nanoimprint materials - sematech almaden research center 3 sematech litho forum 05/24/2006 © 2003...

IBM Almaden Research Center

05/24/2006 © 2003 IBM Corporation

NanoImprint Materials

March, 2006

Ratnam Sooriyakumaran

Hiroshi Ito

Mark Hart

Frances Houle

Geraud Dubois

Robert Miller

Robert Allen


© 2003 IBM Corporation2 Sematech Litho Forum 05/24/2006

Imprint in IBM

IBM Research Division is conducting an exploratory project on Materials for Imprint Lithography and Applications.

This is not part of IBM’s Semiconductor Lithography Roadmap.



NanoImprint Materials: Outline

Imprint: A Lithography System – process/materials/toolImprint Materials RequirementsCore Challenges in Imprint Materials with examples– Resists for high speed patterning– Low Dielectric Materials for Dual Damascene– Template Fabrication Materials

Summary and Conclusions



Litho Metrics Tool Impact Material Impact Template Impact Etcher Impact

Resolution HIGH LOW HIGH

HIGH

HIGH

Defects HIGH HIGH HIGH LOW

Throughput HIGH HIGH LOW LOW

LOW

CD control HIGH LOW LOW

Overlay HIGH LOW LOW

TOOLMATERIAL TEMPLATE ETCHER F

DEVELOP

Imprint: The System (thanks to Molecular Imprints!)OR DRY



It’s different this time….with few similarities

Squirt the juice– 1-5 cc of photoresist solution

per wafer

Bake (PAB)Introduce wafer into exposure toolScan/exposeExit wafer out of toolPEBDevelopEtch Transfer

Squirt the juice– onto wafer inside the tool– 1-5 microliters of photoactive

monomers per field

Fill the mold (quickly!)Expose– Material Cures (really quickly!)

Delaminate moldStep and repeatEtch Transfer

“Conventional” (193nm) Imprint



Step and Flash Imprint Taxonomy

Template

Substrate

Transfer Layer

Etch Barrier (Resist)

Adhesion Layer

Adhesion Layer

Release LayerResidual Layer

Patterned Layer

Charge DissipationLayer



Interface energetics and stability in UV-cure nanoimprintlithography: potential sources of defectivity

Resist adhesion to template despite release layer

polymer

Release layer

Cured resist

Failure of resist to wet surfaces

Cohesive failure of resist

Adhesion failure

template

silicon



Imprint Materials Requirements

Low Viscosity Required for high fill rates

Proper Surface Tension and compatibility with release coating

High speed cure (for low dwell times)

Low adhesive forces after cure (Clean Release)

Proper Mechanical Properties after cure?

Etch Resistance for pattern transfer– In resist (Si Resist)

– In planarization material (reverse tone process)



Core Challenges: Materials for NIL

Sacrificial (resist) layers

Image reversal materials

Permanent Materials (e.g., Dual Damascene ILD Material)

Template fabrication materials

Materials

fundamentalsHigh Performance Release (Low Defectivity)

Durability of release coating

Control/robustness of surfaces



Release Investigations

glass

cure conditions:365nm (unfiltered), 30s, 35mW/cm2

separate or delaminate in double cantilever beam mode for adhesion measurement

XPS, contact angle, AFM

XPS, contact angle, AFM

resist

silicon

Resists: acrylates, vinyl ethers and NID with varying chemical characteristicsRelease layers: fluorosilanes



Chemical degradation of release layer during cure: XPS of SiA resist and release surfaces shows fluorine loss and oxidation

No release: resist transfer to glass

Release: some C, F loss and O increase on glass, little F on resist

310 305 300 295 290 285 280 275

CF,O

(CF2)x

C,O

C-C,H

SiA resist, glass sideC region

release layer after cure

release layer (unused)

material on glass after cure, no release treatment

inte

nsity

, arb

uni

ts

binding energy (eV)310 305 300 295 290 285 280 275

C,F

C,O

C-C,H

resist cured in contactwith glass, no release

SiA resist, silicon sideC region

resist cured in contact withrelease layer

inte

nsity

, arb

. uni

ts

binding energy (eV)

Surface compositions Si/C F/C Si/O

Glass, no release 3.64 0

0

1.91

1.71

0.004

0.45

Resist, no release 0.07 0.21

Virgin release layer 0.65 0.6

Glass, release 0.99 0.39

Resist, release 0.12 0.36



Cure Chemistry Options for Imprint Resists

Higher Viscosity

Carefully balanced volatility

High Speed Cure

Simple formulations

Low Viscosity

High Speed Cure Possible– Although most are slow!

