Bijkerk, Frederik

Stilhano Vilas Boas, Cristiane Regina

Sturm, J.M.

University of Twente Research Information

Low Energy Ion Scattering (LEIS)Sputter depth profile – Peak analysis LEIS peaks: outermost surface characterization Sensitive to scattered ions Concentration of species with accuracy at each sputter step LEIS Sputter DP – determine change in oxygen concentrationin depthStatic depth profile – Background signal analysis Species scattered at deeper layers may reionize at surface Ion/target interaction  Stopping Power (S) Metal and oxide: differences in electronic stopping powers Thicker oxide: higher ΔE between surface peak and interface LEIS Static DP – Change oxide thickness with oxygen exposuretime in a non-destructive wayMethodology• 3 keV He+  Ru, Zr and Mo – single layers (15 nm)• Atomic O: RT, 10-4 mbar Mechanisms and kinetics of oxide growth of thin filmsResultsOxide growth through Sputter and Static depth profile Static DP: oxide thickness with accuracy and non-destructively Sputter DP: O concentrationfollows non-linear diffusionRT thin film oxidation- Cabrera-Mott mechanism Rapid formation Saturation thickness with time Inverse logarithmic growth Adsorbed oxygen layer + Metal = Potential: Generating a field:  Driving force of oxide growth Effective while potential drop in unit cell is comparable to diffusion activation energyConclusions and next steps LEIS Static DP: Fast and non-destructive way to determineoxidation of ultrathin films Static + Sputter DP: complete picture of thin-film oxidation Thin films (Ru, Zr, Mo) oxidation at RT: Cabrera-Mott theory Apply evaluation to different systems (varying T, materials)Cristiane Stilhano Vilas Boas1*, Marko Sturm1 and Fred Bijkerk1*e-mail: c.r.stilhanovilasboas@utwente.nl1Industrial Focus Group XUV Optics, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The NetherlandsOxygen diffusion characterization in ultrathin films by low energy ion scatteringAcknowledgementsIndustrial Focus Group XUV Optics at the MESA+ Institute at the Universityof Twente, industrial partners: ASML, Carl Zeiss SMT GmbH, PANalytical,TNO, as well as the Province of Overijssel and the Foundation NWO.Literature1. H. Brongersma et. al. (2007). Surf. Sci. Rep. 62, 63–109.2. N. Cabrera and N.F. Mott (1949). Rep. Progr. Phys. 12, 163-184.AbstractExperimental determination of oxygen diffusion kinetic parameters for ultrathin films is of interest for applications as electronicdevices and protective layers of extreme ultraviolet optics. Techniques usually applied to derive these data (XPS, SIMS) often lackdetails regarding surface chemistry and/or resolution. In this work, the oxygen diffusion in ultrathin films is analysed through LEIS, atechnique that provides the possibility of correlating the selective analysis of the outermost atomic layer with high-resolution staticdepth profiling.𝐸𝑓𝑖 = 𝑘(𝜃,𝑚𝑖𝑜𝑛, 𝑚𝑡𝑎𝑟𝑔𝑒𝑡) ∙ 𝐸0He+, Ne+, Ar+, Kr+1 < E0 < 8 [keV]θoutE0Ef1 Ef2++< ∆𝐸 > = න𝑥𝑆 𝐸, 𝑥 𝑑𝑥Ef2Ef1𝑆𝑖 ~ 𝐴𝑡𝑜𝑚𝑖𝑐 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛S1S2𝐺𝑒𝑜𝑚𝑒𝑡𝑟𝑖𝑐𝑎𝑙 𝑓𝑎𝑐𝑡𝑜𝑟EMe1𝑑𝑜𝑥∝ A Φ, d ∙ ln(𝑡)Metal oxide 𝑤𝑜𝑟𝑘 𝑓𝑢𝑛𝑐𝑡𝑖𝑜𝑛Metal oxide 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠𝑑𝑜𝑥꞊𝐸𝑀𝑒 − 𝐸𝑖2.2 ∙ 𝑆𝜕𝐶𝜕𝑡= 𝐷𝜕2𝐶𝜕𝑥2O Diffusivity (D)Me Oxidation𝑑𝑜𝑥(𝑡)Sputter Depth Profile Static Depth Profile𝑉𝑀 = 𝑒−1(Φ𝑀𝑒 −Φ𝑜−)𝐸𝑏 = − ൗ𝑉𝑀𝑑𝑜𝑥(𝑡)1 2 34 5 6EiReionizied Particles = Background signalOxide thicknessincreaseEiEMeMeOxMe123465

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Oxygen diffusion characterization in ultrathin films by low energy ion scattering

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Oxygen diffusion characterization in ultrathin films by low energy ion scattering

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