© RWTH Aachen

Serhiy Danylyuk

RWTH Aachen University

21.02.2016, San Jose, CA

PELLICLE AND THIN FILM SHORT-WAVELENGTHMETROLOGY

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Pellicle requirements

Page 2

*C. Zoldesi, et al., “Progress on EUV pellicle development,” Proc. SPIE 9048 (2014)

Pellicle requirement HVM Target

EUV transmission 90% single pass

Spatial non-uniformity of the transmission <0.2%

Angular non-uniformity of the transmission <300 mrad

Dynamic heat load 5.6 W/cm2 (250 W IF)

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Pellicle illumination conditions NXE:3300

Page 3

NAmask = 0.0825 illumination angles (Y-axis) are between 1.27° and 10.73°

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Pellicle illumination conditions NXE: High NA

Page 4

illumination angles in X direction are between -7.9(-6.6°) and 7.9°(6.6°)illumination angles in Y direction are between 2.1°(1.8°) and 9.9°(10.2°)

NAwafer = 0.55 NAmask_x ~ 0. 1375 (0. 115), NAmask_y ~ 0.068(0.073)

MAGx= 4(4.8)MAGy= 8(7.5)

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Ray Tracing Analysis

Page 5

Defects on the pellicle can lead to a non-uniform transmission through the pellicleat different reticle coordinates

The target specification states a transmission of 90% with <0.2% uniformity

Via ray tracing, the influence on theillumination profile of differently sizeddefects is investigated

NA = 0.33/4

pellicle

reticleprojectionoptics

defect

2.5 mm

reti

cle

coo

rdin

ate

pellicle

defect

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Influence of defect size

Page 6

Different types of defectsare investigated

Circular absorber defects

100% absorption

50% absorption

circular hole defects(100% transmissioninstead of 90% pellicletransmission)

The defect size (diameter ofcircular defect) is varied

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Effective pellicle pixel model

0 20 40 60 80 10088

89

90

91

Tra

nsm

issio

n [

%]

Defect diameter [µm]

100% absorption defect

50% absorption defect

10% transmission defect

±0.2% zone

Page 7

𝑇 = 𝑇𝑝𝑒𝑙𝑙𝑖𝑐𝑙𝑒 − 𝑇𝑑𝑒𝑓𝑒𝑐𝑡 ×𝐴𝑟𝑒𝑎𝑑𝑒𝑓𝑒𝑐𝑡

𝐴𝑟𝑒𝑎𝑝𝑒𝑙𝑙𝑖𝑐𝑙𝑒_𝑝𝑖𝑥𝑒𝑙

𝐴𝑟𝑒𝑎𝑝𝑒𝑙𝑙𝑖𝑐𝑙𝑒_𝑝𝑖𝑥𝑒𝑙 ≈ 𝑑 × (tan 𝜃𝑚𝑎𝑥 − 𝜃𝑚𝑖𝑛)

NXE 3300 : 420-450µm (2.5 mm stand-off)

NXE High NA: X-direction (~700(600)µm)Y-direction (~350 (375)µm)

For off-axis illumination pellicle pixel has to be multiplied with pupil fill factor (PFR), this can reduce the allowed defect size to sub-10µm

In the worst case (100% absorbing) defects with <20µm diameter size is allowed per effective pellicle pixel (350-700µm)

For pellicle transmission uniformity metrology even for aggressive dipoles there is no need to resolve pellicle uniformity better than 50µm

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Transmission uniformity measurements

Page 8

Intensity after pellicle

Uniformity noise floor s=0.13% for the choosen data stack (10 pictures)

4 5 6 7 8 925

30

35

40

45

50

Tra

nsm

issio

n[%

]

Position [mm]

0.2% band

3,80 3,82 3,84 3,86 3,88 3,90

0,0

0,1

0,2

0,3

0,4

0,5

Tra

nsm

issio

n

Position [mm]

Knife-edge resolution 48µm

Membrane is fixed at 6 mm distance to the EUV-sensitive CCD with 13µm pixels

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Pellicle OoB reflectivity

*Park et al, Proc. SPIE 9048, Extreme Ultraviolet (EUV) Lithography V, 90480S (2014)

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Pellicle OoB reflectivity

50 100 150 200 250 300 350 400

0

10

20

30

40

50

60

Pelli

cle

OoB

reflectivity [%

]

Wavelength [nm]

a-C (25 nm)

B4C (4nm)/a-C(25 nm)/B

4C (4nm)

