Transcript Optical Digital Profilometry Test Patterns, Database, and

1
Optical Digital Profilometry Test
Patterns, Database, and Strategy
Wojtek Poppe, Ben Yu, Jing Xue, Marshal Miller, and Andy
Neureuther
University of California Berkeley
April
16th,
2007
FLCC
2
Collaborative FLCC Experiments
Original
Experiments
Optical Digital
Profilometry (ODP)
FLCC
FLCC
Experiments
Experiments
Designs from industry
April
16th,
2007
FLCC
3
Outline
• New set of masks from Toppan and experiments
at SVTC with the help of ASML
• Web accessible database for data aggregation
and analysis
• Optical Digital Profilometry
• New Defocus Test Structures
• Measuring Mask Edge Effects
• Illumination and 2-D Patterns
• Conclusion
April
16th,
2007
FLCC
4
New Company New Process
Cypress
65nm CMOS
Flow
April
16th,
2007
SVTC
Silicon Valley
Technology Center
FLCC
5
New Company New Process
Cypress
65nm CMOS
Flow
April
16th,
2007
SVTC
Silicon Valley
Technology Center
FLCC
6
New Company New Process
Cypress
65nm CMOS
Flow
SVTC
Silicon Valley
Technology Center
Developing new vanilla CMOS flow
• No Cypress customizations, so more representative
• More synergy and direct benefit for SVTC
translates to more wafers
FLCC
April 16th, 2007
7
Old Test Chip Layout
• Over 15,000 Electrical Test Structures
• Six students, six sets of conclusions, one chip
178 30-pad
cells
April
16th,
2007
Cypress Test
Structures
FLCC
8
Old Test Chip Layout
• Over 15,000 Electrical Test Structures
• Six students, six sets of conclusions, one chip
178 30-pad
cells
April
16th,
2007
Cypress Test
Structures
FLCC
9
New FLCC06.v2 Chip
ODP Etch
(Cadence)
Electrical Test
Structures (Magma)
New Overlay
Structures (ASML)
ODP litho (Yu
Ben)
• 21 extra 30-pad cell structures (199 total)
ODP Mask
Edge
(Marshal
Miller)
• 256 gratings for Optical Digital Profilometry (ODP)
• Two more students and three companies contributing
April
16th,
2007
FLCC
10
1mm x 1mm block
4 Layers Per Mask
9X
8 450um x 220um gratings
April
16th,
2007
FLCC
11
3mm x 2mm block
4 Layers Per Mask
Wojtek
Marshal
48 450um x 220um gratings
April
16th,
2007
Yu
FLCC
12
Space Available on Dark Field Mask
• Atten PSM + 90 degree phase etch
• Mosi or Chrome
• Glass can have extra 90 degree
etch
All four layers
available
Thirty-Two 1mm x 1mm
blocks
Four 2mm x 3mm blocks
April
16th,
2007
FLCC
13
Outline
• New set of experiments at SVTC and a new set
of masks
• Web accessible database for data aggregation
and analysis
• Optical Digital Profilometry
• New Defocus Test Structures
• Measuring Mask Edge Effects
• Illumination and 2-D Patterns
• Conclusion
April
16th,
2007
FLCC
14
Tons of Test Structures, Tons of
Data, One Chip
Looking at
• Systematic CD
variation
• LWR
• Defocus
• Enhanced Transistors
• Contact hole variation
(correlate with pattern
noise work)
• BSIM model fitting
• Oxide thickness and
channel doping
April
16th,
2007
• Poly corner rounding
• Active corner rounding
• Non-rectangular transistors
• Poly overlap
• Electrical Overlay Error
• SRAMs and Standard
Cells
• Poly Etch
• Poly CMP
• Mask edge effects
FLCC
15
Tons of Test Structures, Tons of
Data, One Chip
Looking at
• Systematic CD
variation
• LWR
• Defocus
• Poly corner rounding
• Active corner rounding
• Non-rectangular transistors
• Poly overlap
Data
Management
• ETEC-M validation
• Electrical Overlay Error
• Contact hole variation
Nightmare
• SRAMs and Standard
(correlate with pattern
noise work)
• BSIM model fitting
• Oxide thickness and
channel doping
April
16th,
2007
Cells
• Poly Etch
• Poly CMP
• Mask edge effects
FLCC
