JPH09219143A - Electric field emitting cold cathode and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently pull electrons out, and thereby enlarge the quantity of current capable of being available by forming a gate electrode layer which is provided with an insulating layer having an opening, and also having an extruded part extruded higher than an opening end over the insulating layer. SOLUTION: An emitter 31 is made out of metals such as Mo and W, or Si and the like, and is opened at its tip end 32. Its opening part 33 is in a quadrangle, a recessed part 34, at its substrate side is filled with a core material, layer 35 spattered with Si , and is furthermore joined with a glass substrate 37 by way of an emitter feeding electrode layer 36 composed of Ta and the like. A gate electrode 38 has an extruded part extruded higher than an opening end over an insulating layer 40, and is so formed that the emitter tip end part 32 is thereby enclosed. A Si O2 layer 40 is formed between the electrode 38 and the emitter 31, and the opening part 33 at the tip end of the emitter is selectively etched so as to be removed in such a way as to be exposed thereto. By this constitution, the emitter tip end part 32 is thereby extruded, so that an emitter portion 31 is therefore completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field emission cold cathode used in ultra-high speed microwave devices, power devices, electron beam devices, flat panel image display devices and the like.

[0002]

2. Description of the Related Art In recent years, field emission type cold cathodes have been actively developed by utilizing advanced Si semiconductor processing technology, and ultra-high speed microwave devices, power devices, electron beam devices, flat plate type images. Application to display devices is being promoted. In particular, application to high-current electron sources is a field with wide application and high expectations.

As an example of such a field emission type electron-emitting device, there is a method utilizing anisotropic etching of Si, which is proposed by Gray (HF Gray). This method will be described with reference to FIGS. First, as shown in FIG. 14, a layer 2 (SiO ₂ , Si ₃ N ₄ ) serving as an etching mask material is formed on a Si (100) wafer 1. Next, as shown in FIG. 15, a square etching mask 3 of, for example, 2.4 μm square is formed by lithography and etching, and anisotropic etching (KO
H: 15% solution, liquid temperature: 40 ° C. for 13 minutes) to process Si under the mask 3 into a pyramidal shape 4. Then, FIG.
As shown in FIG. 6, a SiO ₂ layer 5 to be an insulating layer and a metal layer 6 to be a gate electrode layer are sequentially deposited. Finally, FIG.
As shown in, the mask 3 on the upper part of the emitter is removed by ultrasonic cleaning or the like to form the field emission cold cathode 7.

However, in such a pyramid-shaped cold cathode, the electron emission portion 8 is dot-shaped, so that the electron emission area is small and a large current cannot be obtained. On the other hand, a field emission type cold cathode capable of obtaining a large current is described in Proceedings 29p-ZT-1 of the 56th Academic Meeting of the Applied Physics Society of Japan.

In the field emission cold cathode described herein, first, as shown in FIG. 18, a dot mask 12 is formed on a Si single crystal substrate 11 by g-line exposure and dry etching, and then wet etching is performed. After miniaturizing and dry etching Si vertically, as shown in FIG.
Anisotropic etching is performed using an EPW-based solution to form a cocktail glass structure 13, and then, as shown in FIG. 20, after removing the dot mask 12, thermal oxidation for sharpening the emitter edge is performed and vapor deposition is performed. The insulating film 14 and the gate electrode 15 are formed by the method, and finally, as shown in FIG. 21, the insulating film 14 and the gate electrode 15 are lifted off with a BHF solution. In such a cold cathode 16, the electron emission area can be made large, and the emitter tip-gate distance can be made short, so that the emission current amount can be made large and the operating voltage can be suppressed to some extent low.

Further, as shown in FIG. 22, the electric field type cold cathode described in Proceedings of the 42nd Joint Lecture on Applied Physics, 30a-T-4, uses RI of Si as a mask with a circular thermal oxide film as shown in FIG.
Etching was performed by E, etching was stopped before the tip was sharpened, thermal oxidation was performed, amorphous Si was deposited by plasma CVD, and finally the circular thermal oxide film mask was removed by HF. It is a thing. Even in such a field emission cold cathode, the amount of emission current can be increased by increasing the electron emission area.

However, in the case of the cocktail glass type field emission cold cathode 16 shown in FIGS. 18 to 21, since the gate electrode 15 is formed close to the electron extraction direction, the current emitted from the emitter is reduced. Even if the amount is large, a considerable part of the amount is captured by the gate electrode 15, which is very inefficient.

