) into the growing film. Based on the results of capacitance-voltage (CV) measurements and ab initio calculations we conclude that Si is a source of defects responsible for leakage currents.
5) Initial stages of praseodymium sesquioxide films on Si(111) studied by LEED and STM
L. Libralesso, T. Schroeder*, T.-L. Lee and J. Zegenhagen
ESRF, European Synchrotron Radiation Facility, 6 rue Jules Horowitz, 38043 Grenoble, France
*IHP Microelectronics, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany
Surface Science Letters 598, L347 – L354 (2005).
The initial stages of the molecular beam epitaxy growth of praseodymium sesquioxide on atomically clean Si(111) have been studied in ultra-high vacuum by low energy electron diffraction and scanning tunnelling microscopy. At very low coverages, the oxide nuclei decorate the dimer rows at the silicon surface as line structure forming open triangles. At higher coverages, two-dimensional, equilateral, triangular islands with a fairly narrow size distribution and a well defined thickness are observed. Island nucleation occurs both at step edges and on the terraces. Upon coalescence at coverages beyond one monolayer, the surface is covered by a flat and pseudomorphic oxide film with a (1x1) surface unit cell.
PDF published by Elsevier Science (http://www.elsevier.com/wps/find/journaldescription.cws_home/505676/description?navopenmenu=-2)