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© Hitachi High-Tech Corporation. 2020. All rights reserved.
Electron Beam Metrology for Advanced Patterning
IWAPS2020
Hitachi High-Tech Corporation
Metrology Systems Solution Development Dept.
11/5/2020
Masami Ikota
© Hitachi High-Tech Corporation. 2020. All rights reserved.
1. Device Trend and Requirement for Metrology Tools
2. High Precision Measurement by CD-SEM
2.1 Tool to Tool Matching
2.2 LCDU (Roughness) Measurement
3. New Metrology
3.1 Overlay Measurement with Buried Patterns by HV-SEM
3.2 3D NAND BCD Monitor with Auto Beam Tilt Function
3.3 EUV Issues and Solutions
4. Summary
Contents
1
© Hitachi High-Tech Corporation. 2020. All rights reserved.
1. Device Trend and Requirement for Metrology Tools
2. High Precision Measurement by CD-SEM
2.1 Tool to Tool Matching
2.2 LCDU (Roughness) Measurement
3. New Metrology
3.1 Overlay Measurement with Buried Patterns by HV-SEM
3.2 3D NAND BCD Monitor with Auto Beam Tilt Function
3.3 EUV Issues and Solutions
4. Summary
Contents
2
3© Hitachi High-Tech Corporation. 2020. All rights reserved.
1.1 Device Trend and Metrology Needs (Logic)
2020IRDS More Moore
* Edge Placement Error** Local CD Uniformity
σEPE*2 = σCD
2 + σOverlay2 + σLCDU**
2
For logic, 1D/2D pattern shrink and 3D technology proceed concurrently. For 1D/2D pattern shrink EPE is becoming critical. For further shrink, EUV light source is being implemented and overlay with buried patterns need to be monitored.
4© Hitachi High-Tech Corporation. 2020. All rights reserved.
1.2 Device Trend and Metrology Needs (Memory)
D. James, ”Nano-scale flash in the mid-decades ,” ASMC2007D. James, ”Recent advances in memory technology ,” ASMC2013A. Tilson, ”STEM/EDS metrology and statistical analysis of 3D NAND devices ,” IPFA2018
For NAND memory, 1D/2D pattern shrink is reaching its limit and structure is switching to 3D.New process issues related to high aspect ratio pattern are arising.
5© Hitachi High-Tech Corporation. 2020. All rights reserved.
1.3 Required EPE Based on IRDS
σEPE2 = σCD
2 + σOverlay2 + σLCDU
2
For Fin/LGAA patterns, sub-nanometer level of CD/LCDU control is required and its target is tighter than Overlay.
Based on 2020IRDS Metrology tables
6© Hitachi High-Tech Corporation. 2020. All rights reserved.
1.4 Required Precision for Metrology Tools
Generally, required metrology tool uncertainty is less than 20% of tolerance. For Fin/LGAA patterns, less than 0.15nm of precision is necessary for metrology tools.
σEPE2 = σCD
2 + σOverlay2 + σLCDU
2
Si latticeconstant~0.543 nm
Based on 2020IRDS Metrology tables
© Hitachi High-Tech Corporation. 2020. All rights reserved.
1. Device Trend and Requirement for Metrology Tools
2. High Precision Measurement by CD-SEM
2.1 Tool to Tool Matching
2.2 LCDU (Roughness) Measurement
3. New Metrology
3.1 Overlay Measurement with Buried Patterns by HV-SEM
3.2 3D NAND BCD Monitor with Auto Beam Tilt Function
3.3 EUV Issues and Solutions
4. Summary
Contents
7
8© Hitachi High-Tech Corporation. 2020. All rights reserved.
2.1.1 Metrology Budget Analysis
Process Metrology factors
CD uniformity (global & local) : ~0.10 nm
Repeatability <0.10 nm
Inter wafer
Intra wafer
Intra chip
Intra
pattern
σ(𝑃𝑟𝑜𝑐𝑒𝑠𝑠)2 + σ(𝑚𝑒𝑡𝑟𝑜𝑙𝑜𝑔𝑦)2
Process variation =
σ (𝑚𝑒𝑡𝑟𝑜𝑙𝑜𝑔𝑦) =
σ(𝑚𝑎𝑡. )2 +σ(𝑢𝑛𝑖. )2 +σ(𝑟𝑒𝑝. )2
Tool matching: 0.10 ~ 0.20nm
Tool matching tops metrology topic
Z. Wang, et al., “High-accuracy, high speed, and smart metrology in the EUV era,”Proc. of SPIE 11325, 113251Q-1 (2020)
9© Hitachi High-Tech Corporation. 2020. All rights reserved.
