Fourteenth Topical Conference on Quantitative Surface Analysis (QSA 14)

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1 Fourteenth Topical Conference on Quantitative Surface Analysis (QSA 14) 2D and 3D Nanomaterials Analysis Program and Abstracts Sunday, October 28 th, 2012, room 20 Convention Center Tampa, Florida, USA Sponsored by: AVS Applied Surface Science Division

2 Conference committee: Don Baer Lance Lohstreter Tony Ohlhausen Cedric Powell Vince Smentkowski Fred Stevie Amy Walker 1

3 Table of Contents Schedule Summary 4 Conference Program Session 1: Best Practices for Surface Analysis 6 Session 2: Quantification in SIMS 12 Session 3: Quantitative Surface Analysis 16 Poster Session 22 2

4 Fourteenth Topical conference on Quantitative Surface Analysis (QSA 14) Theme: 2d and 3d Nanomaterials Analysis Sunday, October 28 th, 2012, room 20 Convention Center 7:30am Registration, continental breakfast and coffee 8:00am Introduction and Welcome Session 1 Best Practices for Surface Analysis 8:15am XPS/AES: John Wolstenholm (45min) 9:00am ToF-SIMS: Bergit Hagenhoff (45 min) 9:45am Discussion (45 min) 10:30am Break - coffee (15min) Session 2 Quantification in SIMS 10:45am Dopant Profiling in Semiconductors with SIMS : Properties and Limitations: Wilfried Vandervorst (45 min) 11:30am 12:00pm Discussion (30 min) Lunch (provided in room) Session 3 Quantitative Surface Nanoanalysis 12:45pm Nanoscale Calibration By Means of Electron Beam Attenuation: Wolfgang Werner (45min) 1:30pm Discussion (45min) 2:15pm Break-snacks/drinks (15min) 2:30pm 2-D and 3-D Quantitative Analysis in soft Samples using Secondary Ion Mass Spectrometry: Challenges and applications Christine Mahoney (45min) 3:15pm Discussion (45min) 4:00pm dismiss 4

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6 Session 1 Best Practices for Surface Analysis Moderator: Tony Ohlhausen 8:15am 9:00am 9:45am XPS/AES: John Wolstenholm (45min) ToF-SIMS: Bergit Hagenhoff (45 min) Discussion (45 min) 6

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8 Best practices for surface analysis: XPS J. Wolstenholme 1 Thermo Fisher Scientific, The Birches Industrial Estate, Imberhorne Lane, East Grinstead, West Sussex, RH19 1UB, UK In the last twenty years, there has been a steady increase in the quantity of XPS data appearing in the published literature. The advent of high powered, but simple to use XPS instrumentation has also broadened the user base of the technique within industry. The benefits of this increased use of XPS are obvious: the chemical selectivity and surface specificity of XPS are now widely employed in the characterisation and development of many advanced and novel materials, such as graphene. Additionally, industrial XPS users are able to monitor and control production processes with improved precision. The wider use of XPS in these environments also brings greater challenges, however, and there is a responsibility on tool manufacturers to provide instruments which generate trustworthy and traceable data on a daily basis. Calibration of XPS instruments is a particularly important task, strongly influencing quantification of elemental and chemical states, but because the instruments have many component parts it has traditionally been a time consuming task, only to be undertaken by an expert user. Within the new environments of modern XPS users, it is now necessary to provide automated and software driven calibration routines, which allow non-expert users to regularly calibrate and characterise their systems. Furthermore, since industrial users typically have to work to internal or external quality standards, it is critical to be able to trace the historical performance of the instrument from installation. This talk will discuss the implementation of best practice techniques on an XPS tool, describing how they allow users to generate correctly calibrated XPS data on a regular basis. 1 Tel.: +44 (0) , john.wolstenholme@thermofisher.com. 8

