JP3585739B2 - Diamond electron-emitting device and method of manufacturing the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electron-emitting device and a method of manufacturing the same , and in particular, a diamond electron-emitting device using a material having a low work function as an electron-emitting material, such as diamond, a diamond-like carbon material, and an amorphous diamond-like material, and the like. It relates to a manufacturing method .
[0002]
[Prior art]
2. Description of the Related Art In recent years, a field emission type electron-emitting device as fine as a semiconductor device has been developed using a developed Si semiconductor fine processing technology. Recently, attention has been paid to low work function materials such as diamond as the electron-emitting substance. One of the reasons is that, unlike conventional electron-emitting devices that form an emitter that emits electrons by processing a refractory metal such as Mo three-dimensionally, a planar emitter that can be easily manufactured is realized. Is raised.
[0003]
FIG. 4A shows an example of a planar electron-emitting device using diamond. An emitter layer 2 made of diamond, an insulating layer 3 and a conductive gate layer 4 are formed on a conductive substrate 1 as shown in the figure, and an opening 5 is formed through the gate layer 4 and the insulating layer 3. Have been. An anode electrode 7 is provided on the element 6 configured as described above. When a positive voltage exceeding a certain threshold is applied to the gate 4 with respect to the emitter 2 in a vacuum, electrons are emitted from the emitter 2. Released. At this time, if the voltage applied to the anode 7 is low, the emitted electrons go to the gate 4, but as the voltage applied to the anode 7 becomes high, the emitted electrons go to the anode 7.
[0004]
FIG. 4B shows an electric field distribution _Ez and an emission current density J on the emitter surface in the opening 5 having the diameter D in FIG. 4A. The electric field becomes maximum at the edge of the gate layer 4 where r = ± D / 2 and becomes minimum at the center of r = 0. Since the field emission strongly depends on the magnitude of the electric field, this tendency is further increased in the emission current density J. Therefore, most of the emission current comes from the vicinity of r = ± D / 2. Most of the electrons starting from this portion are collected on the gate layer because the gate layer 4 is located immediately above the gate layer. Therefore, most of the emission current is the gate current. This means that a large current flows in the circuit on the control side, and the efficiency is greatly reduced.
[0005]
To solve this problem, the following method has been proposed (Japanese Patent Laid-Open No. 8-55564). In the electron-emitting device described here, an emitter layer 2 made of diamond, a contact conductive layer 8, an insulating layer 3, and a conductive gate layer 4 are illustrated on a conductive substrate 1 as shown in FIG. The opening 5 is formed through the gate layer 4, the insulating layer 3 and the contact conductive layer 8.
[0006]
Figure 5 (b) shows the electric field distribution E _z of the emitter surface at the opening 5 of the diameter D of FIG. 5 (a). If the thickness of the contact conductive layer 8 is about a fraction of the thickness of the insulating layer 3, the electric field is 0 at the end of the gate layer where r = ± D / 2, and becomes maximum at the center of r = 0. For this reason, field emission does not occur near r = ± D / 2, and most of the emission current is from the central portion. Most of the electrons starting from this portion are collected by the anode electrode 7. Therefore, it is possible to avoid the problem that the efficiency in the conventional example described above is reduced.
[0007]
However, in the electron-emitting device having the contact conductive layer 8 as described above, the peak value of the electric field at the center of r = 0 is reduced, so that a new problem that the operating voltage of the device is increased arises.
[0008]
[Problems to be solved by the invention]
In the above-mentioned conventional flat-type electron-emitting device using diamond or the like, there has been a problem that the gate current is large and the efficiency is low. When the contact conductive layer is used, the gate current can be reduced and the efficiency can be increased, but on the other hand, there is a problem that the operating voltage is increased.
[0009]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a high-efficiency diamond electron-emitting device capable of reducing a gate current without increasing an operating voltage, and a method of manufacturing the same. Is to do.
[0010]
[Means for Solving the Problems]
The invention according to claim 1 is
A diamond layer formed on the substrate, a coating layer having a larger work function than the diamond layer formed on the diamond layer, or insulatingly coating the diamond layer, and an insulating layer formed on the coating layer A gate layer formed on the insulating layer; an opening formed in the gate layer and the insulating layer; and an effective emission surface that etches the coating layer and contributes to electron emission by the coating layer. And an exposed plane of the diamond layer having a diameter smaller than the diameter of the opening .