2.1.2 What is Atomic Tool Matching?
Z. Wang, et al., “High-accuracy, high speed, and smart metrology in the EUV era,”Proc. of SPIE 11325, 113251Q-1 (2020)
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
#1
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4#
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CG5000 CG6300
CD
ma
tchin
g (
nm
)Tool
CD
[n
m]
Daily Control chart
Device size5.00nm
Process tolerance0.50nm
Metrology budget≦0.05nm
Productivity (~100kWPM) for tool fleet consisting 10-100 prevalent CD-SEMs
Courtesy ofIMEC
100.11nm
100.09nm100.11nm
100.09nm
100.10nm
H atom radius ~0.053 nm
10© Hitachi High-Tech Corporation. 2020. All rights reserved.
2.1.3 Budget Analysis of CD-SEM Matching
Hardware variation
Optics,
Contamination, etc.
Signal processing and imaging
Sample geometry
Beam control
QC monitor errors
Measurement
repeatability, Sample
variation, etc.
Tool calibration errors
Column/Beam
alignment, Focus offset,
etc.
Environment effects
Electro-magnetic
noise, Mechanical
vibration, etc.
Z. Wang, et al., “High-accuracy, high speed, and smart metrology in the EUV era,”Proc. of SPIE 11325, 113251Q-1 (2020)
11© Hitachi High-Tech Corporation. 2020. All rights reserved.
2.1.4 Efforts for Matching Improvement
Hardware variation
Optics,
Contamination, etc.
Signal processing and imaging
Sample geometry
Beam control
QC monitor errors
Measurement
repeatability, Sample
variation, etc.
Tool calibration errors
Column/Beam
alignment, Focus offset,
etc.
Environment effects
Electro-magnetic
noise, Mechanical
vibration, etc.
H/W
uniformity
Precise column
manufacturing
Beam
Adjustment
Focus height
adj.
Noise Robustness
with shield
equipped
Detection / image
level matching Detector
AdjustmentImage level
tuning
Z. Wang, et al., “High-accuracy, high speed, and smart metrology in the EUV era,”Proc. of SPIE 11325, 113251Q-1 (2020)
12© Hitachi High-Tech Corporation. 2020. All rights reserved.
2.1.5 Evaluation Data of Atomic Tool Matching
Hitachi standard wafer, HR mode, 800 V and 8pA
Atomic level of tool matching can be achieved.
Before Shipping
After Installation
H atom radius ~0.053 nm
Z. Wang, et al., “High-accuracy, high speed, and smart metrology in the EUV era,”Proc. of SPIE 11325, 113251Q-1 (2020)
© Hitachi High-Tech Corporation. 2020. All rights reserved.
1. Device Trend and Requirement for Metrology Tools
2. High Precision Measurement by CD-SEM
2.1 Tool to Tool Matching
2.2 LCDU (Roughness) Measurement
3. New Metrology
3.1 Overlay Measurement with Buried Patterns by HV-SEM
3.2 3D NAND BCD Monitor with Auto Beam Tilt Function
3.3 EUV Issues and Solutions
4. Summary
Contents
13
14© Hitachi High-Tech Corporation. 2020. All rights reserved.
2.2.1 LCDU(Roughness) Measurement Issue
bia
s
bia
s
left right
Equalized bias still
remains in both sides.
LER
normal-direction
scanalternative directed
scan
left right
LER
bia
s
bia
s
bia
s
bia
s
tru
eL
ER
tru
eL
ER
tru
eL
ER
tru
eL
ER
① ②
① Due to asymmetric SEM-
signal, bias in right-LER
is larger than left-LER.
② By the alternative scan,
bias remains equally in
right- and left-LERs.
