US 5,703,380 A · Laminar composite lateral field-emission cathode

Abstract

A lateral-emitter electron field emission device structure incorporates a thin film laminar composite emitter structure including two or more films composed of materials having different etch rates when etched by an etchant. In its simplest form, the laminar composite emitter consists of two ultra-thin layers, etched differentially so that a salient remaining portion of the more etch-resistant layer protrudes beyond the less etch-resistant layer to form a small-radius tip. In a preferred form of the laminar composite emitter, it is a multi-layer laminar emitter, of which the most etch-resistant layer is doped-diamond. The diamond layer is doped using one or more N-type dopants. In this preferred emitter structure, the edge of the thin film diamond layer is the dominant electron emitter with a very low (nearly zero) work function. Hence the new device can operate at applied voltages substantially lower than in prior art. The laminar structure may be a sandwich structure with three layers. Upper and/or lower supporting metallic layers act as both physical supporting material and as an integral electrical conducting medium. This allows the diamond layer to be very thin, on the order of tens of angstroms (i.e. less than 100 angstroms). The laminar composite emitter is specially adapted to fabrication by a method using semiconductor integrated circuit fabrication processes.

Claims41

Dependent claims

A microelectronic device of the type using a cold-cathode field-emission electron source, comprising:

a) a substrate having a substrate upper surface defining a first plane;
b) an anode;
c) a composite lateral field-emission electron emitter spaced apart from said anode by a first predetermined distance and disposed on a second plane parallel to said first plane, said composite lateral field-emission electron emitter comprising:
i) a first conductive film having an upper major surface disposed substantially parallel to said second plane, and
ii) a second conductive film disposed in contact with said upper major surface of said first conductive film, one of said first and second conductive films comprising a carbon film, said first and second conductive films being characterized by having differing etch rates to an etchant, whereby one of said first and second conductive films may be differentially etched from a portion of the other to remove at least an edge portion of said one of said first and second conductive films, while leaving at least a salient edge portion of the other to form an emitting tip;
d) a first conductive contact connected to said first conductive film of said electron emitter to provide a cathode contact;
e) a second conductive contact spaced apart from said first conductive contact and connected to said anode to provide an anode contact, whereby said device may have an electrical bias voltage applied;
and
f) means for applying said electrical bias voltage.

6 more elements

A microelectronic device of the type using a cold-cathode field-emission electron source, comprising:

a) a substrate having a substrate upper surface defining a first plane;
b) an anode;
c) a field-emission electron emitter spaced apart from said anode by a first predetermined distance and disposed on a second plane parallel to said first plane, said electron emitter comprising:
i) a thin carbon film having upper and lower major surfaces disposed substantially parallel to said second plane, said thin carbon film further comprising a diamond film containing a predetermined quantity of a material characterized as an N-type dopant for diamond,
ii) a first conductive film disposed in contact with said upper major surface of said carbon film, and
iii) a second conductive film disposed in contact with said lower major surface of said carbon film;
d) a first conductive contact connected to at least one of said first and second conductive films of said electron emitter to provide a cathode contact;
e) a second conductive contact spaced apart from said first conductive contact and connected to said anode to provide an anode contact, whereby said device may have an electrical bias voltage applied;
f) a conductive control electrode spaced apart from said anode by a second predetermined distance and disposed in a third plane spaced from said second plane;
g) an insulating layer selectively disposed between said second and third planes to insulate said control electrode from said electron emitter;
h) a third conductive contact spaced apart from said first and second conductive contacts and connected to said control electrode, whereby an electrical control signal may be applied to said device;
and
j) means for applying said electrical bias voltage and said electrical control signal.

10 more elements

A microelectronic device of the type having a substrate with a substrate upper surface defining a first plane, an anode, and a lateral cold-cathode field-emission electron source spaced apart from said anode by a first distance and disposed on a second plane parallel to said first plane, said microelectronic device being fabricated by performing the steps of:

a) forming a first insulating layer on said substrate, said first insulating layer having a top major surface;
b) etching a recessed pattern in said top major surface of said first insulating layer;
c) filling said recessed pattern with a conductive material to form a buried conductive layer;
d) polishing said first insulating layer and said conductive material to remove conductive material not in said recessed pattern;
e) depositing a second insulating layer;
f) depositing in sequence
(i) an emitter bottom layer of a first conductive material,
(ii) an emitter top layer of a second conductive material to form a laminar composite emitter layer;
g) patterning and etching said laminar composite emitter layer;
h) depositing a third insulating layer;
i) forming contact holes through selected insulating layers and filling said contact holes with a conductive material;
j) if necessary, removing excess conductive material;
k) forming a trench area having trench sidewalls by selectively and directionally etching through previously formed layers, stopping at said buried conductive layer;
l) etching said laminar composite emitter layer to remove at least an edge portion of one of said emitter top and bottom layers, while leaving at least a salient edge portion of the other of said emitter top and bottom layers to form an emitting tip of said cold-cathode field-emission electron source;
m) depositing a conformal layer of sacrificial material on said trench sidewalls and forming upper and lower surfaces of said conformal layer;
n) directionally etching said conformal layer to substantially remove said upper and lower surfaces while leaving a thickness of sacrificial material on said trench sidewalls;
o) depositing anode material in said trench to form said anode;
and
p) removing said sacrificial material from said trench sidewalls, thus providing a gap to accommodate electron emission from said laminar composite emitter layer to said anode in said field-emission device.

16 more elements

Dependencies are inferred from the claim text.

Laminar composite lateral field-emission cathode

Life of this patent

Laminar composite lateral field-emission cathode

Life of this patent

Abstract

Claims41