Diamond as a future semiconductor material

1
Need of new semiconductor material

• Diamond as a future semiconductor material
• By-Aditya D. Dekhane

2
Need of new semiconductor material
Moores law The driving force for innovations!!!

• High operating temperatures
• High power applications
• Better electrical and electronic properties

3
Why Diamond?
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Diamond
Same valency as Silicon i.e.4

• Very strong SP3 C-C bonds
• Inert for chemical attack!!!

Ref Lecture notes Solid State Physics,
http//www.lcst-cn.org/Solid20State20Physics/Ch1
8.html
5
Doping of diamond

• Needs to be doped for-
• Better electrical properties
• To be used in diodes, transistors
• P-type doping
• Boron (B)
• Sometimes natural diamonds are already p doped
• Boron is the best acceptor for diamond
• Energy band gap 0.2-0.3 eV
• Boron enters as a substitutional impurity

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Doping of diamond continued

• 2. N-type doping

• Nitrogen
• Most successful
• Energy gap 1.7 eV
• Insulators at room temperature due to deep energy
  gap

• Phosphorus
• Shallow energy level dopant
• Energy band gap 0.5 eV
• Electron mobility raised by 100 cm2/V
• Sometimes interfere with electrical properties

• Sulfur
• Energy level 0.37 eV
• Electron mobility raised by 600 cm2/V
• Still under development

• Lithium
• As an interstitial impurity
• Still under development

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Doping techniques

• 1. Chemical Vapor Deposition (CVD)
• Impurity atoms incorporated in diamond during the
  growth of diamond films.
• Vapors containing impurity elements
• APCVD, LPCVD, PECVD!!!!

Impurity Impurity source Solvent gas Impurity/Carbon atom ratio (ppm) Temp. (C) Pressure (Torr) Reference
Boron B2O3 Ethanol 10000 800 100 1
Nitrogen N2 CH4 50000 800 100 1
Phosphorous PH3 CH4 1000-20000 950 80 2
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Doping techniques continued

• 2. Ion implantation
• High energy dose of ions bombarded, breaks
  existing bonds and creates new
• CIRA (Cold Implantation Rapid Annealing) and
• RTI (Room Temperature Implantation)

Dopant Process name Dose (cm-2) Energy (KeV) Annealing temperature (C) Annealing time (min) Reference
Nitrogen CIRA 1013 40-640 1400 10 3
Phosphorus CIRA 1016 84-165 1200 - 4
Boron CIRA 1016 30-60 600 - 4
Lithium RTI 1016 40-50 900 60 5
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Successful applications
1. Dual substrates by SP3 technologies Inc.

• 2. Diamond semicondutor by Nippon Telegraph and
  Tele. Corp., Japan
• Formed a semiconductor with 81 GHz frequency,
  aiming at 300GHz with 30 W/mm power for practical
  usage.

• 3. MEMS technology using Ultra Nanocrystalline
  Diamond (UNCD)
• Diamond materials Inc. developed UNCD doped 3
  with nitrogen
• Manufacturing with CVD method and reactive ion
  etching technique for etching diamond

Ref 6, 7, 8
10
Interview with company
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Interview with company continued...

• Company representative Ms. Nga Vu (Application
  Process Engineer)
• Company- SP3 diamond technologies, Santa Clara,
  CA 95054
• Contact no.- 1-877-773-9940 Ext. 209
• Email- nvu_at_sp3inc.com

• Details of telephonic and email conversation
• Diamond wafers are manufactured on a substrate
  Si, SiO2, W, WC, graphite
• The diamond is deposited on substrates by CVD
  method at 600-900C
• Coefficient of thermal expansion (CTE) mismatch
• Wafers successfully manufactured are of 4, 6,
  8 and 12 sizes.
• Boron as p-type dopant.
• Nitrogen as n-type dopant.
• Sheet resistance method is used to predict the
  percentage of boron
• More the amount of boron more risk of
  interference with diamond properties.
• Facility can manufacture micro as well as nano
  grained diamond wafers.

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Summary

• Diamond has the best property combination
  (Electrical, Mechanical) to be a future
  semiconductor material.
• Research work is necessary to develop n-type
  doping methods
• Reviewed information in paper is verified with
  industry person and is under practical use.
• Manufacturing techniques need to be developed
  which are still costly for industrial scale
  production.

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References

• Yoshiyuki Show, et al., Structural changes in CVD
  diamond film by boron and nitrogen doping.
  Diamond and related materials, 2000. 9(3-6) p.
  337-340.
• S. Koizumi, et al., Growth and characterization
  of phosphorous doped 111 homoepitaxial diamond
  thin films. Applied physics letters, 1997.
  71(1065).
• R. Kalish, C. Uzan-Saguy, and B. Philosoph,
  Nitrogen doping of diamond by ion implantation.
  Diamond and related materials, 1997. 6 p.
  516-520.
• Prins, J.F., Doping of diamond by the diffusion
  f interstitial atoms into layers containing a
  low density of vacancies. Diamond and related
  materials, 1998. 7 p. 545-549.
• R. Job, et al., Electrical properties of
  lithium-implanted layers on synthetic diamond.
  Diamond and related materials, 1996. 5 p.
  757-760.
• Jerry W. Zimmer and G. Chandler, SOD Substrates
  The Next Step in Thermal Control, sp3 Diamond
  Technologies Inc.
• Hara, Y. NTT verifies diamond semiconductor
  operation at 81 GHz. 2003.
• John A. Carlisle and N.D. Kane, Commercializing
  Diamond RF MEMS Devices. IEEE Microwave magazine,
  2007 p. 62.

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Any questions???
Dr. Gordon E. Moore, Intel museum