Further, in the field emission type cold cathode shown in FIG. 22, since the gate 21 is formed inside the crater type emitter 22, the electric field concentration on the emitter tip 23 is weak and the operating voltage is high. turn into.

Further, since the rough shape is formed by using the isotropic etching of Si, there is a problem that the variation between the emitters 22 becomes large.

[0010]

The present invention has been made in order to solve the above-mentioned problems of the prior art, and the concentration of the electric field at the tip of the emitter is at a level at which a sufficiently low voltage operation is possible and electrons are emitted. It is an object of the present invention to provide a field emission cold cathode which can be sufficiently drawn out and can have a large amount of current that can be actually used.

[0011]

The present invention is, firstly, a structural substrate, a core layer formed on the structural substrate and having a cone-shaped projection with a crushed head, and the core layer. An inner side surface formed on a side surface of the protrusion, the tapered side portion extending beyond the head portion of the protrusion, the extending portion having a steep slope with respect to the surface of the structural substrate, An emitter layer including the side surface having a gentler slope than the inner side surface; an insulating layer formed on the emitter layer and the core material layer and having an opening such that the emitter layer extension part is exposed; A field emission type cold cathode, comprising: a gate electrode layer formed on an insulating layer, the gate electrode layer having an extending portion extending beyond an opening end of the insulating layer.

The height of the extension of the emitter layer is preferably equal to the height of the extension of the gate electrode layer.

The present invention secondly comprises a first crystal comprising a Si crystal.
Forming an inverted cone-shaped pointed concave portion by subjecting the substrate to anisotropic etching, forming an insulating layer on the surface of the first substrate having the concave portion, and the concave tip region. An opening is provided on the upper side, the opening end is tapered, and an emitter layer including an inner side surface having a steep slope with respect to the first substrate and an outer side surface having a gentle slope is provided in the recess. A step of forming, a step of forming a core material layer on the insulating layer and the emitter layer so as to fill the recess provided with the emitter layer, and planarizing the surface, and a second substrate on the core material layer. And a step of etching away the first substrate,
Exposing the insulating layer; forming a gate electrode layer on the insulating layer; selectively etching away the tip region of the gate electrode layer to expose the tip region of the insulating layer. An electric field comprising: a step of selectively etching the tip regions of the insulating layer and the core layer to expose the gate electrode layer opening end and the tapered opening end of the emitter layer. Provided is a method for manufacturing an emission type cold cathode.

Here, the inverted cone-shaped concave portion means a concave portion having a hole in which the weight body is inverted.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the field emission cold cathode of the present invention,
An emitter layer is formed on the protrusion side surface of a core material layer having a cone-shaped protrusion with a crushed head, and the emitter layer extends along the side surface like a peripheral wall surrounding the protrusion head. Parts. Since the inner surface of this extension has a steep slope with respect to the structural substrate and the outer surface has a more gentle slope than the inner surface, the tip of the extended emitter layer is at the center of the weight body. It is tapered inward in the direction of the extension of the shaft. Further, a gate electrode is extended around the extended portion so as to surround the extended portion via an insulating layer.

Examples of the opening shape of the extending portion include a circular shape, a square shape, a combination thereof, or a shape in which a plurality of peaks are connected.

The height of the extension of the emitter layer is preferably equal to the height of the extension of the gate electrode layer.

As described above, in the field emission type cold cathode of the present invention, since the gate is formed so as to surround the periphery of the emitter, the level of electric field concentration at the tip of the emitter is hardly lowered.

Further, since the tip of the emitter is inclined in the direction of the central axis of the emitter, electrons are emitted from the central axis of the emitter, and the ratio of trapped electrons to the gate electrode is very small. .

Further, the emitted electrons are subjected to the force emitted from the central axis of the emitter and the force in the direction of the closest gate electrode, that is, the direction away from the extension direction of the central axis of the emitter. The spread of the generated electron beam is suppressed.

The method for manufacturing a field emission cold cathode according to the present invention shows an example of a method for manufacturing the field emission cold cathode described above. The first substrate made of Si crystal is anisotropically etched. By providing, by forming a pointed concave portion having a hole in the shape of inverted weights, after forming an insulating layer on the substrate surface, in the concave portion, having an opening at the tip of the concave portion,
An emitter layer whose opening end surface is inclined inward and whose opening end is tapered is provided, the opening and the recess are filled with a core material layer and flattened, and then a second substrate is provided, and then the first substrate is provided.
The Si crystal portion of the substrate is removed to expose an insulating layer having a pointed cone-shaped protrusion corresponding to the shape of the inner surface of the recess, and a gate electrode layer is formed. The tip end regions of the insulating layer and the core material layer are sequentially etched to extend to the core material layer and its periphery, the inner side surface has a steep slope with respect to the surface of the structural substrate, and the outer side surface is gentler than the inner side surface. A field emission cold cathode having an emitter layer that is inclined and is tapered toward the end and a gate electrode that extends around the emitter layer via an insulating layer is formed.

