JP2002509336A - Self-gettering electron field emitter and fabrication process - Google Patents

Abstract

(57) Abstract: A self-gettering electron field emitter (30) has a first portion (40) formed of a low work function material that emits electrons, and the emitter has a low resistance electrical conductor and a getter. It has an integral second portion (50) that acts as both ring surfaces. A self-gettering emitter (30) disposes a thin film of a low resistance gettering material by disposing a thin film of the low work function material parallel to the substrate and in parallel with the substrate and in contact with the thin film of the low work function material. It is formed by doing. The self-gettering emitter (30) is particularly suitable for use in a lateral field emission device (10). A preferred emitter structure has a tapered edge (60) and a convex portion (45) of low work function material that extends a short distance beyond the edge (55) of the gettering and low resistance material. Also disclosed are fabrication processes (S1-S6) that are particularly adapted for in-situ formation of self-gettering electron field emitters during fabrication of a microelectronic field emission device.

Description

DETAILED DESCRIPTION OF THE INVENTION

FIELD OF THE INVENTION The present invention relates generally to microelectronic devices utilizing field emission and methods of fabricating such devices, and in particular, to electron field emitters having self-gettering characteristics.
Electron field emitter).

BACKGROUND OF THE INVENTION A difficult challenge in fabricating electron field emission arrays, such as those used in field emission displays, is to provide a getter material that is effective to prevent electron emitters from becoming contaminated. It is to prepare. Typically in a field emission display, getter material is placed on the outer edge of the entire array. Typical display width and length are number 1
The getter material may be decomposition products or outgassed because it may be 0 centimeters and the distance between the emitter and the anode of each cell is typically only 50 to 200 micrometers. Effective gettering of the species can be located too far from many emitters of the array. As a result, contamination of the emitter can cause a change in the work function, causing catastrophic failure of the field emission array.

[0003] In (notation and terminology) herein, the term "nitride" as applied to a metal, for example, "a tantalum nitride" or "molybdenum nitride" is, TaN, Ta ₂ N, MoN, or Mo ₂ N Not only stoichiometric compounds such as but also non-stoichiometric partial metal nitrides, i.e., a certain amount of nitrogen is added, although not necessarily in the amount required to form a stoichiometric compound. Metal also refers to The chemical formula of such a material is often written, for example, as MoN _x or Ta _x N. It is known in the art that varying amounts of nitrogen can be introduced into thin metal films by reactive sputtering or ion implantation to produce, for example, a non-stoichiometric nitride composition.

[0004] As used herein, the term "lateral" generally refers to a direction parallel to a substrate on which the electronic device is formed. Therefore, a "transverse field emission device" is a field emission device formed on a substrate and formed such that the anode is spaced from the field emitter along at least a direction parallel to the substrate. Refers to the device. Similarly, the term "lateral emitter" refers to a field emitter made substantially parallel to the substrate of the lateral device, such that emission of electrons toward the anode occurs generally parallel to the substrate. . Examples of such lateral emitters formed of thin films are known in the relevant art.

[0005] Certain authorities author the term "gettering.
ing) to remove residual gases and gases or other contaminants generated during the processing of the equipment.
Gas generated during the life of the device, limited to
Or "keeping" to mean cleanup of other contaminants.
g) ”, but in this specification and the appended claims, the term
"Gettering" is intended to include all such applications. The term "contaminants
The "containants" include the electrons from the emitter of the electron field emission device.
Intended to include any abrupt or unwanted substances that may affect the release
. Such contaminants include atoms, molecules, atom clusters,
It can be said that they are ions, free radicals and the like. Common potential molecular contaminants include, for example, O _Two , H_Two, SO_Two, N_Two, NH_Three, CO_Two, CO, H_TwoO, C_TwoH_Two, C_TwoH_Four, SF₆,
And CCI_TwoF_TwoThere is.

Related Art A number of field emission device structures are known, of which the majority are generally described in Spind (Spi) as described, for example, in US Pat. No. 3,755,704.
ndt) type. The following U.S. patents describe various field emission devices having lateral field emitters and / or their fabrication process. Nos. 5,233,263 and 5,30 by Cronin et al.
No. 8,439, Xie et al., No. 5,528,099, and Potter (P.
No. 5,616,061, No. 5,618,216, and No. 5,62.
No. 8,663, No. 5,630,741, No. 5,644,188, No. 5,64
No. 4,190, No. 5,647,998, No. 5,666,019, No. 5,66
9,802, 5,700,176, and 5,703,380. The use of getter pumping to remove gases from the environment has been known for many years. Recently, gettering has been used in field emission devices with various methods and configurations to prevent contamination of the electron emitting tip.

US Pat. No. 4,041,316 to Todokoro et al. Discloses a field emission electron gun with an evaporation source, ie, an evaporation material that forms an evaporation layer on the inner surface of the vacuum chamber and on the anode surface. Is disclosed. The reactive gas adhered to the inner surface of the vacuum chamber and the anode and embedded therein is suppressed from being extracted by electron impact.

[0008] US Pat. No. 5,063,323 to Longo et al. Discloses a structure that provides for a venting passage for degassed material. During the electrical operation of the field emission device, the degassed material released into the space between the sharp field emitter tip and the electrode is degassed through a passage to a gettering material pump provided in the separation space. .

