development of metal free wet etching chemical for ... - linx …€¦ · © 2019 tokyo ohka kogyo...
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© 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
Development of Metal Free Wet Etching Chemical
for Ruthenium Interconnect
© 2019 TOKYO OHKA KOGYO CO., LTD.
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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
© 2019 TOKYO OHKA KOGYO CO., LTD.
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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
© 2019 TOKYO OHKA KOGYO CO., LTD.
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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
©2019 Tokyo Ohka Kogyo Co., Ltd
© 2019 TOKYO OHKA KOGYO CO., LTD.
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After M1 CMP M2V1 Etching M2 Fill
[Efrain Altamirano Sanchez, IITC2018 Short course, IMEC]
TARGET RUTHENIUM WET-ETCH APPLICATIONS
©2019 Tokyo Ohka Kogyo Co., Ltd
Ru recess for FULLY SELF-ALIGNED VIAS
Metal recess
Ru Bevel and Backside clean
Liner/Metal deposition BV/BS clean CMP
© 2019 TOKYO OHKA KOGYO CO., LTD.
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©2019 Tokyo Ohka Kogyo Co., Ltd
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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©2019 Tokyo Ohka Kogyo Co., Ltd
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]
© 2019 TOKYO OHKA KOGYO CO., LTD.
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OUTLINE
©2019 Tokyo Ohka Kogyo Co., Ltd
1. Introduction
2. Design of Ru wet etch chemical
3. CVD-Ru Bulk CVD-Ru Bulk properties
4. Summary
© 2019 TOKYO OHKA KOGYO CO., LTD.
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©2019 Tokyo Ohka Kogyo Co., Ltd
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.
© 2019 TOKYO OHKA KOGYO CO., LTD.
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©2019 Tokyo Ohka Kogyo Co., Ltd
DESIGN OF RUTHENIUM WET ETCH CHEMICAL
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
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
© 2019 TOKYO OHKA KOGYO CO., LTD.
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©2019 Tokyo Ohka Kogyo Co., Ltd
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
© 2019 TOKYO OHKA KOGYO CO., LTD.
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©2019 Tokyo Ohka Kogyo Co., Ltd
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
© 2019 TOKYO OHKA KOGYO CO., LTD.
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©2019 Tokyo Ohka Kogyo Co., Ltd
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
© 2019 TOKYO OHKA KOGYO CO., LTD.
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©2019 Tokyo Ohka Kogyo Co., Ltd
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
© 2019 TOKYO OHKA KOGYO CO., LTD.
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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
© 2019 TOKYO OHKA KOGYO CO., LTD.
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CVD RUTHENIUM BULK PROPERTIES
IMPACT OF THERMAL BUDGET OF POST DEPOSITION ANNEAL IN N2/H2 (FGA)
© 2019 TOKYO OHKA KOGYO CO., LTD.
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©2019 Tokyo Ohka Kogyo Co., Ltd
IMPACT ON ETCHING BEHAVIOR
By NaOCl 5% wet etching @R.T.
Passivation by surface oxide?
Etching rate decrease and delay for higher anneal temp.
IMPACT OF THERMAL BUDGET OF POST DEPOSITION ANNEAL IN N2/H2 (FGA)
(See SPCC2019 Q.T. Le for more detail)
© 2019 TOKYO OHKA KOGYO CO., LTD.
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RUTHENIUM OXIDE GROWTH
IMPACT OF THERMAL BUDGET OF POST DEPOSITION ANNEAL IN N2/H2 (FGA)
© 2019 TOKYO OHKA KOGYO CO., LTD.
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©2019 Tokyo Ohka Kogyo Co., Ltd
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
© 2019 TOKYO OHKA KOGYO CO., LTD.
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©2019 Tokyo Ohka Kogyo Co., Ltd
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
© 2019 TOKYO OHKA KOGYO CO., LTD.
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©2019 Tokyo Ohka Kogyo Co., Ltd
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
© 2019 TOKYO OHKA KOGYO CO., LTD.
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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
© 2019 TOKYO OHKA KOGYO CO., LTD.
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©2019 Tokyo Ohka Kogyo Co., Ltd
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
© 2019 TOKYO OHKA KOGYO CO., LTD.
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Thank you for your kind attention.