CA2201473A1 - Field emitter display - Google Patents

Abstract

A display having pixels that constitute thin-film-edge field emitter arrays.
The display can provide monochrome or color images of high brightness and high contrast, with wide-angle viewability in a compact and flat package. The power requirement is very low thereby resulting in high luminous efficiency. The display is easily and inexpensively fabricated utilizing well-known integrated circuit and micromachining processes.

Description

W096113848 ~! 2 ~ ~ 4 7 ~ Pcrtuss~/l3264 FIELD El~ ;K DISPLAY
BACKGROUND OF THF INVENTION
The present invention pertains to displays, and particularly to avionics displays.
More particularly, the invention pertains to a flat panel display having high resolution S and bri~htnPee with low power consumption.
No available electronic display meets the above-noted char~cterietics needed fora modern avionics display. The cathode ray tube (CRT) has a high luminous efficiency, superior contrast ratios and excellent viewing angles. However, two deficien-~iee of the CRT are the bulk of the electron gun and large power usage by the deflection amplifiers.
10 There has been much effort expended over the years to develop a flat CRT. Twoapproaches in the development involved, first, folding the electron gun around to be in parallel with the tube face; and second, producing an electron beam for each pixel by means of an areal cathode and a grid system. Of these approaches, the first one was implementPcl in the SONY WATCHMAN and the second one was used in a vacuum 15 fluorescent display (VFD) of ISE. These were the only cornmercial SllC'CÇSSÇS of such approaches.
Others have demonetr~te~l the use of a cone field emitter array (CFEA) as the areal cathode. However, both VFD and the CFEA device do not use high luminous efficiency phosphors from which one can obtain from cathodl~lminescence by 20 employing a high voltage anode circuit. The CFEA device cannot use a high voltage anode because of reliabilit,v problems due to field forming of the emitter tip and emitter erosion by particles desorbed, from ~ulr~ces by electrons.
A device is needed that retains the advantages of cathodl.l...;..t~scr.~-~e such as high brightnPee, high luminous efficiency and good angular viewability, but has the 25 features of compact thinn~ee, random addressability and low power collsul~ ion.
SUMMAl~Y OF TE~F I~VFNTION
The present invention provides all of the above-mentioned features desired in a display. It is a thin-film-edge field emitter array (FEA) dispiay (or lamp) that has a two-limeneional array of matrix addressable thin-film-edge field emitters as electron sources 30 for a cathodolllminescent screen. The advantages of the present invention over previous FEA displays are that the radius of curvature of the emitter is determined by film deposition r~-slllting in better uniformity and higher current densities, the series resistor a~ ~ 41 3 WO 96113848 ~ - PCI/US95/13264 0

-2 -for current bias is easier to implement, the fabrication process is based on integrated circuit (IC) and microm~-hining processes that lead to lower cost m~nllf~-tnrinFr emitter burnout is elimin~te~ by using an on-chip focusing electrode which provides for higher reliability and yield, and higher luminous efficiency results because of the use of high voltage phosphors.
Other advantages of this invention are high bri~htn~ and high contrast because electron emission current increases exponentially with increasing voltage, leading to high brightn~s~, large dynamic range and high transcon~lnct~nce with the use of thin-film-edge ~ ni~ and high-voltage phosphors. Also there is high-yield m~nnf~cturing since each pixel consists of more than 100 emit~in~ edges leading to a high degree of reclnn-l~ncy. Only a current density of < S,uA/cm2 is required for a brightn~ss of 1000 fL, assuming a screen voltage of 15 kilovolts and luminous efficiency of 20 lumen/watt.
Current equalization resistive elements prevent a single failure from pulling the pixel or line/row of pixels low, leading to a defect-tolerant flat-panel display fabrication process.
The edge emitter does not suffer from the deleterious effects of field forming and particle inthlce~l desorbtion emitter erosion. Hence the device can use high-voltage phosphors without any reliability problems. This allows the use of more efficient phosphors and consequently lower power operation for the same brightnP~ and permits high-resolution proximity focusing. High-voltage phosphors have long lifetimes because they require less current, and high luminous efficiency phosphors lead to low power consumption.
BRTFF DF~CE~TPTION OF THF D~AWING
Figure 1 shows a basic comb-tooth edge field emitter.
Figures 2a and 2b illustrate emitter edges.
Figure 3 shows a perspective of an emitter.
Figures 4 and 5 show views of another kind of emitter.
Figure 6 is a side cutaway view of an emitter.
Figure 7 is a cross-section view from figure 6.
Figures 8a-c show three comb structures of an emitter.
Figure 9 reveals an array layout of emitters.
Figure 10 is a cross-section of a thin-film-edge emitter used in a flat panel display.