US Pat. No. 5,223,766 to Nakayama et al. Discloses a thin type of image display that displays an image by emitting light from a phosphor when illuminated with an electron beam. An apparatus is disclosed. The device has a cathode panel between the front panel and the back panel, such that space exists between the cathode panel and the back panel. Getter diffusion through holes are formed in the cathode panel to maintain image quality at the center of the display screen, or the cathode is used to maintain the pressure required to achieve fairly high image quality even on large display screens. The panel is supported by the getter. The gate electrode in this device may be made of a getter material.

US Pat. Nos. 5,453,659 and 5,537 to Wallace et al.
No. 520,563 discloses an anode plate used in a field emission flat panel display with integrated getter material. The anode plate includes a transparent planar substrate having a plurality of conductive parallel stripes containing the anode of the device. The stripes are covered by phosphor and there is gettering material between the stripes. The gettering material is preferably zirconium-vanadium-iron or barium.

[0011] US Patent No. 5,498,925 to Bell et al. Includes a first electrode and a second electrode spaced apart, typically between these two electrodes. 1
A flat panel display with a patterned solid material in contact with one is disclosed. A patterned layer (called a web) includes multiple apertures, with at least one aperture associated with one given pixel. An amount of a second material is placed in the aperture, typically a phosphor for FPFED or a color filter material for LCD. The web may include a getter material or a hygroscopic material.

No. 5,502,348 to Moyer et al. Discloses an integral active contaminant absorbing means.
charge ballistic conduction device (bal) with absorption means
The present invention discloses a "last charge transport device". The charge ballistic conducting device is an edge electron emitter.
This emitter defines an elongated central opening therethrough, with a receiving terminal (eg, anode) at one end of the opening and a getter at the other end. An appropriate potential is applied between the emitter and the receiving terminal to attract the emitted electrons to the receiving terminal;
And different suitable potentials are applied between the emitter and the getter to accelerate and adsorb contaminants such as ions and other undesirable particles to the getter.

US Pat. No. 5,545,946 to Wiemann et al. Discloses a field emission display that includes an insulating layer and an emitting layer on a faceplate. A vacuum chamber is located between the back surface and the emissive layer and includes a getter. An aperture is defined through the insulating and emissive layers to pass contaminants from the faceplate to the vacuum chamber.

US Pat. No. 5,578,900 to Peng et al. Discloses a field emission display with a built-in ion pump for removal of degassed material. An ion pump cathode formed of a gettering material covers the gate electrode so that during display operations, outgassed material is collected at the ion pump cathode. Alternatively, the ion pump cathode may be formed on a focusing electrode, on a focusing mesh, or on another electrode structure.

US Pat. No. 5,606,225 to Levine et al. Discloses a tetrode configuration for a color field emission flat panel display with a barrier electrode on the anode plate. The anode plate comprises a transparent planar substrate having a layer of transparent conductive material thereon, which layer comprises the anode of the display tetrode. A barrier structure comprising an electrically insulating, preferably opaque material is formed on the anode as a series of parallel ridges. At the top of each barrier structure is a series of conductive stripes, which function as deflection electrodes. The conductive stripes are formed in triplicate, and all of the third stripes are electrically interconnected. The deflection electrode may be formed of a gettering quality conductive material, such as zirconium-vanadium-iron.

US Pat. No. 5,610,478 to Kato et al. Conditions a field emitter display emitter to improve electron emission.
ng). The emitter and row are operated at a voltage that triggers electron emission from the emitter. The anode is operated at a voltage that does not attract electrons, such that those electrons are attracted to the rows.

US Pat. No. 5,614,785 to Wallace et al. Discloses an anode plate for a flat panel display having a silicon getter. The display includes a transparent substrate covered by a luminescent material and having a plurality of spaced conductive regions forming an anode. A porous silicon getter material is deposited on the substrate between the conductive areas of the anode plate. The porous getter material is preferably non-conductive, opaque and highly porous.

US Pat. No. 5,635,795 to Itoh et al. Discloses a getter chamber for a flat panel display. An air-tight envelope in which the fluorescent display device has a cathode substrate, an anode substrate provided with a phosphor layer configured to provide a luminescent display, a sealing member, and a vacuum formed on the side of the enclosure. An exhaust hole and a getter chamber communicating with the exhaust hole are included. The getter chamber is disposed outside the sealed container and includes a chamber body and a vacuum exhaust pipe. The getter chamber eliminates the independent formation of evacuation holes in the cathode substrate and thereby prevents damage and contamination of the cathode substrate.

US Pat. No. 5,656,889 to Niiyama et al. Discloses a getter device capable of being reactivated as required and located in a narrow space within a sealed input container. . The getters are arranged in layers in the enclosure to provide a film getter in the enclosure for maintaining a vacuum inside the enclosure of the electronic device. The electrons emitted from the electron supply section are irradiated on the getter and activate it.

Thus, some field emission devices of the prior art include a gettering material associated with the interior surface of the vacuum chamber wall or with the anode, gate electrode, or deflection electrode of those devices. .

