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Micron Confidential
9/11/2010
Evaluation of Modified GiR 2214 Photoresist for Low Defectivity I-line Process
Boris Kaziev
Micron Technology Inc., FAB12, Israel
FUJIFILM Advanced Lithography
Workshop 2010
©2010 Micron Technology, Inc. All rights reserved. Products are warranted only to meet Micron’s production data sheet specifications. Information, products, and/or specifications are subject to change without notice. All information is provided on an “AS IS” basis without warranties of any kind. Dates are estimates only. Drawings are not to scale. Micron and the Micron logo are trademarks of Micron Technology, Inc. All other trademarks are the property of their respective owners.
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
2
• Defectivity study and evaluation
Defectivity evaluation at FFEM
Black residues
Unpatterned defectivity
Patterned defectivity reduction work
GiR 2214 Resist Evaluation Methodology
• Initial conditions definition
to supplier
Resolution
Photospeed
Defectivity level
• Lithographic performance
evaluation on new resist
Thickness uniformity and
stability
Swing curve evaluation
Focus and expose latitude
review
Resolution
CD uniformity
Thermal stability
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
3
Initial Conditions Definition to Supplier
• Resist performance request
Iline low viscosity resist, FT ~1.2µm
Low defectivity (primary target)
Resolution: CD space ≤400nm on 420S:940L printed as 560S:800L (DF)
Fast performance photoresist
• Evaluation process conditions
Substrate: 200mm Si, HMDS primed
Litho Track: SVG-90S
Resist: 1.18µm GiR 2214
Soft Bake: 90ºC/90sec (prox.)
Exposure: Nikon B12 Stepper
Mask: Dark field
Illumination: 0.5 NA, σ=0.68 (ID1)
PEB: 115ºC/90sec (prox.)
Develop: 2.38% TMAH, single nozzle Stream, Single puddle 58ml/60sec
Hard Bake: 100ºC/60sec (prox.)
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
4
• Defectivity study and evaluation
Defectivity evaluation at FFEM
Black residues
Unpatterned defectivity
Patterned defectivity reduction work
GiR 2214 Resist Evaluation Methodology
• Initial conditions definition
to supplier
Resolution
Photospeed
Defectivity level
• Lithographic performance
evaluation on new resist
Thickness uniformity and
stability
Swing curve evaluation
Focus and expose latitude
review
Resolution
CD uniformity
Thermal stability
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
5
Lithographic Performance Evaluation on New Resist:Thickness uniformity and stability
• Desired:
Good coverage with 1.5ml resist dispense using Micron coat recipe
• Findings:
Complete coverage down to 0.5ml
Good and desired resist profile down to 1.1ml
Good process window for thickness stability
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
6
Lithographic Performance Evaluation on New Resist:Swing Curve Evaluation
• Conditions:
Swing Curve tested
on Thermal Oxide
substrate
CD sampling: 7
points across the
wafer (radial)
• Findings:
Good linear behavior
of THK vs. RPM
around the desired
working point
Swing minimum
position revealed at
11800A
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
7
Lithographic Performance Evaluation on New Resist:Focus Latitude of 1.0µm Trench
• Expose conditions:
Substrate: Thermal oxide
Focus: 0µm
DOF [µm]: -1 +1
Exposure: 145 msec
Pitch [µm]: 1L:1S
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
8
Lithographic Performance Evaluation on New Resist:
Focus Latitude of 1.0µm Trench
CDSEM images at 145 msec exposure
Isolated Space
Nested Space
-1 -0.5 0 0.5 1
Focus Offset [µm]
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
9
Lithographic Performance Evaluation on New Resist:Focus Latitude of 1.0µm Trench
Side view on Nested structure at
145 msec exposure
Nested Space
-0.5 0 0.5
Focus Offset [µm]
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
10
Lithographic Performance Evaluation on New Resist:Exposure Latitude at 1.0µm Trench
• Findings:
Almost no Iso. to Nes.
Variation in CD
Good linear fit around
the desired CD
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
11
Lithographic Performance Evaluation on New Resist:Focus Latitude of 0.56µm Trench
• Findings:
~1.5µm DOF process
window around
~550nm nested
space
Minimum resolution
revealed around
400nm
• Expose conditions:
Substrate: Oxide
Focus: 0µm
Mask: Dark field
DOF [µm]: -0.75 +1
Exposure: 185 msec
Pitch [µm]: 1360nm
(1S:1.5L)
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
12
Lithographic Performance Evaluation on New Resist:Focus Latitude of 0.56µm Trench
• Findings:
High DOF of ~1.5µm at ~550nm trench CD
F=-0.75µm; CD=510nm
F=1.0µm; CD=no
F=0.75µm; CD=481nm
F=0.5µm; CD=516nm
F=0.25µm; CD=535nm
F=0µm; CD=545nm
F=-0.25µm; CD=543nm
F=-0.5µm; CD=539nm
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
13
Lithographic Performance Evaluation on New Resist:Minimum Resolution at Focus=0µm
• Under dose margin: 190ms - 155ms = 35ms (~19%)
230msec
644nm
140msec
No
215msec
615nm
200msec
594nm
185msec
545nm
170msec
482nm
155msec
409nm
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
14
Lithographic Performance Evaluation on New Resist:Critical Dimensions Uniformity
• CD variation test groups:
GiR 2214
Ref. resist (Resist A)
• Test methodology:
5 wafers per group measured; 5 sites per wafer
• CD findings for GiR 2214:
Better CD uniformity
WIW variation is lower by factor of 3
Very low CD range vs. Resist A
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
15
Lithographic Performance Evaluation on New Resist:Thermal Stability
• Variation in Hard Bake temperature
FT – 1.2µm on Bare Si
Hard bake – 60sec (prox.)
