Optimizing Materials and Processes for Directed SelfAssembly Applications

(1)

Optimizing Materials and

Processes for Directed

Self-Assembly Applications

Phil Hustad, Jeff Weinhold,

Rahul Sharma, Valeriy Ginzburg,

Erin Vogel, Dan Murray, Vivian Chuang,

Shih-Wei Chang, Peter Trefonas

The Dow Chemical Company

(2)

Chemoepitaxy with HCP Cylinders

Ruiz, Nealey et al.

Science

2008

,

321, 936

O O Pattern rectification Density multiplication “oxidized PS” PS brush

Prepattern with e-beam

O₂plasma etch

Spin coatPS-PMMA

(3)

Registered Spheres from Sparse Posts

Ross

et al.

(4)

Many Sparse Pattern Layouts Possible

<1 0> 0° <1 1> ±30° <2 0> 0° <2 1> ±19° <2 2> ±30° <3 0> 0° <3 1> ±14° <3 2> ±23°

<1 1>

<3 3> ±30°

i

= 1

j

= 1

(5)

(6)

Free Energy of Templated Systems

Ross proposed the BCP will compress or stretch to be commensurate with

nearest lattice

           4 3 4 2 1 6 2 / ₂ 2 L M b Mb L L Mb kT F AB chain 

(7)

Post Graphoepitaxy vs Chemoepitaxy

Favorable:

Cylinder-Spot

Matrix-Space

Unfavorable:

Cylinder-Space

Matrix-Spot

Matrix:

PS (or P(S-r-MMA)

Spots:

oxidized PS

(8)

What About Incommensurate Systems?

<2 2>

L

₀

= 26 nm

Twist 30°

30°

<3 0>

L

₀

= 30 nm

L

₀

= 28 nm

What happens when the BCP is not perfectly

commensurate with the pattern?

(9)

(10)

(11)

(12)

(13)

Surface Area Overlap Model

)

)(

(

2

1

2

cos

2

cos

2 2 2 1 2 2 2 2 1 2

R

r

d

R

r

d

R

r

d

R

r

d

dR

r

R

d

R

dr

R

r

d

r

A













































  For (R – r) < d < (R + r) For d < (R – r)





2

)

,

min(

)

(

d

R

r

A





R r d

(14)

Examples of Commensurability

0°

Pattern: 20 nm spot size BCP: 20 nm cylinder

80 nm pitch 40 nm pitch

(15)

Examples of Commensurability

<2 0> <2 1>

0° 19.1°

(16)

Estimating Grain Size from Overlap

L₀ = 40 nm

(17)

Estimating Grain Size from Overlap

L₀ = 40 nm

L₀ = 39.6 nm

80 nm pitch 39.6 nm pitch

(18)

Estimating Grain Size from Overlap

L₀ = 40 nm

L₀ = 39 nm

L₀ = 39.6 nm

(19)

Experimental Validation

L_pattern = 74 nm <2 0> sparse pattern 2.0* L₀ L_pattern = 72 nm 1.95* L₀ L₀ = 37 nm

(20)

Subtle Effects Are Even Identified

0

o

24

o

36

o

24

o

36

o

36

o

36

o

24

o

0

o

0

o 0.50 0.75 1.00 1.25 1.50 N o rm a li z e d A re a

Pattern: 20 nm spot size 71 nm pitch BCP: 20 nm cylinder 37 nm pitch

0

o

24°

36°

0°

(21)

E-beam vs 193i for Patterning

Pattern: 20 nm spot size, 80 nm pitch BCP: 20 nm cylinder, 40 nm pitch

Small spot sizes and pitch

are possible with e-beam …

O₂ plasma etch

Spin coat PS-PMMA

(22)

E-beam vs 193i for Patterning

Pattern: 20 nm spot size, 40 nm pitch (every other row)

BCP: 20 nm cylinder, 40 nm pitch

Small spot sizes and pitch

are possible with e-beam …

O₂ plasma etch

(23)

E-beam vs 193i for Patterning

Pattern: 20 nm spot size, 80 nm pitch BCP: 20 nm cylinder, 40 nm pitch

… but with 193i lithography, it will be

difficult to make spots smaller than

~40 nm (or closer together than 80 nm)

Prepattern with 193i lithography

O₂ plasma etch

(24)

Effect of Spot Size

Spot CD = 20 nm

(25)

Spot CD = 20 nm

Spot CD = 30 nm

Effect of Spot Size

(26)

Effect of Spot Size

Spot CD = 20 nm

Spot CD = 30 nm Spot CD = 40 nm

(27)

More Complete Model Being Developed

R r d

Model being adapted to account for BCP stretching/compression,

and more details will be shared at SPIE.





















4

3

4

2

1

6

2

/

₂ 2

L

M

b

Mb

L

Mb

kT

F

_chain



AB ) )( )( )( ( 2 1 2 cos 2 cos 2 2 2 1 2 2 2 2 1 2 _d _r _R _d _r _R _d _r _R _d _r _R dR r R d R dr R r d r A _                             For(R–r) <d< (R+r) For d<(R–r)  2 ) , min( ) (d R r A 

+

(28)

Difficult to Integrate with 193i Patterning

PS brush Prepattern with e-beam

Spin coatPS-PMMA

anneal

PS brush Prepattern with 193i lithography

Spin coatPS-PMMA

(29)

Contact Shrink Demonstrated by IBM

J. Cheng, SPIE 2010

Cheng et al. ACS Nano 4, 4815 (2010)

We use modeling to also understand these systems

and optimize conditions to give lowest CDU

(30)

Shrink Determined by Wall Interactions



Cylinder phase is attracted to the wall

−

Morphology from minimization of free energy



Matrix phase is attracted to the wall

−

Morphology is determined by geometry (when no homopolymer is used)

Final hole size is ~¼

the original hole size

For cylindrical BCP, the

PMMA

f

X

D



~.25 X X nm X nm

(31)

Modeling Guides BCP Selection

PMMA-like walls PS-like walls

Hole CD

40



Self Consistent Field Theory (SCFT) can guide when



N

< 30

60

80

100

D X nm ~.25 X X nm PS PMMA Hole

(32)

Modeling Guides BCP Selection



Strong Segregation Theory (SST) used for higher



N

5

10

15

20

25

30

20

40

60

80

100

PM

M

A

Cy

lin

de

rC

D

(n

m

)

Hole CD (nm)

PMMA

Walls

PS

Walls

1.04

1.08

1.12

1.16

1.20

1.24

45

55

65

75

85

95

Fr

ee

En

er

gy

pe

rc

ha

in

/k

T

Hole CD (nm)

Free energy as

function of hole size

(33)

DSA Can Give Very Uniform Holes

Holes too small

Holes too big

Some unopened holes

Very uniform final size!

Large CD variation

DSA

Etch

50-60 nm

ARC

Si

ARC

Si

<20 nm

ARC

Si

(34)

Summary and Conclusions

At Dow, we are using our modeling capability to improve our

understanding of DSA systems and guide selection of materials

and process toward optimal results

A surface area overlap model was developed to help us understand

the factors controlling grain size and defects in chemoepitaxy

systems

Simulations indicates that both incommensurability will cause the

system to break up into multiple grains, while increasing size of

directing spots results in loss of orientation

We are refining this model to account for stretching/compression

and will report on this more complete model at SPIE

We are also applying SCFT and SST modeling to graphoepitaxy

contact shrink scenarios, and have used this understanding to

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Thank You!

Jeff Weinhold (surface model), Valeriy Ginzburg (SCFT)

Erin Vogel, Dan Murray