JP3859782B2 - Method for gas phase synthesis of diamond cold cathode and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas phase synthesis method for diamond cold cathode and a method for producing the same , and in particular, a method for vapor phase synthesis of diamond cold cathode and the production of the cold cathode in order to use the cold cathode for vacuum devices, displays and the like. It is about how to do.
[0002]
[Prior art]
A cold cathode is a cathode from which electrons are emitted without heating. FIG. 2 shows a configuration example of a typical cold cathode. As shown in FIG. 2, the cold cathode includes a glass substrate 11, a metal substrate electrode (cathode) 12 provided thereon, an anode 13 provided opposite to the substrate cathode, and these cathodes. Cathode formed on the substrate electrode 12 in a structure comprising insulators 14a and 14b provided between the electrode 14 and the anode and a gate electrode 15 provided between the insulators 14a and 14b. It consists of a chip 16. Rather than having a conventional vacuum tube structure in which a grid electrode exists between the cathode and the anode, this structure may be considered to have a structure in which the semiconductor portion of the FET is replaced with a vacuum. Therefore, the signal control electrode is generally called a gate instead of a grid.
[0003]
As a cathode material, Si and Mo have been studied and manufactured so far, but in recent years, an idea of using diamond as a cathode material has been issued. Geis et al. First made a p-type diamond surface n-type by ion implantation with carbon to produce a pn-junction mesa diode and demonstrated its potential as a cold cathode for diamond (MWGeis, NNEfremow, JDWoodhouse, MDMcAleese, M. Marchywka, DGSocher and JF Hochedez: IEEE Electron Device Lett., 12, p. 456 (1991)).
[0004]
The reason why diamond is used for the cold cathode is that it has a high electron emission capability. When a high voltage is applied, any material emits electrons, but among these, diamond has the lowest applied voltage.
[0005]
A schematic diagram of a configuration example of a diamond cold cathode is shown in FIG. 2, and CVD thin film technology is usually used to manufacture such a chip. At present, there are few examples of production of stable diamond cold cathodes. This is because the high electron emission ability of diamond is a surface phenomenon, and diamond itself is an insulator. For this reason, methods have been proposed in which diamond is deposited only on the surface of a Si or Mo chip that is a conventional cold cathode, or that a p-type semiconductor is used by impurity doping. However, in the former, in addition to the complexity of the manufacturing process, there is a problem of oxidation of a metal chip, which is a conventional problem. On the other hand, in the latter, the impurity level is several eV lower than the vacuum level, and diamond There is a problem that the high electron emission ability cannot be used.
[0006]
[Problems to be solved by the invention]
As described above, when a diamond cold cathode is produced by the conventional technique, problems such as deterioration due to oxidation of the metal tip and reduction of electron emission ability due to p-type semiconductor formation occur.
[0007]
The present invention solves the problems of the prior art as described above, eliminates the need for a metal chip, and further has a columnar shape having high conductivity and electron emission ability without using a semiconductor manufacturing process by impurity doping. It is an object of the present invention to provide a method for vapor phase synthesis of a diamond cold cathode and a method for producing the cold cathode .
[0008]
[Means for Solving the Problems]
The diamond cold cathode vapor phase synthesis method of the present invention is a method for conducting electrical conductivity on the cathode substrate surface by performing dynamic mixing injection of carbon ions or carbon cluster ions into diamond synthesized simultaneously with the vapor phase synthesis of diamond by the conventional CVD method. It is a method of obtaining the diamond cold cathode which has this. In the present invention, carbon is uniformly distributed in diamond by ion implantation at the time of diamond film formation, thereby making it possible to synthesize a diamond cold cathode with high electron conductivity.
In the method for producing a diamond cold cathode according to the present invention, a SiC layer is formed by ion-implanting carbon ions or carbon cluster ions into the cathode substrate surface, and controlling the substrate temperature during heat treatment or implantation. after forming at least the insulating film above the insulating film by making holes to expose the SiC layer surface, carbon ions or carbon clusters simultaneously synthesized diamond gas phase synthesis Oite diamond on the exposed SiC layer Is performed to obtain a diamond cold cathode having conductivity.
[0009]
Diamond is inherently an insulator and has poor electrical conductivity. However, it is also known that the surface state shows a negative electron affinity and the electron emission ability is high. This means that if diamond with high electrical conductivity can be synthesized, it will be a very good cold cathode.