Complex Formulations

Free Radical (e.g., Acrylate) Cationic (e.g., Epoxy or Vinyl Ether)

OO

O

O

O



Cationically Curable Etch Barrier•Silanol condensation (slow, H2O elimination)•Ring-opening polymerization of Si-containing epoxides (slow especially with perfluoroalkanesulfonic acid, less shrinkage)•Addition polymerization of Si-containing vinyl ethers (fast, more shrinkage)

Viscosity (less viscous than acrylates)

VolatilitySi concentrationPAG solubility

OO

OO

O

OO

OO

SiO

O

O

SiSi

SiSi

1.0 cps at 25oC (UT Austin)poor solvent for PAGSi=16.3%

Si=35.2%

OCF3

0.75 cps at 25oC (UT Austin)volatile, poor solvent of PAG

good solvent for PAG

better release?

OSi

OCF2CF2CF2CF3

Si=21.6%

EGDVE

DEGDVE

TEGDVE

Si-VE

TMS3Si-VE

TMS-VE

TFEVENFHVE Central Glass

E. K. Kim et al., J. Vac. Sci. Technol., B22(1), 131(2004);B23(6), 2967(2005)



Epoxy vs. Vinyl Ether

OO

O O

OO

O O

S

S

SbF6

OSO2CF3

+

+

OO

O S

CH3

OSO2CF3+

OH+

Cure Time (7.4 mW/cm2

at 254 nm without filter)

40-45 sec

>>200 sec

<5 sec

4.9 wt%

4.9 wt%

2.9 wt%

0 1 2 3 4 5 6 7-2

-1

0

1

2

3

4

5

6

7

8

9

10

2766-89BEGDGE + TPSOTf5.0 min exp

2766-89AEGDGE + TPSSbF61.0 min exp

2766-85DDEGDVE + Ph2SPhCH3OTf+anthMeOH0.05 min exp

2797-13A, B, & C250-450 nm, 25 oC

Hea

t Flo

w (W

/g)

Time (min)

photo DSCEGDGE

DEGDVE

Cure Kinetics



AMRC Project on Low-k Dielectric Materials for NIL Grant Willson and team working with IBM Research – (Scope—ILD NIL Materials and Processes for back-end process

simplification)….can NIL be used for semiconductor processing?Almaden Team represented by Mark Hart—Assignee to AMRC/Nanoimprint—Lithography Experiments @ UTMark is backed up by chemists in 3 groups at Almaden– Low-k team (characterization and new materials designs)– Resist (litho materials) Team (Silicon Chemistry)– SDL (Formulation Scale-up)

Willson Group has NanoImprint experienceIBM supplying initial materials to UT with new designIBM supplying low-k know-how and characterization Exchange of personnel for future materials directions

IBM Research Assignee: Mark W. Hart

(External Programs (7/05–1/06), Lithography (1/06–7/06))



M. Neisser et. al, Solid State Technology’

August 2000, Pp.127-132

Up to 18 steps

Current Dual-Damascene Integration Scheme Template

POSS Deriva

Patterned Wa

Dispense

Press and Photocure

Release

High TempThermal cure

BreakthroughEtch

CMP

MetalDeposition

Our Proposed Integration Scheme Why NIL for Integration?



