INA-X System for SNMS and SIMS

Transcription

1 Customized Systems and Solutions Nanostructures and Thin Film Deposition Surface Analysis and Preparation Components Surface Science Application INA-X System for SNMS and SIMS Application Notes The quantitative composition of every single surface layer down to trace elements is often of crucial importance for the quality of products. The INA-X system works on the principle of SNMS (Secondary Neutral Mass Spectrometry). The key feature of the SNMS technique and advantage over the SIMS (Secondary Ion Mass Spectrometry) method is the strict separation between emission and ionization of the sputtered particles from the sample surface. As a result, the INA-X system is capable of high resolution depth profiles with nm resolution and quantification of concentrations down to 1ppm. Innovation in Surface Spectroscopy and Microscopy Systems 1

2 Quantification The SNMS intensity as a function of the specified concentration in a standard sample (NBS 1245a) is shown. Most of the elements have been detected with similar sensitivity, demonstrating the already quantitative behaviour of the raw data. An SNMS signal of 7.4 cps per ppm demonstrates a detection limit below 1 ppm. S (Fe),x (measured) (F) (O) C Be B Ti V Sn Au Ag Pb Co Cr Cd Se As Mn Cu Al Ni P SSi average standard Zn deviation α 0 (Fe)x (calculated) Mg Mo Nb W Experimental, Fe-related sensitivity factors S (Fe)X are determined for 29 elements X from plasma SNMS measurements under standard conditions. Eighteen standard materials, including high alloy steels, brass as well as Cu, Zn, Pb, Ni and Al base alloys, have been used. In addition the S (Fe)X values for O and F are shown in brackets. The measured sensitivity factors are plotted versus the relative postionization probabilitiesαcalculated for the measuring conditions. Except for C,O,N and F the S (Fe),X values lie within two orders of magnitude. It is this narrow range of S (ref)x variation, compared to SIMS, the virtual absence of strong matrix effects and the ease of quantification which are the SNMS figures of merit. Innovation in Surface Spectroscopy and Microscopy Systems 2

3 Composition Analysis The chart below shows a SNMS spectrum of a pure Ge-sample taken with an ion bombarding voltage of 1.4 kv (red) in comparison with the signals for ion bombardment at about 30 ev (black). Note that the low mass signal is independent of the background of cps and the signals in the residual gas range. The C- signal refers to a carbon impurity of about 11 ppm in the Ge-sample Composition determination of doped perovskites Doped perovskites have become a highlight of modern solid state physics due to the discovery of high-temperature superconductivity and colossal magnetoresistance (CMR). Some types of perovskites show superconductivity, others show CMR. The common feature of these two families of compounds is that their electromagnetic properties depend sensitively on oxygen doping level. Apart from doping, oxygen deficiency is influenced by the details of preparation processes. Simultaneous determination of constituents is of crucial importance from sample characterization point of view. Innovation in Surface Spectroscopy and Microscopy Systems 3

4 Color of Topaz With SNMS the Hydrogen and Fluorconcentration in Topas with different color can be measured. It is shown that the color is determined by the H and F concentrations. Innovation in Surface Spectroscopy and Microscopy Systems 4

5 Extremely High Depth Resolution A SNMS depth profile of a W/Si multilayer is shown here. The thickness of a double layer is 3.5 nm. Note that no degradation of the depth resolution takes place with sputter removal of the sample material. TEM micrograph of the W/Si multilayer Fe 56 Pt/Fe 57 Pt/Pt Multilayer on MgO cocentration [at%] Pt The third 56 FePt layer is thicker than the others 56 Fe 57 Fe sputter depth [nm] The SNMS System INA-X is especially developed for extreme depth resolution and is therefore ideally suited for applications in thin film investigations. Shown are recent data of ion Fe 56 Pt/Fe 57 Pt/Pt multilayers on MgO (annealing at 848 K for 4h). The single layers have a nominal thickness of a few nm (MBE - Preparation of FePt multilayers at 623 K by J. Meerschaut, Leuven; Data with courtesy of : Dr. Gabor Langer, Dept. Of Solid State Physics, Unversity of Debrecen and Dr. Kálmán Vad, Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Hungary) Innovation in Surface Spectroscopy and Microscopy Systems 5 Anote_INAX.ppt

6 Investigation of diffusional intermixing in Si/Co/Ta system by SNMS From microelectronic application point of view, investigation of low temperature diffusion and intermixing in Co-Si systems is rather important. Studies of properties and interactions between silicon and transition metals are particularly crucial. In the early stage of the intermixing process, an atomic transport along grain boundaries are difficult to observe. We have investigated a Si//Co/Ta system, where Ta was used as a cap layer. The following processes were identified: - silicon atoms migrate along grain boundaries through the cobalt layer and accumulate at the Ta/Co interface; - the accumulated Si acts as a secondary reservoir for back-diffusion through the low diffusivity grain-boundaries. Si concentration [at %] Ta Co layer Annealing temperature: 310 o C Annealing time: as-deposited 1 h 5 h 10 h 24 h Si substrate Depth [nm] Time evolution of Si concentration profiles at 310 o C. Depth profile of amorphouse silicon solar modules Concentration [at %] ,5 1,0 0,5 P Typical depth profile of the p-i-n:si diode 0, Depth [nm] B Si Silicon based thin film solar cell is a preferable choice for the large-scale production of low cost solar modules for a multitude of reasons: abundance of cheap raw material; no toxic component in the technology; shorter energy payback time and low temperature technology. The development and implementation of thin film technology into the industry may result in reduction of the specific processing costs and increase the efficiency. Besides feed back in production, the detailed analysis of the deposited absorber layers is also important in R&D aiming at increase of efficiency. The quantitative depth profile analysis is one of the methods which can be used to investigate the layer structure of a solar cell. Innovation in Surface Spectroscopy and Microscopy Systems 6

7 Interface Analysis The graph shows the SNMS depth profile for Ge on Si. Strong variation of the concentrations at the interface and the extremly high depth resolution can be observed. The 3D image below shows the uniformity of the sputter crater: Rapid Depth Profile concentration at% ,1 Zn Al Fe The fast sputter profile shown here could be achieved using 2 kv Ar + ions. The removed top layer was 8 µm Zn layer on steel,. The mean sputter rate was 100nm/sec, the acquisition time only 100 sec. 0, sputter depth µm Innovation in Surface Spectroscopy and Microscopy Systems 7

8 Element Mapping Below, the SIMS image of a stainless steel net on a copper sample is shown. The wire thickness is 132 µm, the grid-size is 200 µm x 200 µm. As a focused ion beam source the scannable SPECS source IQE 12/38 has been used. SPECS Surface Nano Analysis GmbH Voltastrasse Berlin Germany Tel Fax support@specs.com Web Innovation in Surface Spectroscopy and Microscopy Systems 8