2 2 ~ ~ 4 7 ~

Figure l l shows the place of the field emitter in a display.
Figure 12 is a portion of the structure of a display having field elllill~l ..
Figure 13 is a ~cl~e~ e view of a field emitter microstructure.
Figure 14 is a flow chart for fabrication of a field emitter array display.
S Figure 15 illu~lla~es a l~min~tçcl emitter structure.
Figure l 6 shows a dual control electrode emitter structure for a display.
Figure l 7 shows a single control electrode emitter structure for a display.
Figure l 8 reveals a planar thin film edge field emitter for a display, having the phosphor layer on the same substrate as the field emitter.
DF~.CRTPTION OF THF SPFCIFIC FMRO~)IMFNT
Figure l shows the basic comb-tooth edge field emitter 20. Emitter 20 has a lead-in conductor l, is in electrical connection with an outside voltage source, and is in contact with an emitter .Llu;lul~ 3, through a resistive element 5, and a conductive element 6 at electrical contact 2. Lead-in conductor l preferably physically contacts l 5 only resistive element 5.
Emitter edge 4 of emitter structure 3 is segm~nt~d into a plurality of comb-likeelelnent~ e~ ... en. The segmçnt~tion of the emitter edge serves to isolate burn-out problems. Lo~1i7ing the edge length will prevent spreading of the burn-out and confine the problem to its origin~ting comb elem~nt A resistive film 5, typically but not limited to tantalum nitride or a polysilicon, is formed through thin film construction techniques to be in contact with emitter structure

3 so that the re~i~t~nce applied is in series with emitter edge 4. The resistive film serves to limit excessive direct current (D.C.) emission ~ L~. to the emitter edge from sharp points or uncontrollable discharges from stray capacitance.
A conductive film 6 and an in~ tor l l, which may be an oxide or nitride. is also obtained through thin film techniques layered above resistive film 5 such that the elements are in parallel with each other. Together, resistive film 5, insulator l l, and conductive film 6 serve as a capacitor which provides a high frequency bypass for altt-rn~ting current (A.C.) through lead-in conductor l. The capacitor enables amplification of high frequency microwave signals as if the current limiting load line were due to a very small resistor, thus greatly increasing the gain of the amplifier. This is so because the D.C. current is limited in its ability to damage the emitter by the :2 2~ ~ ~7 3 - ` O 96/13848 PCr/US95/13264 0

-4-resistor; and because the bypass capacitor provides another way for the high frequencysignal to pass the emitter.
Figures 2a and 2b illustrate two emitter edges 61 and 62, respectively, with arrows suggesting electron flow at the edge of each. The ridged edge 62 type is S presently ~lcfc.lc:d because the corners of edge 61 are likely to cause concentration of electron emission and begin failure.
Figure 3 shows a ~c;ls~e~;Li~e view of the emitter illustrated in figure 1. The structure shown at item 7 serves as a support layer. Also visible in this view is insulating subst~ate layer 12, and upper and lower control electrodes 8 and 9. A control 10 electrode acts as a lateral gate which controls the current flow between anode l O and electron-ennittinE cathode 4.
Figures 4 and 5 show plan and perspective views, re~e-;Li~ely, of a second kind of emitter. In this configuration, the entire emitter structure is segm~nt~cl into comb-like elements 4; Each comb-like elem~nt el ... en has an individual resistor element 5 conn~cting it to conductor contact 2.
The arrangement of the second configuration enables a larger total current to bedrawn without burning out the individual comb elements. The first configuration shown in figures 1 and 3, enables a lesser amount of total current to be drawn than the second configuration (~ rning the two were of the same size), but has a more effective capacitive coupling because of the larger area of the resistive film.
Figure 6 shows a side cutaway view which could ~el~les~llL either one of the twoconfigurations of the emitter. Also shown in figure 6 is dielectric material 11, between conductive element 6 and resistive element 5, as well as in~ ting substrate 12 upon which the emitter is constructed.
Figure 7 is a detailed side view taken at line 7-7 of figure 6. From the top, there is a support layer 15 (preferably nitride, though other well known support layers with similar electrical characteristics could be used). Upper control electrode 8 (preferably TiW, around 2500 angstroms, though other metals or conductive materials could beused), an upper sacrificed layer 16 (preferably SiO2; about 3000 angstroms, although other supporting materials of similar electrical qualities could be substituted); the emitter surrounded by two support layers, i.e., the support layers are nitride 1 1 a and 1 1 b of about 2000 angstroms in thickness and the emitter e, a 300 angstrom layer of TiW, 7 ~
WO 96/13848 PCrlUS95113264

