sub-22 nm line and space patterning using resist reflow ... workshop/oral 47 resist-2 cho.pdf ·...

Sub-22 nm Line and Space Patterning using Resist Reflow Process

for Extreme Ultra-Violet Lithography

In Wook Cho*, Hyunsu Kim, Jee-Hye You, Hye-keun Oh

Department of Applied Physics, Hanyang University, S. Korea

2009 International Workshop On EUV Lithography (RESIST-2), Hawaii

2009. 7. 16

2009 International Workshop On EUV Lithography

Contents

Introduction

Simulation Results– Simulation Conditions– Simulation Window

• Monte-Carlo System• Resist Reflow Process

– Simulation Results

Summary


Introduction

http://www.itrs.net/Links/2007ITRS/2007_Chapters/2007_Lithography.pdf


Motivation

LER reduction by RRP.

Before RRP

LER ~ 6 nm LER ~ 2 nm

After RRP


Resist Reflow Process (RRP)

Resist Reflow Process(RRP) is a simple technique that the resist is bakedat above its glass transition temperature (Tg) after the development process.

Strength : No need for extra Chemicals/ Simple ProcessWeakness : High pitch dependency / Round top profiles after shrink

/ High resist dependency / High shrink rate (~ 5 nm/ )

After RRP


Resist Reflow Process Mechanism

Initial structure /arbitrary process condition

Boundary movement

Fluid flow

Surface tension

Viscosity TemperatureCurve fitting

Navier-Stokes eq.

Output

Temperature,contact angle

Bulk effect & adhesion effect

TemperatureDeveloped patternPitchTime

Input Parameters

CD after reflowResist top / side view

Output


Exposure• Aerial Image(from Solid-EUV)

• Dose

Post Exposure Bake• Time• Temperature

Development• Time• Model

Monte-Carlo System

Input Parameters

Post Exposure Bake

Development

Developed Resist ProfileOutput

Hyunsu Kim, et, al., “Line Width Roughness Investigation through Resist Molecular Structure in Extreme Ultra-violet Lithography” (Resist-3), EUVL 2009, Poster Session. “[email protected]”

More Details :

Exposure Process


Simulation Condition

1:3 (11 nm : 33 nm) Line & Space Aerial Image from Solid-EUV is intentionallymade to make 1:1 (22:22 nm) L/S.

Dose PEB time PEBtemperature Develop time RRP time RRP

temperature10.1 mJ/cm2 60 s 120 60 s 0 ~ 100 s 138 ~ 142


Simulation Condition (cont’d.)

Intentional 1:3 (11:33 nm) L/S after develop is made to make 1:1 (22:22 nm) L/S pattern after RRP.

PAG

ProtectedPolymer


Line Edge Roughness

Post Development Bake: T< Tg (PDB) vs. T>Tg (RRP)

After RRP, LER is reduced from 7 nm down to 2 nm, while after PDB, LER is reduced from 7.5 nm to ~ 5 nm only.

As temperature goes high and time passes by, LER decreases.

<After PDB> <After RRP>


Line Width Roughness

• When RRP is applied, the LWR is shrunken from 6 to ~ 2 nm.• At 142 , shrinkage decreases more rapidly than at 136 because Tg is 136 .• RRP can be used to reduce the surface roughness below 2 nm.

Post Development Bake: T< Tg (PDB) vs. T>Tg (RRP)

<After PDB> <After RRP>


Effect of RRP Temperature

• LER and LWR decreases as RRP temperature increases.• Around Tg, the decrement of LER and LWR after bake is smaller compared to highertemperature RRP.


LER and LWR decrease with RRP time.

1 2 3


Surface roughness reduction & CD increase

After RRP35 s,

142 ℃

Top View

Side View

Top View

Side View


CD increase with RRP time (142, 140, 138 ℃)

As RRP time goes by, resist flows more, and the resist linewidth increases.

1 2 3


Optimum RRP time with 142 ℃

CD ± 10 %


Summary

Resist Reflow Process is suggested to reduce LER and LWR without any additional chemical process in EUV lithography.

Using RRP, we could obtain smaller LER and LWR, ~2 nm.

As RRP time goes by and RRP temperature is higher, LER and LWR decrease, but the linewidth becomes wider.

We could obtain 1:1 22 nm L/S pattern with intentional 1:3 (11:33) L/S pattern and proper RRP condition.


Thank you for your attention!!

sub-22 nm line and space patterning using resist reflow ... workshop/oral 47 resist-2 cho.pdf ·...

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