Photocurable Dielectric Material Requirements

Property/Characteristic

Low Viscosity

Photocurable

Cure Shrinkage

Dielectric Constant

Thermal Stability

Mechanical Properties

CTE

Water Sorption

Requirement

Less than 50 cPs

Fast Chain polymerization

Less than 15%

ε ≤ 3

Less than 1% wt loss/hr @ 400oC

Young’s Modulus ≥ 5 GPa

Less than 25 ppm/oC

Less than 0.5% wt



Nano Imprint Materials for Back End Process(Project Flow)

New Materials SynthesisFormulation Development

Early CharcterizationViscosity

Volatility

Cure kinetics (photoDSC)

Cured film propertiesMechanical and Electrical

Adhesion/Delamination/Interfacial

Printing w/

Imprio-55 and Suss b

P

Interface Crack

a

Adhesion energy

Volatility measurement using the TGS-2 microbalance



Our Material Design

R =

Polymerizable diluent to

adjust the viscosity

Photoinitiators

Polymerizable functional groups

Octo-POSS

(an 8-legged beast)

O

O SiO

O Si

Si

R

R

R R

R

R

O

O O

Si

Si

SiSi

Si

O

O

OO

O

R

R

O

O

O

O

+

+

High Temperature Cure after printing (burn out) (this removes most of acrylic for lower density (lower k)

IBM Process

http://images.google.com/imgres?imgurl=http://pbskids.org/lions/words/images/octopus.gif&imgrefurl=http://pbskids.org/lions/words/octopus.html&h=195&w=195&sz=5&tbnid=cwWz6ca6h_GCpM:&tbnh=98&tbnw=98&hl=en&start=1&prev=/images%3Fq%3Doctopus%26svnum%3D10%26hl%3Den%26lr%3D



Reactive Diluents for NIL Property Adjustment (methacrylates)

OOOO

CH3

OO

OO

MMAIBMA

CHMAEHMA4SiMA

OSi

Si OO

SiSi

O O

Our toolbox

(% silicon adjustor)

(High Tg, high viscosity)

(High Tg, Lower Viscosity)

(Low viscosity, high volatility)

(Low viscosity. Low Tg, Low Volatility)

POSS




NIL Material Data—printing on MI-55 @ UT

Reference Acrylate IBM ILD NIL material(1 cP) (25 cP)

50 nm l/s



NIL Material Data—printing on MI-55 @ UTBefore and After Cure

IBM ILD NIL material

(25 cP)(Shrinkage > 25% after 4000 C cure)

k < 2.9

IBM ILD NIL material

(25 cP)

k ~ 3.9



POSS based Low-k NanoImprinting Materials

Properties

Treatment t (nm) RI Density (g/cm3)

k (250 C)

E Modulus (GPa)

UV/ RT 1075 1.4901 1.348 4.33 6.29+-0.12

UV/RT

400oC / 1h

664 1.4811 1.268 3.05 5.97+-0.10



Summary

IBM engaged with UT (Willson Group) and Sematech on exploratory projecton materials for NanoImprint Litho for Back End Process SimplificationSeveral chemical approaches toward NIL ILD’s have been indentified.

We’ve created a class of materials with low viscosity and volatility, good printability and low k after curing/burning.– OctoPoss/monofunctional methacrylate formulationsSi/C ratio is easily modulated for etch property control

Several approaches for NIL back end processes beginning– Permanent (complex template, difficult materials)– Standard (sacrificial) (template easier, materials easier, etch difficult)

POSS




Template Materials (e-beam resists)

Desire positive and negative tone materials with the following characteristics for this 1X application– Resolution to support 22nm node

– Low LER

– Relatively fast writing speeds



nABLE-An Internally developed negative resist (e-beam) 200 nm pitch/200uC/cm2

Linewidth = 31 nmHeight = 119 nm



Conclusions and Recommendations

Template is Achilles Heel– Industry focus on mask technology should be leveraged

– Better Resists for mask/template making (resolution/speed/LER)

Imprint R&D should be enabled by Sematech for 22nm node– Tooling

– Materials Testing

nanoimprint materials - sematech almaden research center 3 sematech litho forum 05/24/2006 © 2003...

Documents