Molecular Organometallic Resists for EUV (MORE)ieuvi.org/TWG/Resist/2013/100613/8_Molecular... · Molecular Organometallic Resists for EUV (MORE) October 6, 2013 I. Introduction II

EUV Symposium TWG, Toyama Japan

Molecular Organometallic Resists for EUV (MORE) October 6, 2013

I. Introduction

II. Organo-Tin Complexes

III. Ligand Studies: Oxalate Anions

IV. Summary

Brian Cardineau,1 James Passarelli,1 Miriam Sortland,1 Ryan Del Re,1 Westly Tear,1

Hashim Al-Mashat,2 Miles Marnell,2 Kara Heard,2 Amber Aslam,2 Jason Pavlich,2

Rachel Kaminski,2 Peter Nastasi,2 Chandra Sarma,3 Dan Freedman,2 Robert Brainard1

1. CNSE

2. SUNY New Paltz

3. Sematech

Presenter Wang Yueh, Intel

1

Financial Support by

Intel and Sematech


Recent Advances in Inorganic Photoresists

7-nm h/p lines

294 mJ/cm2

A B

Hafnium-Oxide Nanoparticles

Inpria

12-nm h/p lines

25 mJ/cm2

8-nm h/p lines

47 mJ/cm2

36-nm h/p lines

12 mJ/cm2

Cornell

Recently, some researchers have developed new EUV resists based on

inorganic compounds and nanoparticles with excellent performance.

HSQ

Ekinci et al., Proc. SPIE, 2013, 8679.

Trikeriotis et al., Proc. SPIE, 2012, 8322.

2


Molecular Organometallic Resists for EUV (MORE)

We have proposed a new EUV resists consisting of

molecular inorganic or organometallic compounds that

utilize metal centers with high EUV optical density.

Potential Benefits:

1. High EUV OD: Maximize the use of precious EUV photons.

2. High Mass Density: The mean-free path of secondary-electrons is shorter in

high mass-density materials. For resists this would result in a decrease in

electron blur.

3. No Acid Diffusion: No acid catalysis.

4. Excellent Etch Rates: Metal oxide films can have significantly better etch

performance than even the best organic films (HfO2 ~ 25x better).*

5. High Uncatalyzed Reactivity: Since metals have a large range of redox

potentials, resist chemistry can be engineered for high sensitivity without

acid catalysis.

3

* Trikeriotis et al., Proc. SPIE, 2012, 8322.


Optical Density of the Elements The MORE program is exploring the utility of compounds made from

the darkest elements in the periodic table.

4


Processing of MORE Compounds

5

Pure MORE compounds were spin-cast from organic solvents

• 1.5 to 3% Solids

• Solvents: Mixtures of MEK, THF, Hexane, CH2Cl2, Water, IPA.

• Most films had no other additives

• Soft bakes were generally not used.

• Film thicknesses were 30-50 nm.

EUV Exposures

• Berkeley exposures used the DCT and produced contrast curves.

• PSI exposures produced dense-line patterns. 18 nm was the smallest

feature on the masks.

Development

• Solvents were selected that just cleared the resists in 30-60 seconds.

• Developer Solvents: Mixtures of MEK, THF, Hexane, CH2Cl2, Water,

IPA.

Negative Tone

• Although some positive-tone behavior has been observed, everything

presented today is of negative-tone resists.


II. Organo-Tin Complexes

Tin is one of the darkest elements in the periodic table.

Tin is used as “fuel” in many EUV sources.

Kuhlman et al., 2005 US Patent 20050288176 .

A. Mononuclear Tin Complexes

B. Sn-12 Oxo Complexes

Cl-

Cl-

Preliminary Results

showed 20 mJ/cm2

Negative-Tone Sensitivity

6


A. Evaluation of Eleven Mononuclear Tin Complexes

7


B. Possible Mechanisms for Photoreactivity of

Sn-12 Oxo Clusters 1. Anionic Ligand Dissociation

2. Homolysis of Sn-C Bond

3. Sn-O Metathesis

8


Tin-12 Oxocluster Investigation

1) Anionic Ligand Dissociation

What effect does changing the anionic ligand have on resist performance?

9


Effect of Counter-Ion Structure on ESize

Bond Dissociation Energy (Kcal/mol)

Luo, Handbook of Bond Dissociation Energies in Organic Compounds, (2003).

* - Value calculated through H-R bond energy

10


BMET Results: Contrast Curves

Expected Decarboxylation Reactivity

The resist sensitivity seems to

be affected more by ligand bulk

and less by decarboxylation.

Therefore, anion decomposition

is probably NOT the

photochemical mechanism.