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10 Best Practices for Surface Analysis: ToF-SIMS Birgit Hagenhoff, Tascon GmbH, Heisenbergstrasse 15, Muenster, Germany From its origin in the 1970s SIMS and (starting in the 1980s) ToF-SIMS has come a long way to develop from a tool for scientists only into a work horse for daily routine analysis. However, together with the increasing performance also the complexity of the instruments and the number of operational modes increased significantly (see table). Monoatomic PI Polyatomic PI Spectrometry 1970 (Ar) 2002 (Au x ) 2004 (Bi x ) Depth profiling 1970 (O 2, Ar) 1990 (dual beam) 2003(C + 60 ) 2010 (Ar + n ) Imaging (chemical mapping) 1980 (Ga) 2000 (Cs) 2002 (Au x ) 2004 (Bi x ) 3D Imaging 2000 (Ga, dual beam) 2003(C + 60 ) 2010 (Ar + n ) Nowadays instruments therefore need to be equipped with recipes for unattended operation as well as operating levels which allow the use of less trained technicians even for complex tasks. In addition the pressure is rising to run ToF-SIMS laboratories under protocols and guidance which allows the accreditation as testing laboratory according to ISO/IEC The talk will cover all aspects of running a ToF-SIMS laboratory ready for ISO/IEC This includes the sample transport and handling, options for instrument calibration, the choice of suited operational modes as well as data evaluation strategies. Specific challenges in 2D and 3D imaging of inorganic as well as organic samples will be discussed. 2 General requirements for the competence of testing and calibration laboratories 10

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12 Session 2 Quantification in SIMS Moderator: Fred Stevie 10:45am 11:30am Dopant Profiling in Semiconductors with SIMS : Properties and Limitations: Wilfried Vandervorst (45 min) Discussion (30 min) 12

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14 Dopant profiling in semiconductors with SIMS : properties and limitations W.Vandervorst, Imec, Leuven, Belgium In order to meet the scaling trends for the sub-24 nm next technology nodes, it has become necessary to engineer very precisely the doping profiles in the devices. The main characteristics to achieve are very highly doped, very shallow (10-20 nm) junctions with very well controlled lateral extension and abruptness. These are fabricated using advanced doping techniques such (cocktail) ion implantation, plasma immersion, vapor phase deposition, and ultra fast anneal methods (LTA, flash, RTA, SPER ), msec anneal for which predictive modeling is still very immature and accurate experimental carrier profile determination is required. As in several of these applications, high depth resolution (<1 nm) needs to be combined with high sensitivity (< ppm) and quantification accuracy (<3%), Secondary Ion Mass spectrometry (SIMS) is quite often the only technique able to fulfill these needs. The success of SIMS appears somewhat surprising as it based on a very crude concept i.e using an ion beam sputtering process to obtain depth information and relying on spontaneous ionization to produce the secondary ions. Nevertheless SIMS has become a very well established technique for dopant profiles in semiconductor materials (in particular Si) with very high sensitivity, depth resolution and quantification accuracy. We will outline these beneficial aspects of SIMS by showing examples of cases whereby films differing only by 0.5 nm in thickness clearly could be identified, and small compositional variations in composition of SiGe-films can be probed. Unfortunately many cases exist where SIMS is limited I performance as well. As will be shown in this presentation, many of the SIMS properties and limitations can be understood by a careful analysis of the interaction between the primary ion and the substrate focusing on the temporal changes in (matrix) sputter yields, the retention of the primary species and defect-induced migration of constituents. For instance the main reason for the success of SIMS is the enhanced ionization probability (leading to high sensitivity) due to use of the reactive primary ions such as oxygen and cesium, coupled with very low primary beam energy (down to 150 ev). Unfortunately the use of an energetic oxygen and Cs primary ion implies that the target is heavily modified during the analysis which does lead to some transient effects as well as (in a number of cases) unwanted distortions due to ion beam mixing, surface topography (ripples), loss in depth resolution by segregation, changes in ionization probability at interfaces in multilayer systems due to a different retention of the primary species,. This necessitates the need for very advanced (extremely low energy) protocols as well as the concurrent use of alternative methods like MEIS, H-RBS and H-ERD and emerging concepts like Atomprobe analysis. 14