DISCLOSURE OF THE INVENTION Problems Solved by the Invention There are many sources of contamination that may affect the performance of electron field emitters, including degassing the materials used to fabricate the device. , Electron-induced decomposition, electron-induced desorption,
There is residual gas present in the vacuum system used during device fabrication, gas penetration into the environment around the field emitter. The present invention prevents contamination of the electron field emitter, and therefore
A means is provided for preventing unwanted changes in the work function of the electron field emitter. Such changes, if not prevented, can cause the field emission device or an array of such devices to function improperly.

OBJECTS AND ADVANTAGES A primary object of the present invention is to prevent the electron field emitter from being contaminated, and thus to prevent undesirable changes in the work function of the field emitter. The general purpose is therefore a more reliable electron field emission device. It is therefore an object of the present invention to getter potentially contaminating atoms, also molecules, and ions from the evacuated space or ambient gas near the electron field emitter, especially near the tip of the field emitter. A special purpose is to provide a self-gettering electron field emitter. A similar object is to provide a gettering material integral with the electron field emitter. A related object is a getter that will automatically have the same negative potential as the emitter to improve cation attraction and gettering and to avoid electron-induced desorption of the gettered species. . Another related purpose is to provide an emitting part (emitting p
(ortion) is a self-gettering emitter comprising a nitrided form of the material constituting the gettering portion. Another object is a fabrication process for a microelectronic device having a self-gettering electron field emitter. A related object is a fabrication process that is particularly adapted for in-situ formation of self-gettering electron field emitters during fabrication of microelectronic field emission devices. These and other objects will become apparent from reading this specification and the appended claims, taken in conjunction with the drawings.
This is achieved by the present invention.

BRIEF SUMMARY OF THE INVENTION A self-gettering electron field emitter has a first portion formed of a low work function material that emits electrons, and the emitter has a low resistance electrical conductor and a gettering surface. Has an integral second part that acts as both. Self-gettering emitters are provided by placing a thin film of low work function material parallel to the substrate and by placing a thin film of low resistance gettering material parallel to the substrate and in contact with the thin film of low work function material. It is formed. Self-gettering emitters are particularly suitable for use in lateral field emission devices. A preferred emitter structure has a tapered edge and a convex portion of low work function material (gettering and extending a short distance beyond the edge of the low resistance material).
(salient portion). Also disclosed is a fabrication process particularly adapted for in-situ formation of self-gettering electron field emitters during fabrication of a microphone electronic field emission device.

Definitions of Reference Numbers Used in the Drawings The reference numbers used in FIGS. 1, 2, 4a-4e, and 5 will become clear from the detailed description of the preferred embodiments in the following sections. Does not require a definition. The following reference numbers are used in the flowchart of FIG. 3 to specify the process steps indicated below. S1 A substrate is prepared. S2 Deposit the anode layer. S3 Deposit an insulating layer. S4 Deposit an integrated self-gettering emitter layer parallel to the substrate. S4a Deposit the emission portion of the emitter layer. S4b Deposit the gettering portion of the emitter layer. S5 Optionally deposit a second insulating layer. S6 Directional etch the openings to form emission edges.

Modes for Carrying Out the Invention The following detailed description, read with reference to the drawings, begins with a detailed description of a preferred embodiment of an electron field emission device made in accordance with the present invention. The device description is followed by a detailed description of the preferred fabrication process. The device drawings are not drawn to scale and, in particular, vertical dimensions are exaggerated relative to horizontal dimensions.

FIG. 1 shows a side sectional view of an electron field emission device 10 formed on a substrate 20. The emitting body 30 includes an emitting portion 40 and a gettering portion 50. Emission portion 40 is a thin layer of a material having a low work function, preferably parallel to substrate 20, to form a portion of the lateral field emitter. Gettering portion 50 is a thin layer of gettering material disposed at least partially adjacent to emission portion 40, preferably parallel to substrate 20 and emission portion 40. The gettering portion 50 acts as both a low resistance electrical conductor and a gettering surface. Emission portion 40 and gettering portion 50 together form integrated self-gettering electron field emitter 30. The emitter 30 has an extremely narrow emission tip 60. Anode 70 is spaced from emitter 30.
When the anode 70 is properly biased positively with respect to the emitter 30 to create a high electric field at the emission tip 60, the Fowler-Nordheim equation (Fowler-Nordh)
The electrons emitted from the emission tip 60 in accordance with the
Attracted to zero. Therefore, the anode 70 receives the electrons emitted from the emission tip 60 of the emitter 30, particularly from the emission portion 40. If the anode 70 is formed at least on its surface with a cathodoluminescent phosphor, it emits light from the anode 70 when excited by electrons. Anode 70 may be comprised entirely of a conductive phosphor. The emitter 30 is preferably insulated from the anode 70 by an insulating layer 80. The emitter 30 is also preferably covered by another insulating layer 90. The preferred structure shown in FIG. 1 involves a lateral emission device, in which the field emitter 30 is
Spreads horizontally parallel to zero.

The emitting portion 40 of the emitter 30 is preferably low because electron field emission according to the Fowler-Nordheim equation is very sensitive not only to the radius of the thin emitting tip 60 but also to its work function. Has work function. Many known materials are suitable for the emitting portion 40. Refractory transition metals such as titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, or tungsten may be used. Field emitter tips have also been made of silicon, carbon (especially in the form of diamonds), lanthanum hexaboride, and other materials. In the structure of the present invention, the emitting portion 40 is made of the transition metal nitrides listed above, most preferably titanium nitride, tantalum nitride, or molybdenum nitride. For some applications,
An alternative embodiment having an emission portion 40 made of diamond (carbon with a diamond crystal structure) doped with one or more N-type dopants to provide a low work function emitter may be used.

