VISUALISIERUNG VON OBERFLÄCHENVERUNREINIGUNGEN UND SCHICHTARTEFAKTEN

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1 VISUALISIERUNG VON OBERFLÄCHENVERUNREINIGUNGEN UND SCHICHTARTEFAKTEN J. Baier, U. Beck, A. Hertwig, Th. Lange, M. Sahre, J. M. Stockmann, M. Weise Fachbereich 6.7 Oberflächenmodifizierung und -messtechnik Unter den Eichen 87, Berlin, Germany 11. ThGOT, Zeulenroda, 15. &

2 Outline 1. Surface inspection for quality control (QC) 2. Near-field vs. far-field techniques 3. Imaging by means of microscopic techniques (MT) 4. Imaging by means of imaging ellipsometry (IE) 5. Application examples - nano-scaled pattern - stratified and particulate residues - imperfections & defects 6. Summary and outlook Folie 02 von 23

3 Surface Inspection for QC General Requirements Key product functionalities on the surface: µm- and nm-scale, mostly film-based Huge variety of applications: micro- and optoelectronics, micro-devices, smart windows, sensor-onchip, lab-on-chip, precision & ophthalmic optics, QC-1: material quality & chemical purity, qualitatively (fingerprints) QC-2: structural dimensions, film thickness, quantitatively (within spec) QC-3: applicable both to R&D and QC QC-4: non-destructive, non-invasive QC-5: high lateral and vertical resolution, high depth of field QC-6: high sensitivity and material contrast to contaminations & defects QC-7: ease of use, fast, atmospheric pressure QC-8: in-line, at-line, in-situ, on-line, i.e. technical far-field QC-9: robustness, reproducibility, maintenance-free Folie 03 von 23

4 Surface Inspection for QC Metrology & Evaluation Demands Folie 04 von 23

5 Near-field vs. Far-field Techniques Near-field: a Must for R&D AFM atomic force microscopy s-snom scattering-type scanning nearfield optical microscopy Au/PS nano-structure on Si atmospheric corrosion at an atomically smooth HOPG double layer (600 pm vs. 671 pm) Source: R. Hillenbrand, MPI Martinsried, Germany Folie 05 von 23

6 Near-field vs. Far-field Techniques Far-field: a Must for QC Conventional microscopic techniques: normal incidence, i.e. p- and s-polarization undistinguishable FM fluorescence microscopy LM light microscopy SM stereo microscopy IR-M IR-microscopy Advanced microscopic techniques: normal incidence, i.e. p- and s-polarization undistinguishable, but with z-quantification FM: visible, not measurable CLSM confocal laser scanning microscopy WLIM white light interference microscopy Diffraction limit: 0.5 µm/10 µm FWHM xy = 0.4l /(n sina) FWHM z = 0.45l /(1 - cosa) n LM-DF: visible, not measurable Folie 06 von 23

7 Microscopic Techniques (MT): LM, SM, FM, IR-M LM: microstructure of AlSi10Mg FM: PDA-Rhodamin/PS on SiO 2 LM: rolling texture of steel SM: glass fibre mat IR-M: adhesive failure LM: electroplated Zn-deposit Folie 07 von 23

8 Microscopic Techniques (MT): WLIM & CLSM WLIM: broad R-range Dz, Dx, Dy R a, S a, CLSM: R & T Dz, Dx, Dy laser ripples on 100Cr6 - laser crater in glass fibre - single laser shot in ABS 1.14 µm, 2.15 µm, 5.17 µm and 10.2 µm monodisperse MF-beads Folie 08 von 23

9 State-of-the-art in Microscopy STED: - stimulated emission depletion, fluorescence required - normal incidence - below diffraction limit down to 10 nm protein (FHWM 14 nm) MT (FM,, CLSM): not an all-in-one QC tool - measurement of dimensions x, y and z - no identificaction of materials - no verification of chemical bonds, except for IR-M - no direct determination of thicknesses h i QC-requirement: physical (µm-range) vs. technical (dm-range) far-field Source: St. Hell, Biophysical J., Vol. 105, issue 1, 07/2013, L01-L03 BAM: Brewster angle microscopy - oblique incidence - ML-sensitivity - R p polarization matters monopalmitoyl-rac-glycerol air/water interface Source: Accurion GmbH, Göttingen Folie 09 von 23

