New technique for EUV mask Defect mitigation : “Reversal...
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W/H variation After Reversal Process y = 1.180x R 2 = 0.956 0 2 4 6 8 10 0 1 2 3 4 5 6 W/H expected W/H after coating (nm) Reverse W/H variation with e-beam lithography y = 1.049x R 2 = 0.962 0 2 4 6 8 10 0 1 2 3 4 5 6 W/H before coating (nm) W/H after coating (nm) e-beam W/H Width variation with Mo/Si coating y = 1.415x R 2 = 0.7631 0 2 4 6 8 10 0 1 2 3 4 5 6 W/H before coating (nm) W/H after coating (nm) Mo/Si New technique for EUV mask Defect mitigation : “Reversal Technology” C. Constancias 1 , C. De Nadaï 1 , R. Tiron 1 , J.Y. Robic 1 , B. Beatrice 1 , M. Richard 1 , M. Besacier 2 1 CEA/DRT/LETI - 2 CNRS /LTM - 17 rue des Martyrs -38054 Grenoble, France [email protected] The European EUV (Extreme Ultra-Violet) program MORE MOORE deals to push the limits of lithography to enable and exceed the requirements for the 22nm node. One of the main topic concerns new approaches for low defect Mo/Si mirror mask blank manufacturing. CEA-LETI is developing innovative process techniques for clean mask blank fabrication. One of them, namely “Reversal Technology” should minimize the impact of large defects like nodular defects or decorated defects. The technological approach (CEA patent) is based on the transfer of multilayer mirror from a starting substrate A to a final substrate B. The method to demonstrate the mitigation effect was to carry out programmed defects at the substrate level, and to monitor their impact at each step of the process. Defects of 25nm, 50nm, 75nm and 100nm width, and 20nm, 40nm and 80nm height have been fabricated on 8 inches silicon wafer and characterized by several techniques: Top view CD-SEM, particular counting by light scattering and AFM. Acknowledgments : The authors are indebted to the European Commission, for the funding of the European projects IST- More MOORE 1. EUV mask defect : critical issue 2. Programmed Defects : Fabrication Total defect density Process added defects + « Decorated » defects + Handling defects Mo/Si coating process Substrate defect enhanced by the coating Induced by the operator Substrate I Step 2: Mirror 40 x Mo/Si Mo/ Mo/Si Si I I Nodular type defect Step 3: Cleaning/ Coating B on A Substrate II Step 4 : Grinding substrate I Reflected intensity standard incidence Defect size : Top : 50nm x 20nm Substrate 20nm x 20nm Simulations show that apparent size of the defect is smaller in reverse incidence compared to the standard incidence. Reflected intensity reverse incidence I Step 1: Absorb. coating I II II II Reverse approach for Mask fabrication Step 5: Absorber patterning The goal : study the impact of decorated defects on mirrors performances Programmed defect layout : various defect sizes (width&height) d=50μm, 150μm, 300μm, 500μm d d d d d 5 μm > < CD 25nm CD 50nm CD 75nm CD 100nm d d d Compatibility with characterisation tools SEM, AFM 20 nm 52 nm 73 nm 102 nm 1F 17 nm 50 nm 75 nm 92 nm 27 nm 50 nm 73 nm 100 nm 5 9 F h=80nm h=40nm h=20nm h = 80nm, 40nm, 20nm AFM 2D VEECO tool •NanoWorld AR5T tip •Lower radius of curvature and tilt compensated high aspect ratio •Well adapted for height measurements •Less accurate for CD determination 3. MoSi Coating : Defect enhancement CD and height in accordance with expected values. Programmed defects are qualified (using different techniques. 