JP3084768B2 - Field emission type cathode device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field emission type cathode device.

[0002]

2. Description of the Related Art Spindt (S) is a small-sized field emission cathode having a cathode size of several μm or less.
Pindt) type field emission cathode devices are known.
This Spindt-type field emission cathode device will be described with reference to FIG.

In FIG. 6, reference numeral 1 denotes a conductive material such as Si.
A first electrode comprising:
Made of high melting point and low work function metals such as W and Mo
For example, a conical cathode 9 having a sharp tip
Is formed, and SiO2 is formed around the _TwoThe insulating layer 2 consisting of
Formed on the insulating layer 2 such as Mo, W, and Cr.
The second electrode 3 serving as a gate electrode made of a high melting point metal is
The structure arranged as a counter electrode to the sword 9 is adopted.
You.

As a method for obtaining such a field emission type cathode device, for example, as shown in FIG. 7A, first, a substrate 1 made of Si or the like is prepared, and then a substrate 1 having a required thickness of, for example, 1.
An insulating layer 2 made of SiO ₂ or the like having a thickness of about 1.5 μm is entirely deposited by a CVD (chemical vapor deposition) method or the like, and a metal layer made of a high melting point metal such as Mo or W is further provided. 3
The thickness a is set to about several thousand Å, for example, 4,000 Å, and the entire surface is deposited by vapor deposition, sputtering, or the like, and a resist 4 is further entirely coated thereon.

[0007] As shown in FIG. 7B, the resist 4 is subjected to pattern exposure and development by application of photolithography or the like to form, for example, a circular opening 5 a having a width w, for example, a diameter of about 1 μm. I do. Further, RI is applied to the metal layer 3a through the opening 5a.
Anisotropic etching such as E (reactive ion etching) is performed to form an opening 5 having the same opening width as the opening 5a, thereby forming the gate electrode 23 made of the electrode layer 3a. Then, the insulating layer 2 is etched through the opening 5 to form the cavity 6. The etching of the insulating layer 2 is over-etched, and the gate electrode 23
Of the opening 5 project from the inner wall of the cavity 6 of the insulating layer 2.

Next, as shown by an arrow a in FIG. 7C,
Oblique deposition is performed while rotating the base 1 at an angle that does not cause the gate electrode 23 to adhere to the inside of the opening 5 and the cavity 6.
An intermediate layer 7 is formed thereon. The intermediate layer 7 is formed of, for example, Al, such as Al or Ni, which has etching selectivity with respect to a material layer to be described later, which is deposited thereon, and the angle θ of oblique deposition with respect to the surface of the base 1 at this time. Is 5
° to 20 °. The opening 5
Above, the diameter of the intermediate layer 7 is substantially narrowed and applied.

[0007] Thereafter, as shown in FIG. 7D, a material layer 8 made of, for example, Mo is entirely deposited by vertical evaporation or the like to form, for example, a conical cathode 9 in the cavity 6. At this time, since the diameter of the intermediate layer 7 around the opening 5 is reduced by the above-described oblique vapor deposition and is applied, the substantial diameter of the periphery of the opening 5 of the material layer 8 is accordingly reduced with time. The cathode 9 deposited on the substrate 1 through 5 is formed in a conical shape, for example, a conical shape having a smaller diameter as its thickness gradually increases.

Thereafter, the intermediate layer 7 is etched using an etching solution capable of melting and removing only the intermediate layer 7 such as NaOH.
, And at the same time, a so-called lift-off for removing the material layer 8 thereon, to obtain the field emission type cathode device shown in FIG.

The field emission type cathode device formed in this manner has a potential of about 10 ⁶ between the gate electrode 23 and the cathode 9.
By applying a voltage of about V / cm or more, electron emission can be performed without heating the cathode 9. In particular, according to the field emission type cathode device having a small size as described above, it is possible to operate at a relatively low gate voltage of several tens to several hundreds of volts.

However, in the field emission type cathode device as described above, Mo, W, C
Although a high-melting point metal such as r is used, such a material is relatively easily oxidized, so that the electrical conductivity may be reduced, and as a result, it is difficult to obtain stable electron emission. There's a problem.

