JPH05159696A - Electric field emission type electron element - Google Patents

Abstract

PURPOSE:To provide an electric field emitting type electron element suitable to high speed operation. CONSTITUTION:On a high resistance monocrystalline silicon base 4 such as a non-dope Si (silicon) base, an anode electrode layer 3 of molybdenum metal is formed. Further, on the anode electrode layer, a cathode electrode layer 1 through an insulating layer 5 and a gate electrode layer 2 through an insulating layer 6 are provided, both layers being opposed to each other with a groove 7 between and mutually insulated. The insulating layers 5, 6 are formed of silicon dioxide, and the cathode electrode layer 1 and the gate electrode layer 2 are formed of molybdenum metal. The two layered part with the groove 7 between have saw-tooth shaped flat surfaces, and the top end part of the saw-tooth part of the cathode electrode layer 1 forms an electron emitting part. A plurality of linear array-like saw-tooth parts having a number of electron emitting parts are juxtaposed. The top end part 1a of the cathode electrode layer 1 is inclined and sharpened toward the direction of the gate electrode layer 2, and the sharpened top end part 1a is protruded from the insulating layer 5 in the direction of the groove 7. The top end part 2a of the gate electrode 2 is similarly protruded from the insulating layer 6 in the direction of the groove 7.

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 electronic device which operates on the principle of field emission.

[0002]

2. Description of the Related Art In recent years, due to the microfabrication technology used in the field of integrated circuits or thin films, the field emission type electron element manufacturing technology for emitting electrons in a high electric field has made remarkable progress, and in particular, an electric field having an extremely small structure Emissive cold cathodes are being manufactured. This type of field emission cold cathode is a basic electron emission device that constitutes a triode type micro electron tube or a micro electron gun.

The field emission type electronic device was devised as a constituent element of, for example, a micro triode or a thin display device.
In particular, Stanford Research Institute's C.I. A. Journal of Applied Physics by CASpindt et al.
No. 47, No. 12, 5248 to 5263 (December 1976), and other publicly known research reports. F. It is also disclosed in US Pat. Nos. 4,307,507 and 4,513,308 by HF Gray et al.

FIG. 13 is a schematic perspective view of a basic type field emission type electronic device of a known type, and FIG. 14 is a sectional view taken along line DD of FIG.

In consideration of compatibility with fine processing technology in the field of integrated circuits or thin films, cost reduction, and monolithicization with other electronic circuit elements, the substrate electrode 104 has a low resistance single crystal Si ( Silicon) substrates are used.
A large number of cone-shaped cold cathode chips 101 are formed on the substrate electrode 104.
1 is made of the same low resistance single crystal Si as the substrate electrode 104 or a high melting point metal material such as W (tungsten) or Mo (molybdenum). An insulating layer 105 is formed on the substrate electrode 104 around the cold cathode chip 101, and a gate electrode 102 is further stacked on the insulating layer 105. An anode electrode 103 is provided so as to cover the cold cathode chip 101 and the gate electrode 102 with a vacuum kept therebetween.

In such a structure, the cold cathode chip 1
01 and the gate electrode 102 as a gate voltage of 10
When a voltage of about 0 to 200 V is applied, the cold cathode chip 1
A strong electric field of about 10 ⁷ V / cm is generated between 01 and the gate electrode 102, and electrons are emitted from the cold cathode chip 101 by the principle of field emission. Furthermore, the anode electrode 1
The electrons reach the anode electrode 103 by the anode voltage of 300 to 500 V applied to the anode 03.