A very important feature of the preferred structure shown in FIG. 1 is that the location of the gettering portion 50 as close as possible to the emitting portion 40 of the integrated emitter structure 30, in particular as close as possible to the emitting tip 60. It is. Gettering portion 50 is made of a material capable of gettering unwanted gases that may contaminate emission portion 40. Preferably, the gettering material should be a substance that is reactive with contaminants.

A number of materials that are generally known to be effective for gettering are listed in references, including: Chapter "Getter", author EP Bartin, "Encyclopedia of Chemistry" 2nd edition (edited by GL Clark et al.) Reynold Publishing, New York (1966) 484-485 (the chapter "Getters").
"By EP Bertin in" The Encyclopedia
of Chemistry "2nd edition (GL Clark)
et al. eds. ) Reinhold Publishing, New
York (1966) pp. 484-485), book, author S. Dashman, "Scientific Fundamentals of Vacuum Technology," 2nd Edition, John Wiley and Sons, New
York (1962), pages 174-175 (the book by S. Dus)
hman, "Scientific Foundations of Vacu.
um Technique ”2nd edition, Johon Wiley
& Sons, New York (1962) pp. 174-175), and Chapter 18, "Getter Materials", WH Cole, "Handbook of Materials and Techniques for Vacuum Equipment," Reynold Publishing, New York (1967) 545-56.
Page 2 (Chapter 18, "Getter Materials" in W
. H. Kohl, "Handbook of Materials and T
techniques for Vacuum Devices ”Reinho
ld Publishing, New York (1967) pp. 545-5
62). The materials discussed in these references include aluminum, barium, beryllium, calcium, cerium, copper, cobalt, iron, lanthanide, magnesium, misch metal, nickel, palladium, thorium, uranium, zinc, titanium, There are zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten and their suitable alloys, also compounds, and also mixtures. In general, any of these or other known gettering materials may be used for gettering portion 50 of emitter 30. Preferred materials for the gettering portion 50 are high melting point transition metals titanium, zirconium, hafnium, vanadium,
Niobium, tantalum, chromium, molybdenum, tungsten and their alloys, also compounds, and also mixtures (most preferably zirconium).

It is worth noting that there are certain advantages to using the transition metal in its pure form as the gettering portion 50 and with the nitrided form of the same metal as the emissive portion 40. It is. During fabrication, the nitrided and pure forms of the metal can be sequentially deposited by appropriately introducing or suppressing nitrogen. However, the particular application of the device can affect the choice of material. Due to other considerations such as work function, the preferred metal nitride used for the emitting portion 40 may be a different metal than the metal included in the gettering portion 50. Therefore, if the preferred refractory transition metals and their nitrided forms are used, they may be the same metal or different metals. A preferred combination is zirconium for gettering portion 50 and nitride of titanium, tantalum, molybdenum, or a mixture or alloy thereof for emitting portion 40.

FIG. 2 shows a side sectional view of the discharge tip 60. The emitter 30 preferably has a tapered edge, which defines the shape of the emission tip 60. The discharge tip 60 is preferably
By forming a gettering portion 50 with an edge 55 and a discharge tip 60
By forming a discharge portion 40 with a convex corner 45 extending beyond the edge 55 of the gettering portion to form FIG. 1 shows the anode 70 near the bottom of the final structure (as would typically be the case if it were phosphor for display applications), but this arrangement is for illustrative purposes only. Not just.
Similarly, FIGS. 1 and 2 show the emission portion 40 of the emission body 30 below the gettering portion 50.
, But this arrangement is also merely illustrative. The reverse order of these layers (or other spatial arrangements that preserve the adjacency between gettering and emitting portions) would also be functional. An overall device structure, such as the structure shown in FIG. 1, and a discharge tip structure, such as that of FIG. 2, are formed in a preferred fabrication process described in detail below.

Preferred Fabrication Process FIG. 3 shows a flow chart illustrating the steps of the preferred fabrication process, and FIGS. 4a-4e show a series of side views of the apparatus at various stages during its fabrication. The process steps are indicated by reference numbers S1, S2,..., S6.

The overall fabrication process includes the steps of providing a substrate, depositing an integrated emitter with an emission layer and a gettering layer parallel to the substrate, an emission layer to form an emission edge on the integrated emitter. And etching through the gettering layer, arranging an anode spaced from the emission edge to receive electrons emitted from the emission edge, providing means for applying an appropriate electrical bias voltage to the emitter and the anode. Including steps. In practice, an additional step typically also provides an insulating layer. The steps of the preferred process are described in detail in the following paragraphs with reference to FIG. 3 and FIGS. 4a-4e.