82nm 100nm 40nm 75nm 20nm 25nm 4. Defect after Reversal Technology 9F 100x100x80nm 3 Programmed defect printed Programmed defect Coated with 40Mo/Si 25.8 9.4 46.1 21.7 27.0 118.8 18.9 89.1 1F 25x25x20nm 3 139.5 101.8 153.6 83.2 185.6 80.1 259.8 82.6 40 x Mo(28Å) / Si(41.5Å) coated by Sputtering AFM measurements Defects of different widths and heights are manufactured, with FOX12, all together on the same wafer by e-beam lithography. Programmed defects printed as expected : Heights & Widths Defect heights kept constant after Mo/Si coating Defect Widths not correlated after Mo/Si coating Defect Width/Height (W/H ratio) after MoSi coating depend on original W/H with a factor 1.4 Sticking of substrat A on substrat B, Grinding of substrat A back side and HF 1% silica dissolution to develop Programmed Defects 25x25x20nm 3 defect not detected with SEM nor AFM Ø 20cm → S=314cm² 25x25nm² ⇔ Pizza Ø 20cm Reversal process Unchanges multilayer Reflectivity Mitigates the decorated defects 100.2 43.7 56.5 84.6 Conclusion Programmed defects fabricated to demonstrate improvement by reversal technology Mo/Si coating induce decorated defects with a Width/Height ratio enhanced by a factor 1.4 Reversal process allows the mitigation of decorated defects keeping Mo/Si reflectance Height variation with Mo/Si coating y = 0.953x R 2 = 0.966 0 20 40 60 80 100 0 20 40 60 80 100 Height before coating, H (nm) Height after coating (nm) Mo/Si TOP Width variation with Mo/Si coating y = 1.151x R 2 = 0.174 0 25 50 75 100 125 150 0 25 50 75 100 125 150 Width before coating, W (nm) Width after coating (nm) Mo/Si Width variation with e-beam lithography y = 0.957x R 2 = 0.945 0 20 40 60 80 100 0 20 40 60 80 100 120 Width expected, W (nm) Width after lithography (nm) e-beam Height variation with e-beam lithography y = 0.991x R 2 = 0.988 0 20 40 60 80 100 0 20 40 60 80 100 Height expected, H (nm) Height after lithography (nm) e-beam Width variation After Reversal Process y = 1.061x R 2 = 0.940 0 20 40 60 80 100 120 0 20 40 60 80 100 120 Width expected, W (nm) Width after Reversal Process (nm) Reverse Height variation after Reversal Process y = 0.985x R 2 = 0.966 0 20 40 60 80 100 0 20 40 60 80 100 Height expected, H (nm) Height after Reversal process (nm) Reverse Reflectivity JVX measurement: 40xMoSi versus incidente angle 1 10 100 1000 10000 100000 1000000 0.5 1 1.5 2 2.5 3 3.5 Incident angle θ, λ θ, λ θ, λ θ, λ=1.54Å Reflectance, R [u.a] Before Revers ing After Reversing Peak due to Polishing Stop Layer Defect size as printed after Reversal Process
Transcript of New technique for EUV mask Defect mitigation : “Reversal...
W/H variation After Reversal Process
y = 1.180x
R2 = 0.956
0
2
4
6
8
10
0 1 2 3 4 5 6W/H expected
W/H
afte
r co
atin
g (n
m)
Reverse
W/H variation w ith e-beam lithography
y = 1.049x
R 2 = 0.962
0
2
4
6
8
10
0 1 2 3 4 5 6W /H before coating (nm )
W/H
afte
r co
atin
g (n
m)
e-beam
W /H W id th var ia tio n w ith M o/S i co atin g
y = 1 .415xR 2 = 0 .7631
0
2
4
6
8
10
0 1 2 3 4 5 6
W /H b efo re co at in g (n m )
W/H
afte
r co
atin
g (n
m)
M o /S i
New technique for EUV maskDefect mitigation : “Reversal Technology”
C. Constancias 1, C. De Nadaï1, R. Tiron 1, J.Y. Robic 1, B. Beatrice 1, M. Richard 1, M. Besacier 2
1CEA/DRT/LETI - 2CNRS /LTM - 17 rue des Martyrs -38054 Grenoble, France
The European EUV (Extreme Ultra-Violet) program MORE MOORE deals to push the limits of lithography to enable and exceed the requirements for the 22nm node. One of the main topic concerns new approaches for low defect Mo/Si mirror mask blank manufacturing. CEA-LETI is developing innovative process techniques for clean mask blank fabrication. One of them, namely “Reversal Technology” should minimize the impact of large defects like nodular defects or decorated defects. The technological approach (CEA patent) is based on the transfer of multilayer mirror from a starting substrate A to a final substrate B. The method to demonstrate the mitigation effect was to carry out programmed defects at the substrate level, and to monitor their impact at each step of the process. Defects of 25nm, 50nm, 75nmand 100nm width, and 20nm, 40nm and 80nm height have been fabricated on 8 inches silicon wafer and characterized by several techniques: Top view CD-SEM, particular counting by light scattering and AFM.
