Copper Electrodeposition on Diffusion

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209th ECS Meeting-Denver, CO May 07-12,
2006 J1-Electrochemical Processing in ULSI and
MEMS II Electrodeposition
Copper Electrodeposition on Diffusion Barrier
Films- A literature review by Batric Pesic
University of Idaho Department of Materials
Science and Engineering Moscow, ID 83844-3024
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ACKNOWLEDGMENT
This work was supported by Micron Technology
Foundation under grant MF134
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INTRODUCTION

• Barrier Materials
• Physical and Chemical Properties

• Electrochemical Deposition Methods
• Electroless
• - Soluble reducing agent
• - Insoluble reducing agent
• Electrodeposition
• - Direct plating on a barrier film
• - Direct plating on a seed layer

• Some chemistry

• My research plans
• - Techniques
• - Plating systems

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J.A. Cunningham, Solid State Technology, June 18,
2003
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Copper Diffusion Barrier Types According to J.A.
Cunningham, Solid State Technology June 18, 2003
Resistance to diffusion increases
Adhesion increases
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IDEAL DIFFUSION BARRIER REQUIREMENTS

1. Electronically conductive
2. Should not react with Cu, Si and dielectric
   materials
3. Should have an amorphous microstructure

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C.E. Ramberg et al., Microelectronics Engineering
50 (2000) 357-368
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C.E. Ramberg et al., Microelectronics Engineering
50 (2000) 357-368
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C.E. Ramberg et al., Microelectronics Engineering
50 (2000) 357-368
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C.E. Ramberg et al., Microelectronics Engineering
50 (2000) 357-368
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Si3N4 everywhere
No Si3N4
Stable and unstable Cu-Ti alloys
No Cu-Ta
C.E. Ramberg et al., Microelectronics Engineering
50 (2000) 357-368
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1. MATERIALS SELECTION ISSUE
The answer is almost clear Ta, Ta-N
2. MICROSTRUCTURE ISSUE
What is better to use, crystalline or amorphous
Ta-N?
The answer not consistent
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Amorphous TaNx film is more appropriate to use
than crystalline TaN according to
C.-C. Chang, J.S. Chen, and W.-S. Hsu, Failure
mechanism of amorphous and crystalline Ta-N films
in the Cu/Ta-N/Ta/SiO2 structure J.
Electrochemical Society, 151 (11) G746-G750
(2004).
No Cu reaction products When amorphous TaNx film
at interlayer
W.-F. Wu, K.-L. Ou, C.-P. Chou, C.-C. Wu Effects
of nitrogen plasma treatment on Ta Diffusion
barriers in copper metallization, J.
Electrochemical Society, 150 (2) G83-G89, (2003)
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Crystalline structure of TaN outperforms
amorphous TaN according to
G.S. Chen and S.C. Huang, Intrinsic properties
and barrier behaviors of thin Films of
sputter-deposited single-layered and
alternatively layered tantallum Nitrides
(Ta2N/TaN), J. Electrochem. Soc., 148(8) G424-429
(2001)
Ta2N
TaN
Si
Cu
Si
Cu
Si
Ta2N/TaN/Ta2N/TaN
Cu
Crystalline TaN no Cu at 800 oC
Alternate Ta2N/TaN Cu still present at 800 oC
Amorphous Ta2N no Cu at 700 oC
Reason for amorphous film deterioration
crystallization grain growth of a-Ta2N.
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Amorphous films develop low density columnar
boundaries as pathway for Cu diffusion?
Crystalline TaN is more efficient
S. Tsukimoto, M. Moriyama, M. Murakami, Microstruc
ture of amorphous tantalum nitride thin films,
Thin Solid Films 460 (2004) 222-226
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ELECTROMIGRATION
Two interesting points

• Electromigration and stress migration are caused
  by impurities (H, F, O)
• introduced during processing

T.C. Wang, J. Electrochem. Soc. 152(1) G45-G49
(2005)
2. Direction of current flow plays an important
role
Gan et al. Effect of current direction on the
lifetime of Different levels of Cu dual-damascene
metallization Appl. Phys. Letters, 79 (27) (2001)
4592-4594
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RESISTIVITY
Resistivity f(grain size) Grain size f(stress)
Low stress copper can be deposited only on low
stress substrate (seed layer)
TaN
TaN
Ta/TaN
Ta/TaN
TaSiN
TaSiN
Ta/TaN
TaSiN
Balakumar et al. Electrochemical and Solid-State
Letters 7(4) G68-71 (2004)
T. Hara and K. Namiki Electrochemical and
Solid State Letters, 7(5) C57-C60 (2004)
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ADHESION
Adhesion f(stress, orientation)
T. Hara et al. Electrochemical and Solid State
Letters, 7(2) G28-G30 (2004)
T. Hara and K. Sakata, Electrochemical and Solid
State Letters, 4(10) G77-G79 (2001)
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CHEMISTRY
Direct Electrodeposition

• Main purpose to form a Cu seed layer
• ? Fill by electrodeposition
• Catalyst required (Pd is the best)
• 2. Complete fill by electroless
• a) by solution reductant
• b) by contact displacement

