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1. Introduction
Bringing EUV Lithography (EUVL) forward to high volume manufacturing (HVM), one of the mainchallenges to date is to deliver a high level of EUV power at intermediate focus (IF). One of themost promising methods to meet the joint requirements from all leading scanner manufacturers isa laser produced plasma (LPP) source. The required 13.5 nm radiation is generated by highlyionized plasma which is created by depositing laser energy at 10.6 µm wavelength into tin (Sn).The radiation of this plasma is collected by a 5 sr near normal incidence EUV collector(Ø 660 mm) and focused to the IF (Figure 1).
2. Coating Challenges
3. Technical Coating Setup: NESSY
5 sr collector mirror coatings
for high power laser produced plasma EUV sources
Marco Perske* , Hagen Pauer, Torsten Feigl, Norbert Kaiser
Fraunhofer-Institut für Angewandte Optik und Feinmechanik, Albert-Einstein-Str. 7, 07745 Jena, Germany
Acknowledgements
The authors gratefully acknowledge the financial support for this work from Cymer Inc. The authors would like to thank Wieland Stöckl, Michael Scheler and Thomas Müller for technical support. Wethank Frank Scholze, Christian Laubis and team (PTB Berlin) for EUV reflectivity measurements.
Fig. 4: New EUV Sputtering SYstem NESSY
Fig. 1: Schematic illustration of Laser
Produced Plasma (LPP) source.
Collector Dimensions:
Diameter: > 660 mm
Lens sag: > 150 mmSubstrate tilt: > 45 deg
Weight: > 40 kg
Requirements for HVM:
Reflectivity : > 65 %
Wavelength: λ = (13.50 ± 0.05) nmAccuracy of
lateral thickness gradient: ∆d < 25 pmPhi = 0°
Phi = 180
Phi = 90°
Phi = 270°
0%
10%
20%
30%
40%
50%
60%
70%
12,7 12,9 13,1 13,3 13,5 13,7 13,9 14,1 14,3
Wavelength, nm
Refl
ecti
vit
y
r=310mm (Φ=90)
r=300mm (Φ=90)
r=290mm (Φ=90)
r=280mm (Φ=90)
r=270mm (Φ=90)
r=260mm (Φ=90)
r=250mm (Φ=90)
r=240mm (Φ=90)
r=230mm (Φ=90)
r=220mm (Φ=90)
r=210mm (Φ=90)
r=200mm (Φ=90)
r=190mm (Φ=90)
r=180mm (Φ=90)
r=170mm (Φ=90)
r=160mm (Φ=90)
r=150mm (Φ=90)
r=140mm (Φ=90)
r=130mm (Φ=90)
r=120mm (Φ=90)
r=110mm (Φ=90)
r=100mm (Φ=90)
r=90mm (Φ=90)
r=80mm (Φ=90)
r=70mm (Φ=90)
r=60mm (Φ=90)
0%
10%
20%
30%
40%
50%
60%
70%
12,7 12,9 13,1 13,3 13,5 13,7 13,9 14,1 14,3
Wavelength, nm
Refl
ecti
vit
y
r=310mm (Φ=270)
r=300mm (Φ=270)
r=290mm (Φ=270)
r=280mm (Φ=270)
r=270mm (Φ=270)
r=260mm (Φ=270)
r=250mm (Φ=270)
r=240mm (Φ=270)
r=230mm (Φ=270)
r=220mm (Φ=270)
r=210mm (Φ=270)
r=200mm (Φ=270)
r=190mm (Φ=270)
r=180mm (Φ=270)
r=170mm (Φ=270)
r=160mm (Φ=270)
r=150mm (Φ=270)
r=140mm (Φ=270)
r=130mm (Φ=270)
r=120mm (Φ=270)
r=110mm (Φ=270)
r=100mm (Φ=270)
r=90mm (Φ=270)
r=80mm (Φ=270)
r=70mm (Φ=270)
r=60mm (Φ=270)
0%
10%
20%
30%
40%
50%
60%
70%
12,7 12,9 13,1 13,3 13,5 13,7 13,9 14,1 14,3
Wavelength, nm
Refl
ecti
vit
y
r=310mm (Φ=180)
r=300mm (Φ=180)
r=290mm (Φ=180)
r=280mm (Φ=180)
r=270mm (Φ=180)
r=260mm (Φ=180)
r=250mm (Φ=180)
r=240mm (Φ=180)
r=230mm (Φ=180)
r=220mm (Φ=180)
r=210mm (Φ=180)
r=200mm (Φ=180)
r=190mm (Φ=180)
r=180mm (Φ=180)
r=170mm (Φ=180)
r=160mm (Φ=180)
r=150mm (Φ=180)
