development of reflective coatings for beuv lithographypresented by l. sjmaenok phystex, vaals,...
TRANSCRIPT
Presented by L. SjmaenokPhysTeX, Vaals, Netherlands
Development of Reflective Coatings for BEUV Lithography
2010 International Workshop on Extreme Ultraviolet Sources November 13-15, 2010
University College Dublin ▪ Dublin, Ireland
Authors
N. Salashchenko, M. Barysheva, N. Chkhalo, V. PolkovnikovInstitute for Physics of Microstructures, Nizhny Novgorod, Russia
International Workshop on EUV Sources, Dublin, 14-11-10 2
Authors
N. Salashchenko, M. Barysheva, N. Chkhalo, V. PolkovnikovInstitute for Physics of Microstructures,
Nizhny Novgorod, Russia
L. SjmaenokPhysTeX, Vaals, Netherlands
V. Banine, D. Glushkov, A. YakuninASML, Veldhoven, Netherlands
Agenda
• Calculated reflectivity near 6.7 nm
• Fabrication of La/B4C(B9C) MLMs for 6.7 nm
• Reflectivity measurements and experimental data
• Study of internal structure of La/B4C MLMs
• Anti-diffusive barrier layers in La/B4C(B9C) MLMs
• Current tasks
International Workshop on EUV Sources, Dublin, 14-11-10 3
International Workshop on EUV Sources, Dublin, 14-11-10 4
La‐on‐B4C: 0.9 nmB4C‐on‐La: 0.4 nmRm: 44.3% FWHM: 0.040 nm
0.4 nm ‐ 0.4 nmRm: 62.7%FWHM: 0.052 nm
0.3 nm ‐ 0.3 nmRm: 67.2%FWHM: 0.057 nm
Calculated reflectivity contours R(λ) for La/B4C structures
International Workshop on EUV Sources, Dublin, 14-11-10 5
0.4 nm ‐ 0.4 nmRm: 66.0%FWHM: 0.054 nm
0.3 nm ‐ 0.3 nmRm: 70.2%FWHM: 0.060 nm
Calculated reflectivity contours R(λ) for La/B9C structures
La/B4C(B9C) growing process
International Workshop on EUV Sources, Dublin, 14-11-10 6
• Substrate: Si, σ ≈ 0.3 nm
• Ar-pressure: 9⋅10-4 mbar background: <10-6 mbar
• DC and RF sputtering
• Number of sputter sources (materials): 2 and 4
• Power: 220 and 450 W
Reflectivity measurements
International Workshop on EUV Sources, Dublin, 14-11-10 7
RT – X-ray tube A,S – entrance and exit slitsG – spherical diffraction grating with: R = 6 m (range 0.6-5 nm)R = 4 m (range 1.6-9 nm) R = 2 m (range 4-50 nm) TM – thoroidal mirrorD, M – master and monitor detectors MLM – sample under studyG5 – 5-axis goniometer
Results of near-normal incidence measurements
International Workshop on EUV Sources, Dublin, 14-11-10 8
MLM θmax (°) λ/Δλ Rmax (%) Rid (%)
La/B4C
PM680 74.35 126 >44
65
A2397 80.61 115.5 33A2408 78.7 122 38A2413 79.66 116 37A2418 77.91 111.5 37A2419 80.45 120 40
La/B9C A2428 72.08 107 38 66
Ce/B4CLVP27 80.6 108 33
57LVP31 82.88 109 36LVP32 77.71 110 35
The measured reflectivities are at least by 30% lower than the predicted onesWHY?
Best spectral reflectivity profile obtained by Jan. 2009
International Workshop on EUV Sources, Dublin, 14-11-10 9
0
5
10
15
20
25
30
35
40
45
6.55 6.6 6.65 6.7 6.75 6.8 6.85
Ref
lect
ivity
, %
Wavelength, nm
If optical constants of La at λ=6.7 nm are incorrect, large-d MLM would exhibit same deviation from theoretical values
International Workshop on EUV Sources, Dublin, 14-11-10 10
MLM θmax (°) λ/Δλ Rexp (%) Rtheor (%)
La/B4C A2420 28.95 34 60 60
Ce/B4C LVP33 28.82 32 47 49
La/B9C A2427 27.06 29 59 64
Reflectivity is close to the theoretical prediction
Reason of the poor reflection – bad interfaces
Fitting angular dependencies of reflection for La/B4C structures
International Workshop on EUV Sources, Dublin, 14-11-10 11
27 28 29 30 31
0.0
0.2
0.4
0.6 (a)
R (a
bs.u
nits
)
θ (deg.)0 1 2 3 4
1E-91E-81E-71E-61E-51E-41E-30.01
0.11
(b)
R(a
bs.u
nits
)
θ(deg.)Number of periods N = 150. (а) λ = 6.69 nm; (b) λ = 0.154 nm. Fittingparameters: d = 7.12 nm, β = 0.48, σ = 0.47 nm, ρLa = 5.5 g/cm3,ρB4C = 1.8 g/cm3. Blue curve corresponds to “ideal” MLM.
