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Fabrication of Diamond Films for Microelectronic Applications

Fabrication of Diamond Films for Microelectronic Applications. Patrice Allen & Twanaze Mitchell ELEC 6750 Introduction to Plasma Engineering Y. Tzeng. OUTLINE. Explain objective of research Describe CVD process for diamond fabrication List complications with this process

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Fabrication of Diamond Films for Microelectronic Applications

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  1. Fabrication of Diamond Films for Microelectronic Applications Patrice Allen & Twanaze Mitchell ELEC 6750 Introduction to Plasma Engineering Y. Tzeng

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

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

  4. OBJECTIVE • Properties of diamond • Strongest known material • Most chemically inert • Excellent thermal shock resistance • Extreme thermal conductivity http://www.me.berkeley.edu/diamond/submissions/diam_review/review.htm

  5. OBJECTIVE • Diamond vs. Other Materials www.p1diamond.com/prop_ref.html

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

  7. 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).

  8. HOT FILAMENT REACTOR FIG 2. http://www.tlchm.bris.ac.uk/pt/diamond/rolythesis/chapter3.htm

  9. HOT FILAMENT REACTOR FIG 3. http://www.tlchm.bris.ac.uk/pt/diamond/rolythesis/chapter3.htm

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

  11. 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).

  12. 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).

  13. 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

  14. 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.

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

  16. 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

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

  18. 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.

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

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

  21. Questions ??

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