r=140mm (Φ=180)
r=130mm (Φ=180)
r=120mm (Φ=180)
r=110mm (Φ=180)
r=100mm (Φ=180)
r=90mm (Φ=180)
r=80mm (Φ=180)
r=70mm (Φ=180)
r=60mm (Φ=180)
0%
10%
20%
30%
40%
50%
60%
70%
12,7 12,9 13,1 13,3 13,5 13,7 13,9 14,1 14,3
Wavelength, nm
Refl
ecti
vit
y
r=310mm (Φ=0)
r=300mm (Φ=0)
r=290mm (Φ=0)
r=280mm (Φ=0)
r=270mm (Φ=0)
r=260mm (Φ=0)
r=250mm (Φ=0)
r=230mm (Φ=0)
r=220mm (Φ=0)
r=210mm (Φ=0)
r=200mm (Φ=0)
r=190mm (Φ=0)
r=180mm (Φ=0)
r=170mm (Φ=0)
r=160mm (Φ=0)
r=150mm (Φ=0)
r=140mm (Φ=0)
r=130mm (Φ=0)
r=120mm (Φ=0)
r=110mm (Φ=0)
r=100mm (Φ=0)
r=90mm (Φ=0)
r=80mm (Φ=0)
r=70mm (Φ=0)
r=60mm (Φ=0)
Φ = 0° Φ= 90°
Φ = 180°Φ= 270°
rmin=60 mm, AOI 7.7° rmax=320 mm, AOI 35.9°
Fig. 6: 4 measured lines with 25 reflectivity
curves each for radii 60 mm < r < 315 mm.
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
0 50 100 150 200 250 300 350
Collector Radius, mm
Refl
ecti
vit
y, %
Phi = 0°
Phi = 90°
Phi = 180°
Phi = 270°
Phi = 0° Phi = 180°
Phi = 90°
Phi = 270°
Reflectivity curves:
Figure 6 demonstrates the excellent wavelength matching for the 4 measured lines on thecollector surface. Each line contains 25 single reflectivity curve measurements for radii between60 mm and 315 mm and hence for angles of incidence from 7.7°to 35.9°.
Maximum reflectivity:
Measured along 4 lines of thecollector mirror for s-polarizedlight (Fig. 7):
R ~ 65% @ r < 240 mm
R ~ 59% @ r = 250 … 320 mm
Fig. 7: Top view of mirror surface with 4 measured lines (left); maximum reflectance for radii
50 mm < r < 325 mm on 4 different lines on the collector surface (right).
0,95
1,00
1,05
1,10
1,15
1,20
1,25
1,30
0 50 100 150 200 250 300 350
Collector Radius, mm
Normalized Multilayer Period
ideal
experimental
Lateral multilayer gradient:
The error bars in Figure 5 correspond to a relative multilayer period error of d = 25 pm and henceto the specified peak wavelength of (13.50 ± 0.05) nm.
Fig. 5: Multilayer gradient, ideal and
experimental data (normalized).
4. Results
In order to achieve the required peak reflectivity of morethan 65 %, the ellipsoidal collector was coated with a highlyreflective, laterally graded multilayer using dc magnetronsputtering. Coating results of the world's largest EUVcollector are presented.
Fig. 2: 5 sr LPP collector. Fig. 3: Collector dimensions and schematic period thickness gradient along
collector radius.
NESSY specifications
Technology: dc magnetron sputtering
Conception: deposition of laterally graded multilayers on curved substrates
Substrate size: up to Ø 660 mm (load locking up to Ø 400 mm)
Thickness homogeneity: ± 0.1 % on 300 mm
5. Conclusion
The paper presents the successful coating of the world’s largest ellipsoidal EUV collector mirrorwith a diameter of 660 mm. A maximum reflectivity of the laterally graded Mo/Si multilayer of morethan 65 % was achieved for radii smaller than 230 mm. For radii between 240 mm and 325 mmthe reflectivity decreases to a minimum of 59 %. The wavelength remains constant at(13.50 ± 0.50) nm over the entire collector surface which is well within the specifications for HVM.
