CUBARRIER CMP PROTECTION FILM

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CU/BARRIER CMP PROTECTION FILM CHARECTERIZATION
USING ELECTROCHEMICAL TECHNIQUE
Sunny Xu, Shumin Wang Anji Microelectronics
(Shanghai) Corp., Ltd., Shanghai, 201203, China
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Introduction

• Protection film formation is one of the key steps
  to address some critical Cu/barrier CMP issues
  such as
• Material removal rate
• Planarity
• Dishing
• Corrosion, scratch, slurry residue and other
  surface related defects etc..

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Outline

• Electrochemical data can provide protection film
  formation information.
• These information not only related with Cu
  corrosion protection, but also related to some
  critical aspects of slurry CMP performance.
• Primarily correlation between electrochemical
  data and some aspect of slurry CMP performance
  were established.

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Cu Planarization Mechanism
Preferable removal of the protruding area
Protection film formation is one of the key steps
Well protection of the recessed area
Preferable removal of the protruding area
Well protection of the recessed area
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Cu/Barrier CMP Dishing Control Mechanism

• Abrasive particles
• Down force, pad, rotation speed, flow rate etc..
• For given CMP process, it is more or less fixed

• Slurry composition
• oxidizer, chelating agent, abrasive
  particles( particle surface chemistry etc..),
  inhibitors and other additives interaction with
  Cu surface in the CMP process

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Schematic Illustration for Cu/Barrier CMP with
Electrochemical Data
Polishing
Non Polishing
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Electrochemical Data for Cu Removal Rate Study
Cu removal rate can be correlated with
corrosion potential for both polishing and non
polishing condition
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Cu Removal Rate Correlation with Corrosion
Potential

• The higher the corrosion potential the lower the
  Cu removal rate
• Corrosion potential of a system should be
  optimized for proper removal rate and good
  dishing control.

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Open Circle Potential for Cu Formulation
Protection Film Study
Protection film forming speed calculation

• Corrosion potential increase indicating
  protection film formation.
• The very first a few second are extremely
  important to quantify a protection film forming.

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Correlation Dishing Performance with Protection
Speed

• CMP dishing performance is related with average
  protection film formation speed,
• Control the film formation speed is the key to
  control dishing

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Correlation Dishing Performance with Protection
Speed Cont.
CMP dishing performance is inverse proportional
to average protection film formation speed
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Electrochemical Data for Cu Planarity Study
Tafel Plot of with and without polishing
Cu planarity ?1- I/I0 (I without polishing, I0
with polishing)
For Cu slurry formulation D, I01.74E-05 A,
I2.04E-06 A, ? 88

• Cu slurry formulation D planarity is about 88

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Correlation Cu Planarity with Electrochemical
Data
Detected Cu planarity were well correlated with
electronically data
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Conclusions

• 1.Electrochemical data can not only provide the
  information for Cu corrosion protection, but also
  can be correlated with slurry CMP performance.
• 2.The protection film forming speed, film
  corrosion resistant and Cu planarity can be
  extrapolated from electrochemical data.
• 3.It was correlated with slurry CMP performance
  to achieve desirable material removal rate, good
  dishing control and high planarity.
• 4.Further study with protection film thermal
  stability are still under investigation.

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References

• 1 F. B. Kaufman, D. B. Thompson, R. E. Broadie,
  M. A. Jaso, W. L. Guthrie, D. J. Pearson and M.
  B. Small, J. Electrochem. Soc., 138, 3460 (1991)
• 2 Du T, tamboli D, Desai V, Seal S. J.
  Electrochem. Soc., 154, G231 (2004)
• 3 Yuzhuo Li, Microelectronic applicationa of
  chemnical mechanical planarization, 249 (2007)
• 4 V. Brusic, M. A. Frisch, B. N. Eldridge, F.
  P. Novak, F. B. Kaufman, B. M. Rush, and G. S.
  Frankel, J. Electrochem. Soc., 138, 2253 (1991)

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Acknowledgements
The authors gratefully acknowledge support for
this work from the colleagues of Anji
microelectronic Corporation.
Thank you !