Surface and Thin Film Analysis

Monday, April 10, 2000 10:30 AM in Room San Diego

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10:30 AM F3-1 A Novel Approach to Thin Film Analysis by XPS
K.S. Robinson, Unknown White, Unknown Belcher, Unknown Wolstenholme (VG Scientific, United Kingdom)
The variation in surface sensitivity in XPS which arises from decreasing the take-off angle of the photoelectrons and can be used to qualitatively and quantitatively determine thin overlayer structure and thickness. These measurements are particularly important for the semiconductor and hard disk drive industries. However, the size of the sample can prevent tilting of the sample so it may not be possible to analyse all points on a large sample. Angle dependent XPS from small features is also complicated as the size of the analysis area may change as the sample is tilted. @paragraph@In this paper we describe and present results from two different methods of acquiring angle dependent XPS measurements without moving the sample. The first method involves the use of two separate hemispherical analysers with conventional input lenses mounted at normal and grazing emergence angles. The second method uses a single hemispherical analyser with a new design of electron input lens which allows photoelectrons from near normal or grazing take-off angles to be selected. Alternatively, photoelectrons from a larger range of angles can be integrated for maximum sensitivity. In both instruments, the analysis area is defined using a focused monochromatic X-ray source, enabling analysis of small features without any change in the size, shape or angle of incidence of the monochromator spot.
10:50 AM F3-2 High Resolution in Sims Depth Profiling - Issues and Applications for Characterisation of Shallow Junctions and Thin Film Structures
H. Kheyrandish (MATS, United Kingdom); G.A Cooke (University of Warwick, United Kingdom)
There is a growing demand in many areas of materials science for ultra high depth resolution SIMS depth profiling of a new generation of materials possessing structure on the nanoscale. These materials include ultra shallow junctions in silicon devices, the MQW regions of optoelectronic materials, superlattices, thin high-k dielectric films, such as oxynitrides, and carbon-based materials amongst others. The requirement to resolve very thin layers in these materials has been the driving force for the development of a new generation of SIMS instruments and analytical protocols. The main factors, which effect depth resolution in ion beam sputtering techniques, are (a) ion beam mixing effects and (b) surface roughening or the formation of "topography" as result of ion bombardment. Ion beam mixing effects are minimized by the use of ultra low energy ions. Ion induced surface roughening effects are, however, a function of the bombarding ion species, their angle of incidence and the "chemistry" of matrix. One thus requires the use of primary ions with energies as low as 100 eV AND precise control over their angle of incidence with the sample surface. This paper will demonstrate the benefits of depth profiling at near normal angles of incidence (0° to 30°) using low energy oxygen primary ions. Control of ion bombardment induced surface topography is a pre-requisite for good depth resolution. AFM studies of crater bottoms clearly show that ion induced topography is minimized using normal incidence profiling conditions. SIMS depth profiling of delta layers and ultra shallow junctions will also be presented showing improved decay length and smooth crater bottoms. The optimum conditions for depth profiling using low energy cesium are different to those using oxygen. In this case the use of oblique angles is the preferred option in order to avoid cesium build up which otherwise takes place at normal incidence conditions. Finally a number of applications showing depth profiling of delta layers, the distribution of nitrogen in thin oxynitide films, ultra shallow B implants in silicon and MQW regions in III/V materials will presented showing that under optimum conditions depth resolutions of the order 1 nm or better may be achieved.
