Date of Award

Fall 1992

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Electrical Engineering - (Ph.D.)

Department

Electrical and Computer Engineering

First Advisor

Robert Boris Marcus

Second Advisor

Ken K. Chin

Third Advisor

Roy H. Cornely

Fourth Advisor

William N. Carr

Fifth Advisor

Walter F. Kosonocky

Abstract

This dissertation describes the fabrication technology and characterization of a gated silicon field emission micro triode that is a novel electron tunneling device for generating electron emission into a vacuum. Conic (point) and wedge field emitter structures with nm-scale radii were fabricated in silicon and GaAs by etching, MOCVD and dry oxidation. A new self-aligned process was developed for fabrication of vertical field emission triodes. This process allows control of gate opening to less than 0.5 μm diameter without the need of electron-beam writing. It also provides a planar gate electrode and a thick dielectric layer for reduction of the gate-cathode capacitance. Gated silicon field emission triodes, with silicon resistivity of 0.005 - 0.02 Ω-cm were studied. Gate and collector currents were measured in a vacuum of 2 x 10-8 Corr, and current-voltage (I vs. V), current-time (I vs. t), Fowler-Nordheim (I/V2 vs. 1/V), and triode characteristics were determined. The data showed that the electron emission followed Fowler-Nordheim behavior. Single emitters had turn-on gate to cathode voltages (V) above 25 volts (typically 50 - 90 volts) and reproducible emission currents were measured in the range 5 pA - 1 μA. Emitting areas of 1.0x10-16 -1.5x10-11 cm2 and field conversion factors α/r (where electric field = V α/r) of 3x105 - 8x105 cm-1 were calculated. Temporal fluctuations in emission current of 10%, 16%, and 40% were found for emission currents of 0.35 nA, 50 nA, and 0.5 μA, respectively. The triode characteristics showed an Ig/Ic ratio of 0.25% and higher. Transconductances were found to be 3 x10-8 mhos/tip.

Leakage characteristics of various dielectric materials used in the new self-aligned process (thermal oxide, CVD oxide, polyimide and spin-on-glass) were measured and evaluated. Electrostatic discharge and other device failure mechanisms have been observed and explained.

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