Folie 1

Polarization resolved measurements with the new
EUV Ellipsometer of PTB
Frank Scholze and Victor Soltwisch
Outline
• Motivation
• Existing capabilities
• New instrumentation and concepts
• First results
Frank Scholze, PTB 7.12
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
2
Motivation
• EUV to be used for lithography in semiconductor industry
• EUV systems use rather large oblique angles of incidence
• Example: collector mirror for EUV plasma-source
only RS
fig. courtesy of
Frank Scholze, PTB 7.12
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
3
Projection Optics for EUV Lithography
Model based calculations
AOI: 10° to normal
calculated with IMD, layer
model fitted to measured RS
RS , RP, phase shift ∆
EUV mirror = multilayer Bragg-reflector
•
high quality optics require wave-front error of λ/20 for a six-mirror system
error budget for single mirror typically < 0.2 nm.
•
phase shift of RP vs. RS exceeds this value
•
effects must be well understood and verified
Frank Scholze, PTB 7.12
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
4
Storage Rings in Adlershof
BESSY II
Frank Scholze, PTB 7.12
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
5
PTB @ BESSY I, II, MLS
1982 – 1999: BESSY I
since 1999: BESSY II
BESSY II:
circumference 250 m
electron energy 1.7 GeV
PTB:
10 beamline branches
from 400 nm (3 eV)
to 0.02 nm (60 keV)
UV
since 2008: MLS
X-ray
EUV
Metrology Light Source MLS
circumference 48 m
electron energy 100 - 630 MeV
8 beamlines
from 8 mm
to 4 nm (300 eV)
THz
Frank Scholze, PTB 7.12
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
UV
EUV
6
Soft X-ray radiometry beamline
Wavelength
0.7 nm to 35 nm
At 13 nm
Radiant Power
Higher diffraction orders
Diffuse scattered light
Frank Scholze, PTB 7.12
0.5 µW
0.06 %
0.2 %
• sample not in focus
• spot at sample > 0.5 mm
• no field aperture
• low divergence
(< 1 mrad vert. , < 2 mrad hor.)
• beam halo suppressed by aperture
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
7
Soft X-ray radiometry beamline
Polarimeter: multilayer at Brewster angle with
photodiode for detection of the reflected light. The
mount is rotated around the incident beam direction
using the Φ axis of the reflectometer.
Polarimeter scans at different vertical entrance
aperture setting
Frank Scholze, PTB 7.12
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
8
Soft X-ray radiometry beamline
Polarization properties of bending magnet radiation
Frank Scholze, PTB 7.12
Degree of polarization and main axis orientation as
function of entrance aperture position.
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
9
EUV-Ellipso-Scatterometer
Detector
azimuthally
110° 0.0002°
polar
210° 0.0002°
flip
358° 0.01°
X
Y
Z
rot.-X
rot.-Y
rot.-Z
Sample
100 mm
100 mm
25 mm
130°
130°
358°
sample size:
weight:
0.5 µm
0.5 µm
0.5 µm
0.0002°
0.0002°
0.0002°
190 x 190 x 70
up to 5 kg
no lubricants used
(no organic contaminants)
Frank Scholze, PTB 7.12
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
10
EUV-Ellipso-Scatterometer
Linear polarization analyzer
sample and detector stages of the Ellipsometer
Frank Scholze, PTB 7.12
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
11
EUV-Ellipso-Scatterometer
Measurement capabilities
of EUV Ellipsometer
incident polarization: linear
plane of reflection:
arbitrarily oriented
reflected radiation:
linear polarization
analyzer
spectral range:
1 nm to 25 nm
(soft X-ray beamline)
broad-band multilayer mirrors for
Brewster-angle reflection
Frank Scholze, PTB 7.12
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
12
Reflectance at Brewster angle
Reflectance close to the Brewster angle
measured with different polarizer setting.
Frank Scholze, PTB 7.12
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
13
Reflectance at Brewster angle
calculated reflectance RP
(model parameters adopted to measured RS)
S- and P-reflectance measured at
the Brewster angle.
log. contours from 5⋅10-6 (black) to 0.01 (red)
S / P reflectance ratio of 104 in
agreement with calculated values
(IMD).
Frank Scholze, PTB 7.12
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
14
Reflectance at Brewster angle
Fresnel equation for P-reflection,
surface to vacuum (n1=1):
tan (Θ B ) =
n2
n1
mit n1 = 1 : n2 = tan (Θ B )
P-Reflectance and centre wavelength as function of angle of incidence.
• Brewster angle corresponds to the Mo index of refraction
• Comparison to calculation shows slightly shifted Brewster angle
=> Option to measure the index of refraction (not surface sensitive !)
Frank Scholze, PTB 7.12
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
15
Conclusions
• New ellipsometer at the soft X-ray radiometry beamline
installed
• Successful proof of principle for linear polarizer
• Potential for highly selective polarizer optics in EUV proven
• New options for the determination of EUV optical constants
Frank Scholze, PTB 7.12
8th-Workshop-Ellipsometry, Dresden, March 10.-12.
16
Acknowledgements
EUV radiometry working group (A. Fischer, A. Lewin)
our cooperation partners from the EUV community
Thank you for your attention
Physikalisch-Technische Bundesanstalt
Braunschweig und Berlin
Abbestrasse 10-12
10587 Berlin
Frank Scholze
EUV Radiometry
Telefon: 030 3481 7120
E-Mail: [email protected]
www.ptb.de

Download Report