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Relational Database for Data Aggregation
• Over 15,000 transistors, 150 die per wafer, and dozens of wafers
• Slice and dice the data in any way
• Each data point will be associated with many different tables
• Comparing simulation and experiment results
• Finding Correlation
• Can find correlation between transistors with specific attributes such as
proximity or distance from center
• Looking at subsets of test structures
• Filtering out confounding effects (systematic CD variation)
• Platform for Collaboration
• Each designer can access and update the database online
• Outside people can log on as guests and explore different pattern dependent
phenomena
April
16th,
2007
FLCC
17
Data
Analysis
Reports
Testing
Strategy
Store All Possible Data
user
(1,n)
Pin Config
Characterized Wafer map
has
(1,1)
o,t
Store
Process
Conditions
guest
(1,n)
Process conditions
Test Strategy
has
generates
die
is_at
(1,1)
(1,1)
(1,1)
is_like
(1,n)
date
Probe Card
(1,n)
by
(1,n)
(1,n)
(1,n)
has
(0,n)
(1,1)
(1,n)
Modified
Dimensions
o,t
April
2007
has
Is
Characterized
by
(1,1)
CD_SEM_data
(1,n)
Is
Characterized
by
(1,1)
Electrical Data
(1,1)
(1,1)
from
(1,1)
from
using
(1,n)
Transistor Model
(1,n)
(1,n)
Transistor Attributes
Measurement Conditions (ex. Temp)
16th,
(1,n)
has
(1,n)
Optical Model
Tester
(1,1)
Other_values
Transistor_type
(1,n)
(1,1)
Electrical Dimensions
(1,1)
(1,n)
(1,n) Simulated Dimensions
from
(1,1)
Electrical Measurements using
Simulated Currents
from
E-beam
Machine
(1,1)
contains
location
(1,1)
Has
extra
(1,n)
(1,1)
has
Measured Dimensions
(1,1)
(1,n)
Cell
(1,1)
transistor
Non_idealities
from
contains
(1,1)
Created by
(0,n)
(1,1)
has
(1,1)
Is of
generates
(1,1)
(1,1)
Upload
process nonidealities
(1,1)
(1,n)
(1,n)
reports
contains
(1,n)
See next page
For non-transistor
types
(1,n)
designer
(1,n)
Transistor
Location
Cell_type
(1,n)
reads
Is
processed
at
(1,1)
(1,1)
(1,1)
(1,n)
(1,1)
Simulation results for
different process conditions
FLCC
18
Data
Analysis
Reports
Testing
Strategy
Store All Possible Data
user
(1,n)
Pin Config
Characterized Wafer map
has
(1,1)
o,t
Store
Process
Conditions
guest
(1,n)
Process conditions
Test Strategy
has
generates
die
(1,1)
(1,1)
(1,1)
transistor
(1,1)
is_like
(1,n)
date
Probe Card
(1,n)
by
(1,n)
has
(1,1)
(1,n)
Modified
Dimensions
o,t
April
2007
(1,n)
has
has
Is
Characterized
by
(1,1)
CD_SEM_data
Is
Characterized
by
(1,1)
Electrical Data
(1,1)
(1,n)
(1,n)
(1,n)
(0,n)
(1,1)
from
(1,1)
from
using
(1,n)
Transistor Model
(1,n)
(1,n)
Transistor Attributes
Measurement Conditions (ex. Temp)
16th,
(1,1)
Other_values
(1,n)
Optical Model
Tester
(1,1)
Transistor_type
(1,n)
(1,1)
Electrical Dimensions
(1,1)
(1,n)
(1,n) Simulated Dimensions
from
(1,1)
Electrical Measurements using
Simulated Currents
from
E-beam
Machine
contains
location
(1,1)
Has
extra
(1,n)
(1,1)
has
Measured Dimensions
(1,1)
(1,n)
Cell
What else should
I look at???
is_at
Non_idealities
from
contains
(1,1)
Created by
generates
(1,1)
(1,1)
has
(1,1)
Is of
(0,n)
(1,1)
Upload
process nonidealities
(1,1)
(1,n)
(1,n)
reports
contains
(1,n)
See next page
For non-transistor
types
(1,n)
designer
(1,n)
Transistor
Location
Cell_type
(1,n)
reads
Is
processed
at
(1,1)
(1,1)
(1,1)
(1,n)
(1,1)
Simulation results for
different process conditions
FLCC
19
Web Accessible and Centrally
Probe Station
Designers
Located
• Upload results for
others to see
Download test
scripts
Upload test results
• Update database
with calculated
process offsets
• Download data for
analysis.
