Curvature Measurement of Ion Deposited ThinFilm

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Curvature Measurement of Ion Deposited Thin-Film

• Hoa Truong
• Saint Louis University
• Faculty Mentor
• Dr. Joseph J. Rencis
• Graduate Student Mentor
• Sachin Terdalkar

June 1st, 2007
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Outline

• Background
• Ion Deposition
• Objectives
• Molecular Dynamics
• Why Is the Curvature Important?
• Curvature Measurement

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Background

• Nano-scale control of thin-film contour is
  crucial in
• MEMS (Micro Electro Mechanical System)
  applications where gap between mating surfaces is
  at nanometer scale.
• Micro-mirrors where the surface needs to be
  perfectly planar.
• Micro-fabrication of these devices introduces
  residual strain, which curves the surface.
• Ion deposition presents an effective technique to
  planarize initially curved surface.

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Ion Deposition

• Chemically neutral ions are accelerated towards
  the surface (substrate) to form a thin-film.
• Modifies the atomic structures of the thin-film
  to planarize the surface.

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Objectives

• 1. Measure the curvature of the ion deposited
  thin-film.
• 2. Compute numerically the curvature of the ion
  deposited thin-film.

Deposited Atoms
Substrate Atoms
The curved thin-film due to ion deposition.
Note Deposited and Substrate Atoms are carbon.
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Molecular Dynamics (MD)

• Computer simulation to model the behavior of
  molecules.
• In MD simulation, carbon atoms are used to
  represent a cantilever beam where we fixed one
  end and free the other.
• Ions are bombarding randomly on the substrate
  atoms.
• Periodic Boundary Conditions (PBC)
• To simulate a small portion of MD simulation of
  molecules.

The MD simulation.
The PBC method. Kriz, R.D.,1995
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Why Is the Curvature Important?

• Because there is a relation between the stress
  and the curvature.
• The film stress times film thickness is directly
  related to the curvature of the thin-film

For low potential, the deposited ions cause
the substrates to bend upward.
For high potential, the deposited ions cause
substrates to bend downward.
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Curvature Measurement
Equations for Curvature

• Large Deflection

• Small Deflection

Numerically Computation

• To find the curvature of the thin-film by using
  any numerically technique.

Gere et al. (Mechanics of Materials 1990)
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Acknowledgments

• Dr. Joseph J. Rencis Professor Department
  Head
• for being a helpful mentor and for his excellent
  advices
• Sachin Terdalkar Ph.D Candidate
• for providing awesome images and great assistance

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Works Cited

• Elimelech, M., Particle deposition and
  aggregation measurement, modelling, and
  simulation. Oxford, England. 9781591242901
  (electronic bk.). 1998
• Gere, J. M. Timoshenko, S. P., Mechanics of
  Materials. Wadsworth, Inc., Boston,
  Massachusetts, 1990.
• Haile, J. M., Molecular Dynamics Simulation.
  Canada. Wiley Professional Paperback Edition,
  Toronto, Canada, 1997.
• Kriz, R.D. Understanding Molecular Models.
  August 5, 1995 (Last modified).
  lthttp//www.sv.vt.edu/class/surp/Yilma/MolecDyn/Mo
  lec.htmgt

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Thank You!

• Questions?

The MD simulation generated by the Fortran
language. Kriz, R.D., Understanding Molecular
Models,1995