10 Brewster-angle Microscopy vs. Imaging Ellipsometry near Brewster Angle From optically thin to thick medium, Brewster angle has to be considered Folie 10 von 23

11 Imaging Ellipsometry vs. Microscopy Oblique incidence: p- & s-amplitudes (Y ) and phase (Δ) matter Near/at Brewster angle: tan ϑ B = n and for incidenting p- polarized light, there is no reflected intensity, i.e. the (known) substrate vanishes in reflection high surface sensitivity (to unknown contaminations) Settings to adjust: PCA-configuration, AOI (ϑ), wavelength l, n(l), light source three images (video, Y, Δ) with material, chemical, dimensional and thickness information: video-image (R), Y-image ( / ), Δ-image (φ p - φ s ) Folie 11 von 23

12 Imaging Ellipsometry vs. Microscopy Measurement: r = r p / r s = tany exp (id) - p-and s-polarization contrast (IE) instead of intensity and colour contrast (microscopy) good news - just one line in the FOV sharp (IE) instead of the entire FOV (microscopy) bad news Data evaluation: solution: Scheimpflug-configuration information QC-demands: separation: material, chemical, dimensional and thickness further improvements: measurement speed & FOIdimensions Folie 12 von 23

13 Imaging Ellipsometry Scheimpflug Configuration automated variable angle, flow cell, SPR kit Dual head configuration: gonio-spectroscopic imaging ellipsometer IE & AFM Scheimpflug configuration: sharp image over entire FOV with ultraobjective Folie 13 von 23

14 Application Example 1 Dried Stain: Native SiO 2 -Si Surface Xe-lamp: 560 nm laser: 637 nm Xe-lamp: 560 nm laser: 637 nm IE - image-scan: 100x, PCA:0/0/0, Xe & laser IE - delta-map: 100x, PCA: 45/35/25-Xe, 35/25/15-laser Folie 14 von 23

15 Application Example nm Film Pattern: AFM vs. IE AFM: FOV (2 x 2) µm 2 IE: image-scan & delta-map FOV (1200 x 1800) µm 2 Folie 15 von 23

16 Application Example 3 30 nm Filtered-arc ta-c on Si IE (image-scan, delta-map): macro contamination, micro particles, cleaning residue, particle-inlayer, layer bumps Folie 16 von 23

17 Application Example 4 Hidden Forensic In-layer Features LM-DIC: - polarized light, special illumination - almost invisible using LM,, WLIM IE (delta-map): - phase-contrast imaging - depolarisation-contrast imaging Folie 17 von 23

18 Application Example 5 Micro-patterned Glass Surfaces IE (image-scan): residue from chemical etching Folie 18 von 23

19 Application Example 6 1nm ta-c/graphene on Glass IE: image-scan (a, b) and delta-map (c) LM: special illumination, polarized light, DIC Folie 19 von 23

20 Reference Compensated Ellipsometry for Small Deviations - defined reference sample at AOI ref - deviating sample at AOI sam = AOI ref - 90 turned reference sample at AOI ref - reference and deviating sample, 90 turned one behind the other with AOI ref = AOI sam Folie 20 von 23

21 Graphene Mono-, Bi- and Tri-Layer Video, Delta (D) & Psi (Y ) bi- & tri-layer mono-layer IE: (50 200) µm graphene flakes on 300 nm SiO 2 on Si Folie 21 von 23

22 Summary & Outlook Gefördert vom Imaging ellipsometry vs. microscpoy: - materials (n, k, e 1, e 2 ) - chemistry (residue from cleaning, dried stain, fingerprint-contamination) - dimensions (micro-pattern: structured films and wet etching in glass; particles; preparation artefacts) - thickness (0.3 nm graphene, 0.5 nm island film, 1 nm ta-c, 30 nm ta-c) Mapping & imaging: - image-scan, psi- and delta-maps, ROI: 10 µm 2 to 2 mm 2 - Scheimpflug-objective and reference-compensated ellipsometry are further steps to QC-applications - faster search for best contrast, larger areas, further improvement of measurement speed, and tailored SOPs to selected industrial applications Folie 22 von 23

23 Thanks for Your Attendence and Attention Organizing Committee: Nobert Esser (ISAS) Uwe Beck (BAM) Karsten Hinrichs (ISAS) Andreas Hertwig (BAM) International Conference on Spectroscopic Ellipsometry (ICSE-7): Seminaris Conference Center & Hotel , Berlin, Germany ThGOT Folie 23 von 23