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1 L. Pang, eBeam Initiative Reception at BACUS 2015
Mask Metrology in the ILT World
Linyong (Leo) Pang D2S, Inc.
Sept. 29, 2015 Managing Company Sponsor
2 L. Pang, eBeam Initiative Reception at BACUS 2015
A Decade of ILT!
6 Papers
2 Foundries
1 Memory
1 Mask shop
2005
3 L. Pang, eBeam Initiative Reception at BACUS 2015
ILT Adopted as the Way Forward
>200 Papers Officially
announced
2014 panel
Today
ILT expertise proliferated
4 L. Pang, eBeam Initiative Reception at BACUS 2015
But What About CD Metrology?
VS
B.G. Kim, et al., BACUS, 2012
New World: ILT Mask Pattern
Old World: Conventional Mask Pattern
B.G. Kim, et al., PMJ, 2009
5 L. Pang, eBeam Initiative Reception at BACUS 2015
ILT CD is not just line width: it’s 2D!
What to use as a reference?
Which mask issues impact the wafer?
Contour and EPE
Simulated mask pattern
Wafer plane analysis
What is CD In the ILT World?
6 L. Pang, eBeam Initiative Reception at BACUS 2015
Mask Plane Metrology: Contour and EPE Measurements
• EPE measured on entire contour • Histogram: mean, 3 sigma
7 L. Pang, eBeam Initiative Reception at BACUS 2015
Mask Plane Metrology: Contour and EPE Measurements
EPE measured on entire contour
PV band
8 L. Pang, eBeam Initiative Reception at BACUS 2015
Mask Plane Metrology: Contour and EPE Measurements
0
5000
10000
15000
20000
-6 -5.6 -5.2 -4.8 -4.4 -4 -3.6 -3.2 -2.8 -2.4 -2 -1.6 -1.2 -0.8 -0.4 0
EPE Histogram (Mask)
Count 95883 Min (nm) -6.00 Max (nm) -0.84 Mean (nm) -1.83 Median (nm) -1.71 3 Sigma (nm) 2.14
9 L. Pang, eBeam Initiative Reception at BACUS 2015
Mask Plane Metrology: What is the Target for EPE?
OPC Design • No corner
rounding • Affected by
corner EPE
• What OPC thinks the mask shape will be
Simulated mask pattern • Model of
actual mask shape
Mask Shape
10 L. Pang, eBeam Initiative Reception at BACUS 2015
Wafer Plane Metrology: Traditional CD and Wafer Impact in One Simulation
11 L. Pang, eBeam Initiative Reception at BACUS 2015
Wafer Plane Metrology: Traditional CD and Wafer Impact in One Simulation
12 L. Pang, eBeam Initiative Reception at BACUS 2015
Wafer Plane Metrology: Traditional CD and Wafer Impact in One Simulation
0 500
1000 1500 2000 2500 3000 3500 4000
-10 -9.6 -9.2 -8.8 -8.4 -8 -7.6 -7.2 -6.8 -6.4 -6 -5.6 -5.2 -4.8 -4.4 -4
EPE Histogram (Wafer)
Count 23468 Min (nm) -9.14 Max (nm) -4.12 Mean (nm) -5.91 Median (nm) -5.81 3 Sigma (nm) 2.80
13 L. Pang, eBeam Initiative Reception at BACUS 2015
Mask CDU ≠ Wafer CDU: Wafer Metrology is Required
0 500
1000 1500 2000 2500 3000 3500 4000
-10 -9.6 -9.2 -8.8 -8.4 -8 -7.6 -7.2 -6.8 -6.4 -6 -5.6 -5.2 -4.8 -4.4 -4
EPE Histogram (Wafer)
0
5000
10000
15000
20000
-6 -5.6 -5.2 -4.8 -4.4 -4 -3.6 -3.2 -2.8 -2.4 -2 -1.6 -1.2 -0.8 -0.4 0
EPE Histogram (Mask)
14 L. Pang, eBeam Initiative Reception at BACUS 2015
Old World: Mask CD Only ILT World: Mask and Wafer
Mask CD Metrology
Mask Plane Metrology
Contour
EPE
Wafer Plane Metrology
CD
EPE
2D Metrology
Convert back to 1D Metrology
15 L. Pang, eBeam Initiative Reception at BACUS 2015
With GPU, the Simulation-based Wafer Plane Metrology is Real Time
16 L. Pang, eBeam Initiative Reception at BACUS 2015
2D 3D
Mask
Aerial image
0
500
1000
1500
2000
2500
3000
FRM3D GPU FDTD CPU GPU 3D mask sim >1000 times faster
Runtime (seconds)
With GPU, the Simulation-based Wafer Plane Metrology is Real Time
17 L. Pang, eBeam Initiative Reception at BACUS 2015
Future: Improve Mask and Wafer Quality
Mask plane & wafer plane
metrology
Mask writer GEC
Wafer dose map
• Shorten time to get wafer CDU map
• Attain SEM-level repeatable accuracy
• Improve mask writing
18 L. Pang, eBeam Initiative Reception at BACUS 2015
The New ILT World Calls for New CD Metrology: Mask and Wafer!
Mask Wafer
19 L. Pang, eBeam Initiative Reception at BACUS 2015
The New ILT World Calls for New CD Metrology: Mask and Wafer!
Wafer
CD, EPE, PV Band, Histogram
0
2000
4000
-10
-9.6
-9.2
-8.8
-8.4 -8
-7
.6 -7
.2 -6
.8 -6
.4 -6
-5.6
-5.2
-4.8
-4.4 -4
EPE Histogram (Wafer)
Mask
Contour, EPE, PV Band, Histogram
0
10000
20000
-6
-5.6
-5.2
-4.8
-4.4 -4
-3
.6 -3
.2 -2
.8 -2
.4 -2
-1.6
-1.2
-0.8
-0.4 0
EPE Histogram (Mask)
GPU = Real-time for mask + wafer
20 L. Pang, eBeam Initiative Reception at BACUS 2015
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