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16 Session 3 Quantitative Surface Nanoanalysis Moderators: Don Baer and Lance Lohstreter 12:45pm 1:30pm 2:15pm 2:30pm 3:15pm Nanoscale Calibration By Means of Electron Beam Attenuation: Wolfgang Werner (45min) Discussion (45min) Break-snacks/drinks (15min) 2-D and 3-D Quantitative Analysis in soft Samples using Secondary Ion Mass Spectrometry: Challenges and applications Christine Mahoney (45min) Discussion (45min) 16

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18 Nanoscale calibration by means of electron beam attenuation W. S. M. Werner Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, Vienna A-1040, Austria A survey is given on the status quo and future potential of electron beam techniques such as (hard)-xps, AES and others for calibrating dimensions on the nanoscale and quantifying the composition of nanosctructures. The attenuation of (signal) electron beams can be utilised to calibrate dimensions of objects at the nanoscale, in particular along the depth coordinate. If the combined energy/angular distribution is analysed, information about the nanomorphology along the lateral coordinates is also accesible. Quantitative XPS of nanostructures needs to take into account in significant detail the physical processes of relevance for the signal generation. These processes include elastic electron scattering, the dependence of the inelastic mean free path on the position of the electron in the specimen, the anisotropy of the photoelectric cross section, etc. The National Institute of Standards and Technology (NIST) Database for the Simulation of Electron Spectra for Surface Analysis (SESSA) [1,2] is a unique tool for interpretation of experimental data on nanostructured surfaces as well as for experiment design. SESSA has recently been modified to allow a user to simulate XPS spectra of nanostructured surfaces, such as surfaces covered with rectangular islands, nanowires, pyramids, spheres, layered spheres, etc. A systematic study of the effect of the nanomorhphology on the emitted angular and energy distribution of photoelectrons is presented and comparison of simulated data with experimental results is given. Finally, the full potential of XPS for obtaining nanostructure information is explored by means of a systematic feasibility study using SESSA-simulations W. Smekal, W. S. M. Werner, and C. J. Powell, Surf. Interface Anal. 37, 1059 (2005). 18

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20 Intensity P104 Concentration (%) 2-D and 3-D Quantitative Analysis in Soft Samples using Secondary Ion Mass Spectrometry: Challenges and Applications Christine M. Mahoney Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MSIN K8-93, Richland, WA, 99352, USA. Secondary Ion Mass Spectrometry (SIMS) is becoming increasingly important for surface and in-depth characterization of soft materials. This is, at least in part, attributed to the advent of cluster primary ion sources, which have enabled the user to retain molecular information under higher primary ion doses, with concurrent increases in sputter and secondary ion yields. Thus, when employing polyatomic sources, one can obtain molecular depth profiles, assuming the optimum conditions are met. Furthermore, the low damage sputtering, combined with the enhanced sputtering yields, allows for a dramatic improvement of the sensitivity of the method. Nowadays, 2-D and 3-D qualitative analysis using SIMS for characterization of soft samples is commonplace. However, the true challenge that remains is the ability to perform quantitative analysis. This remains a difficulty, particularly in complex biological systems, which have complex matrices, and have no appropriate standards. In this talk, I will discuss the recent advancements in SIMS for 2-D and 3-D molecular characterization of soft samples. Some instances of successful quantitative depth profiling in polymeric biomaterials will be given, such as the example shown in Figure 1. This will be followed by a brief discussion of the challenges that are faced by the SIMS analyst for quantitative analysis. a) b) PLA (56) m/z 28 m/z 56 m/z 59 Si (28) Pluronic (59) Sputter Time (s) Depth (nm) Figure 1. Demonstration of quantitative depth profiling in a polymer blend system comprised of 10% pluronic (P104) surfactant in a poly(lactic acid) (PLA) matrix. (a) positive secondary ion intensities characteristic of PLA (m/z 56), P104 (m/z 59) and Si substrate (m/z 28) plotted as a function of sputtering time with an SF 5 + polyatomic primary ion source, and b) quantitative depth profile of pluronic surfactant (P104), obtained through using a series of standards for calibration. Bi 3 + was used as an analysis beam. 20

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22 POSTER SESSION -To be held during morning and afternoon breaks and during lunch- ABSTRACTS 22