[0010]
As described above, the present invention provides a technique for forming a diamond cold cathode with high conductivity in which carbon is uniformly distributed by co-implanting carbon ions or carbon cluster ions during diamond formation. By implanting carbon ions, etc., it was possible to uniformly distribute carbon in the diamond and to form an electronic conduction path in the insulator diamond. As a result, it is no longer necessary to use a metal tip for the diamond cold cathode, the problem of deterioration due to oxidation of the metal tip can be solved, and further, the problem of the decrease in electron emission ability due to the p-type semiconductor can be solved. .
[0011]
In the present invention, as a pretreatment, for example, carbon ions or carbon cluster ions are ion-implanted into the cathode substrate surface, heat treatment, or by controlling the substrate temperature at the time of implantation, not only the formation of nucleation sites, It is desirable to form the surface of the SiC layer. Thereafter, as described above, simultaneously performing ion implantation of carbon ions or carbon cluster ions with the gas phase synthesis of diamond in the surface of the SiC layer, obtaining a holder Iyamondo cold cathode having a conductive.
[0012]
As such a pretreatment, not only the formation of nucleation sites but also the formation of an intermediate layer such as a SiC layer on the surface by implantation of carbon ions or the like onto a cathode substrate such as a Si substrate, Hetero-epitaxial growth of diamond on the cathode substrate was made possible. When diamond is heteroepitaxially grown, the growth can be divided into growth in the <111> direction (planarization growth) and the <100> direction (chip growth). In the present invention, diamond can be heteroepitaxially grown by the SiC layer as described above, and a gas mixture of hydrogen and a hydrocarbon gas such as methane, ethane, butane, propane, or benzene is used as a gas phase raw material. As a result, [001] selective growth can be realized and chip-shaped diamond can be formed. This epitaxial growth also has the effect of making a cathode tip such as a diamond tip into a columnar shape suitable for a cold cathode.
[0013]
In the present invention, a normal diamond vapor phase synthesis method (for example, a gas phase synthesis method such as a hot filament CVD method or a plasma CVD method) using, for example, a nucleation site formed by pretreatment as a nucleus, carbon ions, or the like The columnar carbon-based cold cathode is fabricated by simultaneously performing the ion implantation method, so that the selective nucleation density can be increased in a minute region, and a chip-shaped diamond cold cathode epitaxially grown at high speed can be fabricated. It becomes. The diamond vapor phase synthesis can be performed by a method described in, for example, Japanese Patent Publication Nos. 7-23278 and 7-23279.
[0014]
Thus, in the present invention, the diamond cold cathode can be produced by using a combination of the conventional Si microfabrication technology and the diamond vapor phase growth method, which solves the problems of the conventional technology and provides high conductivity. A diamond cold cathode having an electron emission capability can be produced.
[0015]
【Example】
Next, examples of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following examples.
[0016]
Example 1
According to the synthesis method of the present invention, for example, a diamond cold cathode could be produced according to a production process as shown in FIGS.
[0017]
First, as shown in FIGS. 1A and 1B, a Si substrate (Si cathode) 2 is formed on a glass substrate 1, and carbon ions or carbon cluster ions A are ionized in the arrow direction on the Si cathode substrate 2. After the implantation, the surface 3 of the SiC layer capable of epitaxially growing the diamond cold cathode material was formed by heat treatment or controlling the substrate temperature at the time of implantation. Specifically, carbon ions are accelerated and implanted at 15 keV (generally several keV to several hundred keV), and then 1200 ° C. (generally 1000 to 1400 in a vacuum or inert gas). And a SiC layer was formed.
[0018]
An insulating film 4 made of SiO ₂ and a gate film (Si gate electrode) 5 were formed on the SiC layer 3 (FIG. 1C). Next, as shown in FIGS. 1D to 1F, a hole having a diameter of about 1 to 2 μm is formed in the gate film 5 by ion etching, and then only the layer portion of the SiO ₂ insulating film 4 is further etched through this hole. Alternatively, the surface of the SiC layer 3 was exposed by removing by an ion etching method. Next, a Ni film 6 was formed on the gate film 5 including a portion corresponding to the wall surface of the hole. In the process shown in FIGS. 1B to 1F, a conventional Si micromachining technique is used.