In step S1, a suitable substrate 20 such as silicon, silicon oxide, silicon nitride, glass, or sapphire is provided. In step S2, an anode layer 70 is deposited on the substrate (FIG. 4a) and optionally patterned. If all field emission devices on the substrate are to share a common anode, patterning is not required. Optional sub-steps of patterning are not shown in these figures. Generally, the anode layer 70 has a suitable thickness (eg, 100 nanometers).
May be made of any suitable conductive material. For display applications, at least the surface of the anode layer 70 should be a cathodoluminescent phosphor. Many cathodoluminescent phosphors are known in the art that have various properties such as light emission color, emission rate, stability, and the like. Some suitable phosphors are disclosed in U.S. Patent Nos. 5,618,216, 5,630,741, 5,639 to Potter.
Nos. 44,188, 5,644,190, and 5,647,998, the entire disclosures of each of these patents being incorporated herein by reference. is there. In one version of the preferred process, the anode is over-stoichiometric in excess of a certain amount of Z to produce a display that emits green light.
n is a zinc oxide (ZnO) (usually indicated by ZnO: Zn). In another version of the preferred process, to produce a display that emits blue light,
A Ta ₂ Zn ₃ O ₈ phosphor is disposed on at least the surface of the anode.

In step S 3, an insulating layer 80 of a predetermined thickness is deposited, preferably parallel to the substrate 20, to provide an insulating gap between the anode layer 70 and subsequent elements of the device (FIG. 4 b). ). The insulating layer 80 may be made of any suitable insulator, such as silicon oxide, silicon nitride, aluminum oxide, etc., compatible with other steps of the process. In a preferred process, insulating layer 80 is silicon oxide. The preferred thickness is about 500 nanometers.

In a preferred fabrication process, the self-gettering emitter 30 is made in-situ during fabrication of the microelectronic field emission device. In step S4, the self-gettering integrated emitting body 30 is disposed so as to cover the insulating layer 80 parallel to the substrate 20 (
FIG. 4c). In the most preferred embodiment, step S4 consists of two sub-steps S4a
And S4b. In a sub-step S4a, an emission part 40 comprising a layer of a material having a low work function for electron emission is deposited. In a sub-step S4b, a gettering portion 50 consisting of a layer of gettering material is deposited. The thickness of the emitting portion 40 is preferably about 10 to 30 nanometers. Gettering portion 50 preferably has a thickness of about 100-200 nanometers. Various materials suitable for each of these layers of the emitter are described above in the detailed description of the device structure. Emitter 30
The deposition of the layer may be any conventional method suitable for the substrate to be deposited, such as evaporation, chemical vapor deposition, molecular beam deposition, plating, etc., instead of the preferred method of sputtering. This may be done by a deposition method. The emitter 30 may be patterned in a conventional manner as in known photolithographic methods commonly used in semiconductor fabrication processes. Such patterning is described in the Potter patent, the contents of which are incorporated herein by reference. This conventional patterning sub-step is not shown in the drawing. The two parts of the self-gettering emitter are of a refractory transition metal, namely a refractory transition metal nitride deposited as the release portion 40 in sub-step S4a and a refractory transition metal deposited as a gettering portion in sub-step S4b. An important feature of the most suitable in-situ process is realized when based on layers. The transition metal main component of the two parts may be different elements or based on the same element, for example, both based on titanium, titanium nitride such as TiN as the emitting part and pure titanium as the gettering part. May be. Preferred embodiments using different elements have an emitting portion comprising a nitrided form of titanium, tantalum, molybdenum, or a mixture or alloy thereof, and a gettering portion comprising zirconium metal. When the transition metal element is the same in the two portions of the emitting portion 30, by reactively sputtering the metal in the presence of nitrogen to form a nitride layer for the emitting portion 40, then pure metal gettering By continuing to sputter the metal while suppressing the nitrogen to sputter portion 50, it is possible to deposit emitter 30 in a continuous process. Using such a process, the two parts 40
There is not always a sharp boundary delineating between and 50, and the nitrogen content decreases more or less from a relatively high level in the discharge portion 40 to a low level in the gettering portion 50, preferably zero. Similar gradual variations in composition are obtained even if different transition metals are used for the two parts 40 and 50, if the two metals form a solid solution alloy in the thin film.

While the preferred embodiment described herein has an emitter 30 with two layers 40 and 50, an alternative embodiment (shown in FIG. 5) has three layers, the middle emission layer 40 And a stacked composite emitter having upper and lower gettering layers 50 with one gettering layer above the emission layer and one gettering layer below the emission layer. US Pat. No. 5,647,998 to Potter, a field emission device structure having a three-layer composite lateral emitter (without self-gettering features), the contents of which are incorporated herein by reference. Described in the issue.

In step S5, a second insulating layer 90 is optionally deposited over the emitter 30 (FIG. 4d). This second insulating layer may be of the same insulating material as layer 80 and may be about 50-200 nanometers thick. Silicon oxide is a preferred material. Insulating layer 90 protects the emitter and controls the flow of electrons from emission tip 60 to anode 70 from the emitter to any electrodes located above the face of emitter 30. Provide an insulating spacer.

