- 1. Summary: (Dec, 1976) #9
- a. Microfabricate metal tips by evaporation through holes
- b. 5 cm Si substrate (0.75 mm thick)
- c. Tips on 12.7 um centers, 6.4E+5 tips/cm^2
- d. Tips ~1.5 microns high, r ~ 200 Angstroms
- a. Begin with Si wafer: heavily doped (0.01 Ohm cm)
- b. Grow 1.5 um oxide with standard methods
- c. Coat oxide with 0.4 um molybdenum using e-beam evaporation
<DT> e. Expose array of 1 um e-beam spots
<DT> f. Remove PMM; etch down to Si with HF <P>
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- g. Put in vacuum deposition system and rotate horizontally
- h. Deposit aluminum at grazing incidence to decrease hole size
- i. Deposit molybdenum through holes with e-beam evaporator (perpendicular source)
- j. Initial aperture size, oxide thickness, and distance between substrate & source affect pyramid dimensions
- k. Dissolve aluminum layer to release top molybdenum film
- b. Grow 1.5 um oxide with standard methods
- B. Gray/Temple Process (Nav Resrch Lab, MCNC)
- 1. Summary: (Jan, 1995) #12
- a. Microfabricate silicon pyramids by anisotropic etching
- b. 4" Si Substrate, 3E+6 tips/cm^2
- c. Pyramids formed first
- d. Self-alignment of gate electrode to the pyramids
- e. Tips r < 200 Angstroms, 2 um high, 6 um center array
- f. Only one precise mask; crude masks for electrodes
- g. Sharpen pyramids with oxidation
- h. Good uniformity and device yield
- b. 4" Si Substrate, 3E+6 tips/cm^2
- 2. The Process: #3 and #12
- a. Begin with Si wafer: <100> n-type doping (2 Ohm cm)
- b. Grow 150 nm oxide layer
- c. Deposit ~0.5 um Si3N4 layer
- d. Photolithographically pattern array of 1 um circles
- e. Reactive ion etch nitride to form mask
<DT> g. Anisotropic etch Si with ethylenediamine-based solution: square pyramids bounded by <111> planes <P>
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- h. Use BCl3, Cl2, O2, He gas RIE to form columns
- i. Oxidize Si to sharpen pyramids (850 C, dry furnace); grow oxide half as thick as pyramid's flat top (top = 2W, want T = W)
- j. E-beam evaporate SiO2 insulator onto substrate
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- n. Lift-off excess metal by dissolving photoresist in acetone
- o. Etch nitride cap and oxide on pyramid with HF
C. Diamond FED Process (SIDT) - 1. Summary (May, 1995) #5
- a. Simple process involving no micron-scale lithography
- b. Just depositing diamond and metal films on substrate
- c. Smallest feature size is 100 ums (not 1 um like other FED's)
- b. Just depositing diamond and metal films on substrate
- 2. Process #5
- b. Grow 150 nm oxide layer
- a. Use crude shadow mask processes for large-area substrates
- b. Deposit metal with standard methods
- c. Deposit up to 1.5 um of amorphic diamond film as follows:
- b. Deposit metal with standard methods
- 1) Pulsed Nd:YAG laser beam vaporizes graphite target
- 2) Highly ionized C atoms condense to form diamond film
- 3) Substrate can be silicon, glass, or metal plate
- 4) Can deposit the films at room temperature
- 2) Highly ionized C atoms condense to form diamond film