1The Institute of Scientific and Industrial Research, Osaka University

Nanoscale chemical reaction induced in chemically amplified resists upon exposure to extreme ultraviolet radiation

Takahiro Kozawa

Simulation

line & space

Aerial image of incident EUV

( ) ( )zFp

xCAzyxI απ−

⎪⎭

⎪⎬⎫

⎪⎩

⎪⎨⎧

+⎥⎦

⎤⎢⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛+= expcos1

21,,

2/1

Pattern

SFETK. Tawarayama et al. Jpn. J. Appl. Phys. 47 (2008) 4866.

FlareContrast

e-

e-

e-

e-

++++

EUV photon

Secondary electronsDeprotonation

Electron migration

Latent images were calculated on the basis of reaction mechanisms of chemically amplified EUV resists.

Chemical gradient was evaluated at half-depth.

2

*2*

xID

tI

∂∂

=∂∂

( )⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛−⎟⎟

⎠

⎞⎜⎜⎝

⎛+= 2

2/1

2

2/1

* expcos12

,,,p

Dtp

xCAtzyxI ππ

)2

(1 2/1*

*2/1* p

xI

IpNILS

∂∂

=

⎟⎟⎠

⎞⎜⎜⎝

⎛−=⎟

⎟⎠

⎞⎜⎜⎝

⎛−

∂∂

=2

2/1

22

22/1

22

2/1 2exp

2exp1

pNILS

pxI

Ip πσπσ

( ) ( )

( )nm

ECfdrrp

drrpdrrrp

EUVAGexcitationelectronAG

electronAGelectronAG14.3

30 )(

0 )(0 )(=

⎥⎦⎤

⎢⎣⎡ +

≈

∫∫∫

∞

∞∞

σ

Effect of secondary electron migration on acid image quality

▲ Without secondary electron migration● With secondary electron migration○ Replotted using NILS*

Photon migration approximation

Dt2=σ : electron diffusion length

Effect of secondary electron migration on chemical gradient

Fig. Relationship between NILS and chemical gradient in (a) high- and (b) low-Ea resists. Solid circles and triangles were calculated with and without considering the effect of secondary electron migration, respectively. The open circles represent the solid circles replotted using NILS*. The chemical gradient was normalized by the initial concentration of protected units. The exposure dose is 10 mJ cm-2.

Fig. Relationship between effective reaction radius and chemical gradient. Solid and broken lines were calculated with and without the preneutralization, respectively. In the graph, H and L denote the cases with and without the preneutralization. Numerical values next to H and L represent NILS*. HP represents half-pitch. H: Annealing type resist L: Non-annealing type resist

Fig. Relationship between NILS* and LER. Solid and broken lines were calculated with and without the preneutralization, respectively. In the graph, H and L denote the cases with and without the preneutralization. Numerical values next to H and L represent the effective reaction radius in nm. The half-pitch is 16 nm.

H: Annealing type resist L: Non-annealing type resist

Relationship between NILS* and LER

Dose-pitch matrix of line width (deviation from nominal line width) and LER

Hal

f-pi

tch

(nm

)

22232425262830323540455060

Exposure dose (mJ cm-2)

-15

15

Dev

iatio

n fr

om h

alf-

pitc

h (n

omin

al li

ne w

idth

) (nm

)

-5-10

0

105

Hal

f-pi

tch

(nm

)

22232425262830323540455060

Exposure dose (mJ cm-2)

0

15

LER

(nm

)

10

5

Lin

e w

idth

(Dev

iatio

n fr

om

nom

inal

line

wid

th)

LE

RSSR3 SSR4

Hal

f-pi

tch

(nm

)

22232425262830323540455060

Exposure dose (mJ cm-2)

Hal

f-pi

tch

(nm

)

22232425262830323540455060

Exposure dose (mJ cm-2)

Fitting range of dissolution point

Fig. Relationship between normalized protection ratio and dissolution rate of SSR3 and SSR4. Protection ratio was normalized by initial protection ratio.

The best-fit dissolution point was surveyed within the range of 0.4-0.6 (normalized protected unit concentration).

Hal

f-pi

tch

(nm

)22232425262830323540455060

Exposure dose (mJ cm-2)

-15

15

Dev

iatio

n fr

om h

alf-

pitc

h (n

omin

al li

ne w

idth

) (nm

)

-5-10

0

105

22232425262830323540455060

Exposure dose (mJ cm-2)

16.7

15.9

22232425262830323540455060

Exposure dose (mJ cm-2)

30

-30-20

-10

010

20

Erro

r (%

)

Hal

f-pi

tch

(nm

)

22232425262830323540455060

Exposure dose (mJ cm-2)

(a) Experimental (b) Simulation0

15

LER

(nm

)

10

5

22232425262830323540455060

Exposure dose (mJ cm-2)

11864

60

-60-40

-20

020

40

Erro

r (%

)

(c) Error distrubtion

22232425262830323540455060

Exposure dose (mJ cm-2)

Analysis of SSR3Line width(deviation)

LER

R: 0.1 nm

100.

..×

−sim

simmes

100.

..×

−sim

simmes

Analysis of SSR4 R: 0.05 nm

100.

..×

−sim

simmes

100.

..×

−sim

simmes

Summary

The enhancement of chemical gradient is essential to the reduction of LER without sacrificing resolution and LER.

The effective reaction radius for catalytic chain reaction is an important factor to determine the chemical gradient.

The effective reaction radius is smaller than the molecular radius. By increasing the effective reaction radius, LER can be still reduced.