In this field emission type cold cathode manufacturing method, since anisotropic etching of Si is used to form the general shape of the emitter, an extremely uniform emitter can be manufactured, and Since the sharp tip can be made of metal, the electron emission capability can be improved.
Furthermore, since the inside of the emitter having the opening is filled with the core material, the reliability of the emitter can be improved.

An embodiment of the present invention will be described below with reference to the screen.

First Embodiment FIG. 1 is a sectional view schematically showing the structure of the first embodiment of the present invention. FIG. 2 is a perspective view showing the appearance of the first embodiment. The emitter 31 is made of a metal such as Mo and W, or Si, etc., and its tip 32 is open. In the present embodiment, the opening 33 has a quadrangular shape. The concave portion 34 on the substrate side is filled with a resistance layer 35 (core material layer) such as sputtered Si, and is further joined to a glass substrate 37 via an emitter feeding electrode layer 36 such as Ta. The gate electrode 38 is formed so as to have an opening 39 that surrounds the emitter tip 32 while following the shape of the emitter. Gate electrode 38 and emitter 3
1, a SiO ₂ layer 40 is formed as an insulating layer, and is selectively etched and removed so that the opening 33 at the tip of the emitter is exposed like the gate electrode layer 38.

Next, a method of manufacturing the field emission cold cathode shown in this embodiment will be described with reference to FIGS.
First, as shown in FIG. 3, a SiO ₂ thermal oxide film (not shown) having a thickness of 0.1 μm is formed on a p-type (100) crystal plane orientation Si single crystal substrate 41 by a dry oxidation method. Further, a resist (not shown) is applied by spin coating. Next, using a stepper, for example, patterning such as exposure and development is performed so that a square opening of 1 μm square is obtained, and then SiO _{2 is} mixed with a NH ₄ F / HF mixed solution.
Etch the oxide layer. 3 after removing the resist
Anisotropic etching is performed using a 0 wt% KOH aqueous solution to form an inverted quadrangular pyramidal recess 42 having a depth of 0.71 μm on the Si substrate 41.

Next, as shown in FIG. 4, NH ₄ F.HF
After removing the SiO ₂ thermal oxide layer using a solution,
The SiO ₂ thermal oxidation insulating layer 40 is formed on the substrate 41 including the inside of the recess 42. In this embodiment, the film thickness is 0.4 μm.
The thermal oxidation insulation layer 40 was formed by the wet oxidation method so that Then, the emitter layer 3 is formed on the insulating layer 40.
1. For example, a W layer or a Mo layer is provided on the tip region 4 of the recess 42.
It is formed except for 3. For forming the W layer and the Mo layer, for example, a vacuum vapor deposition method can be used, and the vapor deposition angle is smaller than the angle with the central axis of the inverted quadrangular pyramid that passes through the tip of the recess with respect to the substrate surface. Further, it can be set within a range larger than the angle with the inclined surface of the recess, that is, the side surface of the inverted quadrangular pyramid. The angle of this vapor deposition is preferably closer to the angle with the side surface of the inverted quadrangular pyramid, and as shown in FIG. 4, for example, while rotating the Si substrate 41 about the central axis 44 of the recess 42, the Si substrate 41 is Then, the emitter layer can be formed by using the vacuum vapor deposition method so that the thickness of the flat portion becomes 0.1 μm from the direction indicated by the arrow A in the drawing which is closer to the angle with the side surface of the inverted quadrangular pyramid. Obtained emitter layer 40
Has an opening end face inclined inward, and the opening end is tapered.

Then, as shown in FIG.
1 is spin-coated with a resist 45. At this time, as shown in the drawing, the entire recess 42 for forming the emitter including the tip end region 43 is sufficiently filled with the resist 45 so that the resist surface has a nearly flat shape.

Further, as shown in FIG. 6, the resist 45 is etched back by oxygen plasma to remove the resist and the metal layer, leaving only the metal layer 31 and the resist layer 45a in the recess 42 for forming the emitter. .