Further, in the step of removing the intermediate layer 7 by wet etching, the intermediate layer 7 made of Al, Ni, or the like is difficult to completely dissolve from above the gate electrode 23 and tends to remain as a residue. In particular, for example, in the case of using this field emission type cathode device as an electron gun in a flat display or the like, it is necessary to arrange field emission cathode devices having a small size of about several hundred million at a pitch of 10 μm. As described above, when a portion where the conductive intermediate layer 7 remains on the gate electrode 23 is generated,
The electron emission characteristics and the cutoff characteristics may fluctuate, and a short circuit between the gate electrode 23 and the cathode 9 may be caused.

The applicant of the present invention has previously described Japanese Patent Application Laid-Open No. 56-160.
In Japanese Patent Publication No. 740, a method of manufacturing a field emission type cathode device that does not use oblique deposition is proposed. This method uses single-crystal Si as a substrate for forming the above-described field emission type cathode device.
And the like. First, a mask layer having a required through hole is formed on one main surface of a Si base or the like, and a crystallographic etching is performed through the through hole to form a conical concave portion. An electrode layer is deposited by vapor deposition, sputtering, or the like, and an insulating reinforcing material is further deposited so as to fill the recess. Then, normal or non-crystallographic etching is performed from the other surface of the base, that is, the back surface, so that the top of the cone of the electrode layer in the recess formed on the main surface is exposed, and this is used as the cathode tip, Thereafter, an insulating layer is deposited on the back surface so as to embed the cathode once exposed, and a conductive layer is further deposited. Then, the insulating layer and the conductive layer are formed in the same manner as in the example described with reference to FIGS. Through holes are formed in the layer, and the cathode is exposed to obtain a field emission type cathode device.

According to such a method, the tip of the cathode can be reliably formed in a conical shape with an acute angle.
Further, it is possible to avoid a change in characteristics due to the residue of the intermediate layer 7 as described above. However, even in this case, the problem of a decrease in electrical conductivity due to oxidation of the gate electrode still exists, and since the gate electrode has a small thickness of at most several thousand Å as described above, There is a possibility that a significant decrease in electrical conductivity, that is, a significant increase in resistance value may occur. For this reason, there arises a problem that it becomes difficult to perform an operation with a gate voltage of about several tens to several hundreds of V.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to provide a field emission type cathode device which can suppress oxidation of a gate electrode and stably emit electrons.

[0015]

FIG. 1 is a schematic enlarged sectional view of an example of a field emission type cathode device according to the present invention. In the present invention, as shown in FIG. 1, on a base 1 on which a first electrode is formed,
An insulating layer 2 having a cavity 6 formed therein, a cathode 9 formed on the first electrode 1 inside the cavity 6,
In the field emission cathode device including the second electrode 3 formed on the insulating layer 2, a metal protective layer 13 having excellent conductivity and corrosion resistance is applied to the surface of the second electrode 3.

[0016]

As described above, in the field emission type cathode device of the present invention, since the metal protective layer 13 having excellent conductivity and corrosion resistance is deposited on the surface of the second electrode 3, that is, the gate electrode, the second electrode 3 is formed. It is possible to obtain a field emission type cathode device capable of suppressing the oxidation of the electrode 3, avoiding an increase in the resistance value, and performing stable electron emission by applying a required low voltage.

[0017]

Embodiment 1 An example of a field emission type cathode device of the present invention will be described with reference to FIG.
This will be described in detail. In FIG. 1, 1 is a conductive material such as S
i, etc., serving as a first electrode.
For example, gold having a high melting point and a low work function, such as cone-shaped W, Mo, etc.
, For example, a cone-shaped
A sword 9 is formed, and SiO _Two, Si_ThreeN_Four
An insulating layer 2 is formed on the insulating layer 2.
Is Mo, W, Cr, WSi_xConsisting of high melting point metal such as
The second electrode 3 serving as a gate electrode is paired with the cathode 9.
It is arranged as a counter electrode. And especially the electric field emission of the present invention
In the exit cathode device, a conductive material is provided on the second electrode 3.
Au, Pt, etc., which have excellent heat resistance and corrosion resistance, such as Au
The structure in which the metal protective layer 13 is applied is adopted.

