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

uwe.beck@bam.de

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

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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

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Surface Inspection for QC

Metrology & Evaluation Demands

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Near-field vs. Far-field Techniques

Near-field: a Must for R&D

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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

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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

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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

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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

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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

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Brewster-angle Microscopy vs.

Imaging Ellipsometry near Brewster Angle

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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)

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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

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Imaging Ellipsometry

Scheimpflug Configuration

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Dual head configuration:

gonio-spectroscopic imaging ellipsometer IE & AFM

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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

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IE - image-scan:

100x, PCA:0/0/0, Xe & laser

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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

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AFM:

FOV (2 x 2) µm2

IE:

image-scan & delta-map

FOV (1200 x 1800) µm2

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Application Example 3

30 nm Filtered-arc ta-C on Si

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IE (image-scan, delta-map):

macro contamination, micro particles, cleaning residue, particle-in-layer, layer bumps

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Application Example 4

Hidden Forensic In-layer Features

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LM-DIC:

- polarized light, special illumination - almost invisible using LM, …, WLIM

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IE (delta-map):

- phase-contrast imaging - depolarisation-contrast imaging

Application Example 5

Micro-patterned Glass Surfaces

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IE (image-scan):

residue from chemical etching

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Application Example 6

1nm ta-C/Graphene on Glass

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IE:

image-scan (a, b) and delta-map (c)

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LM:

special illumination, polarized light, DIC

Reference Compensated

Ellipsometry for Small Deviations

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- 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 )

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IE:

(50 – 200) µm graphene flakes on 300 nm SiO2 on Si

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bi- & tri-layer

mono-layer

Summary & Outlook

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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

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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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