In step S 6, the second insulating layer 90, if present, is passed through the emitter 30 to form the emission edge 60 and to form the opening 75 extending below the anode 70. Perform a directional etch through both the emissive layer 40 and the gettering layer 50 and through the insulating layer 80 (FIG. 4e). The width of the opening 75 is not critical; a typical width is about 2 to 20 micrometers. The directional etch is preferably an anisotropic "trench" etch, such as a reactive ion etch commonly used in semiconductor fabrication processes. This etching process etches the insulating layers 80 and 90 selectively with respect to that etching of the emitter 30 material. While such an etch process is generally controlled to be highly anisotropic, the process is preferably controlled herein to include some isotropic etching. This is shown in FIG.
To create the emitter structure detailed in FIG. The etching process of step S6 is performed such that the convex portion 45 of the emission portion 40 extends beyond the edge 55 and thus forms an emission tip 60 having a desired shape and self-gettering characteristics. An edge 60 is formed and an edge 55 is formed on the gettering portion 50. Because gettering portion 50 has a convex portion extending beyond the etched surface of insulating layer 80 and / or 90, convex portion 45 of the emitter also extends beyond the surface of insulating layer 80 and / or 90. . The exposed portion of the gettering portion 50 is provided at the discharge tip 60 and at the convex corner 45 of the discharge portion 40 to make it very convenient to get contaminants.
Position immediately adjacent to.

The formation of the emission tip 60 is preferably performed during the formation of the trench opening 75, but may be performed after the formation of the opening. A small amount of the supporting upper and / or lower gettering layer 50 is removed, for example, by etching in a plasma etch process. Differential etch (differential) so that the emission portion 40 of the stacked emitter is less affected by the etch than the gettering portion 50
etch) Select a process. This leaves an ultra-thin emitting edge or tip 60. For some combinations of materials within the laminated composite emitter 30, the preferred differential etch process is a chemical or electrochemical etch, differential electropolishing.
It may be electropolishing or differential ablation.

Once the device structure of FIG. 1 has been formed, operation of the device is such that a suitable electrical bias voltage sufficient to cause emission of electrons from the emitter to the anode in a conventional manner for a field emission device. Requires means to apply to the emitter and anode. Therefore, the completed device has conductive contacts arranged to allow connection of the appropriate bias voltage from outside the device. Such conductor contact arrangements are described in the Potter patent, the contents of which are incorporated herein by reference.

Industrial Applicability The present invention is effective for manufacturing a field emission device and is particularly effective for a field emission display including an array of field emission devices. This is because each device in the array may have a self-gettering emitter. The preferred fabrication process is particularly suited for the simultaneous fabrication of many devices in such an array. The self-gettering emitter made according to the present invention may also be used as an electron-emitting component in an electron gun structure.

From the foregoing description, those skilled in the art will readily be able to ascertain the essential characteristics of the invention, and will violate the spirit and scope of the invention in order to adapt the invention to various uses and conditions. Instead, various changes and modifications of the present invention can be made. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification or practice of the invention disclosed herein. For example, the order of steps in the fabrication process may be varied, and other suitable materials may be substituted for those described herein. Although the preferred embodiment of the emitter has been described in a structure intended for a display, the self-gettering emitter may be made as a single element, for example by removing the substrate. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being defined by the following claims.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an electron field emission device made in accordance with the present invention.

FIG. 2 is a side sectional view of details of the electron field emission device of FIG. 1;

FIG. 3 is a flowchart showing the steps of a preferred fabrication process.

FIG. 4 is a series of cross-sectional side views of an electron field emission device at various stages during its fabrication according to a preferred process, wherein ae are each a sequential stage.

FIG. 5 is a side sectional view of an alternative embodiment of the electron field emission device.

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] November 12, 1999 (November 12, 1999)

[Procedure amendment 1]

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FIG. 4a

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Claims (39)