Within the state of the art, the gate electrode 1
02 and the diameter d of the groove 106 provided in the insulating layer 105.
₁₀₁ (see FIG. 14) is a minimum of about 1 μm, and the height h ₁₀₁ of the cold cathode chip ₁₀₁ is a minimum of about 1 μm. In addition, variations in electron emission characteristics among the chips due to variations in cold cathode chip shape due to miniaturization are unavoidable in manufacturing. Therefore, in the present circumstances, trial manufacture is mainly performed on a thin display device in which the anode electrode of the conventional field emission type electronic element is a transparent electrode coated with a phosphor and the cold cathode chip is used only as an electron emission source. There is. When this type of field emission type electronic device is used in a thin display device, high precision control of emitted electrons may not be required, and 1000 or more electron emission cold cathode chips per pixel are arranged in an array. A method is used in which the variations in the electron emission cold cathode chips are averaged and the required amount of emitted electrons is obtained by arraying and driving in parallel.

On the other hand, by constructing a microminiature vacuum triode using this field emission cold cathode, there is a possibility of realizing an element that overcomes the drawbacks and limitations of conventional solid-state elements such as semiconductors. In the solid-state device, the moving speed of electrons in the solid is c /
There is a limit to saturation at about 1000 (c is the speed of light), and there is a problem that it is vulnerable to high temperature and radiation.
On the other hand, in the field emission type electronic device, since the emitted electrons move in vacuum, the moving speed of the electrons can be higher than the moving speed in the solid by one digit or more, and is resistant to high temperature and radiation. There is an advantage that. For example, when a voltage of 50 V is applied between electrodes having an interval of 1 μm, the moving speed of electrons is 2 × 10 ⁸ cm / s on average.
Therefore, the travel time for a distance of 1 μm is 0.5 psec.

Therefore, there is a possibility that an ultrahigh-speed device having a response speed of about terahertz can be realized by a vacuum triode having a device size on the order of submicron.

[0010]

In order to realize high speed operation with the structure of the conventional field emission type electronic device, there are the following problems. That is, since the distance between the cold cathode chip, which is the cathode electrode, and the gate electrode cannot be reduced so much from the manufacturing limit, it is necessary to obtain a strong electric field required for electron emission at the tip of the cold cathode chip. The applied voltage (gate voltage) between the cathode electrode and the gate electrode must be increased. Furthermore, since the distance between the cathode electrode and the anode electrode is large, it takes time to move the electrons between the cathode electrode and the anode electrode.

On the other hand, the cut-off frequency f of the cold cathode chip
_T is generally represented by the following equation.

F _T = g _m / (2πC _gc ) where g _m is the mutual conductance and C _gc is the gate electrode −
It is the capacitance between the cathode electrodes.

Therefore, in order to realize a cold cathode chip capable of high-speed operation, it is necessary to increase the mutual conductance g _m or decrease the capacitance C _gc . However, in the structure of the conventional field emission type electronic device, electrons are emitted only from the tip portion of the cold cathode chip, and it is difficult to reduce the interval between the cold cathode chips in terms of manufacturing. Therefore, the electron emission area is small. , The amount of emitted electrons also becomes smaller. Therefore, it is difficult to increase the mutual conductance g _{m of the} element, which depends on the current density due to field emission. Further, since the conventional field emission type electronic device has a structure in which the gate electrode layer and the cathode electrode layer face each other with the insulating layer interposed therebetween, the value of the capacitance C _gc between the gate electrode and the cathode electrode must be large. I don't get.

Therefore, the present invention solves the above problems and provides a field emission type electronic device suitable for high speed operation.

[0015]

According to the present invention, an anode electrode, a cathode electrode formed on the anode electrode via an insulator, and a gate electrode formed on the anode electrode via an insulator. And a cathode electrode and a gate electrode are arranged with a gap serving as an electron transfer space.

Further, according to the present invention, a semiconductor or metal substrate, a cathode electrode formed on the substrate via an insulator, and a gate electrode formed on the substrate via the insulator are provided. There is provided a field emission type electronic device in which a cathode electrode and a gate electrode are arranged with a gap serving as an electron transfer space, and an anode electrode is formed on a substrate so as to face the gap.