Embodiment 2 A description will be given with reference to an enlarged schematic sectional view of FIG. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted. In this case, a substrate 1 made of glass or the like is coated with a conductive layer serving as a first electrode 11 made of Al, Cr, or the like to form a base 1, and as shown in FIG.
The electrodes 3, a polycrystalline Si layer 12, W, WSi _x, Mo
Si _x, metal made of refractory metal such TiSi _x layer 22
And was constituted by. Also in this example, a structure in which a metal protective layer 13 made of, for example, Au such as Au or Pt having excellent conductivity and corrosion resistance is applied on the second electrode 3 is adopted.

The theory of such a field emission type cathode device of the present invention.
In order to facilitate the solution, an example is described in the first embodiment.
3A to 3D for the method of manufacturing the disclosed field emission cathode device.
I will explain. For example, as shown in FIG.
Prepare a substrate 1 consisting of
SiO having a thickness of about 1 to 1.5 μm_Two, Si _Three
N_FourSuch as SiO_TwoInsulating layer 2 made of CVD or the like
With Mo, etc., and several thousand mm thick
Made of a metal layer 3a of, for example, 4000
Metal protective layer 13 having a thickness of about several tens to several thousand degrees, for example, 100 degrees
And the entire surface by evaporation, sputtering, etc.
Then, a resist 4 is applied over the entire surface.

Then, as shown in FIG. 3B, the resist 4 is subjected to pattern exposure and development by application of photolithography or the like to form, for example, a circular opening 5a having, for example, a circular opening width w, that is, a diameter of about 1 μm. I do. Further, RI is applied to the metal layer 3a through the opening 5a.
Anisotropic etching such as E (reactive ion etching) is performed, and an opening 5 having the same opening width or diameter as the opening 5a is formed.
Is formed in the metal protection layer 13 and the metal layer 3a to form the second electrode 3 on which the electrode protection layer 13 is adhered. Then, the insulating layer 2 is etched through the opening 5 to form the cavity 6. The etching of the insulating layer 2 is over-etched so that the periphery of the opening 5 of the second electrode 3 protrudes from the inner wall of the cavity 6 of the insulating layer 2 in an eaves shape.

Next, as shown by an arrow a in FIG. 3C,
The oblique deposition is performed while rotating the substrate 1 at an angle such that the intermediate layer 7 does not adhere to the cavity 6, and the intermediate layer 7
Is formed. The intermediate layer 7 is made of Al, which has an etching selectivity with respect to a material layer to be deposited thereon, which will be described later,
The oblique deposition angle θ with respect to the surface of the base 1 at this time is about 5 ° to 20 °. Due to this oblique deposition, the diameter of the intermediate layer 7 is substantially reduced over the opening 5 and is applied.

Thereafter, as shown in FIG. 3D, a material layer 8 made of, for example, Mo is entirely deposited by vertical deposition or the like to form, for example, a conical cathode 9 in the cavity 6. At this time, since the diameter of the intermediate layer 7 around the opening 5 is reduced and applied by the above-described oblique vapor deposition, the substantial diameter of the periphery of the opening 5 of the material layer 8 is accordingly reduced with time. The cathode 9 deposited on the substrate 1 through the opening 5 is formed in a conical shape, for example, a conical shape having a smaller diameter as its thickness gradually increases.

Thereafter, the intermediate layer 7 is etched using an etching solution capable of melting and removing only the intermediate layer 7 such as NaOH.
Is removed, and at the same time, so-called lift-off for removing the material layer 8 thereon is performed, whereby the field emission type cathode device shown in FIG. 1 can be obtained. In this case, since Au is used as the metal protective layer 13 and Al is used as the intermediate layer 7, the intermediate layer 7 is easily separated from the metal protective layer 13 in this lift-off step, and the intermediate layer 7 can be surely separated and removed. Accordingly, the material layer 8 on the intermediate layer 7 can be selectively and reliably removed.

The field emission type cathode device thus formed has a voltage of about 10 ⁶ V between the second electrode 3 and the cathode 9.
By applying a voltage of about / cm or more, electron emission can be performed without heating the cathode 9.
In particular, in this case, since the diameter of the conical cathode 9 is formed to be about 1.5 μm and the height is about several thousand degrees, the gate voltage can be set to about several tens to several hundreds of volts. Can work.