After that, all the remaining resist 45a is removed, and a Si layer 35 having a thickness of 1 μm, for example, is formed by a sputtering method. The surface of the Si layer 35 is polished and flattened, and an electrode for supplying power to the emitter 31 and the glass substrate 3 are formed.
A metal layer 36 made of, for example, Ta, which also serves as a metal layer for joining with 7, is formed. On the other hand, as the structural substrate 37 to be the second substrate, for example, an Al layer 46 having a thickness of 0.3 μm is formed on the back surface.
Pyrex glass substrate 37 with a thickness of 1 mm
Then, as shown in FIG. 7, the glass substrate 37 and the Si substrate 41 can be bonded to each other with the metal layer 36 interposed therebetween. An electrostatic adhesion method is preferably used for adhesion. A minus voltage is applied to the glass substrate 37 side and a plus voltage is applied to the Si substrate 41 side, and the glass substrate 37 is heated to several hundreds of degrees Celsius, whereby the bonding is performed.

Further, as shown in FIG. 8, a glass substrate 37
After removing the Al layer 46 on the back surface with a mixed acid solution of NHO ₃ , CH ₃ COOH, and HF, a mixed aqueous solution of ethylenediamine, pyrocatechol, and pyrazine (ethylenediamine: pyrocatechol: pyrazine: water = 75 cc: 12 g: 3 m
With g: 10 cc), only the Si substrate 41 is removed by etching to expose the insulating layer 40 and the convex portion 47 having the emitter layer 31 covered with the insulating layer 40.

Subsequently, as shown in FIG. 9, the gate electrode layer 3
As the reference numeral 8, for example, a Cr layer, the convex portion 4 covered with the insulating layer 40
It is formed on the insulating layer 40 so as to have a film thickness of 0.3 μm, for example, along the shape of 7. The W layer can be formed by using, for example, a sputtering method. Further, the photoresist layer 48 is formed by spin coating so that the tip of the protrusion 47 covered with the gate electrode layer 38 and the insulating layer 40 is slightly hidden, for example, with a thickness of about 0.9 μm.

Next, as shown in FIG. 10, etching by oxygen plasma is performed, and the tip 38a of the gate electrode layer 38 (including the tip of the insulating layer 40) along the emitter protrusion 47 is, for example, 0.7 μm. The resist 48 is removed by etching so as to appear.

After that, as shown in FIG. 11, the gate electrode layer 38a located on the tip of the convex portion 47 is removed by, for example, a reactive ion etching (RIE) method, and the convex portion of the gate electrode layer 38 is removed. Open the part corresponding to the tip.

Then, as shown in FIG.
8 is removed, the insulating layer 40 around the tip of the emitter protrusion 47 is selectively removed by etching using a NH ₄ F / HF mixed solution, and finally, the lowest portion 43 of the emitter formation recess 42 is removed. Si (at the tip of the convex portion) is removed by etching with the above mixed aqueous solution of ethylenediamine, pyrocatechol and pyrazine to expose the tip of the emitter. As a result, the emitter tip portion is extended, and the emitter portion 31 having the sharp opening 33 at the tip is completed.

The feature of the field emission type cold cathode and the manufacturing method thereof shown here is that the tip 31 of the emitter is inclined in the direction of the central axis of the emitter, so that electrons are drawn out from the central axis and the gate 38 is exposed. The ratio of trapped electrons can be significantly reduced. Further, a force acts on the electron beam extracted from the central axis of the emitter in the direction of the closest gate electrode, that is, in the direction away from the central axis of the emitter, and as a result, the spread of the emitted electron beam is suppressed.

Further, since the inside of the emitter electrode layer 31 is filled with the core material layer 34, the durability and reliability of the emitter are improved, and the deformation of the emitter due to stress can be prevented. Further, when the emitter electrode layer 31 is formed, the lowest portion 4 of the recess 42, which is the tip portion in the past, is formed by using the rotary oblique vapor deposition method.
By selectively forming with the exception of 3, the electron emission portion, which was conventionally dot-like, is made linear (quadrilateral formed by four lines in the present embodiment), and thus the electron emission area is increased. And the amount of emission current can be increased.

Second Embodiment FIG. 13 is a perspective view of a field emission cold cathode according to the second embodiment. In this cold cathode, the opening tip portion 32 of the emitter, which is an electron emitting portion, has a shape having four sharp peaks 50, which allows the electron emitting region to be formed between the point-like shape and the line-like shape. Have the same performance.

[0038]

As described above, according to the field emission type cold cathode of the present invention, a large amount of current can be efficiently obtained without causing a significant decrease in the degree of electric field concentration at the tip of the emitter. Further, the spread of the extracted electron beam can be suppressed.