[0017]

In the field emission type electronic device according to the present invention, the distance between the electrodes can be made smaller than that in the conventional field emission type electronic device. Specifically, the distance between the cathode electrode and the gate electrode and the distance between the cathode electrode and the anode electrode can be reduced. As a result, the gate voltage and the anode voltage decrease. Further, in the above structure, the capacitance value between the cathode electrode and the gate electrode can be reduced as compared with the conventional field emission type electronic device in which the cathode electrode and the gate electrode are laminated via the insulator. Further, when the anode electrode is provided on the substrate between the cathode electrode and the gate electrode, the cathode electrode-
The capacitance values between the anode electrodes and between the gate electrode and the anode electrode can also be reduced.

Between the cathode electrode and the gate electrode of the field emission type electronic device having such a structure, for example, 20V to 1
When a voltage of 00 V is applied, it responds rapidly to 10 ⁷ V / cm between the tip of the cathode electrode and the gate electrode.
A strong electric field is generated to some extent, and electrons are emitted from the upper end of the cold cathode chip by the principle of field emission.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of an embodiment of a field emission type electronic device according to the present invention. FIG. 2 is a sectional view taken along the line AA of FIG.

A high-resistance single crystal silicon substrate 4 such as a non-doped Si (silicon) substrate is used as the field emission type electronic device substrate. An anode electrode layer 3 made of molybdenum metal is formed on the silicon substrate 4. further,
On this anode electrode layer 3, there is a cathode electrode layer 1 facing the groove 7 and insulated from each other via an insulating layer 5.
And the gate electrode layer 2 with the insulating layer 6 interposed therebetween. The insulating layers 5 and 6 are made of silicon dioxide,
The cathode electrode layer 1 and the gate electrode layer 2 are made of molybdenum metal. Here, the horizontal distance d ₁ between the cathode electrode layer 1 and the gate electrode layer 2 is set to about 0.1 to 0.5 μm, and the thickness h ₁ of the insulating layer 5 is 0.2 to 1.0 μm.
The thickness h ₂ of the insulating layer 6 is set to about 0.1 m and the thickness h ₂ of the insulating layer 6 is set to about 0.1 to 0.5 μm while maintaining the relationship h ₁ > h ₂ .
That is, spatially, the gate electrode layer 2 is provided between the anode electrode layer 3 and the cathode electrode layer 1.

As shown in FIG. 1, the two laminated portions separated by the groove 7 have a sawtooth-shaped plane, and the tip of the sawtooth-shaped portion of the cathode electrode layer 1 serves as an electron emitting portion. A plurality of linear array sawtooth-shaped portions having a large number of the electron emitting portions are provided side by side. As shown in FIG. 2, the tip portion 1 a of the cathode electrode layer 1 is formed so as to be inclined and sharpened toward the gate electrode layer 2, and the sharpened tip portion 1 a of the groove 7 is formed. It projects from the insulating layer 5 in the direction. Similarly, the tip portion 2a of the gate electrode 2 has a groove 7
Of the insulating layer 6 in the direction of.

Although molybdenum is used for each electrode layer material, the present invention is not limited to this, and a conventional electrode material such as chromium, tungsten, gold, silver, a cylinder, or aluminum may be used. Although silicon dioxide is used for the insulating layer, the insulating layer is not limited to this as long as it has excellent insulating properties.

In the field emission type electronic device constructed as above, when a voltage of about 20 V to 100 V is applied as a gate voltage between the cathode electrode 1 and the gate electrode 2, the tip of the cathode electrode 1 and the gate electrode 2 are applied. Between 10
A strong electric field of about ⁷ V / cm is generated, and electrons are emitted from the tip of the cathode electrode 1 according to the principle of field emission. The emitted electrons reach the anode electrode layer 3 to which a voltage is applied in advance. Therefore, the groove 7 is the cathode electrode 1.
This is an electron transfer space for electrons emitted from the sharpened tip portion 1a. Here, since the amount of electrons emitted from the cathode electrode 1 increases and decreases in response to the change in the gate voltage, the device operates as a triode structure element in which the change in the gate voltage appears as the change in the anode current.

As described above, the distance between the electrodes, which is about 1 μm in the related art, can be reduced, so that the electric field strength required for field emission can be obtained with a lower gate applied voltage. Further, the distance between the anode electrode and the cathode electrode, that is, the thickness h ₁ of the insulating layer 5 is 0.2.
Since it can be set to about 1.0 μm, it is possible to reduce the voltage applied to the anode and shorten the electron transfer time between the anode electrode and the cathode electrode. Further, in the field emission type electronic device of the above-mentioned embodiment, the area where the cathode electrode and the gate electrode overlap is smaller than that in the case where the cathode electrode and the gate electrode are laminated in the related art, and therefore, the area between the cathode electrode and the gate electrode is small. The capacitance becomes smaller. Therefore, the cutoff frequency of the element is increased, and the element can operate at high speed.

Next, another embodiment of the present invention will be described with reference to FIGS.

FIG. 3 to FIG. 5 show plan views of a laminated portion formed of an insulating layer and a gate electrode layer, a laminated portion formed of an insulating layer and a cathode electrode layer, and a groove separating them. FIG. 3 shows an embodiment having the same planar shape as that of the first embodiment, and has a structure in which the peaks and valleys of the sawtooth-shaped cathode electrode 11 and the gate electrode 12 mesh with each other. .. FIG. 4 shows an embodiment in which the tip of the sawtooth-shaped portion on the cathode electrode 13 side is further sharpened as compared with the case shown in FIG. 3, and the gate electrode 14 is provided so as to surround it. Show. In this case, since the electric field concentration at the tip portion of the cathode electrode 13 effectively works due to the shape effect, the gate voltage can be lowered, but the field emission area is reduced because the field emission occurs only at the tip portion. In addition, FIG. 5 shows an example of a structure in which a cathode electrode and a gate electrode, which are uneven and do not have a sharpened tip portion, mesh with each other. In this case, the ratio of electric field concentration is smaller than in FIGS. 3 and 4, but there is an advantage that the electron emission area can be increased.

Therefore, the first embodiment shown in FIG. 3 has an intermediate characteristic between the embodiment shown in FIG. 4 and the embodiment shown in FIG. In this way, the planar shapes of the cathode electrode and the gate electrode may be set according to the required characteristics.

6 to 8 show another embodiment in which the cross-sectional shape of the tip portion of the cathode electrode layer in the groove as the electron transfer space is different. The embodiment shown in FIG. 6 shows the most basic shape, and the tip portion 21a of the cathode electrode 21 projects from the insulating layer 24 with the same thickness. In this embodiment, the cathode tip portion, which is the electron emitting portion, has excellent mechanical strength and is easy to manufacture. In the embodiment shown in FIG. 7, the tip 31a of the cathode electrode 31 is the gate electrode 32.
Is provided so as to incline toward the direction of (1), and the electric field distribution at the tip of the cathode electrode is optimized by the voltage applied to the gate and the electron emission direction due to field emission is taken into consideration. In the embodiment shown in FIG. 8, the tip portion 41a of the cathode electrode 41 is sharpened in the thickness direction of the cathode electrode, and the tip portion 41 of the cathode electrode 41 due to the shape effect.
Since the electric field concentration at a effectively works, the gate voltage can be lowered. It should be noted that the embodiment shown in FIGS.
The embodiment shown in FIG. 8 and the embodiment shown in FIG. 8 are combined. As described above, since the field emission type electron device according to the present invention has the shape of the cathode electrode electron emission part and the degree of freedom in the direction in which the tip part faces, the electric field concentration at the cathode tip part is effectively obtained. An increase in emission current density due to field emission can be achieved.

As shown in FIG. 9, the field emission type electronic device may include a conductive anode electrode substrate 53 in which a substrate and an anode electrode are integrated. At this time, as the anode electrode substrate 53, a low resistance single crystal silicon substrate may be used, or a metal plate or the like may be used. When the anode electrode substrate 53 is a single crystal silicon substrate, a silicon oxide layer formed by thermal oxidation can be used for the insulating layers 55 and 56 in the manufacturing process. Silicon dioxide obtained by thermal oxidation of single crystal silicon is
It is suitable for use as an insulating layer because it has excellent insulating properties as compared with those formed by a vacuum deposition method or the like. Furthermore, the silicon substrate can be easily monolithic with other electronic elements, and the manufacturing process can be simplified.

In the preferred embodiment, as shown in FIG. 10, a strip-shaped (extending in the direction perpendicular to the plane of the drawing) anode electrode layer 6 on the surface of the silicon substrate 64 at the bottom of the groove 67.
3 are stacked. Further, FIG. 11 shows another embodiment, in which a band-shaped (extending in the direction perpendicular to the paper surface of the figure) anode electrode layer 73 is formed on the surface layer inside the silicon substrate 74 of the groove 77. Here, a high-resistance single crystal silicon substrate such as a non-doped silicon substrate is used as the substrate 74,
A portion corresponding to the anode electrode 73 is composed of an n-type low resistance region in which a part of the substrate 74 is doped in a band shape with an n-type impurity such as phosphorus. This low resistance region may be formed of a p-type low resistance region doped with boron or the like. In the embodiments shown in FIGS. 10 and 11, the area occupied by the anode electrode layer in the substrate plane becomes small, which causes the cathode electrode and the anode electrode to overlap (with respect to the substrate plane) and the gate electrode and the anode electrode to overlap. Since the area is small, the capacitance between the electrodes can be reduced not only between the cathode electrode and the gate electrode but also between the cathode electrode and the anode electrode and between the gate electrode and the anode electrode. As a result, the cutoff frequency f _T of the element can be increased and the element can operate at high speed.

Next, an example of a method for manufacturing a field emission type electronic device according to the present invention will be described with reference to FIG.

The present embodiment is a manufacturing method in which the anode electrode-gate electrode spacing, the gate electrode-cathode electrode spacing, and the anode electrode-gate electrode spacing can be set in independent steps, respectively, and the cathode electrode sharpening, In addition, the sharpening direction can be set in each independent process. Further, since the transfer of the fine mask pattern to the resist is required only once, there is a feature that precise alignment for superimposing the mask patterns is not required.

The sectional views of FIGS. 12A to 12F show each stage of the manufacturing process. First, as shown in FIG. 3A, the anode electrode metal layer 83 is formed on the substrate 84 by 0.1 μm.
After the insulating layer 86a and the gate electrode metal layer 82a are laminated by about 0.3 μm and about 0.1 μm, respectively, a mask 88 of resist is further formed. Here, the distance between the anode electrode and the gate electrode is set by the thickness of the insulating layer 86a. Although the electron beam evaporation method was used to form the electrode metal layers 83 and 82a and the insulating layer 86a, the invention is not limited to this, and a sputtering method, a CVD method, or the like may be used depending on a material to be used. You can go.

Next, as shown in FIG. 12B, the gate electrode metal layer 82a is selectively removed by etching according to a mask 88 made of a resist, and the gate electrode metal layer 82a is formed by a width indicated by d ₈₁ in the figure. Side etching is performed. The side etching amount d ₈₁ here is finally
This corresponds to the horizontal distance between the cathode electrode 81 and the gate electrode 82. Then, the gate electrode metal layer 8
Similarly to the etching removal of 2a, the insulating layer 86a is removed by etching.