Em

ax

BMET

11


4.9 560 4.5 520 2.9 380 5.6 380 8.9 350

LER (nm) Dose (mJ/cm2)

9.4 560 6.2 520 7.7 380 8.1 380 13 350

3.9 500 3.6 480 3.8 350 5.5 350 14 320

3.9 560 3.6 520 3.8 380 5.5 760 14 700

7.3 560 9.0 520 7.6 380 9.0 380

3.0 560 2.5 520

Tin metal-oxide

films are capable of

resolving 18-35 nm,

but sensitivity is a

problem.

18 22 25 35 50 h/p CD (nm)

(PSI March 2013)

12


III. Ligand Studies: Oxalate Anions

1. Known, useful photochemistry:

2. Ease of synthesis for a wide variety of metals

and ancillary ligands. - We have synthesized over 30 new compounds, selected to give

systematic information on the EUV photochemistry of metal oxalate

compounds.

• Crosslinking through open

coordination sites.

• Metal is both reduced and

has lower coordination

number, changing solubility.

13


Central Metal

Through this work we have tested Cr, Fe, Co, Cu and Ni oxalate complexes.

In general:

• Cu and Ni form 4-coordinate complexes with poor solubility.

• Fe complexes are often very crystalline and difficult to get coatings of.

• The general reactivity is in the order of Cr ≤ Fe < Co.

Cr Co

Emax = 8 mJ/cm2 Emax = 35 mJ/cm2

BMET

14

NP1


Central Metal

Through this work we have tested Cr, Fe, Co, Cu and Ni oxalate complexes.

In general:

• Cu and Ni form 4-coordinate complexes with poor solubility.

• The general reactivity is in the order of Cr < Fe ≤ Co.

The metals are all in the +3 oxidation state.

15

NP1


Oxalate Loading

>1400 ~40 8 3 Emax(mJ/cm2):

Through this work we have also tested the effect of oxalate loading on resist

sensitivity. Increasing oxalate from 0 to 3 improves sensitivity by several

orders of magnitude (1400 to 3 mJ/cm2).

*

BMET

16

NP1


NP1 Imaging Studies

PSI

3.0 3.3 4.0 7.1LER (nm):

Resolution

h/p (nm): 35 25 22 18

MEK Develop / 15s

30 nm Thickness

Dose of 30 mJ/cm2

PAB = 90°/60s

PEB = None

(PSI March 2013) 17


18 22 25 35 50 h/p CD (nm):

A bake study was performed and a PAB of

90° for 60s with no PEB appears to perform

the best.

NP1 – Bake Study MEK Develop / 15s

43 nm Thickness

30 27 20 20 19

30 27 20 20 19

27 25 18 18 17

Dose (mJ/cm2)

4.3

4.9

4.1 3.7

5.7

3.5

PAB (None)

PEB (None)

PAB (90°/60s)

PEB (90°/60s)

PAB (90°/60s)

PEB (None)

LER (nm)

Imaging Conducted at PSI 18


IV. Summary

• Over a hundred compounds were tested for spin-coating and EUV

sensitivity during Year 1 under Intel.

• About half of the complexes have good coating and good air

stability.

• We have discovered 6-10 new MORE complexes with 18 nm

resolution.

• Most coatings showed some EUV sensitivity, although some were

quite slow (70-700 mJ/cm2).

• Oxalate has proven to be an excellent ligand and produces highly

sensitive non-chemically amplified resists.

• Our best resist (NP1) is capable of ~22 nm dense lines at ~20

mJ/cm2.

• In year 2 of MORE, under Sematech, we plan to continue to develop

the successful resists we have, while developing new platforms:

o Improve Current Platforms

o Explore New Platforms

19


Acknowledgements

Michaela Vockenhuber

Yasin Ekinci

And you for your time…

Staff at PSI: Financial Support:

Intel Corporation

Steve Putna

Wang Yueh

Sematech

Mark Neisser

Stefan Wurm

Patrick Naulleau

Brian Hoef

Lori Mae Baclea

Gideon Jones

Paul Denham

Staff at LBNL:

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Appendix

21


Expected Metal-Oxide Etch Rates

The etch rates for most metal oxides are unknown. However, due to the high

melting points / boiling points of the metal fluorides, we expect extremely

good etch rates.

SnF4 >700

BiF3 649

CoF3 927

CoF2 1217

FeF3 >1000

FeF2 970

CrF3 1100

CrF2 894

CF4 -184 -128

SiF4 -90 -86

Fluoride MP (ºC) BP (ºC)

Unlike the fluorides of

carbon and silicon which

volatilize during the etch,

MORE materials should

remain solid, dramatically

improving etch resistance.

Traditional

CAMP:

MORE

Resists:

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Molecular Organometallic Resists for EUV (MORE)ieuvi.org/TWG/Resist/2013/100613/8_Molecular... · Molecular Organometallic Resists for EUV (MORE) October 6, 2013 I. Introduction II