Superconformal Film Growth

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Superconformal Film Growth
T.P. Moffat, D. Wheeler, C. H. Lee, D.
Josell Materials Science and Engineering
Laboratory
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Superconformal electrodeposition
Objective Void and seam-free filling of
recessed surface features with metals and alloys
for passive 3-D conductors or active magnetic
elements. Advantages Build interconnected or
isolated 3D structures that are easily integrated
with existing platforms associated with CMOS,
MEMS, etc New avenue for device manufacture the
possibility of novel architectures otherwise
unavailable with existing processes

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Superconformal or Bottom-up Filling of
Submicron Features

• As a function of TIME

• As a function of ASPECT RATIO

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????? How does superconformal film growth occur
?????
?? How general is the phenomenon ??
1. Curvature Enhanced Accelerator Coverage Model

• Quantitatively Explains Superfilling of
  Submicrometer Features

• Electrodeposition of Copper, Silver and Gold

• Chemical Vapor Deposition of Copper

• Quantitative Model of Brightening

2. Transient Inhibition Breakdown Model

• Explains Superfilling of Nickel and related
  Ni-Co-Fe alloys

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The Important Role of Surface Chemistry
Competitive and co-adsorption of specific
surfactants can lead to strong acceleration or
inhibition of the metal deposition rate.
No copper deposition on Au-S-(CH2)3-CH3
Catalyzed copper deposition on Au-S-(CH2)3-SO3-
10 mm
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Curvature Enhanced Accelerator Coverage Mechanism

• Dilute catalyst floats on the surface during
  metal deposition.
• Local catalyst coverage increases as local area
  decreases.
• Converse also true.
• Local metal deposition rate increases with
  catalyst coverage.

CEAC is most important when changes in adsorbate
coverage due to area change dominates adsorption
or consumption processes!!
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Superfilling Trenches with Copper
CEAC Simulation and Experiment
70 s
50 s
40 s
35 s
30 s
Copper deposition in an electrolyte containing
6 uM SPS 88 uM PEG 1mM NaCl
25 s
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Ag has a higher conductivity than Cu
Ag Superfilling from a KSeCN-KAg(CN)2-KCN
Electrolyte
Deposition Time
AR
Derivitization Time 10 s (fixed amount of
adsorbed catalyst)
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Au is the metallization of choice in GaAs
technology
Pb catalyzed Au superfilling from a
KAu(CN)2-KCN-KOH
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3-D metallization for ULSI and MEMS

• NIST offers measurements and metrology for
  understanding and optimizing superconformal
  electrodeposition of Cu, Ag and Au for use as
  conductors.

ITRS
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What about active magnetic materials?

• Applications of ferromagnetic materials (Ni, Co,
  Fe)
• - Magnetic recording heads and recording media
• - Magnetic sensors, actuators, motors for MEMS
  devices
• - Memory devices (MRAM, race track memories) and
  bio-medical systems
• However conventional fabrication of magnetic
  structures uses a inherently 2-D process that is
  difficult to combine with CMOS LIGA process for
  building 3-D structures.
• NIST has developed a deposition process that
  allows void-free filling of recessed features
  with nickel and related iron group alloys that
  can be easily integrated with existing Damascene
  processes and related tool sets.

Electrodeposition
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Superfilling of Ferromagnetic Materials
- Easy to realize various 3-D magnetic
structures - Suitable for integration with
existing CMOS fabrication processes

• Damascene process for ferromagnetic structures

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Collaboration Opportunities

• NIST has developed a wide range of measurements
  and modeling capabilities for exploring and
  optimizing superfilling processes.
• Intellectual Property
• Superconformal Electrodeposition of Ni-Fe-Co
  Magnetic Alloys
• Provisional Patent Application filed 1/25/2008
• Serial 61/023,593
• Superconformal Metal Deposition Using
  Derivatized Substrates
• Provisional Patent Application filed 5/23/2003
• Serial 10/444,060

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• For further information please contact
• Thomas P. Moffat
• Materials Science and Engineering Laboratory
• National Institute of Standards and Technology
• Bldg 224, B166
• Mail Stop 8551
• Gaithersburg, Md 20899
• thomas.moffat_at_nist.gov