Development of Metal Free Wet Etching Chemical for ... - Linx …€¦ · © 2019 TOKYO OHKA KOGYO CO., LTD. 2 OUTLINE ©2019 Tokyo Ohka Kogyo Co., Ltd 1. Introduction 2. Design of

© 2019 TOKYO OHKA KOGYO CO., LTD.

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TOK (Tokyo Ohka Kogyo Co., Ltd.), Japan *Takuya Ohashi, Yukihisa Wada, Mai Sugawara, Tomoya Kumagai

IMEC, Belgium Quoc Toan Le, Els Kesters, Yusuke Oniki, Jens Rip, Frank Holsteyns

*[email protected]

Development of Metal Free Wet Etching Chemical

for Ruthenium Interconnect


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OUTLINE

©2019 Tokyo Ohka Kogyo Co., Ltd

1. Introduction

2. Design of Ru wet etch chemical

3. CVD-Ru Bulk properties

4. Summary


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OUTLINE


1. Introduction



4. Summary


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ALTERNATIVE METAL FOR INTERCONNECT

Ruthenium has been recently considered as a promising candidate to replace copper and cobalt as MOL and BEOL interconnect material.

[Marleen H. van der Veen et al, IITC2018, IMEC]

✔ Low resistivity in the scaled dimensions

✔ Better EM



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After M1 CMP M2V1 Etching M2 Fill

[Efrain Altamirano Sanchez, IITC2018 Short course, IMEC]

TARGET RUTHENIUM WET-ETCH APPLICATIONS


Ru recess for FULLY SELF-ALIGNED VIAS

Metal recess

Ru Bevel and Backside clean

Liner/Metal deposition BV/BS clean CMP


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

Cs Ba La Hf Ta W Re Os Ir Pt Au Hg TI Pb Bi Po At Rn

Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Cn Hn FI Mc Lv Ts Og

RUTHENIUM IN THE PERIODIC TABLE

The periodic table

La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Platinum-Group Metal


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CHEMICAL RESISTANCE OF RUTHENIUM

Commodity chemistry

CVD-Ru* E.R. @R.T.

HCl 0.0nm/min

H2SO4 0.0nm/min

HNO3 0.0nm/min

HF 0.0nm/min

H2O2 0.0nm/min

SC1 0.0nm/min

SC2 0.0nm/min

NH3 0.0nm/min

KOH 0.0nm/min

TMAH 0.0nm/min

CAN+HNO3** 1.1nm/min

NaOCl 5% 11.9nm/min

Pourbaix diagram of Ru-water system

* As depo CVD-Ru

** 50mM CAN (Ceric Ammonium Nitrate) + HNO3 1M

NaOCl

CAN

SC2 H2O2

SC1

Strong oxidizers (CAN, NaOCl, ...) can etch ruthenium.

Ru(s) + 4H2O ⇔ RuO4 + 8H+ + 8e- E0= 1.032V

[M. Pourbaix, Atlas of Electrochemical Equilibria in Aqueous Solutions p. 346, National Association of Corrosion Engineers, 1974-644]


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OUTLINE


1. Introduction


3. CVD-Ru Bulk CVD-Ru Bulk properties

4. Summary


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DESIGN OF RUTHENIUM WET ETCH CHEMICAL

Metal free solution

Metal impurities should be avoided for advanced semiconductor processing.

Currently, most of the strong oxidizers include metal elements. (CAN, NaOCl etc.)

Prevent ruthenium tetroxide (RuO4) generation

Volatile and toxic RuO4 should be avoided for EHS reasons.

High selectivity to low-k, SiOx, SiNx, TiN and TaN

Preservation of surface roughness to be targeted after controlled Ru recess

TOK Ruthenium Wet Etch chemical is targeting the following requirements.


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Chemical Metal Ru etching Low-k (2.55) SiN TiN TaN

NaOCl Yes Good - - - -

CAN Yes Good - - - -

Chemical A No Good <0.1nm/min <0.1nm/min <0.1nm/min <0.1nm/min

Chemical B No Good <0.1nm/min <0.1nm/min <0.1nm/min <0.1nm/min

Chemical C No Good <0.1nm/min <0.1nm/min <0.1nm/min <0.1nm/min

Metal free solution








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Metal free solution








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RUTHENIUM TETROXIDE

[H. Aoki et. al Extended Abstracts of the 2001 International Conference on Solid State Device and Materials. 2001]

Mechanism of RuO4 toxic gas generation

Ru(s) + *CAN(Ⅳ) ⇒ RuO4↑ + Ce(Ⅲ)↓

Ruthenium tetroxide is volatile and toxic.

