IAA-99-IAA.12.1.02 DIAMOND FILM DEPOSITION BY CHEMICAL VAPOR TRANSPORT

IAA-99-IAA.12.1.02DIAMOND FILM DEPOSITION BYCHEMICAL VAPOR TRANSPORTLiya L. Regel and William R. WilcoxInternational Center for Gravity MaterialsScience and Applications, Clarkson University,

Potsdam, New York 13699-5814, USA

International Astronautical CongressAmsterdam, October 1999

• Some current and many potential applications for diamond films. Improvements needed.

• Techniques and apparatus will be described.• Deposited on silicon, molybdenum, graphite,

carbon felt and glass without typical pre-treatment with diamond powder.

• Selective deposition on copper pattern on oxidized silicon

• Deposition enhanced by centrifugation.• Modeling and current understanding:

radiation heat transfer, buoyancy convection, surface and gas chemistry.

Current applications of CVD diamond

• Heat spreaders for semiconductor devices, photonic devices, high-power amplifiers and Multi Chip Modules

• Hard coatings for tools for cutting, grinding, microdrilling, etc.

• Highly transparent hard windows useful from the infrared to the ultraviolet, and as a radome.

• Chemically resistant coatings, e.g., for biomedical implants.• Cold-cathode field emitters for flat panel displays, electron

guns, amplifiers, oscillators, miniature x-ray sources, etc.

• High frequency speaker diaphragms.

Techniques• Previous techniques use flowing hydrogen gas at ~1/10 atm

containing ~1% methane. Either a hot tungsten filament or a plasma is used to generate H atoms and C-containing deposition species. Nucleation is often difficult and sometimes requires diamond powder. Deposition rates are ~1 micron/hr.

• Our new technique uses hydrogen at ~1/10 atm in a sealed chamber. Hot graphite generates both hydrogen atoms and carbon-containing deposition species. Seems to nucleate on anything without special surface treatment. Deposition rate can be ~10 micron/hr. Appears to be self regulating.

Cooling water

Cooling water TC 1

TC 2

Graphite rod

Substrate

Hydrogen Vacuum Pressuretransducer

Power supply Power supply

This shows the original apparatus. A larger apparatus has been constructed with improved cooling and better control. Power requirement about 300 watts -- a large light bulb!

Complete coating on entire 8.8 sq cm Mo sheet. Grain size ~0.4 micron.

Optical interference pattern from fine-grained deposit on molybdenum

Diamond deposited on roughened (111) silicon for 40 minutes under different conditions.

Deposition of diamond on graphite

Before deposition After deposition

Selective deposition of diamond on copper pattern on oxidized silicon

Cu pattern (lighter color) After deposition

Comparison of temperature distribution in chamber with silicon and glass substrates.

Comparison of convection field in chamber with silicon and glass substrates.

Equilibrium compositions versus temperature.

2400 2600 28001E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0.01

0.1

C2H3

C2

CH2

C2H

C2H4

CH3

C2H2

CH4

H

Gr

H2

H2/C = 1.1P = 5000 Pa

Gr C2 C2H C2H2 C2H3 C2H4 CH2 CH3 CH4 H2 H

Mol

e Fr

actio

n

Temperature, oC