[Claims] 1. An electron field emission device comprising: a) a first layer of an electron emitting material; and b) a second layer, the second layer including a material capable of gettering contaminants.
An electron field emission device comprising: a layer; 2. An electron field emission device formed on a substrate, comprising: a) a first layer of an electron emission material, wherein the first layer is disposed parallel to the substrate.
An electron field emission device comprising: an emitter comprising: a layer; b) a second layer disposed parallel to the substrate and comprising a material capable of gettering contaminants. 3. An electron field emission device formed on a substrate, comprising: a) an emitter; i) a first layer of an electron emitting material, the first layer being disposed parallel to the substrate. An emitter comprising: ii) a second layer, the second layer being disposed parallel to the substrate and comprising a material capable of gettering contaminants; and b) from the emitter. Anodes spaced and arranged to receive electrons emitted from the first layer of the emitter; c) electricity suitable for causing electron field emission from the first layer of the emitter An electron field emission device comprising: means for applying a bias to the emitter and the anode. 4. The electron field emission device according to claim 1, wherein said second layer of said emitter is disposed in direct contact with said first layer. 5. The electron field emission device according to claim 1, wherein the first layer of the emitter has a low work function for electron emission. 6. The electron field emission device according to claim 1, wherein the second layer of the emitter contains a substance reactive with the contaminant. 7. The electron field emission device according to claim 1, wherein said first layer of said emitter has a lower etch rate for a given etchant than said second layer of said emitter. An electron field emission device whereby the second layer of the emitter may be differentially etched with a portion of the emitter. 8. The electron field emission device according to claim 1, wherein the second layer of the emitter contains a transition metal. 9. The electron field emission device according to claim 1, wherein the second layer of the emitter is made of aluminum, barium, beryllium, calcium, cerium, copper, cobalt, iron, and lanthanide. Element, magnesium, misch metal, nickel, palladium, thorium, uranium, zinc, titanium, zirconium, hafnium, vanadium, niobium, tantalum,
An electron field emission device comprising a substance selected from the list consisting of chromium, molybdenum, tungsten, their alloys, their compounds, and mixtures thereof. 10. The electron field emission device according to claim 1, wherein the first layer of the emitter contains a transition metal nitride. 11. The electron field emission device according to claim 1, wherein said second layer of said emitter comprises a first transition metal and said first layer of said emitter comprises a second transition metal nitride. Discharge device. 12. The electron field emission device according to claim 1, wherein said second layer of said emitter has an edge and said first layer of said emitter forms an emission tip. An electron field emission device comprising a convex corner portion extending beyond the edge of the layer. 13. The electron field emission device according to claim 8, wherein the transition metal is titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, and an alloy thereof. And an electron field emission device selected from the list consisting of these compounds and mixtures thereof. 14. The electron field emission device according to claim 10, wherein said transition metal nitride is titanium, zirconium, hafnium, vanadium, niobium.
An electron field emission device selected from the list consisting of nitrides of tantalum, chromium, molybdenum, tungsten, their compounds, and mixtures thereof. 15. The electron field emission device according to claim 11, wherein the first transition metal and the second transition metal are the same. 16. The electron field emission device according to claim 11, wherein said first transition metal and said second transition metal are different. 17. An electron field emission device formed on a substrate, comprising: a) an emitter; i) a first layer for gettering contaminants, comprising a first transition metal and comprising: Ii) a second layer emitting electrons, comprising a second transition metal nitride and arranged parallel to the substrate and at least partially in contact with the first layer; B) an anode spaced from the emitter and arranged to receive electrons emitted from the second layer of the emitter; c) the anode of the emitter. An electron field emission device comprising: the emitter comprising: means for applying an electrical bias suitable for causing electron field emission from the second layer to the emitter and the anode. 18. The electron field emission device according to claim 17, wherein the first transition metal is zirconium, and the second transition metal is titanium, tantalum,
An electron field emission device selected from the list consisting of molybdenum, their compounds, their mixtures, and their alloys. 19. An electron field emission device of the type using a cold cathode field emission electron source, comprising: a) a substrate having a substrate upper surface defining a first surface; b) an anode; c) a first predetermined distance. A field emission electron emitter disposed only on the second surface parallel to the first surface and spaced from the anode, i) an upper main body disposed substantially parallel to the second surface. A thin film having a surface and a lower main surface, the thin film having a work function suitable for field emission of electrons; and ii) a first gettering film disposed in contact with the upper main surface of the thin film. And iii) a second gettering film disposed in contact with the lower main surface of the thin film, wherein at least one of the first gettering film and the second gettering film is conductive. And the second gettering film, wherein: D) a first conductive contact connected to said at least one of said first gettering film and said second gettering film of said electron emitter to provide a cathode contact; e. A) a second conductive contact spaced from the first conductive contact and connected to the anode to provide an anode contact, whereby the device may be subjected to an electrical bias voltage; An electron field emission device comprising: two conductive contacts; and f) means for applying said electrical bias voltage. 20. The electron field emission device according to claim 19, wherein the thin film of the emitter is lower with respect to a predetermined etchant than the first gettering film and the second gettering film of the emitter. Having an etch rate, whereby the first gettering film and the second gettering film of the emitter may be differentially etched with a portion of the emitter, whereby the second The first gettering film and the second gettering film are formed so that an edge is formed at each of the first gettering film and the second gettering film, and a sharp emission tip of the field emission electron emitter is prepared. An electron field emission device for forming a convex corner of the emitter extending beyond the edge. 21. A process for making a field emission device with a self-gettering electron field emitter, comprising: a) providing a substrate; b) a first layer of a first transition metal nitride nitride parallel to said substrate. C) disposing a second layer of a second transition metal parallel to and in contact with said first layer; and d) forming an emitter having an emission edge. Etching said first and second layers; and e) said emitting to receive electrons emitted from said emitting edge when a suitable electrical bias voltage is applied to said emitter and anode. Disposing the anode spaced from the edge. 22. The fabrication process of claim 21, further comprising: f) patterning said first layer and said second layer. 