23 Spectral Chemical State Imaging with High Spatial Resolution Scanning Auger J. S. Hammond and D. F. Paul Physical Electronics USA, Lake Drive East, Chanhassen, MN USA Recent improvements of field emission Scanning Auger instruments have led to the ability to provide elemental imaging of surfaces with a spatial resolution better than 10 nm. The introduction of a high energy resolution capability with a CMA analyzer on the PHI 700Xi system also provided the capability to provide chemical state spectroscopy and depth profiling with similar spatial resolution. The new PHI 710Xi now provides the capability to combine high energy resolution spectra with high spatial resolution chemical state imaging. The system software provides LLS separation of different chemical states from the Auger imaging data. A semiconductor structure with multiple silicon chemical states will be presented. The 0.1% energy resolution spectra for silicide, silicon oxide and silicon oxynitride are extracted from the scanning Auger image. These basis spectra are then used for quantitative presentation of the different chemical state images. The resulting overlay chemical state images demonstrate the ability of the CMA analyzer to image different chemical states at high energy resolution without topographical artifacts. 23

24 Sample-Morphology Effects on X-ray Photoelectron Peak Intensities C. J. Powell Surface and Microanalysis Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland S. Tougaard Department of Physics and Chemistry, Southern Denmark University, DK-5230 Odense M, Denmark W. S. M. Werner and W. Smekal Institute of Applied Physics, Technical University of Vienna, Wiedner Hauptstrasse 8-10, A-1040, Austria We have used the National Institute of Standards and Technology Database for the Simulation of Electron Spectra for Surface Analysis (SESSA) [1,2] to simulate photoelectron spectra from the four sample morphologies considered by Tougaard [3]. These simulations were performed for two classes of materials, two instrument configurations, and two conditions, one in which elastic scattering is neglected (corresponding to the Tougaard results) and the other in which it is included. We considered the Cu/Au morphologies analyzed by Tougaard and similar SiO 2 /Si morphologies since elastic-scattering effects are expected to be smaller in the latter materials than the former materials. Film thicknesses in the simulations were adjusted in each case to give essentially the same chosen Cu 2p 3/2 or O 1s peak intensity. Film thicknesses with elastic scattering switched on were systematically less than those with elastic scattering switched off by up to about 25 % for the Cu/Au morphologies and up to about 14 % for the SiO 2 /Si morphologies. For the two morphologies in which the Cu 2p 3/2 or O 1s peak intensity was attenuated by an Au or Si overlayer, respectively, the ratios of film thicknesses with elastic scattering switched on to those with elastic scattering switched off varied approximately linearly with the singlescattering albedo, a convenient measure of the strength of elastic scattering. This variation was similar to that of the ratio of the effective attenuation length to the inelastic mean free path for the photoelectrons in the overlayer film [4]. For the two morphologies in which the Cu 2p 3/2 or O 1s photoelectrons originated from an overlayer film, the ratios of film thicknesses with elastic scattering switched on to those with elastic scattering switched off varied more weakly with the single-scattering albedo. This weaker variation was attributed to the weaker effects of elastic scattering for photoelectrons originating predominantly from near-surface atoms than for photoelectrons that travel through an overlayer film [5]. [1] W. Smekal, W. S. M. Werner, and C. J. Powell, Surf. Interface Anal. 37, 1059 (2005). [2] [3] S. Tougaard, J. Vac. Sci. Technol. A 14, 1415 (1996). [4] A. Jablonski and C. J. Powell, J. Vac. Sci. Technol. A 27, 253 (2009). [5] A. Jablonski and S. Tougaard, Surf. Interface Anal, 26, 17 and 374 (1998). 24