③ To remove the bias, we
calculate it individually
in right- and left- LERs.
left right
LER
tru
eL
ER
tru
eL
ER
H. Kawada, et al., “How to measure a-few-nanometer-small LER occurring inEUV processed features,” Proc. of SPIE 10585 (2018)
15© Hitachi High-Tech Corporation. 2020. All rights reserved.
2.2.2 Bias Removal by Random Noise Reduction (RNR)
Random noise contribution is large especially for resist patterns and it cannot be negligible. Even after RNR, roughness is far beyond the target and eats up EPE budget.Accurate roughness monitoring is important.
K. Takamasu, et al., “Line Width Roughness of Advanced Semiconductor Featuresby Using FIB and Planar-TEM as Reference Metrology,” Proc. of SPIE 10585 (2018)
16© Hitachi High-Tech Corporation. 2020. All rights reserved.
2.2.3 Accuracy Verification of Roughness with RNR
H. Kawada, et al., “How to measure a-few-nanometer-small LER occurring inEUV processed features,” Proc. of SPIE 10585 (2018)
Frequency (1/ nm)
No random-noise (bias)
in high-frequency band
( ~ 1nm) .
Accuracy of RNR function of CD-SEM was verified by Planar-TEM.The reference PSD of Planar-TEM has no random noise and has good agreement with PSD of CD-SEM after RNR.
Pow
er
Spectr
al D
ensity(n
m3)
Frequency (1/ nm)
© Hitachi High-Tech Corporation. 2020. All rights reserved.
1. Device Trend and Requirement for Metrology Tools
2. High Precision Measurement by CD-SEM
2.1 Tool to Tool Matching
2.2 LCDU (Roughness) Measurement
3. New Metrology
3.1 Overlay Measurement with Buried Patterns by HV-SEM
3.2 3D NAND BCD Monitor with Auto Beam Tilt Function
3.3 EUV Issues and Solutions
4. Summary
Contents
17
18© Hitachi High-Tech Corporation. 2020. All rights reserved.
Upper SE※1
Detector
Electron Source
Lower BSE※2
Detector
Objective Lens
Wafer
Top BSE※2
Detector
SE
BSE
BSE
High Vacc
※1 SE(Secondary Electron)※2 BSE(Back Scattering Electron)
3.1.1 Overlay Measurement by HV-SEM
K. Hasumi et al., “SEM based overlay measurement between Via patterns and buried M1 patterns using high voltage SEM,” Proc. of SPIE 10145, 101451J (2017)
BSE image(Under-Layer)
SE image(Upper-Layer)
SiO2_HM Trench
Resist Trench
++++++++
++++++++
++++++++
++++++++
++++++++
++++++++
++++++++
++++++++
++++++++
++++++++
x
x
x
x
x
x
x
x
x
x
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x
x
Overlay
M1B
M1A
M1B
M1A
M1B@ADI
SE is used to observe the surface while BSE is used to observe material contrast of the lower layer. Thus, overlay between upper and under layer can be measured.
19© Hitachi High-Tech Corporation. 2020. All rights reserved.
Vacc
5kV 10kV 15kV 20kV 25kV 30kV
SEM
image
SEUpper-Layer
M1B resist
SEM
image
BSEUnder-Layer
M1A Trench
Pitch 96nm, Upper/M1B_Resist 48nmTrench, Lower/M1A_HM 24nmTrench
0.9um
M1B@ADI
M1B
M1A
Accelerated Voltage 15kV was chosen based on image contrast.SEM OVL results at ADI show good correlation to Optical OVL.
K. Hasumi et al., “SEM based overlay measurement between Via patterns and buried M1 patterns using high voltage SEM,” Proc. of SPIE 10145, 101451J (2017)
y = 0.95x + 0.22 R² = 0.99y = 0.92x - 0.51 R² = 0.98
-10
-5
0
5
10
15
20
-10 -5 0 5 10 15 20
OVL_Y
OVL_X
SE
M_
OV
L a
t A
DI
Correlation SEM – μDBO
μDBO at ADI
3.1.2 Overlay by HV-SEM (M1B-M1A)
225nm
20© Hitachi High-Tech Corporation. 2020. All rights reserved.
