A. Original Spindt Process (SRI)

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

2. The Process: #9
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

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. 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

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

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

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)

2. Process #5
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:

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

  • Main Outline
  • V. Conclusion
  • Sources