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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, 12205 Berlin, Germany
11. ThGOT, Zeulenroda, 15. & 16.09.2015
15.09.2015
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
15.09.2015 11. ThGOT Folie 02 von 23
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-on-
chip, 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
15.09.2015 11. ThGOT Folie 03 von 23
Surface Inspection for QC
Metrology & Evaluation Demands
15.09.2015 11. ThGOT Folie 04 von 23
Near-field vs. Far-field Techniques
Near-field: a Must for R&D
15.09.2015 11. ThGOT
AFM
atomic force microscopy
s-SNOM
scattering-type scanning near-
field optical microscopy
atmospheric corrosion at an
atomically smooth HOPG double
layer (600 pm vs. 671 pm)
Au/PS nano-structure on Si
Source:
R. Hillenbrand, MPI Martinsried, Germany
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Near-field vs. Far-field Techniques
Far-field: a Must for QC
15.09.2015 11. ThGOT
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
‒ CLSM confocal laser scanning microscopy
‒ WLIM white light interference microscopy
Diffraction limit: 0.5 µm/10 µm
FWHMxy = 0.4l /(n × sina)
FWHMz = 0.45l /(1 - cosa) × n
FM: visible, not measurable
LM-DF: visible, not measurable
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Microscopic Techniques (MT):
LM, SM, FM, IR-M
15.09.2015 11. ThGOT
LM: microstructure of AlSi10Mg
LM: rolling texture of steel
SM: glass fibre mat
IR-M: adhesive failure
LM: electroplated Zn-deposit
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FM: PDA-Rhodamin/PS on SiO2
Microscopic Techniques (MT):
WLIM & CLSM
15.09.2015 11. ThGOT
WLIM: broad R-range Dz, Dx, Dy Ra , Sa, …
CLSM: R & T Dz, Dx, Dy
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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
State-of-the-art
in Microscopy
15.09.2015 11. ThGOT
STED:
- stimulated emission
depletion, fluores-
cence required
- normal incidence
- below diffraction limit
down to 10 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 hi
QC-requirement:
physical (µm-range) vs. technical (dm-range) far-field
protein (FHWM 14 nm)
Source: St. Hell, Biophysical J., Vol. 105, issue 1, 07/2013, L01-L03
BAM: Brewster angle microscopy - oblique incidence - ML-sensitivity - Rp polarization matters
monopalmitoyl-rac-Glycerol air/water interface
Source: Accurion GmbH, Göttingen
Folie 09 von 23
Brewster-angle Microscopy vs.
Imaging Ellipsometry near Brewster Angle
15.09.2015 11. ThGOT
From optically thin to thick medium, Brewster angle has to be considered
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Imaging Ellipsometry
vs. Microscopy
Oblique incidence: p- & s-amplitudes (Y ) and phase (Δ)
matter
Near/at Brewster angle: tan ϑB = 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 (φp - φs)
15.09.2015 11. ThGOT Folie 11 von 23
Imaging Ellipsometry
vs. Microscopy
Measurement:
r = rp / rs = 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 (micros-
copy) – bad news
solution: Scheimpflug-configuration
Data evaluation:
separation: material, chemical, dimensional and thickness
information
QC-demands:
further improvements: measurement speed & FOI-
dimensions
15.09.2015 11. ThGOT Folie 12 von 23
Imaging Ellipsometry
Scheimpflug Configuration
15.09.2015 11. ThGOT
Dual head configuration:
gonio-spectroscopic imaging ellipsometer IE & AFM
Folie 13 von 23
Scheimpflug configuration:
sharp image over entire FOV with ultra-objective
EP3@BAM EP3-ultra@BAM EP4@Accurion automated variable angle, flow cell, SPR kit
Application Example 1
Dried Stain: Native SiO2-Si Surface
15.09.2015 11. ThGOT
IE - image-scan:
100x, PCA:0/0/0, Xe & laser
Folie 14 von 23
IE - delta-map:
100x,
PCA: 45/35/25-Xe, 35/25/15-laser
Xe-lamp: 560 nm laser: 637 nm Xe-lamp: 560 nm laser: 637 nm
Application Example 2
0.5 nm Film Pattern: AFM vs. IE
15.09.2015 11. ThGOT
AFM:
FOV (2 x 2) µm2
IE:
image-scan & delta-map
FOV (1200 x 1800) µm2
Folie 15 von 23
Application Example 3
30 nm Filtered-arc ta-C on Si
15.09.2015 11. ThGOT
IE (image-scan, delta-map):
macro contamination, micro particles, cleaning residue, particle-in-layer, layer bumps
Folie 16 von 23
Application Example 4
Hidden Forensic In-layer Features
15.09.2015 11. ThGOT
LM-DIC:
- polarized light, special illumination - almost invisible using LM, …, WLIM
Folie 17 von 23
IE (delta-map):
- phase-contrast imaging - depolarisation-contrast imaging
Application Example 5
Micro-patterned Glass Surfaces
15.09.2015 11. ThGOT
IE (image-scan):
residue from chemical etching
Folie 18 von 23
Application Example 6
1nm ta-C/Graphene on Glass
15.09.2015 11. ThGOT
IE:
image-scan (a, b) and delta-map (c)
Folie 19 von 23
LM:
special illumination, polarized light, DIC
Reference Compensated
Ellipsometry for Small Deviations
15.09.2015 11. ThGOT Folie 20 von 23
- defined reference sample at AOIref
- deviating sample at AOIsam = AOIref
- 90° turned reference sample at AOIref
- reference and deviating sample, 90° turned one behind the other with AOIref = AOIsam
Graphene Mono-, Bi- and Tri-Layer
Video, Delta (D) & Psi (Y )
15.09.2015 11. ThGOT
IE:
(50 – 200) µm graphene flakes on 300 nm SiO2 on Si
Folie 21 von 23
bi- & tri-layer
mono-layer
Summary & Outlook
15.09.2015 11. ThGOT
Imaging ellipsometry vs. microscpoy:
- materials (n, k, e1, e2)
- 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 µm2 to 2 mm2
- 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
Gefördert vom
Thanks for Your
Attendence and Attention
15.09.2015 ThGOT
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
06.06. – 10.06.2016, Berlin, Germany
http://www.icse-7.de/homepage/committees/
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