Vacc
5kV 10kV 15kV 20kV 25kV 30kV
SEM
image
SEUpper-Layer
V0B resist
SEM
image
BSEUnder-Layer
V0A Hole
1.1um
Pitch 64nm, Upper/V0B_Resist 40nm Hole, Lower/V0A_HM 40nm Hole
V0B@ADI
V0B
V0A
y = 1.00x - 1.17 R² = 1.00
y = 0.98x - 0.79 R² = 0.99-20
-10
0
10
20
30
-20 -10 0 10 20 30
SE
M_
OV
L a
t AD
I
Yield Star at ADI
y
x
Correlation SEM – μDBO
μDBO at ADI
Accelerated Voltage 25kV was chosen based on image contrast.SEM OVL results at ADI show good correlation to Optical OVL.
K. Hasumi et al., “SEM based overlay measurement between Via patterns and buried M1 patterns using high voltage SEM,” Proc. of SPIE 10145, 101451J (2017)
3.1.3 Overlay by HV-SEM (V0B-V0A)
225nm
21© Hitachi High-Tech Corporation. 2020. All rights reserved.
Accelerated Voltage 30kV was chosen based on image contrast.SEM OVL results at ADI show good correlation to Optical OVL.
K. Hasumi et al., “SEM based overlay measurement between Via patterns and buried M1 patterns using high voltage SEM,” Proc. of SPIE 10145, 101451J (2017)
3.1.4 Overlay by HV-SEM (V0B-M1A)
Vacc
5kV 10kV 15kV 20kV 25kV 30kV
SEM
image
SEUpper-Layer
V0B resist
SEM
image
BSEUnder-Layer
M1A Trench
1.1um
V0B@ADI
V0B
M1A
370nm
y = 0.96x - 0.32 R² = 1.00
y = 1.02x + 1.14 R² = 0.97-30
-20
-10
0
10
20
30
40
-30 -20 -10 0 10 20 30 40
SE
M_
OV
L a
t AD
I
Yield Star at ADI
y
x
Correlation SEM – μDBO
μDBO at ADI
Pitch 96nm, Upper/V0B_Resist 40nm Hole, Lower/M1A_HM 24nm Trench
© Hitachi High-Tech Corporation. 2020. All rights reserved.
1. Device Trend and Requirement for Metrology Tools
2. High Precision Measurement by CD-SEM
2.1 Tool to Tool Matching
2.2 LCDU (Roughness) Measurement
3. New Metrology
3.1 Overlay Measurement with Buried Patterns by HV-SEM
3.2 3D NAND BCD Monitor with Auto Beam Tilt Function
3.3 EUV Issues and Solutions
4. Summary
Contents
22
23© Hitachi High-Tech Corporation. 2020. All rights reserved.
3.2.1 3D NAND Process Issues
L. Tu, et al., “3D-NAND wafer process monitoring using high voltage SEM with auto e-beam tilt technology,” Proc. of SPIE 11325, 113250L-1 (2020)
Bending
Top / Bottom CD
Under Etch
Bowing
Tilt structure (Slant hole)
3D NAND suffered from several process issues such as Under Etch Bending Bowing Top/Bottom CD difference Slant
Today’s topic
24© Hitachi High-Tech Corporation. 2020. All rights reserved.
3.2.2 Auto Electron Beam Tilt Function
Distance( The gravity center of Top – that of Bottom)
Bottom CD
[ Step-0 ]
Calculate the correlation between
beam tilt and overlay.
[ Step-1 ] Measure overlay with no tilt.
[ Step-2 ] Measure Bottom CD with beam tilt
matched with the hole (trench) slope.
L. Tu, et al., “3D-NAND wafer process monitoring using high voltage SEM with auto e-beam tilt technology,” Proc. of SPIE 11325, 113250L-1 (2020)
Auto beam tilt function is for accurate bottom CD measurement when hole slant exists.
25© Hitachi High-Tech Corporation. 2020. All rights reserved.
large
small
large
small
Top CD does not change
【After beam tilt】【Before beam tilt】
【Before beam tilt】 【After beam tilt】
large
small
large
small
Real BCD measurement are demonstrated
【Before beam tilt】 【After beam tilt】
For slant hole
Real BCD is available after beam tilt
Not real BCD Real BCD
Slant hole Slant hole
L. Tu, et al., “3D-NAND wafer process monitoring using high voltage SEM with auto e-beam tilt technology,” Proc. of SPIE 11325, 113250L-1 (2020)
3.2.3 BCD Monitor with Auto Electron Beam Tilt Function
After Beam tilt measurement, CDU of Top CD does not change while BCD becomes larger .This means Real Bottom CD can be measured.
