Evaluation of Modified GiR 2214

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.

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• 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


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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.)


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Black residues





to supplier

Resolution

Photospeed

Defectivity level




stability



review

Resolution

CD uniformity

Thermal stability


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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


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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


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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


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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]


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Side view on Nested structure at

145 msec exposure

Nested Space

-0.5 0 0.5

Focus Offset [µm]


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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


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• 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)


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• 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


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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


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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


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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


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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


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Black residues





to supplier

Resolution

Photospeed

Defectivity level




stability



review

Resolution

CD uniformity

Thermal stability


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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


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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


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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


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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


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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


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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.


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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


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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


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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

Evaluation of Modified GiR 2214

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