-5-although ~ub~Li~uLe m~ten~l~ may be used as in the similar above layers). Below this, is another "lower" sacrifice layer 17, similar in makeup and thickness to upper sacrifice layer 16 and lower electrode 9, about 1000 angstroms of TiW. The whole structure is ~ul~o~L~d by another support layer 11 (of about 1000 angstroms) and laid down upon S SiOz wafer 12 (again, here too, sul~liluL~s such as crystalline silicon could be substituted, for inct~n-~e Most r~t n~hle substitute m~t~n~l~ will occur easily to one of oldill~y skill in these arts.).
Figures 8a, 8b and 8c illustrate three alternatives for comb structure 4 combined with resistor elements 2. Figure 8d is a side cross-section view of element e of the configuration shown in figure 8b.
Figure 9 shows a piece 40 of an array employing ~ 41, 42, 43, and 44, and resistor elements 2a, 2b and 2c. Control electrode wires 50, 52 and 54 (met~li7~tion or other current carrying structures) and lines 63 and 65 are connPct~d at junctions 51 and 53, '~jlJe~ VelY~ to turn on emitter 41.
Figure 10 is a ~ gr~Tn that reveals further details of a thin-film-edge emitter 70 that is used in an FEA flat panel display. On a substrate 71 is a nitride layer 72 of about 2500 angstroms. Formed on layer 72 is a gate electrode 73 which is of about 1000angstroms thick of TiW. Forrned on layer 72 is a 3500 angstrom layer 74 of oxide.
Found on oxide layer 74 is a 1500 angstrom layer 75 of nitride which is used to support 200 to 300 angstroms of TiW as emitter edge layer 76. A 1500 angstrom nitride layer 77 is formed on emitter edge layer 76. Nitride layers 75 and 77 provide structural ~u~ulL for emitter layer 76. Formed on layer 77 is a 3500 angstrom layer 79 of silicon dioxide. Gate electrode 80 of about 2500 angstroms of TiW is formed on a portion of oxide layer 79. A 2500 angstrom layer 81 is formed on gate electrode 80 and oxide layer 79.
The edges of gate electrodes 73 and 80, and nitride layers 72, 75, 77 and 81 areapproximately aligned with the emitting edge of emitter edge layer 76. A via is etched in layers 77, 79 and 81 for forming emitter control via resistive metal 78, which is effectively a resistor in connected in series with emitter edge 76. Metal 78 is TaN.
Oxide layers 74 and 79 are etched back about 0.5 micron from the emitting edge of emitter edge layer 76. Also formed on substrate 71 is nitride layer 82 of about 2500 angstroms that is apart from the emitter edge wafer 70. Formed on layer 82 is anode 83 ~20 ~ ~7 3