In the field emission type cathode device of the present invention, the metal protective layer 13 made of Au or the like having excellent corrosion resistance is deposited on the second electrode 3 made of Mo, W, Cr or the like. Since the chemical property and the like are also improved, and the fluctuation in the electric conductivity can be suppressed, the electron emission can be stably performed at a predetermined low voltage of about several tens to several hundreds V as described above. .

Further, since the metal protective layer 13 is formed of a material having good conductivity, the electric conductivity of the second electrode 3 as a gate electrode is also improved, so that stable electron emission can be obtained even when an overcurrent flows. And the electron emission characteristics can be improved. Further, for example, even when electrons are scattered and reflected at the anode of a phosphor or the like and the scattered reflected electrons or secondary electrons therefrom reach the second electrode 3, the second electrode 3, that is, the gate electrode is broken. And the life of the field emission type cathode device can be extended.

In each of the above embodiments, the cathode 9 of the field emission type cathode device is formed in a conical shape. However, the cathode 9 may be formed in a pyramid shape or, for example, in a direction perpendicular to the plane of FIG. 1 and FIG. Various other shapes and configurations can be employed, such as an extended conical stripe.

In the above-described example, the metal protective layer 13 is formed at the same time as the second electrode 3.
After forming the cathode 9 by peeling off the intermediate layer 7, the material layer 8 and the like on the second electrode 3, the cathode 9 may be formed by oblique deposition or the like. In this case, by appropriately selecting the angle of the oblique deposition, the film can be formed so as not to be adhered in the cavity 6.

Further, the above-mentioned JP-A-56-1607 has been disclosed.
In the case where the field emission type cathode device of the present invention is formed by a method of forming a cathode by subjecting a single crystal substrate to crystallographic etching shown in Japanese Patent Publication No. 40, the metal protective layer 13 is formed on the second electrode 3. The metal protective layer 13 can be formed by various methods, such as forming the metal protective layer 13 at the same time or finally forming the metal protective layer 13 by oblique deposition.

An example in which the field emission type cathode device of the present invention is used in a flat display device will be described with reference to FIGS.

FIG. 4 is a schematic enlarged cross-sectional view of a field emission type cathode device of the present invention used as an electron gun of a flat display device. In FIG. 4, reference numeral 31 denotes a conductive layer which is a first electrode made of, for example, Cr, Al, or the like, which is adhered on a substrate 10 made of glass or the like. For example, a conical cathode 9 made of a metal having a high melting point and a low work function and having a sharp tip shape is formed at a pitch of, for example, 10 μm, and an insulating layer 2 made of SiO ₂ or the like is formed therearound. Above 2, A
Metal protective layer 1 having excellent conductivity and corrosion resistance such as u, Pt, etc.
3, a second electrode 3 made of a refractory metal such as Mo, W, or Cr is arranged as a gate 33 for the cathode 9. Then, the glass 35 on which the phosphor 34 is adhered is arranged such that the phosphor 34 is opposed to the plurality of cathodes 9. And the cathode 9
The electrons emitted through the openings 5 formed in the gate 33 are directed to the phosphors 34 arranged opposite to the respective cathodes 9 as shown by arrows e. The distance L between the metal protective layer 13 and the phosphor 34 is, for example, about several mm.

FIG. 5 is a schematic exploded perspective view of an example of a flat display device in which a plurality of such field emission cathode devices are arranged. In FIG. 5, reference numeral 10 denotes a substrate made of glass or the like, on which a conductive layer 31 made of, for example, Al is deposited and formed so as to be arranged in parallel in a stripe shape extending in a direction indicated by an arrow x in the figure. Insulation layer 2 on top
And a gate 33 composed of the second electrode 3 and the electrode protection layer 13 is formed so as to be arranged in parallel in a stripe shape extending in a direction orthogonal to the direction of the arrow x as shown by the arrow y in the drawing. . In the square area where the conductive layer 31 and the gate 33 intersect, a plurality of openings 5 are formed in the gate 33, and each cathode (not shown) is formed at a pitch of, for example, 10 μm in a cavity formed in the insulating layer 2. And formed on the above-described square area.