Acknowledgments : The authors are indebted to the European Commission, for the funding of the European projects IST- More MOORE
1. EUV mask defect : critical issue 2. Programmed Defects : FabricationTotal defect density
Process added defects + « Decorated » defects + Handling defects
Mo/Si coating process Substrate defect enhanced by the
coatingInduced by
the operator
Substrate I
Step 2: Mirror 40 x Mo/SiMo/Mo/SiSiI
I
Nodular
type defect
Step 3: Cleaning/
Coating B on A
Substrate II
Step 4 : Grinding substrate I
Reflected intensity standard incidence
Defect size :Top : 50nm x 20nmSubstrate20nm x 20nm
Simulations show that apparent size of the defect is smaller in reverse incidence
compared to the standard incidence. Reflected intensity reverse incidence
IStep 1: Absorb. coating
I
II
II
II
Reverse approach for Mask fabrication
Step 5: Absorber patterning
The goal : study the impact of decorated defects on mirrors performances
Programmed defect layout : various defect sizes (width&height)
d=50µm, 150µm, 300µm, 500µm
d
d
d
dd
5 µm
> <
CD 25nm
CD 50nm
CD 75nm
CD 100nmd
d
d
Compatibility with characterisation toolsSEM, AFM
20 nm 52 nm 73 nm 102 nm
1F
17 nm
50 nm
75 nm 92 nm
27 nm 50 nm 73 nm
100 nm
5
9
F
h=80nm
h=40nm
h=20nm
h = 80nm, 40nm, 20nm
AFM 2D VEECO tool•NanoWorld AR5T tip
•Lower radius of curvature and tilt
compensated high aspect ratio
•Well adapted for height
measurements
•Less accurate for CD determination
3. MoSi Coating : Defect enhancement
CD and height in accordance with expected values .
Programmed defects are qualified
(using different techniques.
82nm100nm
40nm75nm
20nm
25nm
4. Defect after Reversal Technology
9F100x100x80nm 3
Programmed defectprinted
Programmed defect Coated with 40Mo/Si
25.8
9.4
46.1
21.7
27.0
118.8
18.9 89.1
1F25x25x20nm 3
139.5
101.8
153.6
83.2
185.6
80.1
259.8
82.6
40 x Mo(28Å) / Si(41.5Å) coated by SputteringAFM measurements
Defects of different widths and heights are manufactured, with FOX12, all together on the same wafer by e-beam lithography.
Programmed defects printed as expected : Heights & Widths
Defect heights kept constant after Mo/Si coating
Defect Widths not correlated after Mo/Si coating
Defect Width/Height (W/H ratio) after MoSicoating depend on original W/H with a factor 1.4
Sticking of substrat A on substrat B,Grinding of substrat A back side
and HF 1% silica dissolution to develop Programmed D efects
25x25x20nm3
defect not detected with SEM nor AFM
Ø 20cm → S=314cm²
25x25nm² ⇔Pizza Ø 20cm
Reversal process
� Unchanges multilayer Reflectivity
� Mitigates the decorated defects
100.2
43.7
56.5
84.6
Conclusion�Programmed defects fabricated to demonstrate improvement by reversal technology
�Mo/Si coating induce decorated defects with a Width/Height ratio enhanced by a factor 1.4
�Reversal process allows the mitigation of decorated defects keeping Mo/Si reflectance
H e ig h t va ria t io n w ith M o /S i c o a t in g
y = 0 .9 5 3 x
R 2 = 0 .9 6 6
0
20
40
60
80
1 00
0 2 0 4 0 60 8 0 1 00H e ig h t b e fo re c o a tin g , H (n m )
Hei
ght a
fter
coat
ing
(nm
)
M o /S i
T O P W id th varia tio n w ith M o /S i co a tin g
y = 1 .1 51xR 2 = 0 .174
0
25
50
75
100
125
150
0 25 50 75 100 125 150
W id th be fo re co a ting , W (n m )
Wid
th a
fter
coat
ing
(nm
)
M o/S i
W id th va ria tio n w ith e -b eam lith o g rap h y
y = 0 .9 57x
R 2 = 0 .945
0
2 0
4 0
6 0
8 0
1 0 0
0 2 0 4 0 60 8 0 1 0 0 1 20W id th exp e c ted , W (n m )
Wid
th a
fter
litho
grap
hy
(nm
)
e-be a m
H e ig h t v a r ia t io n w ith e -b e a m l i th o g ra p h y
y = 0 .9 9 1 x
R 2 = 0 .9 8 8
0
2 0
4 0
6 0
8 0
1 0 0
0 2 0 4 0 6 0 8 0 1 0 0H e ig h t e x p e c te d , H (n m )
He
ight
aft
er li
thog
raph
y (n
m)
e -b e a m
Width variation After Reversal Process
y = 1.061x
R2 = 0.940
0
20
40
60
80
100
120
0 20 40 60 80 100 120Width expected, W (nm)
Wid
th a
fter
Rev
ersa
l Pro
cess
(n
m)
Reverse
Height variation after Reversal Process
y = 0.985x
R2 = 0.966
0
20
40
60
80
100
0 20 40 60 80 100Height expected, H (nm)
Hei
ght a
fter
Rev
ersa
l pro
cess
(n
m)
Reverse
Reflectivity JVX measurement: 40xMoSi versus incide nte angle
1
10
100
1000
10000
100000
1000000
0.5 1 1.5 2 2.5 3 3.5
Incident angle θ, λθ, λθ, λθ, λ=1.54Å
Ref
lect
ance
, R
[u.a
]
Before Reversing
After Reversing
Peak due to Polishing Stop Layer
Defect size as printed after Reversal Process