23. The fabrication process of claim 21, further comprising the step of: g) disposing the phosphor on the anode that emits light when the phosphor is excited by the electrons. 24. The fabrication process according to claim 21, wherein said etching step (d) comprises the step of: projecting said first layer with a first edge of said first layer extending beyond a second edge of said second layer. A fabrication process comprising forming the first edge on the first edge and the second edge on the second layer to terminate a corner and thus form the emission edge. 25. The fabrication process of claim 21, further comprising: h) disposing a first insulating layer between the substrate and the emitter. 26. The fabrication process of claim 21, further comprising: i) disposing a second insulating layer over the emitter. 27. The fabrication process according to claim 21, wherein the step of disposing the first transition metal nitride layer (b) is performed by disposing a transition metal nitride and disposing the second transition metal layer. A fabrication process in which step (c) is performed by placing the same first transition metal as in step (b), which is in its pure form without nitrogen. 28. The fabrication process of claim 21, wherein the step (b) of disposing the first transition metal nitride layer comprises reactive sputtering the first transition metal while supplying an amount of nitrogen. By removing nitrogen while step (c) of depositing the second transition metal layer continues to sputter the first transition metal, thereby depositing the second transition metal without nitrogen The fabrication process performed. 29. The fabrication process according to claim 21, wherein the step (b) of disposing the first layer comprises titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum. A fabrication process performed by depositing a nitride of a transition metal selected from a list consisting of tungsten, their alloys, their compounds, and mixtures thereof. 30. The fabrication process of claim 21, wherein the step (c) of disposing the second layer comprises titanium, zirconium, hafnium, vanadium, niobium, and tantalum. And chrome,
A fabrication process performed by depositing a transition metal selected from a list consisting of molybdenum, tungsten, their alloys, their compounds, and mixtures thereof. 31. The process for fabricating a self-gettering electron field emission device according to claim 25, wherein: i) the emitter and the first insulating layer while etching the first layer and the second layer. Forming an opening through the fabrication process. 32. The manufacturing process of the self-gettering electron field emission device according to claim 26, wherein: j) the second insulating layer and the emission layer while etching the first layer and the second layer. Forming an opening through the body and through the first insulating layer. 33. A process for making a self-gettering electron field emission device, comprising: a) providing a substrate; b) placing an anode on the substrate, wherein the anode has a top surface. Disposing an anode; c) disposing a first insulating layer over the anode; d) disposing a first layer of a first transition metal nitride in parallel with the substrate; Arranging a second layer of a second transition metal parallel to and in contact with the first layer; f) optionally patterning the first and second layers; g. A) disposing a second insulating layer over the second layer; and h) etching the first layer and the second layer to form an emitter having an emission edge spaced from the anode. And the top of the anode Extending through the first insulating layer, the second insulating layer, the first layer of the first transition metal nitride, and the second layer of the second transition metal while leaving substantially no etch. I) sufficient to cause emission of electrons from the emitter to the anode;
Providing means for applying an appropriate electrical bias voltage to said emitter and said anode. 34. The process for fabricating a self-gettering electron field emission device according to claim 33, wherein the step of disposing the anode comprises disposing a phosphor to form at least the top surface of the anode. Manufacturing process including: 35. The fabrication process of a self-gettering electron field emission device according to claim 33, wherein the step (d) of disposing the first transition metal nitride layer is performed by disposing a transition metal nitride. The fabrication process wherein step (e) of disposing a second transition metal layer is performed by disposing the same first transition metal as in step (d) but in its pure form without nitrogen. 36. The process for fabricating a self-gettering electron field emission device according to claim 33, wherein the step (d) of disposing the transition metal nitride layer reacts the transition metal while supplying an amount of nitrogen. And (e) depositing the transition metal layer and removing nitrogen while continuing to sputter the transition metal, thereby removing the same first transition metal as in step (d). A fabrication process performed by depositing in its pure form without nitrogen. 37. A process for making a self-gettering electron field emission device, comprising: a) providing a substrate; and b) placing a conductive phosphor anode on the substrate, wherein the anode is Disposing said conductive phosphor anode having a top surface; c) disposing a first insulating layer of silicon oxide over said anode; and d) reacting said transition metal in the presence of nitrogen. Placing a first layer of a transition metal nitride parallel to the substrate by sputtering; e) parallel to the first layer and the first layer by continuing to sputter the transition metal while removing the nitrogen. Disposing a second layer of the transition metal in contact with one layer; f) optionally patterning the first layer and the second layer; and g) covering the second layer. Placing a second insulating layer of silicon oxide, h) the first to form a second edge of said first edge of said first layer a second layer
Etching a layer and the second layer such that the first layer includes a convex edge extending beyond the second edge of the second layer, thereby having an emission edge spaced from the anode The first insulating layer, the second insulating layer, and the first layer of a first transition metal nitride while forming an emitter and while leaving the top surface of the anode substantially unetched; Forming an opening by directional etching through the second layer of a second transition metal; i) sufficient to cause emission of electrons from the emitter to the anode;
Providing a means for applying a suitable electrical bias voltage to said emitter and said anode, whereby said means for exciting said phosphor to emit light are provided. 38. A process for making a self-gettering electron field emission device of the type having a lateral electron emitter, comprising: a) providing a substrate; b) forming a first insulating layer parallel to the substrate. Forming the first insulating layer having a top major surface; c) on the top major surface of the first insulating layer; i) below the emitter of the first gettering material. Ii) an emitter center layer of a material having a work function suitable for field emission of electrons; and iii) an emitter upper layer of a second gettering material to form a laminated composite emitter layer. Sequentially depositing; d) optionally depositing a second insulating layer; e) forming an opening by selective and directional etching through the previously formed layer; f) emitter edge To Stacking to remove at least an edge portion of each of the emitter upper layer and the emitter lower layer while leaving at least a convex edge portion of the emitter central layer to form an emitter. Etching the composite emitter layer; g) spaced from the emission edge to receive electrons emitted from the emission edge when a suitable electrical bias voltage is applied to the emitter and the anode. Disposing the anode. 39. A field emission device comprising at least one self-gettering electron field emitter, wherein the field emission device is made by any of the fabrication processes of claims 21-38.