On the other hand, for example, phosphors of each color of a square, that is, red phosphors indicated by R, green phosphors indicated by G, and blue phosphors indicated by B are provided opposite to the cathode 9 with the same size and pitch. . Each of these phosphors 34 is I
It is formed on a glass 35 via a transparent conductive layer such as TO (composite oxide of In and Sn) or the like, and the glass 35 and the substrate 1 are connected via a spacer of, for example, about several mm. The enclosed space is required, for example, 10 ^-6
It is hermetically sealed so as to maintain a degree of vacuum of about Torr.

The conductive layer 31 extending in the x direction indicated by the arrow x and the gate 33 extending in the y direction indicated by the arrow y require a relatively low voltage of about tens to hundreds of volts, for example, 100 volts. And an acceleration voltage of about 500 V is applied between the conductive layer below the phosphor 34 such as ITO and the gate 33 to emit electrons from the cathode opposed to the phosphors 34 of each color, thereby causing the phosphors 34 of each color to be emitted. Can emit light. Thus, a low-profile flat display device with low voltage and low power consumption can be obtained.

In such a display device, the distance between the phosphor 34 and the gate 33 is 30 m.
In the case of about m, the above-described acceleration voltage is set to about 3 kV, and similarly, electrons are emitted from the cathode 9 so that the phosphors 34 of each color can emit light. Furthermore, the phosphor 3
4 is directly deposited on the glass 35, a thin metal layer of Al or the like is thinly deposited thereon, and an acceleration voltage is applied to the metal layer and the gate 33. By applying an appropriate voltage higher than the voltage value, the phosphor 34 can emit light similarly.

As described above, when the field emission type cathode device of the present invention is used as an electron gun of a flat display device, electrons can be emitted stably, without being affected by scattered reflected electrons and secondary electrons. In addition, since the surface of the gate 33 is hardly oxidized, a long-life flat display device having an electron gun with stable characteristics can be obtained.

[0037]

As described above, according to the field emission type cathode device of the present invention, the corrosion resistance of the second electrode, that is, the gate, is improved, and the second electrode is less likely to be oxidized. Further, the chemical resistance can be improved.

Further, since the electrical conductivity of the gate is improved, stable electron emission characteristics can be obtained, and damage and destruction of the gate due to scattered reflected electrons, secondary electrons, etc. can be suppressed for the same reason. As a result, the life of the field emission type cathode device can be extended.

In the manufacturing process of the field emission type cathode device, when the gate, that is, the upper material layer 8 of the second electrode 3 is peeled off by lift-off or the like when forming the cathode, the metal on the second electrode 3 The selection of the protective layer 13 facilitates the removal and removal thereof, and the material layer 8 can be reliably and selectively removed, so that the field emission cathode device can be reliably formed.

Therefore, when a flat display device or the like is constructed by using such a field emission type cathode device, several hundred million cathodes are required by improving the stability of the electron emission characteristics and ensuring the manufacturing process. The field emission type cathode device having the above structure can be surely formed, so that the yield of such a display device can be improved and the life thereof can be prolonged.

[Brief description of the drawings]

FIG. 1 is a schematic enlarged sectional view of an example of a field emission type cathode device of the present invention.

FIG. 2 is a schematic enlarged sectional view of another example of the field emission type cathode device of the present invention.

FIG. 3 is a manufacturing process diagram showing a manufacturing method of an example of a field emission type cathode device.

FIG. 4 is a schematic enlarged sectional view of an example of a field emission type cathode device.

FIG. 5 is a schematic exploded perspective view of an example of the flat display device.

FIG. 6 is a schematic enlarged cross-sectional view of an example of a conventional field emission cathode device.

FIG. 7 is a manufacturing process diagram showing an example of a method for manufacturing a field emission cathode device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base (1st electrode) 2 Insulating layer 3 2nd electrode 4 Resist 5 Opening 7 Intermediate layer 8 Material layer 9 Cathode 10 Substrate 11 1st electrode 13 Metal protective layer

Claims (1)

(57) [Claims] 1. An insulating layer having a cavity formed on a base on which a first electrode is formed; a cathode formed on the first electrode inside the cavity; and a cathode formed on the insulating layer. And a second electrode provided with a metal protective layer having excellent conductivity and corrosion resistance on the surface of the second electrode. Cathode device.