Fitting for λ=0.154 nm is poor in many Bragg peaks.
A model with symmetrical interfaces does not work!
Reconstruction of electron density profile with reflection coefficients Rm at λ=0.154 nm in higher orders. If the profile is asymmetric and quantity of La and B4C materials is close to 1:1, am can be neglected.
International Workshop on EUV Sources, Dublin, 14-11-10 12
dm qz)(qbz)(qaε(z) mm
mmm
mm0 /2,sincos11
πε =∑+∑+=∞
=
∞
=
[ ]⎭⎬⎫
⎩⎨⎧
∑+∑′′−′′+′−′+=∞
=
∞
= 112121 sincos)()(
mm
normm
mm
normm0 z)(qbz)(qaiε(z) εεεεε
[ ] ( ) ( )[ ]2224
221
221
2)()( normm
normmm ba
mNdR +⎟⎠⎞
⎜⎝⎛
⎟⎠⎞
⎜⎝⎛′′−′′+′−′=
πλ
εεεε
β = 0.5 Rm bm
ε(z)
d
Reconstruction results for small-dand large-d La/B4C structures
International Workshop on EUV Sources, Dublin, 14-11-10 13
0 4 8 12 16 20 24 28 32
-4.0x10-6
-2.0x10-6
0.0
2.0x10-6
4.0x10-6
Im ε(z)
-1.0x10-6
0.0
1.0x10-6
A2419 La/B4C (d=3.51nm, β=0.4)
z, nmR
e ε(
z)
0 4 8 12 16 20 24 28 32-8.0x10-6
-4.0x10-6
0.0
4.0x10-6
8.0x10-6
Im ε(z)
-3.00x10-6
-1.50x10-6
0.00
1.50x10-6
3.00x10-6
A2420 La/B4C (d=7.12 nm, β=0.48)
z, nm
Re ε(
z)
We see that interfaces are strongly asymmetric.The interface width is about 1 nm at one side and 2 nm at the other side and dose not depend on the MLM period.
La and B profiles in La/B4C measured by SIMS
International Workshop on EUV Sources, Dublin, 14-11-10 14
20000
22000
24000
26000
28000
30000
32000
34000
36000
38000
0 10 20 30 40 50 60 70
Etching depth, nm
Inte
nsity A2420A La
PM830A La
0
5000
10000
15000
20000
25000
30000
0 10 20 30 40 50 60 70
Etching, nm
Inte
nsity A2420A B
PM830A B
Lanthanum at the left side of the profiles demonstrates it’s implantation into boron films
Conclusion on La/B4C
Due to high chemical activity of La, mixing of La
and B4C films at boundaries takes place, resulting
in interface degradation, causing strong decrease
of reflectivity
International Workshop on EUV Sources, Dublin, 14-11-10 15
Anti-diffusion layers of Mo, Sn and Cr were explored
to weaken intermixing effects, as featured with
International Workshop on EUV Sources, Dublin, 14-11-10 16
• Low absorption at λ=6.7 nm
• Weak chemical interaction with La and B4C
• Suitability of deposition by magnetron sputtering
Mo(Cr)-La and Mo(Cr)-B4C interfaces have exhibited a good quality in corresponding MLMs, with good reflectivity fittings for soft and hard X-rays and relatively small interface width of σ ≈ 0.4-0.5nm
International Workshop on EUV Sources, Dublin, 14-11-10 17
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.51E-81E-71E-61E-51E-41E-30.010.1
1
R
θ (deg.)125 130 135 140 145
0.00.10.20.30.40.50.6
R
λ (A)
27.027.528.028.529.029.530.030.50.00
0.01
0.02
0.03
0.04
0.05R
θ (deg.)
Mo/La MLM (N = 60) at а) λ=0.154 nm, b) λ=6.69 nm; c) λ=13.5 nm (θ = 70°).Fitting: d=7.47 nm, β=0.45, σ=0.52 nm, ρMo = 9.5 g/cm3, ρLa =6.0 g/cm3.
However, application of the studied materials as anti-diffusion layers with admissible thickness of <0.3 nm has not resulted in increase of reflectivity of La/B4C MLMs
International Workshop on EUV Sources, Dublin, 14-11-10 18
FOM group (F. Bijkerk) reported R = 41.5% with anti-diffusion LaN/BN barriers, which enabled the demonstrated 1.2× increase of R
Current tasks• Study and application of less chemically active layer
materials• Search for more effective anti-diffusion barriers• Upgrade and implementation of advanced methods
for treatment of interfaces• Development of structures for 6.x nm wavelength to
match optimized radiation source parameters
International Workshop on EUV Sources, Dublin, 14-11-10 19
Acknowledgment
The work was partially supported by EC Commission
International Workshop on EUV Sources, Dublin, 14-11-10 20