[0019]
Next, as shown in FIG. 1 (g), diamond is deposited on the exposed SiC layer 3 by a conventional hot filament CVD method using a mixed gas C of CH ₄ —H ₂ as a gas phase raw material for the heated filament B. While growing (see R. Eden, Diamond and Related Materials, 2,1051 (1993) and G. Lu: 2nd Int'l Conf. Application of Diamond Films and Related Materials, Tokyo, 269 (1993)), carbon ions Alternatively, dynamic mixing injection of carbon cluster ions A was performed in the direction of the arrow. At this time, the carbon ion implantation was performed by accelerating the carbon ions to 10 keV (possible from several keV to hundred keV).
[0020]
At this time, the diamond is in the shape of an octahedron that is heteroepitaxially grown ([001] selective growth) on the SiC layer, and the highly conductive diamond in which carbon is uniformly distributed by implantation of carbon ions or carbon cluster ions. Chip 7 was formed (FIG. 1 (h)). In this embodiment, diamond can be heteroepitaxially grown by the SiC layer 3, and [001] selective growth can be realized by using a CH ₄ —H ₂ mixed gas as a vapor phase raw material. Formation became possible.
[0021]
Next, an unnecessary diamond layer formed on the Ni film 6 was peeled and removed together with the Ni film 6 by etching with a 10% nitric acid solution for about 20 minutes. Thus, a highly conductive chip-shaped diamond cold cathode 7 in which carbon was uniformly distributed could be produced (FIG. 1 (i)).
[0022]
【The invention's effect】
According to the present invention, a diamond cold cathode having high conductivity and electron emission capability can be produced by using a conventional diamond vapor phase synthesis method and an ion implantation method in combination.
[0023]
The production of a diamond cold cathode was possible by a combination of a conventional Si micromachining technique and a diamond vapor phase growth method.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a manufacturing process for explaining a method for producing a diamond cold cathode according to the present invention. FIG. 2 is a configuration example of a typical cold cathode.
1 Glass substrate 2 Si cathode substrate 3 SiC intermediate layer 4 SiO ₂ insulating film 5 Gate film 6 Ni film 7 Diamond chip A Carbon (cluster) ion B Filament C Gas phase raw material (CH ₄ -CH ₂ gas)
12 Metal substrate electrodes 14a and 14b Insulator 15 Gate electrode 16 Cathode chip

Claims (8)

A diamond cold cathode vapor phase synthesis method is characterized in that a diamond cold cathode having conductivity is obtained by implanting carbon ions or carbon cluster ions into diamond synthesized simultaneously with the diamond vapor phase synthesis on the cathode substrate surface. A gas phase synthesis method of a diamond cold cathode. As a pretreatment, said carbon ions or carbon cluster ions on the cathode surface of the substrate by ion implantation, thermal treatment, or, by controlling the substrate temperature during implantation, claims, characterized in that to form the surface of the SiC layer 2. A method for gas phase synthesis of a diamond cold cathode according to 1 .   The method for vapor phase synthesis of a diamond cold cathode according to claim 2, wherein an implantation acceleration voltage of carbon ions or carbon cluster ions, which is performed simultaneously with the vapor phase synthesis of diamond, is lower than an implantation acceleration voltage at the time of forming the SiC layer. .   The diamond cold cathode gas phase synthesis method according to any one of claims 1 to 3, wherein the diamond cold cathode has a columnar shape.   The method for synthesizing a diamond cold cathode according to any one of claims 1 to 4, wherein the cathode substrate is Si. After carbon ions or carbon cluster ions are ion-implanted on the surface of the cathode substrate, a SiC layer is formed by controlling the substrate temperature during heat treatment or implantation, and at least an insulating film is formed on the SiC layer. a hole to expose the surface of the SiC layer, and subjected to gas-phase synthesis with an ion implantation of carbon ions or carbon cluster simultaneously synthesized diamond Oite diamond on the exposed SiC layer, diamond cold having conductivity A method for producing a diamond cold cathode, comprising obtaining a cathode.   The method for manufacturing a diamond cold cathode according to claim 6, wherein the diamond cold cathode has a columnar shape.   The method for producing a diamond cold cathode according to claim 6 or 7, wherein the cathode substrate is Si.

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