• Preferred approach
• Not developed yet
• Main problem insulating oxide layer

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Direct Electrodeposition
Ta
A. Radisic, G. Oskam, P.C. Searson, J.
Electrochem Soc 151 (6) C369-C374 ((2004) S.B.
Emery, J.L. Hubbley, D. Roy, J. Elecroanal Chem
568 (2004) 121-133
TaN
S. Kim and D.J. Duquette, Electrochem and Solid
State Letters 9(2) C38-C40 (2006) Radisic, et al.
J. Electrochem Soc 150 (5) C362-367 (2003)
TiN
S. Kim and D.J. Duquette, J. Electrochem Soc
153(6) C417-C421 (2006) J.J. Kim, S.-K. Y.S.Kim
J. Electrochem Soc (151 (1) C97-C101 (2004) (Pd
only no Cu seed) L. Magagnin et al.
Microelectronic Engineering 76(2004) 131-136 L.
Graham, C. Steinbruchel, D.J. Duquette, J.
Electrochem Soc 149 (8) C390-C395 (2002) A.
Radisic, et al. J. Electrochem Soc 148 (1)
C41-C46 (2001) G. Oskam, P.M. Vereecken, P.C.
Searson, J. Electrochem Soc 146(4) 1436-1441
(1999)
W
C. Wang et al. Thin Solid Films 445 72-79
(2003) C. Wang et al. Electrochem and Solid-State
Lett 5(9) C82-C84 (2002
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Radisic, et al. J. Electrochem Soc 150 (5)
C362-367 (2003)
TaN
Pt
ROLE of OXIDE LAYER
CuSO4
A. Radisic, G. Oskam, P.C. Searson J. Electrochem
Soc 151 (6) C369-C374 ((2004)
HBF4
Ta
Citrate
EDTA
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S.B. Emery et al. J. Electroanalytical Chemistry
568 (2004) 121-133

• Two cross-over potentials
• Cross-over potential function of vertex
  potential
• No anodic current

Explanation for no anodic current oxide
species of Ta act to induce irreversible lattice
incorporation or alloying of the deposited Cu
CV of Cu2 on Ta in 0.1M NaNO30.6mM Cu(NO3)2
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H.K. Chang et al. Influence of Ti oxide films on
Cu nucleation during electrodeposition Materials
Science and Engineering A 409 (2005) 317-328
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Pipe tunneling along a dislocation core
mechanism for copper nucleation
H.K. Chang et al. Influence of Ti oxide films on
Cu nucleation during electrodeposition Materials
Science and Engineering A 409 (2005) 317-328
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IBM Research

• 1997 First working microprocessor using copper
  electroplating is fabricated
• 1998 P.C. Andricacos, C. Uzoh, J.O. Dukovic,
  J. Horkans, H. Deligianni
• Damascene copper electroplating
  for chip inteconnections
• IBM Research, Vol 42 No 5 (1998) p. 567
• - Introduced shape-induced concentration-field
  effects concept to describe
• additive distribution within
  micron size voids during electrodeposition
• - New terminology subconformal, conformal
  and superconformal
• (superfilling) modes of
  electrodeposition

• 2005 P.M. Vereecken, R.A. Binstead, H.
  Deligianni, P.C. Andriacacos
• The chemistry of additives in
  damascene plating, IBM J. Res.Dev.
• Vol. 49. No. 1 January 2005
• 2005 T.P. Moffat, D. Wheeler, M.D. Edelstein,
  D. Josell, Superconformal
• film growth Mechanism and
  quantification, IBM J. Res.Dev.
• Vol. 49. No. 1 January 2005

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SUPERCONFORMAL FILM GROWTH Mechanism and
quantification T.P. Moffat, W. Wheeler, M.D.
Edelstein, D. Josell, IBM J. Res. Dev. Vol. 49
No. 1 (2005)
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P.M. Vereecken, R.A. Binstead, H. Deligianni,
P.C. Andriacacos, The chemistry of additives in
damascene plating, IBM J. Res.Dev. Vol. 49. No.
1 January 2005
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Ic Cu(H2O)62 e Cu(H2O)4
IIa Cu0 6H2O Cu(H2O)62 2e
Ia Cu(H2O)4 2 H2O Cu(H2O)62 e
IIc Cu(H2O)62 2e Cu0 6H2O
Cu0 Cu(H2O)62 2Cu(H2O)4 2H2O
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OTHER APPROACHES
Electrodeposition must be in kinetic control
regime in order to ensure good quality copper.
In order to increase the convection, i.e. to
avoid diffusion control, various new interesting
studies are appearing

• Effect of gravitational strength M. Morisue et
  al. J. Electronal Chem 559 (2003) 155-163
• Centrifugal fields A. Eftekhari,
  Microelectronic Engineering 69 (2003) 17-25
• Magnetic fields M. Uhlemann et al. J
  Electrochem Soc 151 (9) C598-C603 (2004)
• M. Uhlemann et
  al. J Electrochem Soc 152 (12) C817-C826 (2005)
• Microwave effects U.K. Sur et al. New J.
  Chem., 28, 1544-1549 (2004)
  

For fundamental studies, addition of scanning
electrochemical microscopy can prove to become an
invaluable mechanistic tool.
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CONCLUSIONS

• Damascene copper plating is becoming a mature
  technology.
• Both, the technology development and the
  explanation of reaction mechanisms
• have already been provided by the IBM
  researchers.
• Additional research only confirms what has
  already been postulated, i.e. at most
• adds some marginal knowledge.
• More research (chemistry) is needed in the area
  of direct copper plating
• on diffusion barriers to avoid a processing
  step for formation of a seed layer.
• More research is needed toward development of
  more efficient barriers.
• Among the experimental techniques SECM can
  contribute substantially to
• understand the phenomena within vias and
  trenches.
• By comparing the published literature with the
  technology status of chip
• manufacturers there is a feeling that the
  industry is ahead of the curve and that
• the published research only confirms what the
  industry already knows.