11:10 AM F3-3 A Comparison of In-situ Milling and Ion Beam Sputtering as Surface Preparation Methods for XPS Analysis of PVD Coatings
M.A. Baker (University of Surrey, United Kingdom); S.J. Greaves (University of Surrey, U.K., United Kingdom); V.C. Fox (Company Teer Coatings Ltd., United Kingdom)
Most surface analysis of coatings is performed after transfer of the sample from the deposition chamber through air into the spectrometer. For many important coating systems, atmospheric exposure leads to the formation of a thin oxide on the surface which strongly interferes with the analytical measurement. Ion beam sputtering is generally used to clean the surface in the spectrometer prior to analysis. However, preferential sputtering of one element often occurs (e.g. for CNx @footnote 1@, MoS2 @footnote 2@) precluding analysis or giving rise to inaccuracies in the measurement. This article compares quantified XPS measurements performed on a number of common coating systems in which the surface oxide is removed either by in-situ milling or ion beam sputtering. The effectiveness of in-situ milling as a surface preparation technique and evidence of preferential sputtering for each coating system will be discussed. @FootnoteText@ @footnote 1@ M.A.Baker, P.Hammer Surface and Interface Analysis 25, 629-642 (1997) @footnote 2@ M.A.Baker, R.Gilmore, C.Lenardi, W.Gissler Applied Surface Science 150, 255-262 (1999)
11:30 AM F3-4 Characterization of Binding States and Electronic Structure of Ternary Al-B-N Films
M. Witthaut, R. Cremer, K. Reichert, D. Neuschütz (LTH, RWTH Aachen, Germany)
In the present work, films with compositions along the quasibinary section AlN-BN were deposited on Si(111) and SiC wafers by reactive magnetron sputtering of an Al and a BN or B target, respectively, at substrate temperatures of 100 and 600 @super o@C. The binding states of the components as well as the electronic structure of the films have been analyzed by means of Auger and photoelectron spectroscopy (XAES, XPS) and electron energy loss spectroscopy in reflection mode (EELS). The crystallographic structure and texture of the films has been determined by high energy electron diffraction (RHEED). The analyses have been performed after the transfer of the films in a lock chamber under HV into the analysis chamber. Special attention was paid to the interpretation of peak shifts, Auger parameters, plasmon losses and shake up satellites. The influence of substrate material, temperature, and applied targets to the structure, texture, and crystallinity of the films was examined. The results have shown that it was possible to deposit metastable single-phase (Al,B)N films in sp@super 3@ bonded wurtzite structure with BN contents of at least 33 mol-% by reactive magnetron sputtering. The incorporation of BN, which under equilibrium conditions crystallizes in the sp@super 2@ bonded graphite like structure and therefore shows no solid solubility in AlN, could extend the applications of (Al,Ga,In)N films due to a higher variability concerning band gap and lattice parameters.
11:50 AM F3-5 Coating of Hydroxyapatite Thin Film by Simultaneous Vapor Deposition
M. Hamdi, S. Hakamata, A.M. Ektessabi (Kyoto University, Japan)
Calcium phosphate (Ca-P) bioceramics have received considerable attention in the biomaterial research field because of their positive response to living tissues. Since they are brittle in nature, Ca-P have been coated on metallic substrates, taking advantage of the good mechanical properties of metal and biocompatible properties of Ca-P. Plasma spraying, ion beam assisted deposition, sputter deposition and laser ablation, are some of the techniques used for coating Ca-P. This study is to demonstrate the feasibility of using a new technique of Simultaneous Vapor Deposition (SVD) to produce bioceramic hydroxyapatite (HAp) thin films. The process of SVD was performed in a vacuum environment. Two precursors, CaO and P2O5, were evaporated simultaneously by electron evaporation source and resistive heater respectively. The process parameters, such as deposition rate, annealing temperature and substrate temperature were chosen so as to obtain structures, ranging from amorphous and mixed crystalline phases to crystalline HAp. The thin films produced were annealed at different elevated temperatures and the degree of crystallinity was revealed using an x-ray diffraction (XRD). The surface microstructure and morphology were investigated by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) and electron probe microanalyzer (EPMA) equipped with energy dispersive x-ray (EDX) detector were employed for further characterization. By choosing optimum parameters, Ca/P ratio values close to stoichiometry were achieved and uniformly deposited coatings were obtained. Experimental results suggest that SVD is a promising method for the mass production of HAp coatings on biomedical implants.
12:10 PM F3-6 Phase Changes in the Oxidation of TiN Films
F.H. Lu, H.-Y. Chen (National Chung Hsing University, Taiwan, R.O.C.)
The oxidation of TiN films was investigated by using both X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The films were prepared by a cathodic arc plasma deposition method onto copper substrates. The oxidation of the film was preformed at 300, 400 and 50 @super o@C for 2 hr. The obtained Ti-2p spectra of the XPS results showed that a phase transformation from amorphous TiO@sub 2@ to crystalline TiO@sub 2@ occurred on the TiN film surface. The crystalline phases present on the film surface after annealing at 500@super o@C were further identified to be a mixture of anatase and rutile phases by TEM. The phase changes from anatase to rutile during the oxidation of TiN films have been discussed and compared to those available in the literature.