• Access any data
through SQL queries
or pre-built filters
• Run some basic
statistical analysis
Server
April
16th,
2007
FLCC
20
ODP Data Management and Sharing
Process conditions
(1,n)
Is
processed
at
(1,1)
die
location
is_at
date
(1,1)
(1,1)
contains
(256,256)
(1,1)
grating
(1,1)
is_like
(1,1)
has
(1,1) CDSEM Dimensions (1,1)
(1,n)
from
(1,n)
E-beam
Machine
date
(1,1)
from
assumptions
April
2007
o,t
(1,1)
(1,n)
from
(1,n)
(1,n)
Ellipsometry Output
(1,n)
Measured by
date
16th,
Ellipsometer
ODP Dimensions
making
(1,n)
Grating_type
Tester
FLCC
21
Outline
• New set of experiments at SVTC and a new set
of masks
• Web accessible database for data aggregation
and analysis
• Optical Digital Profilometry
• New Defocus Test Structures
• Measuring Mask Edge Effects
• Illumination and 2-D Patterns
• Conclusion
April
16th,
2007
FLCC
22
Optical Digital Profilometry
SPECTROMETER
R, cos , Tan 
0.35
LIGHT SOURCE
0.3
0.25
0.2
0.15
0.1
0.05
0
Upper
CD
300 350 400 450 500 550 600 650 700 750
Film
Thickness
Lower
CD
wavelength (nm)
Pitch
100um
The goal of scatterometry is to measure the
geometry of fine lines nondestructively with light
April
16th,
2007
FLCC
23
Simulated vs. Measured Results
1.4
Reflectance
1.2
1
0.8
0.6
0.4
0.2
0
200
300
400
500
600
700
800
Wavelength (nm)
Goodness of Fit (GOF) – Indication of best match.
1 is best, 0 is worst. Typical iODP100 GOF > 0.995
Note: Red spectra is simulated and blue is measured
April
16th,
2007
FLCC
24
ODP Overview
1
3
2
1.
2.
3.
4.
April
4
(n,k) values can be determined on Sopra, or from standard table.
Spectra will be collected on Sopra. Data need to be interpreted in the form that can be read by
Timbre ODP TeraGen.
This is what we have from Timbre.
Only for volume production.
16th,
2007
FLCC
25
Step 1: Thin Film Data Collection
(Recommended)
April
16th,
2007
FLCC
26
Step 2: Collect and Import Data of Patterned
Wafer
April
16th,
2007
FLCC
27
Step 3: The Profile Model
April
16th,
2007
FLCC
28
Step 3: The Profile Model
Si3N4
SiO2
Si
April
16th,
2007
FLCC
29
Model Verification
Forward
Simulation
Rigorous Coupled Wave Analysis (RCWA)
1st
Incident
Light
0th
1st

tn
tn
for θ、λ
April
16th,
2007
FLCC
30
Forward
Simulation
Refelctance
Model Verification
Wavelength (nm)
Rigorous Coupled Wave Analysis (RCWA)
1st
Incident
Light
0th
1st

tn
tn
for θ、λ
April
16th,
2007
FLCC
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Model Verification
April
16th,
2007
FLCC
32
Step 4: Library Generation and Verification
• Based on the confirmed model (parameter)
• RCWA simulation generates the library
• The library is applied to the whole data set to verify its
validity
• Export the library to PAS system for in-line metrology
April
16th,
2007
FLCC
33
Outline
• New set of experiments at SVTC and a new set
of masks
• Web accessible database for data aggregation
and analysis
• Optical Digital Profilometry
• New Defocus Test Structures
• Measuring Mask Edge Effects
• Illumination and 2-D Patterns
• Conclusion
April
16th,
2007
FLCC
34
Resonant Even Aberration Testing Mask
0o
90o
0o
-90o
wn
d
0o
d
wb
wb
p
- Periodic testing pattern,
pitch  4d
- Probe width w provides reference 25% CF magnitude:
b
wb ( / NA) 
25%
 0.3
8.5
 90o
- Probe phase
coherent to even (defocus)0.aberration
6 / NA
- Pattern width equal to minimum feature size
- Distance d determines the sensitivity of this aberration and the
orthogonality to the other aberrations
April
16th,
2007
FLCC
35
Line Spread Function vs. Aberration
Spherical
Defocus
Coma
0.02314
0.01817
0.05831
Reference
0.01451
April
16th,
2007
FLCC
36
Resonant Even Aberration Testing
Line & point spread function
- Inverse Fourier transform of even aberration based on line
spread function
- Reciprocity of the electric-field spillover
April
16th,
2007
FLCC
37
Resonant Even Aberration Testing
Sensitivities of defocus and spherical target are at least 28
times larger than the Strehl ratio measurement of aberration
at 0.01 aberration
April
16th,
2007
FLCC
38
Defocus Monitoring + ODP Calibration?