IMD5 model

50 100 150 200 250 300 350 400

0

10

20

30

40

50

60

Pe

llicle

Oo

B r

eflectivity [

%]

Wavelength [nm]

p-Si (65 nm)

a-C (25 nm)

IMD5 model

50 100 150 200 250 300 350 4000

10

20

30

40

50

60

Pe

llicle

Oo

B r

eflectivity [

%]

Wavelength [nm]

B4C capped p-Si

B4C capped a-C

IMD5 model

50 100 150 200 250 300 350 4000,0

0,1

0,2

0,3

0,4

0,5

0,6

IMD5 model

Re

fle

ctivity

Wavelength [nm]

p-Si (25 nm)

p-Si (60 nm)

n,k data: a-C (CXRO+Tarrio et al (1998)+Windt et al (1988)+Palik (1991))p-Si (CXRO+Palik (1985))

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Pellicle OoB reflectivity

50 100 150 200 250 300 350 4000

10

20

30

40

50

60

Pelli

cle

OoB

reflectivity [%

]

Wavelength [nm]

uncapped p-Si

Si3N4 capped p-Si

Mo capped p-Si

B4C capped p-Si

4nm double side caps

IMD5 model

• OoB reflectivity of a pellicle can exceed 50%

• This may have influence on the performance of the scanner

• Capping layers can influence the effect strongly

• OoB reflectivity characterization is necessary

Currently there are no tools for the region between 20 nm and 200 nm

no “fresh” n,k data for modelling either

OoB specification?

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EUV Reflectometer @ Aachen

EUV Source Sample chamber

1st grating 2nd grating

2nd CCD

grating

sample CCDgrating

referenceslit-

aperture

multi angle system (1°-15°)wavelength range 9-17 nm

mirrorAngular dependencies allow to extract refractive index data at each wavelength

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Multi-angle measurement results

Excellent sensitivity to thickness and composition

Layered systems investigation

Page 13

9 nm target thickness of HfO2

HfO2.075 (d=10 nm, ρ=8.43 g/cm3)S iO2(d=0.26 nm)

For complex stacks independent thickness measurement (XRR, ellipsometry, TEM) may be required to decrease ambiguity of the model

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Near-edge EUV Reflectometry

Page 14

Absorption edges of elements in working wavelength range

Element Binding Energy (eV)

Corresponding Wavelength (nm)

Electron state

4 Be 111,5 11,12 K 1s

12 Mg 88,7 13,98 L1 2s

14 Si 99,82 12,42 L2 2p1/2

15 P 136 9,12 L2 2p1/2

37 Rb 113 10,97 M4 3d3/2

38 Sr 136 9,12 M4 3d3/2

57 La 105,3 11,77 N4 4d3/2

59 Pr 115,1 10,77 N4 4d3/2

60 Nd 120,5 10,29 N4 4d3/2

61 Pm 120 10,33 N4 4d3/2

62 Sm 129 9,61 N4 4d3/2

63 Eu 133 9,32 N4 4d3/2

89 Ac 80 15,50 O4 5d3/2

90 Th 92,5 13,40 O4 5d3/2

91 Pa 94 13,19 O4 5d3/2

92 U 102,8 12,06 O4 5d3/2

Grazing incidence angle 5°

Direct elemental sensitivity

Less ambiguous modelling

Near-edge fine structure

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Near-edge EUV Reflectometry

Page 15

Near-Edge X-Ray Absorption Fine Structure (NEXAFS)

[*] M. Banyay, Surface and Thin Film Analysis by Spectroscopic Reflectometry with EUV Emitting Laboratory Sources, PhD (RWTH Aachen, 2011).[**] E. O. Filatova, A. A. Sokolov, E. Yu. Taracheva, I. V. Bagrov, Technical Physics Letters, Vol. 35, Issue 1, Jan 2009, pp. 70-72.[***] E. O. Filatova, A. S. Shulakov, and V. A. Luk’yanov, Phys. Solid State 40 (7), July 1998.

Determination of chemical bonds and local symmetry Quick qualitative interpretation (fingerprinting)

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SUMMARY

Pellicle transmission spec resolution should not be below 50µm

Metrology with this reolution is not a challenge

OoB pellicle reflectivity may become a problem and should be controlled

New reliable n,k data are necessary to model the performance, preferable measured directly on a pellicle

Hard to measure in VUV wavelength region, no reflectometers orellipsometers in the range between 20 and 200 nm

Reflectometry (and n,k) measurements near the absorption edges (e.g. near Si L-edge @12.4nm) are often NEXAFS-modified and difficult tomodel precisely