• Findings:
Stable Pattern remains up to 120ºC
GiR 2214 exhibits strong profile degradation at 140ºC
No Bake 100ºC 120ºC 140ºC
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
16
Lithographic Performance Evaluation on New Resist:Evaluation Summary
• Good and desired lithographic performance
reviewed, without any process modifications
• Stable thickness performance and uniform resist
profile
• High focus and exposure latitude
• Minimum resolution of 400nm trench
• Highly uniform CD across the wafer
• Stable resist profile up to 120ºC
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
17
• Defectivity study and evaluation
Defectivity evaluation at FFEM
Black residues
Unpatterned defectivity
Patterned defectivity reduction work
GiR 2214 Resist Evaluation Methodology
• Initial conditions definition
to supplier
Resolution
Photospeed
Defectivity level
• Lithographic performance
evaluation on new resist
Thickness uniformity and
stability
Swing curve evaluation
Focus and expose latitude
review
Resolution
CD uniformity
Thermal stability
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
18
Defectivity Study and Evaluation:
Defectivity Evaluation at FFEM
• SP1 and KLA evaluation performed at FFEM/Japan
• FFEM investigated modifications to filtration processes, resist processing
and resist component (Novolak, PAC etc.) choice in order to achieve the
“cleanest” sample to meet Micron’s defectivity targets
Formulation
Designation
SP1
(Part/8” wafer)
Avg of 2 wafers
KLA Pattern
Blob/ Residue D0
(Defect/cm2)
Avg of 2 wafers
Comments
1 Alternative 1 88 1.14• SP1 well within Micron target range
• KLA is too high for Micron Target
2 Alternative 2 1905 0.51• SP1 is high
• KLA is still high
3 GiR 2214 11 0.06
• Exhibits very low defectivity both for SP1 and KLA
4 Alternative 3 366 1.78
• SP1 is higher than Micron UCL
• KLA is high
• Similar to previous KLA results at Micron
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
19
Defectivity Study and Evaluation:
Black residues
• Location: edge of resist wall
• Defects calculation: invisible
• Risk: unclear
• Profile review:
Small undercut at the bottom of the resist
Tiny resist residues at this area
• Purposed solution: Developer puddle time reduction
• Solution limitation: lithography process window and photospeed impact
Initial State
Lower Puddle Time; higher NA
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
20
Defectivity Study and Evaluation:
SP1 after Coat Defectivity
• Findings:
Initial state - low defect
count for GiR 2214
Filter B implementation
by Micron - additional
significant defect level
reduction
• 2 types of filter tested at Micron for new sample:
Filter A – Nylon-based filter
Filter B – DUO-based filter
• SP1 monitor sensitivity is up to 90nm
• The results shown are average of 2 wafers each
group
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
21
Defectivity Study and Evaluation:
Patterned Defectivity Reduction Work• Patterned defectivity tested using KLA instrument,
on Bare Si wafers
• Initial Evaluation Process Conditions:
Mask – Bright Field; Pitch=2µm (1:1)
Resist dispense – 1mL/sec; 1.5mL
PEB - 110ºC/90sec (prox.)
Develop - Single puddle 40sec
• Initial findings revealed 3 types of defects:
1. “Cone shape” like defects – small amount
2. Particles – high amount
3. Resist residues, especially in dense areas
Particles
Cone shape
Residues
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
22
Defectivity Study and Evaluation:
Patterned Defectivity Reduction Work
• Initial state: resist defectivity
level is very high
• Process modification efforts
performed at Micron for
defectivity reduction
Patterned Defectivity Initial Results
0
0.5
1
1.5
2
2.5
3
3.5
4
GiR 2214 Initial state Resist A (ref.)
De
fec
t D
en
sit
y
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
23
Defectivity Study and Evaluation:
Patterned Defectivity Reduction Work
• Each result consist of 2 individual tests
Combination of • Higher Develop puddle time;
• Higher PEB temperature; •Filter type;
•Dispense rate (DR) and dispense spin speed (DSS) decreaseallow significant defectivity reduction.
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
24
Defectivity Study and Evaluation:
Evaluation Summary
• GiR 2214 well meets Micron defectivity requirements
• Micron process optimization results:
Cone shape defects eliminated
Significant reduction of particles
Significant reduction of residues
• Process optimization contributors:
Lower dispense rate -> micro bubbles reduction
New filter -> particles amount decrease in the resist
Longer develop time -> residues reduction by effective resist
dissolving
Higher PEB temp. -> residues/particles easier washed off during
the develop process
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
25
GiR 2214 Micron Evaluation Summary
• Litho:
GiR 2214 resist exhibits high focus latitude performance
Minimum resolution request is achieved
Good CD uniformity across the wafer
The resist answers fast performance requirement
• Defectivity:
After process modification at Micron GiR 2214 resist met specified
requirements for low defectivity resist, both for Patterned and
Unpatterned evaluations
Black residues risk is defined as minor, but still is unclear
• Overall GiR 2214 sample meets Micron targets; further integrated
evaluations will be performed
©2010 Micron Technology, Inc.
9/11/2010
Micron Confidential
26
Acknowledgments
• Mario Reybrouck - FFEM
• Diti Enidjer - Micron
• Klug Zohar - Micron
• Etay Rosenkrantz - Micron
• Hadad Itzhak - Micron
• Sofer Nirit - Micron
• Thomas Sarubbi - FFEM
• John Ferri - FFEM
• Norihiko Taguchi - FFEM
Thank you for your attention