posresist
negresist
April
16th,
2007
FLCC
39
Outline
• New set of experiments at SVTC and a new set
of masks
• Web accessible database for data aggregation
and analysis
• Optical Digital Profilometry
• New Defocus Test Structures
• Measuring Mask Edge Effects
• Illumination and 2-D Patterns
• Conclusion
April
16th,
2007
FLCC
40
Mask Edge Effects
• Phase Shifting Mask Opening
Cross-Talk
Real
CER
Imag
CEI
April
16th,
2007
– Use TEMPEST time-evolution
to visualize cross-talk as it
occurs among masks openings
– Introduced reduced parameter
edge and line source models
FLCC
41
Simple Mathematical Model for 2nd order Fourier
component
Ideal thin mask model
Edge effects approximated by rectangular
box with height unity and width w
w
x
x
w is assumed to be
small, so the function
is approximated as
constant
x
For 50% duty cycle
2
j x
P
 box  e
April 16th, 2007
0
 rect  e
j
2
x
P
 2w
This value are the quantities CER and CER for the
FLCC
real and imaginary correction components
42
Intuition
E Field
Mag(E)
actual
Mag(E)
ideal
Im(E)
Duty Cycle
f
Horizontal Shift: CER
Vertical Shift: CCEI
50%
Re(E)
Mag(E)
(ideal box)
(actual)
April
16th,
2007
FLCC
43
Simulation Results
Cutline taken far
from interface in
order to analyze
propagating modes
April
16th,
2007
FLCC
44
2nd order component of TE mode
Period
Magnitude
Minimum
Zero
50% Duty
Walls undercut
5 degrees
Expect 2nd
order to go to
zero
Vertical Walls
April
16th,
2007
FLCC
45
Simulation Values for CER and CEI
CER
Real
CEI 
Imag
April
CEI
16th,
2007
E min Period
2

CER  f
Period

FLCC
46
Experiment: FLCC March ‘07 Mask
• Gratings put on current FLCC mask to
explore simulation results
–
–
–
–
Alternating 0o and 180o phase shift regions
4 periods ranging from 3 to 12  (on mask)
Duty cycle ranging from 35-65%
24 different gratings in total
• Compare data from these gratings to the
TEMPEST simulations
April
16th,
2007
FLCC
47
Outline
• New set of experiments at SVTC and a new set
of masks
• Web accessible database for data aggregation
and analysis
• Optical Digital Profilometry
• New Defocus Test Structures
• Measuring Mask Edge Effects
• Illumination and 2-D Patterns
• Conclusion
April
16th,
2007
FLCC
48
ODP Illumination Test Patterns
Normal Incidence
Binary Mask Example
P = 1.7/NA
Center line not print
April
16th,
2007
Spillover Subtracts
FLCC
49
ODP Illumination Test Patterns
s = 0.59 dipole
Binary Mask Example
- 180
0
+ 180
P = 1.7/NA
Spillover Adds!
Center line prints!
April
16th,
2007
FLCC
50
ODP Illumination Test Patterns
s = 0.59 dipole
Binary Mask Example
- 180
0
+ 180
P = 1.7/NA
A richer set of combinations are allowed by
• Phase-shifted openings
• Using spillover from a sizeable 1RU+
programmed focus offset
example P = 1.2/NA => s = 0.83 dipole
April
16th,
2007
FLCC
51
ODP 2-D Test Patterns are Better
Binary Mask Example
r = 0.85/NA
s = 0.45/NA => 0.9 dipole
• More Flexible: spillover separation and
illumination phase can be adjusted somewhat
independently.
April
16th,
2007
FLCC
52
Optical Digital Profilometry Test
Patterns, Database, and Strategy:
Conclusion
• We have been able to respond quickly in generating a new
multi-student test mask for automatic measurement and
profile recognition with ODP.
• The clear field mask includes line patterns. Phase-shifting
patterns will be put on the dark-field mask that tapes out
soon.
• A database is also proposed for assembling and crossinterpreting ODP results.
• Monitoring concepts from pattern-and-probe test patterns and
electronic test patterns have been used to generate novel
ODP-based parameter specific monitors for focus,
illumination, and mask edges.
April
16th,
2007
FLCC