Fabrication of Diamond Films for Microelectronic Applications

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Fabrication of Diamond Films for Microelectronic
Applications

• Patrice Allen Twanaze Mitchell
• ELEC 6750
• Introduction to Plasma Engineering
• Y. Tzeng

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OUTLINE

• Explain objective of research
• Describe CVD process for diamond fabrication
• List complications with this process
• Provide possible solutions/improvements
• Summary
• Questions??

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Questions

• What is CVD? Explain the process.
• Name two complications with this process and the
  discovered improvements.

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OBJECTIVE

• Properties of diamond
• Strongest known material
• Most chemically inert
• Excellent thermal shock resistance
• Extreme thermal conductivity

http//www.me.berkeley.edu/diamond/submissions/dia
m_review/review.htm
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OBJECTIVE

• Diamond vs. Other Materials

www.p1diamond.com/prop_ref.html
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OBJECTIVE

• Applications
• MEMS Technology
• Aerospace Applications
• Micromotors undergo extensive sliding and rolling
  contact
• MMAs (Moving Mechanical Assemblies)
• Tiny pumps, motors, and turbines spin at speeds
  as high as 400,000 RPM
• Silicon cannot withstand these conditions

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CVD Process

• Chemical Vapor Deposition
• General Process
• CHEMICAL VAPOR DEPOSITION (CVD)
• COMMON FEATURES
• GROWTH RATES

FIG 1. A Schematic diagram showing the principle
elements in the complex diamond CVD process
J.E. Butler and R.L. Woodin, Phil. Trans. R. Soc.
Lond. A, 342, 209 (1993).
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HOT FILAMENT REACTOR
FIG 2. http//www.tlchm.bris.ac.uk/pt/diamond/roly
thesis/chapter3.htm
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HOT FILAMENT REACTOR
FIG 3. http//www.tlchm.bris.ac.uk/pt/diamond/rol
ythesis/chapter3.htm
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PECVD TECHNIQUES

• Synthetic Diamond Emerging CVD Science and
  Technology, Edited by K.E. Spear and J.P.
  Dismukes (Wiley, 1994).

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MPECVD PROCESS
C.A. Rego, P.W. May, C.R. Henderson, M.N.R.
Ashfold, K.N. Rosser and    N.M.Everitt, in New
Diamond Science and Technology, MYU, Tokyo, p.485
(1994).
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MORPHOLOGY OF DIAMOND FILMS
FIG 4. Typical appearance of a microcrystalline
CVD diamond film grown on Si.
FIG 5. Cross-section through a 10 µm-thick
diamond film on Si, showing the columnar nature
of the growth up from the surface
FIG 6. Textured (100) diamond film, that is also
preferentially aligned.

• Synthetic Diamond Emerging CVD Science and
  Technology, Edited by K.E. Spear and J.P.
  Dismukes (Wiley, 1994).

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SUBTRATES

• REQUIREMENTS
• MELTING POINT
• Should be higher than the temp window (500-1400)C
• CAPABLE OF FORMING CARBIDE
• REACTIVITY OF CARBON
• Should have low reactivity with carbon

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Complications

• Temperature
• Lower temperatures are desired due to fewer
  choices of material at the conventional 800-900
  C.
• Substrates positioned close to hot filament are
  difficult to keep cool.
• When substrate is cooled below 400 C, etching of
  non-diamond phase becomes difficult.
• Atomic Hydrogen used to etch away other hydrogen
  atoms from carbon film becomes insufficient.

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Complications

• Microwave Power
• Increased microwave power applied to plasma
  increases growth rate
• BUT..
• Increased microwave power increases substrate
  temperature

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Improvements

• Temperature
• Fluorine was substituted for hydrogen in etching
  at low temperatures.
• Oxygen containing molecules such as CO, CO2, and
  CH3OH were incorporated as source gases to
  improve removal of non-diamond phase.
• Plasma generation under conditions of lower
  pressure than conventional microwave plasma
• Results a larger depostion area at a lower
  temperature

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Improvements

• Microwave Power
• Contiuous Waveform (CW) vs. Pulse-Modulate
  Waveform (PMW)

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Improvements

• Microwave Power
• Pulse-modulation of microwave power
• peak 5 kW
• 50 duty cycle
• Results overcome low growth rate at 2.5 kW and
  high temperature of substrate at 5 kW.

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Answers

• What is PECVD? Explain the process.
• Plasma Enhanced Chemical Vapor Deposition

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Answers

• Name two complications with this process.
• Temperature
• Microwave Power

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Questions ??