© Hitachi High-Tech Corporation. 2020. All rights reserved.
1. Device Trend and Requirement for Metrology Tools
2. High Precision Measurement by CD-SEM
2.1 Tool to Tool Matching
2.2 LCDU (Roughness) Measurement
3. New Metrology
3.1 Overlay Measurement with Buried Patterns by HV-SEM
3.2 3D NAND BCD Monitor with Auto Beam Tilt Function
3.3 EUV Issues and Solutions
4. Summary
Contents
26
27© Hitachi High-Tech Corporation. 2020. All rights reserved.
3.3.1 EUV Lithography Challenges
Britt. Turkot, “Preparing for EUV Lithography in High Volume Manufacturing,”2017 International Workshop on EUV Lithography
It is necessary to monitor 1E12 vias!!
28© Hitachi High-Tech Corporation. 2020. All rights reserved.
3.3.2 EUV Lithography Challenges (Cont.)
J. Biafore, et al., “Statistical simulation of resist at EUV and ArF,” Proc. of SPIE7273, 727343 (2009)
Problematic variations—also known as stochastic effects --- by Mark Lapedus (Semiconductor Engineering)
29© Hitachi High-Tech Corporation. 2020. All rights reserved.
3.3.3 Mass Measurement System with AI-SEM
Novel SEM FOV 80um
Large FOV image
Imaging time:15sec @ 2nm/pixel
Electron Source
Corrector
・Aberration・Distortion
Correction lens <LFOV Uniformity>
・Resolution<0.2nm・Distortion<0.02%
Extremely uniform large FOV imaging by aberration/distortion correction technology
Schematic of Large FOV imaging issues Poor Signal /
Time consuming…
Charge-up
Conventional SEM: FOV 1um
Z. Wang, et al., “High-accuracy, high speed, and smart metrology in the EUV era,”Proc. of SPIE 11325, 113251Q-1 (2020)
30© Hitachi High-Tech Corporation. 2020. All rights reserved.
Area Inspection SEM results compatible to conventional SEM, with higher sensitivity and throughput , applicable to stochastic defect evaluation
Courtesy of Peter De Bisschop - imec
Z. Wang, et al., “High-accuracy, high speed, and smart metrology in the EUV era,”Proc. of SPIE 11325, 113251Q-1 (2020)
3.3.4 Mass Measurement System with AI-SEM
© Hitachi High-Tech Corporation. 2020. All rights reserved.
1. Device Trend and Requirement for Metrology Tools
2. High Precision Measurement by CD-SEM
2.1 Tool to Tool Matching
2.2 LCDU (Roughness) Measurement
3. New Metrology
3.1 Overlay Measurement with Buried Patterns by HV-SEM
3.2 3D NAND BCD Monitor with Auto Beam Tilt Function
3.3 EUV Issues and Solutions
4. Summary
Contents
31
32© Hitachi High-Tech Corporation. 2020. All rights reserved.
4. Summary
EPE is the critical parameter and it consists of 3 components, CD error,
overlay error and LCDU such as line edge roughness. For Fin/LGAA patterns,
less than 0.15nm of precision is necessary for metrology tools.
High precision measurement with atomic level of tool to tool matching can be
realized by HW/ Calibration/ Environment /QC monitor improvement.
Accurate LCDU can be measured by RNR function.
Overlay with buried patterns can be measured by HV-SEM and correlation
with optical overlay tool was verified.
Auto electron beam tilt function is effective for channel hole slant monitor for
3D NAND.
Stochastic defect monitor is critical for EUV process and mass measurement
with AI-SEM can be a solution.
© Hitachi High-Tech Corporation. 2020. All rights reserved.
Masami Ikota
11/5/2020
Hitachi High-Tech Corporation
Metrology Systems Solution Development Dept.
END
Electron Beam Metrology for Advanced Patterning
33