25 Quantitative SIMS depth profiling of in-situ doped Si 1-x Ge x on Si(100) with low energy Cs + and O 2 + primary ion beams M.J.P. Hopstaken a, *, H. Wildman a, I. Lauer a, Z. Zhu b, a IBM T.J. Watson Research Center, Yorktown Heights, NY 10598, USA b IBM Systems & Technology Group, Hopewell Junction, NY 12533, USA marco.hopstaken@us.ibm.com Introduction of SiGe in advanced CMOS technology as pfet strain element and/or high mobility SiGe channel has enabled significant enhancement of transistor performance. Quantitative analysis of Si 1-x Ge x composition by means of SIMS depth profiling has been demonstrated within 1-2 at.% accuracy, using either Cs + or O 2 + primary beams [1-5]. Here we explore quantitative analysis of (in-situ) doped SiGe for B, P, and As using low energy Cs + or O 2 + primary beams, in order to meet the depth resolution requirements for thin epitaxial films. Quantitative analysis of [B] in In-Situ Boron Doped (ISBD) SiGe using reactive low energy O 2 + ion sputtering is complicated due to large variations in both sputter and ionization yield with Ge-content [5]. We present a multi-standard calibration protocol based on multiple B-implanted epitaxial Si 1-x Ge x standards on Si(100) with constant [Ge] ranging from 20 to 50 at.%, with the implanted dose confined within the SiGe layer. This approach allows for explicit correction of both SiGe sputter yield and B + and Ge + yield variations as function of [Ge], with Si 1- xge x composition and thickness in excellent agreement with X-Ray Diffraction (XRD). Boron sensitivity was observed to be dependent on [Ge] content, with pronounced effects of O 2 + impact energy in the ev energy range. We propose a quantitative protocol to correct these sensitivity variations and obtain quantitative [B] in Si 1- xge x. For the quantitative analysis of n-type dopants (P, As) in SiGe, we have employed low energy Cs + ion sputtering. Again, use of multi-standard calibration protocol allows for explicit correction of yield variations as function of Ge-content. For positive Cs n M + (n= 1, 2) cluster ions, we observe excellent linear relation between [Ge]/[Si] RBS atomic ratio and Cs n Ge + /Cs n Si + ion intensity ratios up to [Ge]= 50at.%, allowing straightforward determination of Ge-fraction and subsequent correction of erosion rate [3]. We present Cs n M + (M=P, As) yield variations with Ge along with empirical fits, which allow for correction in Si 1-x Ge x. Using negative (cluster-) ions, we find an excellent linear relation between [Ge]/[Si] atomic ratio and GeSi + /Si 2 Si + intensity ratios up to [Ge]= 50at.%. Use of a linear combination of selected MSi - and MGe - (M= P, As) ions in Si 1-x Ge x allows for straightforward quantification of both P and As in SiGe, independent of SiGe composition. In summary, we have demonstrated quantitative analysis of (in-situ) doped SiGe in terms of Si 1-x Ge x composition, thickness and doping, employing low energy Cs + or O 2 + primary beams. Use of a multi-standard calibration approach allows for explicit correction of sputter- and ionization yield variations as function of Gecontent. 1. M. Juhel, F. Laugier, Appl. Surf. Sci. 2004, , C. Huyghebaert, T. Conard, B. Brijs, W. Vandervorst, Appl. Surf. Sci. 2004, , M. Gavelle, E. Scheid, F. Cristiano, C. Armand, J. Hartmann, Y. Campidelli, A. Halimaoui, P. Fazzini, O. Marcelot, J. Appl. Phys. 2007, 102, D. Marseihan, J. P. Barnes, F. Filot, J. M. Hartmann, P. Holliger, Appl. Surf. Sci. 2008, 255, Z. Zhu, P. Ronsheim, A. Turansky, M. Hatzistergos, A. Madan, T. Pinto, J. Holt, Surf. Interface Anal. 43(1-2) (2011)

26 XPS/ESCA of Nanoparticles located and implanted info Tissues for Surface Imaging of Biological Tissues Ernest Lewis Ionwerks, 3401 Louisiana, Suite 355, Houston TX 77002, USA Our research previously included the first demonstration of implanting nanoparticles nanometers below the surface of a biological tissue to provide a completely new method MALDI imaging. Now, we are working towards combining optical histology and molecular surface imaging. In this example, we are looking to compare performance results on biological tissues utilizing the XPS with MALDI performance, trying to obtain an optimal dose for signal ion counts in mass spectrometry. What s unique about this method is the ability to implant nanoparticles into a biological tissue, attempt to characterize those particles with XPS and still retain some potential optical histology capabilities. 26