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Micro-area Field Emitter

IP.com Disclosure Number: IPCOM000109710D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 103K

Publishing Venue

IBM

Related People

Kern, DP: AUTHOR [+2]

Abstract

Described is a micro-area field emitter consisting of an array of closely-spaced field emission tips micro-fabricated with a single extraction electrode. The array is designed to produce higher current densities than that produced by thermionic emission. The basic structure of the emitter and two fabrication techniques are discussed.

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Micro-area Field Emitter

       Described is a micro-area field emitter consisting of an
array of closely-spaced field emission tips micro-fabricated with a
single extraction electrode.  The array is designed to produce higher
current densities than that produced by thermionic emission.  The
basic structure of the emitter and two fabrication techniques are
discussed.

      In prior art, electron columns for microscopy and lithography
used either a thermionic cathode with a 10 mm source diameter and a
demagnifying column to produce a small electron probe or a
field-emitting cathode, cold or thermal, forming a 10 nm source not
requiring demagnification.  The latter approach produced a more
intense spot of electrons at small dimensions but lacked large total
currents in large spot sizes.  It also suffered from severe
mechanical and electromagnetic stability problems because of the
small source size and non-demagnifying column.

      The concept described herein provides a micro-area field
emitter with an array of closely-spaced field emission tips that are
micro-fabricated with a single extraction electrode.  The array
measures 1 to 3 mm in diameter and is capable of producing current
densities greater then that of thermionic emission.  The area field
emitter avoids the positional instability problems of the single
field emission tip in that it has a higher total emission current
available which is spread over a well-defined area.

      Silicon pyramids are fabricated by anisotropic etching of
100-orientation silicon in basic solutions, such as potassium
hydroxide (KOH) or ethylenediamine - pyrocatechol - water (EPW)
etchants.  Single-tip silicon micro-emitters of a few-micron
electrode diameter have been fabricated and the arrays of the
micro-emitters have on the order of 10 mm spacing with the tip having
its own extraction electrode.  With a requirement of only 1-3 mm
diameter and a tip spacing of 0.1 mm, fabricating separate electrodes
for each tip can be difficult to produce.

      When etching bare silicon surfaces in KOH or EPW solutions,
silicon pyramids will form naturally.  However, the spacing between
naturally formed pyramids is typically several microns.  In order to
form pyramids on a separation of 0.1 mm, the surface of the silicon
can be roughened on an appropriate scale by using CF4 reactive ion
etching, chemical etching, or deposition of a metallic film of
suitable grain size, such as gold annealed to form clumps.  The grain
pattern is then transferred into the resist by means of etching.
Roughening of the surface is followed by a brief anisotropic etch to
form...