-6-having about 0.5 micron layer of TiW. The metal of items 73, 76, 80 and 83 may be other than TiW but needs to have a similar work function so as to prevent electroçhPmic~l reactions that would occur between such items composed of di~relel1t metals. Anode 83 functions as a focusing electrode for the electrons emitted from emitter edge 76. Anode 83 is adjustable in ~ t~n~e about 1.5 to 4 microns from edge 76, to effect optimum focusing.
Emitters 70 may be formed as a comb tooth emitter having a plurality of teeth asassemblies 20 and 21 shown in figures 3 and 5, respectively. The number of teeth of the emitter is not critical but a ~lefelled number for a display may be four as field emitter 84 of figure 11 has. Each emitter tooth has a width 85 of about 4 microns wide. Emitter 84 has tlim~n~ion 87 of about 30 microns, and is one of the ~ rs that compose pixel 88 which has a limen~ion 89 of 100 to 300 microns on each side. A two rlimencional array of pixels 88 compose a matrixed addressable pixel array 90, having a ~1imen~jon 91 ~letprmine(l by resolution and pixel size. The numbers of e.,.iLI. i 84 in a pixel 88 and of pixels 88 in array 90 are a matter of design choice.
Figure 12 shows a portion of the structure of display 100, having field emitters84 .~ itll~te-l on substrate 71. Column address cc)nllllrting strip 92 and row address conducting strip 93 select the particular pixel 88 to be turned on to emit electrons which go to an out-of-plane screen 97. Strip 92 is cl nn~ctefl to the gate of field emitter 84 and strip 93 is connected to the resistor/emitter of field emitter 84. Screen 94 is composed of a glass plate or substrate 95. A phosphor layer 96 is formed on glass plate or substrate 95 and a tin al~ .... (Al) layer 97, ll~ls~uclll to beams 98 of electrons but conductive of electric signals, is formed on phosphor layer 96. Layer 97 is connected to a positive terrnin~l of a voltage source that has the other negative terrnin~l connected to the respective emitters 84. Electron emissions 98 impinge pho~ ph~r layer 96 as they go through anode 97. As phosphor layer 96 is impinged by emitted electrons 98, layer 96 emits photons in the area which is impinged by emissions or electrons 98, resulting in a visible indication of light to an observer. Alternatively, layer 96 may be an indium tin oxide (ITO) film, which is conductive of electric signals but Lldl~pdl~llt to light, formed on glass plate or substrate 95; and layer 97 may be phosphor formed on layer 96 which is connected to a positive terrnin~l of a voltage source that has the other negative terminal conn~oct~l to the les~e~;Li~re emitters 84. Film or layer 96 is the anode for WO96/13848 a ;~ 7 ;~ Pcr~usss/l3264 collecting electron emissions 98 of emitters 84. Electron emissions 98 impinge phosphor layer 97 as they go to anode 96. As phosphor layer 97 is impinged by emitted electrons 98, layer 97 emits photons in the area which is impinged by emissions or electrons 98, resulting in a visible indication of light to an observer. On glass plate is coated an antireflective film 111 for enh~ncecl viewing. Screen 94 is supported parallel to substrate 71 by dielectric spacer 99 at a ~ t~n~e of between 200 and 10,000 microns between screen 94 and ~n~str~te 71.
In figure 13 is a configuration of a vacuum microelectronic field emitter microstructure 101 that may be used in arrays for radio frequency (RF) amplification. A
thin-film-edge emitter 102 is sandwiched between control electrodes 103 and 104.Electrons are emitted laterally from emitter 102 and are collected at anode 105 a few microns away from emitter 102. Structure 101 is fabricated with a process which combines silicon integrated circuit (IC) p~ techniques with surface microm~rhinin~, as is outlined as a simrlifie~l process in figure 14.
Field emitter structure 84 of display 100 in figure 12 is similar to structure 101 in figure 13. However, anode 105 of structure 101 would be a focusing electrode.Emitter edge 102 of structure 101 is split into comb elemPnt~ 106 and each emitter comb element or finger 106 is connected individually to a current equalization resistive layer or element 107. Resistive element 107 prevents electromigration and burnout of emitting edge 102 by limiting the D.C. current in each finger 106. Thin-film edge emitter structure 102 having comb resistors 107 for fingers 106, permits individual bias for each emitter thereby preventing a few shorts from pulling the line voltage down.
Lateral series resistor 107 is not sensitive to slight fabrication process variations. Thin-film-edge emitter 102 has low intrinsic capacitance. Series resistor 107 of fingers can be bypassed at the al~propliate frequencies by a bypass c~p~itc-r 108 to allow fast emitter 101 response times.
Emitter edge 102 fingers 106 need to be thin (i.e., ~200 angstroms) to attain the high electric fields for low-voltage emission. The ideal emitter structure is a tapered lateral emitter having a very thin emitting edge, which is difficult to achieve in a thin-film-edge emitter forrn. Figure 15 shows a conl~lomise l~min~t~rl emitter structure 109 that combines the advantages of the thin-film-edge sharpness with the current carrying capability of a thick film. The opeld~hlg gate voltage is kept reasonably low by using a 22~ 47 3 o 96/13848 1 ~,1/u~51l3264 0 low workfunction emitter composed of LaB6, CeB6, C5-implanted Wl or Cs-implantedTiW.
Several field emitter structures, based on the thin-film-edge emitter, are suitable for displays. One is a dual control electrode structure 110 in Figure 16, which S resembles a vacuum transistor used for RF amplification. Emitter 112 is symmetrically placed between an upper control electrode 113 above emitter 112 and a lower control electrode 114 situated on substrate 118 below emitter 112. Electrodes 113 and 114 are electron emission 116 intensity controlling gates. Electrodes 113 and 114 are each spaced at 0.5 microns apart from emitter 112. The anode of a vacuum transistor is used as a focusing electrode 115, situated on substrate 118, which is biased between a minus 20 and minus 50 volts, typically at a minus 35 volts, with respect to emitter 112.
Electrode 115 is about 4 microns from emitter 112. Emitter 112 is set at zero volts and control electrodes 113 and 114 are set at about a plus 100 volts. The negative bias on electrode 115 turn electrons 116 form a lateral direction to a vertical direction toward screen 117. Screen 117 has a glass plate 119 with an ITO layer 120 formed on it. ITO
layer 120 is connected as an anode or collector for electrons 116. Formed on ITO layer 120 is a layer of phosphor 121. Phosphor layer 121 is about 2,500 microns in tli~t~n~e from parallel substrate 118. Collector 120 is biased at a positive 20,000 volts (i.e., at a field of 8 volts per micron). The electron energy spread of emission 116 is about 0.1 electron volt (eV) and the emission angle is + 45 degrees.
Another display field emitter structure is the single control electrode configuration 122 shown in figure 17. Configuration 122 has the same items, physical ~lim~ncions, voltage requirements, and operational characteristics as configuration 110 of figure 16. The only distinction is that there is no lower electrode or gate 114 in configuration 122. The position and height of focus electrode 115 has an effect on the collimation of electrons 116. The best position for electrode 115 is below emitter 112 for configuration 110 and is at the same level as upper control gate 113 for configuration 122. The electrons seem to be better collim~ted in configuration 122.
Both configurations 110 and 122 are little susceptible to emi~ter 112 erosion byenergetic particles desorbed by electron 116 bombardment of phosphor screen 121.The p~lrol--lance specifications of a small FEA display are shown in the following table.