[0011]
The invention according to claim 2 is
On the diamond layer formed on the substrate, a coating layer having a larger work function than that of the diamond layer or covering the diamond layer is formed, and an insulating layer and a gate layer are sequentially formed on the coating layer. Forming an opening by etching the gate layer and the insulating layer on the inner bottom until the coating layer is exposed; and forming a mask layer by rotary oblique deposition on the substrate on which the opening is formed. And etching the coating layer using the mask layer to form an exposed plane of the diamond layer whose effective emission surface contributing to electron emission by the coating layer is smaller than the diameter of the opening. A method comprising the steps of:
[0012]
In the diamond electron-emitting device of the present invention, the diameter of the effective emission surface contributing to electron emission is made smaller than the opening diameter of the gate layer, so that the field emission from the vicinity of the gate layer is eliminated without changing the electric field distribution. In addition, it is possible to realize a highly efficient electron-emitting device by reducing only the gate current without increasing the operating voltage .
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0014]
( First Reference Example )
FIG. 1 is a diagram showing a method for manufacturing a first electron-emitting device which is a reference of the present invention .
[0015]
First, as shown in FIG. 1A, an SiO ₂ layer 12 is formed as an insulating layer on a Si substrate 11 by a CVD (Chemical Vapor Deposition) method, and then a Mo layer 13 is formed as a gate layer by a sputtering method.
[0016]
Next, as shown in FIG. 1B, a resist is applied, the resist is patterned by processing such as exposure and development, and etching is performed by RIE (Reactive Ion Etching) until the Si surface is exposed. To form After that, the resist is removed.
[0017]
Next, as shown in FIG. 1C, an Al layer 15 is formed by so-called rotary oblique deposition in which Al is vacuum-deposited from an oblique direction while rotating the substrate. At this time, as shown in the figure, an angle θ is used so that an Al layer is not formed at the central portion of the Si surface in the opening 14 due to the shielding effect.
[0018]
Next, seeding processing is performed as shown in FIG. seeding is a process of spraying fine diamond particles serving as nuclei for diamond growth, for example, by immersing the substrate in ethanol in which diamond powder is dissolved, applying ultrasonic waves, and then pulling the substrate up and drying it. . Next, for example, only the Al layer 15 is selectively etched away by a mixed aqueous solution of H ₃ PO ₄ : HNO ₃ : CH ₃ COOH: H ₂ O = 80: 5: 5: 10. As a result, the seeded portion is only the 16 portion where the Si surface is exposed.
[0019]
Next, as shown in FIG. 1E, a diamond layer 17 is formed as an emitter layer by a CVD method. Since diamond growth occurs only in the seeded 16 portions, an emitter made of diamond having a diameter smaller than the gate opening diameter is formed as shown.
[0020]
In the present reference example , the diameter of the diamond layer serving as the emitter is formed to be smaller than the diameter of the gate opening, and the size can be controlled by changing the angle θ of the rotary oblique deposition. Therefore, diamond can be formed only in the central portion of the opening that contributes to the anode current. Since the end portion of the gate layer that contributes to the gate current is a Si surface having a large work function, field emission does not substantially occur. Therefore, a highly efficient planar electron-emitting device having a small gate current can be manufactured. Further, since the electric field distribution in the opening is substantially the same as that of the conventional example shown in FIG. 4, the operating voltage does not increase.
[0021]
( Example )
FIG. 2 is a diagram showing a method for manufacturing an electron-emitting device according to one embodiment of the present invention. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0022]
First, seeding is performed on the Si substrate 11 as shown in FIG. 2A, a diamond layer 17 is formed as an emitter layer, a thin Mo layer 18 covering the diamond surface is formed, and then a SiO ₂ layer 12 is formed as an insulating layer. Is formed, and then the Mo layer 13 is formed as a gate layer. "
[0023]
Next, as shown in FIG. 2B, patterning is performed, and etching is performed until the thin Mo layer 18 is exposed, so that the opening 14 is formed.
[0024]
Next, as shown in FIG. 2C, an Al layer 15 is formed by rotary oblique deposition.
[0025]
Next, as shown in FIG. 2D, the thin Mo layer 18 is etched by RIE using the Al layer 15 as a mask.