Next, as shown in FIG. 12C, an insulating layer 85a is formed by the electron beam vacuum evaporation method. Here, as shown by B in the figure, the vapor deposition source is moved, or
By rotating the substrate 84, the angle of the vapor deposition direction is relatively changed from several degrees to several tens of degrees, and vapor deposition is performed so that the thickness of the insulating layer 85a becomes slightly thinner toward the vicinity of the mask 88 made of resist. .. By this, the direction of the tip of the cathode electrode can be set. Further, the distance between the anode electrode and the cathode electrode is set by the thickness of the entire insulating layer 85a. Further, as shown in FIG. 12D, the cathode electrode metal layer 81 is formed by the electron beam vacuum evaporation method. Here, by moving the vapor deposition source or rotating the substrate 84, the angle of the vapor deposition direction is relatively changed from several degrees to ten and several degrees as shown by an arrow C in the figure, so that the mask 88 of the resist is formed. The vapor deposition is performed so that the cathode electrode metal layer 84 is sharpened in the thickness direction toward the vicinity.

Thereafter, the mask 88 made of resist, the insulating material layer 85b and the cathode electrode material layer 81a deposited on the mask 88 are removed, and the structure shown in FIG. 12E is obtained. Further, by side-etching the insulating layers 85a and 86b, the sharpened tip portion of the cathode electrode 81 and the tip portion of the gate electrode 82 are projected into the groove 87, so that the desired electric field as shown in FIG. An emissive electronic device can be obtained.

The above-described method of manufacturing a field emission type electronic device provides a field emission type electronic device which can reduce the operating voltage and can operate at high speed.

[0038]

The field emission type electronic device according to the present invention comprises an anode electrode, a cathode electrode formed on the anode electrode via an insulator, and a gate electrode formed on the anode electrode via an insulator. Since the cathode electrode and the gate electrode are arranged with a gap as the electron transfer space, the distance between the electrodes can be reduced. Therefore, as compared with the conventional field emission type electronic device, it is possible to obtain the electric field strength required for the field emission at a lower gate applied voltage. Further, it is possible to reduce the voltage applied to the anode and shorten the electron transfer time between the anode electrode and the cathode electrode. Further, since the device has a small capacitance between the electrodes, the cutoff frequency of the device becomes large, and the device can operate at high speed.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of a field emission type electronic device according to the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of FIG.

FIG. 3 is a partial plan view of another embodiment of the field emission type electronic device according to the present invention.

FIG. 4 is a partial plan view of another embodiment of the field emission type electronic device according to the present invention.

FIG. 5 is a partial plan view of another embodiment of the field emission type electronic device according to the present invention.

FIG. 6 is a cross-sectional view of an essential part of another embodiment of the field emission type electronic device according to the present invention.

FIG. 7 is a cross-sectional view of an essential part of another embodiment of the field emission type electronic device according to the present invention.

FIG. 8 is a cross-sectional view of an essential part of another embodiment of the field emission type electronic device according to the present invention.

FIG. 9 is a cross-sectional view of an essential part of another embodiment of the field emission type electronic device according to the present invention.

FIG. 10 is a cross-sectional view of an essential part of another embodiment of the field emission type electronic device according to the present invention.

FIG. 11 is a cross-sectional view of an essential part of another embodiment of the field emission type electronic device according to the present invention.

FIG. 12 is a fragmentary cross-sectional view showing an example of a method for manufacturing a field emission type electronic device according to the present invention.

FIG. 13 is a perspective view of a conventional field emission type electronic device.

14 is a cross-sectional view taken along the line DD of FIG.

[Explanation of symbols]

 1 Cathode Electrode 2 Gate Electrode 3 Anode Electrode 4 Substrate 5, 6 Insulation Layer 7 Groove

Claims (2)

[Claims] 1. A cathode electrode comprising: an anode electrode; a cathode electrode formed on the anode electrode via an insulator; and a gate electrode formed on the anode electrode via an insulator. A field emission type electronic device characterized in that the gate electrode and the gate electrode are arranged with a gap as an electron transfer space. 2. A semiconductor or metal substrate, a cathode electrode formed on the substrate via an insulator, and a gate electrode formed on the substrate via an insulator, A field emission type electronic device characterized in that a cathode electrode and the gate electrode are arranged with a gap as an electron transfer space, and an anode electrode is formed on the substrate so as to face the gap.