Plastic coloration by RuO4 reaction

*CAN (Ceric Ammonium Nitrate)

Furthermore, RuO4 is a strong oxidizer.

RuO4 and OsO4 are used as staining agent for TEM observation of polymeric materials.

OsO4 : Oxidize unsaturated type polymer

RuO4 : Oxidize saturated and unsaturated type polymer

C C

H H

Os

O

O

O

O

C C

H H

Os

O

O

O

O

Staining reaction by OsO4

Staining reaction can be used to detect the generation of RuO4


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RUTHENIUM TETROXIDE GENERATION TEST

Bottle A : Reference

Bottle B : Ru wafer dipping (Bottle C : Ru Powder dipping)

CVD-Ru/40ml (2×2cm, 30nm)

or Ru powder 0.01g/10ml

2days

2days

Chemical

Plastic

RuO4 RuO4

RuO4 RuO4

RuO4 RuO4

RuO4

PLASTIC COLORATION BY RUTHENIUM TETROXIDE GAS

Check discoloration of the plastic on top of the bottle


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RESULT OF PLASTIC COLORATION TEST

Chemical Bottle A w/o Ru Bottle B w/Ru WF Bottle C w/Ru powder

NaOCl No change Change to black Change to black

CAN No change Change to black Change to black

Chemical A No change Change to black Change to black

Chemical B No change No change No change

Chemical C No change No change No change

w/Ru WF w/Ru powder

SEM-EDX of plastic C

O

Ru

NaOCl NaOCl

CAN CAN

Chemical A Chemical A

Chemical B Chemical B

Chemical C Chemical C

PLASTIC COLORATION BY RUTHENIUM TETROXIDE GAS

Chemical B and C can prevent RuO4 gas


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OUTLINE


1. Introduction



4. Summary


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CVD RUTHENIUM BULK PROPERTIES

IMPACT OF THERMAL BUDGET OF POST DEPOSITION ANNEAL IN N2/H2 (FGA)


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IMPACT ON ETCHING BEHAVIOR

By NaOCl 5% wet etching @R.T.

Passivation by surface oxide?

Etching rate decrease and delay for higher anneal temp.


(See SPCC2019 Q.T. Le for more detail)


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RUTHENIUM OXIDE GROWTH



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RUTHENIUM WET ETCHING BEHAVIOR NaOCl 5% @R.T. CAN50mM+HNO3 @R.T.

Chemical C @R.T. Chemical C @35°C

Chemical C @35°C can break through

the passivation layer in a short time


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Metal free solution








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SURFACE ROUGHNESS

CAN+HNO3 9.9nm etch

NaOCl 4.8nm etch

Chemical C 6.8nm etch

Chemical C@35°C 8.8nm etch

Reference

30nm CVD-Ru (FGA 420°C 20min)

No significant surface roughness change observed with Chemical C

AFM 5×5um2

0

0.5

1

1.5

2

2.5

Ref. NaOCl CAN+HNO3 Chemical C Chemical C

@35C

Su

rfa

ce

ro

ug

hn

ess

Rq

Ra

: Particle

: Pit corrosion


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OUTLINE


1. Introduction



4. Summary


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Summary

Chemical Metal RuO4 by product Ru etching Roughness Selectivity*

NaOCl Yes Yes Good Non uniform -

CAN Yes Yes Good Non uniform -

Chemical B No Undetected Good Good Good

Chemical C No Undetected Good Good Good

New chemical is developed for Ru BV/BS clean and controlled recess.

TOK Ru etching chemical targets the following requirements

a. Metal free process (no need for an additional clean step)

b. Eco and tool friendly process (no RuO4 by product)

c. Preservation of surface roughness after controlled Ru recess

d. High selectivity to dielectrics and barrier metals

*low-k, SiN, TiN and TaN


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Thank you for your kind attention.

Documents

Development of Metal Free Wet Etching Chemical for ... - Linx …€¦ · © 2019 TOKYO OHKA KOGYO CO., LTD. 2 OUTLINE ©2019 Tokyo Ohka Kogyo Co., Ltd 1. Introduction 2. Design of