[0026]
Next, as shown in FIG. 2E, the Al layer 15 is selectively etched away to complete the device.
[0027]
In the present embodiment , the vicinity of the end of the gate layer is covered with a thin Mo layer having a large work function, and the same effect as in the first reference example can be obtained. An insulating layer may be used as a layer covering the diamond.
[0028]
(Second reference example)
FIG. 3 is a view showing a method of manufacturing a second electron-emitting device which is a reference of the present invention . 3, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0029]
First, seeding is performed on the Si substrate 11 as shown in FIG. 3A, a diamond layer 17 is formed as an emitter layer, a SiO ₂ layer 12 is formed as an insulating layer, and then an Al layer 19 is formed as a gate layer. Next, the Mo layer 20 is formed.
[0030]
Next, as shown in FIG. 3B, patterning is performed, the Mo layer 20 and the Al layer 19 are etched, and then the SiO ₂ layer 12 is etched using an aqueous solution of ammonium fluoride to form an opening 14. Unlike the first reference example and the embodiment of the present invention, since the opening 14 is formed by wet etching, the shape of the opening 14 becomes as illustrated by undercut.
[0031]
Next, as shown in FIG. 3C, the Al layer 19 is selectively etched by a mixed aqueous solution of, for example, H ₃ PO ₄ : HNO ₃ : CH ₃ COOH: H ₂ O = 80: 5: 5: 10. At this time, since the Mo layer 20 functions as a mask, the etching of the Al layer 19 occurs only on the lower surface, and the opening diameter of the Al layer 19 as the gate layer increases as shown in the figure.
[0032]
Next, as shown in FIG. 3D, the Mo layer 20 is selectively removed by RIE to complete the device.
[0033]
This embodiment is equivalent to the embodiment using an insulating layer to cover diamond in the embodiment of the present invention, and has a lower controllability than the first embodiment and the embodiment of the present invention. Is easy.
[0034]
Although the present invention has been described with reference to the illustrated reference examples and embodiments , the present invention is not limited to the above embodiments . Various changes can be made without departing from the spirit of the present invention.
[0035]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the diamond electron-emitting device of this invention and its manufacturing method , there exist effects, such as being able to obtain the high-efficiency electron-emitting device which reduced gate current, without increasing operating voltage .
[Brief description of the drawings]
FIG. 1 is a view showing a method for manufacturing a first electron-emitting device according to a first reference example serving as a reference of the present invention.
FIG. 2 is a diagram illustrating a method for manufacturing an electron-emitting device according to an embodiment of the present invention.
FIG. 3 is a view showing a method for manufacturing a second electron-emitting device according to a second reference example which is a reference of the present invention.
FIG. 4 is a cross-sectional view showing the overall configuration of a conventional electron-emitting device and a diagram for explaining characteristics of the device.
5A and 5B are a cross-sectional view showing an overall configuration of an electron-emitting device using a conventional contact conductive layer and a diagram for explaining characteristics of the device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Substrate 2 Emitter layer 3 Insulating layer 4 Gate layer 5 Opening 6 Anode electrode element 7 Contact conductive layer 11 Si substrate 12 SiO ₂ layer 13 Mo layer 14 Opening 15 Al layer 16 Seeded portion 17 Diamond layer 18 Thin Mo layer 19 Al layer 20 Mo layer

Claims (2)

A diamond layer formed on the substrate, a coating layer having a larger work function than the diamond layer formed on the diamond layer, or insulatingly coating the diamond layer, and an insulating layer formed on the coating layer A gate layer formed on the insulating layer; an opening formed in the gate layer and the insulating layer; and an effective emission surface that etches the coating layer and contributes to electron emission by the coating layer. And an exposed plane of the diamond layer having a smaller diameter than the diameter of the opening . On the diamond layer formed on the substrate, a coating layer having a larger work function than that of the diamond layer or covering the diamond layer is formed, and an insulating layer and a gate layer are sequentially formed on the coating layer. Forming an opening by etching the gate layer and the insulating layer on the inner bottom until the coating layer is exposed; and forming a mask layer by rotary oblique deposition on the substrate on which the opening is formed. And etching the coating layer using the mask layer to form an exposed plane of the diamond layer whose effective emission surface contributing to electron emission by the coating layer is smaller than the diameter of the opening. A method for manufacturing a diamond electron-emitting device, comprising the steps of:

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