7 ~

8 PCT/US95/13264 Full color 8 bits/color Resolution 160 dpi Bri~htne~ 300 fl Contrast ratio >lO0:1 Dimmability 2000: 1 Frame rate 60 Hz Pixel size 200 ~m x 150 ~m Anode/Emitter sp~cin~ 1000 - 2500 llm Gate/Emitter sp7~cing 0.5 ~m Anode/Emitter voltage 20,000 V
Gate/Emitter voltage 100 V
L~lmin~nce (brightn~) 7000 cd/m Filter ~ re 0.1 Intrinsic contrast 300:1 Response time ~ 5 ms Viewing angle + 90 In this example, there is a brightness (lnmin~nce) of 700 cd/m2 (~ploxilllately 210 fL) with the contrast enh~nrement filter. If the tr~n~mitt~nce of the contrast S enhancPment filter T is 0.1, this tr~n~l~tes into a bri~htnP~ (l--min~n~e) L of 7000 cd/m2 at the emitting source. For a Lambertian surface producing directionally uniform l~min~nee~ the luminous exitance M is given by M -- pL

The total luminous flux Fv through each pixel is thus ¦M dA
Fv = ~
MA
7~LA

W096/13848 '~ 2 ~ ~ 'I 4 7 3 PCTtUS95tl3264~

where A is the area. For a pixel size of 200 ,um x 150 ,um, A = 3 x 104 ~Lm2 = 3 x 1 o-8 m2~
Fv = 6.60 x 10-4 lumen 5 The spectral luminous efficacy k(l) at wavelength of l is given by k(l) = FVl where FVl is the spectral lurninous energy flux and Fel is the spectral radiant energy flux Fvl = _ Fel = _1 10 and where Fe is the total radiant flux. The total luminous efficacy is given by K
K = Fv rk(l)Fel dl o rFel dl o With K = 25 lm/W, then the radiant flux is Fe = 0.026 mW
For a display operated at an anode voltage Va = 20,000 volts, then the anode current per pixel is given by F

Ia = vea 1.32 nA /pixel Phosphor layer 121 acts as the anode and may be deposited on the glass. This 20 may be followed by a thin layer 120 of Al which is a con~ cting layer and also acts as a reflector. In operation, the emitted electrons travel to anode 121, causing luminous emission when they impinge on phosphor screen 121. High-voltage phosphors are - much better than low-voltage phosphors because the briPhtnes~ is ~r~pullional to the accelerating voltage and the current density, and phosphor lifetime is inversely wo96113848 ~ 9 4 7 ~ 3264 proportional to the deposited charge density. The following table co~ al~s the characteristics of low- and high-voltage cathodoluminescent phosphors.

Low Voltage High Voltage 200 V, 100 !1A/cm2 16 KV, 4 !1A/cm2 Color Material Efficiency Material Efficiency (lm~W) (lrn/W) Red Zno 2Cdo gS:Ag, Cl 1.3 Y2O3:Eu 18 Green ZnO~62cdO~38S:Ag, 4-5 Gd2O2S:Tb 33.0 Cl Blue ZnS:Ag, Al 0.6 ZnS:Ag 3.0 Bri~htnesc c~ accelerating voltage Brightnec~ ~ current density Life cc l/deposited charge In figure 12, the phosphor screen is part of individual edge emitter array 84.
Array 100 may emit one of several colors, depending on the kind of phosphor 97 that screen 94 has. The above table gives examples of materials used for z~ ining red, green and blue light emitting phosphors. Pixel 88 of an array of field ~nliL~ 84~ along with a phosphor screen 94 like that of figure 12, may be designed to emit red, green or blue light, even light of another color with the a~ o~l;ate phosphor. Thus, red, green and blue pixels can be placed in matrixed addressable pixel array 90, for obtaining a full color field emitter display. The pixel layout, for instance, may be that each pixel of a given color is bordered by pixels of the other colors. Examples of color pixel formats, for three and four color matrix arrays, are set forth in the related art, such as a United States patent, number 4,800,375, by Louis Silverstein et al., issued January 24, 1989, and entitled "Four Color Repetitive Sequence Matrix Array for Flat Panel Displays,"
which is hereby incorporated by reference in this description.
If the required lllminz-nce (brightness) of the flat-panel display with a contrast enhancement filter is L, then for a Lambertian (diffuse) surface, the luminous exitance 20 M is given by M = 7~ L .
SUBSTITUTE Sl IEET (RULE 26) 2 ~ o Wo 96/13848 ` -12- Pcr/uss5/l3264 If the filter Ll~l~llliU~lce is T, then the actual luminous exitance Mo is given by M 7~L
Mo = T = T

5 and the luminous flux ~ v is given by ~LA
~v = MoA =--For a 5-in. x 5-in. avionics display, the area A = 161.3 cm2 = 1.613 x 10-2 m2. If the luminous exit~n~e L = 200 fl, a 700 cd/m2 and the filter LldllsllliLLi~lce T ~ 0.3, then Mo ~ 7300 cd/m2 and the luminous flux ~Pv is given by ~ v = MoA (~ 120 lm .

For a phosphor with luminous efficacy of K and anode voltage Va, the current density 15 required is J (P r KA Va The phosphor lifetime t is det~nnin~d by the total charge density QL deposited;

QL = Jt, and = Q, = Q, KA V,/
J (1)"

Typically QL = 106 COU1Omb/m2 t = 2.688 x 102 KVa sec.

WO96/13848 ~ 7 ~ i."95/l3264 For low-voltage phosphors, K = 2 lm/W and Va = 200 V, thus t = 15 h (2 days at 8 h/day).

S For high-voltage phosphors, K = 25 lm/W and Va = 20,000 V, thus t = 37,500 h (210 years at 8 h/day).

For lifetime considerations, high-voltage phosphors are better than low voltage phosphors. An issue that needs to be addressed is the breakdown of dielectric spacers due to the high anode voltages. However, dielectric breakdown should not be an issue since at 20,000 volts, the electric field of dielectric spacers 99 (in figure 12) is below 105 V/cm.
A third display field emitter structure is an on-chip phosphor screen configuration 124 in figure 18. Configuration 124 is a derivative of configuration 110.
A trench 125, between 1.0 to 2.5 microns deep, is etched (with microm~inin~) in ~ulJ~ 118intheareaofformerfocusingelectrode 115. Ananode 123 isdeposited in trench 125. After the anode 123 deposition, a phosphor layer 127 is defined by e-beam evaporation and lift-off. Electrons 126 go from emitter 112 towards phosphor screen 127 and anode 123, to emit photons for viewing. Laterally, anode 123 is between 2 to 10 microns from the nearest edge of emitter 112. The anode 123 voltage is equal to or greater than positive 500 volts relative to emitter 112 which is at a zero voltage.
Upper control gate 113 and lower control gate 114 are at 100 volts and situated similarly relative to emitter 112 as in configuration 110 of figure 16.

Claims (21)

THE CLAIMS

1. A thin-film-edge field emitter array display comprising:
a substrate;
a plurality of field emitters situated on said substrate, the emitters arranged on said substrate in rows and columns, each emitter having first and second terminals;
a plurality of row address conductors connected to the first terminals of said plurality of emitters;
a plurality of column address conductors connected to the second terminals of said plurality of emitters; and a phosphor screen at a distance from said substrate; and wherein:
excitation of each emitter is effected by an application of a signal to a row address conductor and a column address conductor connected to the emitter; and excitation of each emitter results in emission of electrons to said phosphor screen resulting in emission of photons from said phosphor screen.

2. The display of claim 1 wherein each emitter comprises:
a cathode connected to the first terminal;
an anode connected to the second terminal; and a first control electrode.

3. The display of claim 2 wherein each emitter further comprises a second control electrode.

4. The display of claim 3 wherein said phosphor screen comprises:
a glass sheet;
a layer of phosphor formed on the glass sheet, and a metal film formed on the layer of phosphor film.

5. The display of claim 3 wherein said phosphor screen comprises:
a glass sheet;
a metal film formed on the glass sheet; and a layer of phosphor formed on the metal film.

6. The display of claim 4 further comprising at least one dielectric spacer for supporting phosphor screen relative to said substrate.

7. The display of claim 6 wherein the anode of said emitter is a focusing electrode.

8. The display of claim 2 wherein said phosphor screen is situated on the anode of said emitter.

9. The display of claim 8 wherein said field emitter further comprises a comb emitter structure.

10. The display of claim 9 wherein said field emitter further comprises a resistive element inserted and connected in series between the cathode and the first terminal, for limiting current to the cathode.

11. The display of claim 9 wherein said field emitter further comprises:
a resistive element inserted and connected in series between the cathode and the first terminal, for limiting current to the cathode; and a capacitive element connected in parallel with the resistive element.

12. A thin-film-edge field emitter array display comprising:
a plurality of pixels, wherein each pixel comprises at least one field emitter, each pixel having first and second terminals;
a plurality of row address conductors connected to the first terminals of said plurality of pixels; and a plurality of column address conductors connected to the second terminals of said plurality of pixels; and wherein:
activation of each pixel to emit light, is effected by an application of a signal to a row address conductor and a column address conductor connected to the pixel.

13. The display of claim 12 wherein said plurality of pixels comprises a phosphor screen.

14. The display of claim 13 wherein the field emitter of each pixel, comprises:
a cathode;
a resistor connected in series between the cathode and the first terminal of the pixel;
a focusing electrode proximate to the cathode; and a first control electrode.

15. The display of claim 13 wherein the field emitter of each pixel, further comprises a capacitor connected in parallel with the resistor.

16. A field emitter display comprising a plurality of pixels wherein each pixel of said plurality of pixels comprises at least one field emitter, having a phosphor screen, for emitting light.

17. The display of claim 16 wherein said plurality of pixels comprises:
a first group of pixels having the capability of emitting light of a first color;
a second group of pixels having the capability of emitting light of a second color; and a third group of pixels having the capability of emitting light of a third color.
a first control electrode.

18. The display of claim 17 wherein said plurality of pixels are arranged on the display such that each pixel of one group of pixels is proximate to pixels of the other two groups of pixels.

19. The display of claim 18 wherein:
the phosphor screen of each pixel of the first group of pixels, has a first kind of phosphor for causing emitted light to be of the first color;
the phosphor screen of each pixel of the second group of pixels has a second kind of phosphor for causing emitted light to be of the second color; and the phosphor screen of each pixel of the third group of pixels has a third kind of phosphor for causing emitted light to be of the third color.

20. The display of claim 19 wherein the at least one field emitter of each pixel, comprises:
a cathode for emitting electrons;
a resistor element, connected in series with the cathode, for limiting electrical current to the cathode; and an anode, proximate to the phosphor screen of each pixel of said plurality of pixels, for attracting electrons emitted by the cathode to impinge the phosphor screen and thereby emit light.

21. The display of claim 20 wherein:
the at least one field emitter of each pixel further comprises a capacitive element connected in parallel with the resistive element, for conducting varying amplitude electrical current signals to the cathode; and the cathode has a comb-like shape.