Further, according to the field emission type cold cathode of the present invention, it is possible to provide the field emission type cold cathode having excellent uniformity and reproducibility of the emitter.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of a field emission cold cathode according to a first embodiment.

FIG. 2 is a perspective view showing the external appearance of the field emission cold cathode according to the first embodiment.

FIG. 3 is a diagram for explaining a manufacturing process of the field emission cold cathode according to the first embodiment.

FIG. 4 is a view for explaining the manufacturing process of the field emission cold cathode according to the first embodiment.

FIG. 5 is a view for explaining the manufacturing process of the field emission cold cathode according to the first embodiment.

FIG. 6 is a view for explaining the manufacturing process of the field emission cold cathode according to the first embodiment.

FIG. 7 is a view for explaining the manufacturing process of the field emission cold cathode according to the first embodiment.

FIG. 8 is a view for explaining the manufacturing process of the field emission cold cathode according to the first embodiment.

FIG. 9 is a view for explaining the manufacturing process of the field emission cold cathode according to the first embodiment.

FIG. 10 is a view for explaining the manufacturing process of the field emission cold cathode according to the first embodiment.

FIG. 11 is a view for explaining the manufacturing process of the field emission cold cathode according to the first embodiment.

FIG. 12 is a view for explaining the manufacturing process of the field emission cold cathode according to the first embodiment.

FIG. 13 is a perspective view showing the appearance of a field emission cold cathode according to a second embodiment of the invention.

FIG. 14 is a view for explaining the manufacturing process of the conventional field emission cold cathode.

FIG. 15 is a view for explaining the manufacturing process of the conventional field emission cold cathode.

FIG. 16 is a diagram for explaining a manufacturing process of an example of a conventional field emission cold cathode.

FIG. 17 is a diagram for explaining a manufacturing process of an example of a conventional field emission cold cathode.

FIG. 18 is a diagram for explaining a manufacturing process of another example of the conventional field emission cold cathode.

FIG. 19 is a diagram for explaining a manufacturing process of another example of the conventional field emission cold cathode.

FIG. 20 is a diagram for explaining a manufacturing process of another example of the conventional field emission cold cathode.

FIG. 21 is a view for explaining the manufacturing process of another example of the conventional field emission cold cathode.

FIG. 22 is a diagram showing an appearance of an emitter portion of still another example of the conventional field emission cold cathode.

[Explanation of symbols]

31 ... Emitter Layer 32 ... Emitter Tip 33 ... Emitter Tip Opening 34 ... Core Material Layer 35 ... Resistor Layer 36 ... Emitter Feeding Layer 37 ... Glass Substrate 38 ... Gate Electrode Layer 39 ... Gate Electrode Opening 40 ... SiO ₂ Thermal Oxidation Insulation layer

Claims (3)

[Claims] 1. A structural substrate, formed on the structural substrate,
The core material layer has a cone-shaped protrusion with a crushed head portion, and a tapered extension portion formed on the side surface of the protrusion of the core material layer and extending from the protrusion head portion. Formed on the emitter layer and the core material layer, and the emitter layer including an inner side surface having a steep slope with respect to the surface of the structural substrate, and a side surface having a gentler slope than the inner side surface And an insulating layer having an opening such that the emitter layer extended portion is exposed, and a gate electrode layer formed on the insulating layer and having an extended portion extending beyond the opening end of the insulating layer. A field-emission cold cathode, comprising: 2. The field emission cold cathode according to claim 1, wherein the height of the extension of the emitter layer is equal to the height of the extension of the gate electrode layer. 3. A step of forming an inverted cone-shaped pointed concave portion by subjecting a first substrate made of Si crystal to anisotropic etching, and insulating the surface of the first substrate having the concave portion. A step of forming a layer, an opening is formed on the tip region of the concave portion, the opening end portion is tapered, and an inner side surface having a steep slope with respect to the first substrate and an outer side surface having a gentle slope. And a step of forming a core material layer on the insulating layer and the emitter layer so as to fill the recess provided with the emitter layer and planarizing the surface. A step of providing a second substrate on the core material layer,
A step of etching away the first substrate to expose the insulating layer; a step of forming a gate electrode layer on the insulating layer; Exposing the tip region of the insulating layer, and selectively etching the tip regions of the insulating layer and the core layer to expose the gate electrode layer opening end and the tapered opening end of the emitter layer. A method for manufacturing a field emission cold cathode, comprising: