JPH11130589A - Deposition of diamond film or diamondlike carbon film and apparatus therefor and cold anode produced by using the same deposition and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate problems that the content of a crystal component in a diamond film or a diamondlike carbon film is low by depositing the film according to a conventional laser ablation method or a chemical vapor deposition(CVD). SOLUTION: A deposition surface of a diamond film or a diamondlike carbon film is irradiated with a polyvalent ion beam [indicated by a multiple circle in figure (b)] of carbon or impurities during or after the deposition of the diamond film or diamondlike carbon film onto a substrate when depositing the diamond film or diamondlike carbon film on the substrate according to a laser ablation method or a chemical vapor deposition(CVD) method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming a diamond film or a diamond-like carbon film. Method and apparatus. The present invention also relates to a cold cathode manufactured using the above-described film forming method and apparatus.

[0002]

2. Description of the Related Art Cold cathodes are applied to display devices for images and characters in combination with phosphors, imaging devices in combination with photoconductive films, and in various fields such as ultra-high frequency devices and magnetic sensors. Applications are being considered.

The electron emission efficiency of a cold cathode that emits electrons by an electric field by applying a voltage between a cathode having a sharp cone shape and a gate electrode surrounding the cathode depends on the concentration of the electric field generated on the surface of the cathode and the cathode. It largely depends on the work function φ of the material. Since the electric field concentration is determined by the sharpness of the cathode shape and the distance between the cathode and the gate electrode, a significant improvement in the electric field concentration must wait for the progress of cold cathode processing accuracy mainly in lithography.

On the other hand, refractory metals such as molybdenum (Mo) and nickel (Ni) and silicon have been mainly used as cold cathode materials, but φ = 4-5 in these materials.
Because of eV, a material with a lower work function has been required. From this perspective, diamond is not only chemically stable and hard, but also has a negative electron affinity (NE).
A: Negative Electron Affinity) properties are considered promising as a cold cathode material.

[0005] Usually, diamond crystals are CH ₄ , C ₂
Growth is performed on a substrate by a method such as chemical vapor deposition (CVD) using a hydrogen carbide such as H ₂ or CO as a raw material. In this method, the substrate is heated to a temperature of about 800 ° C. or higher, and the above-described raw materials are decomposed to deposit a diamond film on the substrate. Since these materials are difficult to process into the shape of a cold cathode as they are because of the above properties, when producing a cold cathode, molybdenum (Mo) or silicon (S
A cold cathode consisting of a cathode having a sharp cone shape at i) and a gate electrode surrounding the cathode via an insulator is prepared in advance, and polycrystalline diamond is deposited from above the cathode by CVD. A method has been adopted in which it is deposited on the tip of a cathode and its surface is coated.

Further, a method has been attempted in which a pyramid-shaped dent is formed in advance on a substrate such as silicon, polycrystalline diamond is deposited on the dent by CVD, and then the substrate is removed. In such a coating,
As described above, it has been reported that the substrate cold cathode needs to be heated to a high temperature of 800 ° C. or higher, and that the surface layer of diamond contains a large number of defects or is an amorphous layer. Since the characteristics of the cold cathode greatly depend on the state of the surface layer, such a structure of the surface layer is not preferable.

Further, a thin-film type cold cathode having no sharp-pointed cone shape can be manufactured at a low temperature.
A laser ablation method of irradiating a graphite target with a powerful laser beam to evaporate carbon atoms, molecules, ions, clusters and the like and depositing it on a substrate has also been attempted.
ArF (wavelength: 193 nm), K
Excimer laser pulse light such as rF (wavelength: 256 nm) is used. However, there is also a report that the size of a diamond crystal produced by this method is very small and a diamond-like carbon film is formed. It is considered that such a film has not yet exhibited sufficient performance as a cold cathode because the ratio of the crystal component to the entire diamond film is small.

[0008]

As described above, when a diamond film is formed by the CVD method, it is usually necessary to raise the substrate temperature to 800 ° C. or higher. Nevertheless, the deposition rate is as low as 0.1 μm / hr, and sufficient quality cannot be obtained. One of the reasons is considered to be that the diffusion coefficient of carbon is very small and the atom transfer for crystal growth is not sufficient.

[0009] The reason why a large-sized good quality crystal cannot be grown by the laser ablation method is as follows.
At normal pressure, the graphite phase is more stable than the diamond phase, so the pulsed laser ablation method causes the graphite phase to appear during film formation, which covers the diamond crystal surface and inhibits the diamond phase growth. 2) High energy ions are required for diamond crystal growth, but laser ablation involves a large amount of low energy ions and neutral molecules, such as neutral molecules, that are not necessary for crystal growth. It is thought that this is because growth is hindered.

As another method, a method of applying a bias voltage to a substrate by a CVD method in order to attach high-energy carbon ions to the surface of a deposited film has been adopted. But,
The purpose of this method is to increase the kinetic energy of ions, and it can be said that the effect is still insufficient according to the experimental results so far.

A first object of the present invention is to increase the ratio of crystal components in a formed diamond film or diamond-like carbon film to the whole film and to provide a cold cathode capable of emitting good electrons. It is an object of the present invention to provide a method and an apparatus for forming a diamond film or a diamond-like carbon film which can be used for producing a diamond film.

It is a second object of the present invention to provide a cold cathode manufactured by using the method and apparatus for forming a diamond film or a diamond-like carbon film of the present invention.

[0013]

In order to achieve the above-mentioned object, a method for forming a diamond film or a diamond-like carbon film according to the present invention comprises a laser ablation method and a C-type carbon film.
In forming a diamond film or a diamond-like carbon film on a substrate by the VD method, during or after the deposition of the diamond film or the diamond-like carbon film on the substrate, a polyvalent carbon or impurity is deposited on the deposition surface of the film. It is characterized in that an ion beam is irradiated.

Further, in the method for forming a diamond film or a diamond-like carbon film according to the present invention, the multivalent ion beam of carbon or impurities is focused and the focused multivalent ion beam is locally applied to the deposition surface. Is irradiated.

Further, in the method of forming a diamond film or a diamond-like carbon film according to the present invention, the local irradiation is performed by one-dimensional or two-dimensional scanning of the irradiation point of the focused polyvalent ion beam. It is characterized in that it is performed.

Further, the apparatus for forming a diamond film or a diamond-like carbon film according to the present invention is a film formation apparatus for forming a diamond film or a diamond-like carbon film on a substrate by a laser ablation method or a CVD method. Means for irradiating a deposition surface of a diamond film or a diamond-like carbon film on or above the substrate with a polyvalent ion beam of carbon or impurities during or after the deposition of the diamond film or the diamond-like carbon film on the substrate. It is.

In the apparatus for forming a diamond film or a diamond-like carbon film according to the present invention, the apparatus may further include means for supplementarily heating or cooling the substrate and / or applying a negative bias voltage. It is characterized by the fact that

Further, the cold cathode according to the present invention is characterized in that a diamond film or a diamond-like carbon film formed by the film forming method covers the cathode.

The cold cathode according to the present invention has a low-resistance pattern used as a cathode formed on a silicon substrate, and a high-resistance diamond is formed on the surface of the silicon substrate including the pattern by laser ablation or CVD. Depositing a film or a diamond-like carbon film, and locally irradiating the surface of the deposited film with a polyvalent ion beam of impurities, thereby changing the irradiated portion of the film into a low-resistance region to emit electrons. And a gate electrode having a large-area opening including the region inside on the surface of the film.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on embodiments of the present invention with reference to the accompanying drawings. First,
In the present invention, in order to promote the crystallization of diamond,
C ⁺⁴ , C during laser ablation or CVD
A multiply charged ion of carbon such as ⁺⁵ is irradiated on the deposition surface of the diamond film or the diamond-like carbon film. This principle will be described with reference to FIG. 1 taking the case of the laser ablation method as an example.

Usually, in a laser ablation method or a CVD method, a deposited film is an amorphous diamond-like carbon film as shown in FIG. In this state, multi-charged ions of carbon such as C ⁺⁴ , C ⁺⁵ (FIG. 1)
(Indicated by multiple circles in (b)), charge transfer occurs between the multiply charged ion and surrounding atoms so as to fill the inner shell vacancy of the multiply charged ion with electrons. As shown in FIG. 1 (see FIG. 1B), a plurality of peripheral atoms are ionized. This group of ionized atoms enters a high energy state due to Coulomb repulsion. For example, when the inner shell electrons of the SiH ₄ molecule are excited, the Si ⁺⁴ , Si
It is known that polyvalent ions such as ⁺⁵ and Si ^{+ 6} are formed, and the so-called “Coulomb explosion” causes SiH ₄ molecules to be separated.

The process shown in FIG. 1B is similar to the previous stage of the "Coulomb explosion". The region consisting of the ionized atom group is in a high-energy state electrostatically, but has an energy level having a potential energy that cannot be reached by heating with a normal electric furnace or the like. As a result, FIG.
As shown in (c), crystallization of the film is promoted in the process of neutralizing ions.

In the above-mentioned example, irradiation of polyvalent ions was performed during the laser ablation or the CVD deposited film. Crystallization in the solid phase can be promoted even by irradiation with a polyvalent ion beam of carbon such as C ⁺⁴ , C ^{+5, for} example, by auxiliary heating.

Next, a method or an apparatus for forming a diamond film or a diamond-like carbon film according to the present invention will be described.
A detailed description will be given based on the embodiment. FIG. 2 shows that the present invention is applied to a normal Spindt-type cold cathode comprising a cathode having a sharp cone shape at the tip of a cone and a gate electrode sandwiching the insulating film, and the tip of the cathode is formed by a laser ablation method. The embodiment in the case of coating with a diamond-like carbon film is shown. In FIG. 2, 1 is
A Spindt-type cold cathode, which has a cone-shaped cathode 2 made of silicon (Si) and the like connected at the bottom thereof, and a cathode for applying an electric field between the cathode 2 and an insulating layer 3 And a gate electrode 4 insulated by the gate electrode 4.

In order to deposit a diamond film or a diamond-like carbon film 5 on the conical portion of the cathode 2 so as to easily emit electrons from the conical portion, an ArF excimer laser (wavelength: 193 nm) is applied to a graphite target by a laser ablation method. Irradiation is performed on the surface of the cold cathode 1 (substrate on which the particles are deposited) (shown by a broken line). Up to this point, there is no change in the formation of a diamond film by the conventional laser ablation method.

[0026] In the present invention, after deposition during or deposition of the diamond film or a diamond-like carbon film by laser ablation, as shown in FIG. 2, C ⁺⁴ or C
^The cold cathode 1 is irradiated with a carbon multiply charged ion beam such as ⁺⁵ (shown by a solid line) so that the crystallization of the diamond film or the diamond-like carbon film deposited at the cathode tip, particularly at the cone-shaped portion, is promoted. In addition, by applying a negative bias to the cathode 1 from the bias power supply 7 during the irradiation of the carbon multiply-charged ion beam, crystallization of only the tip of the cathode can be promoted.

FIG. 3 shows an embodiment in which the cathode tip of the same Spindt-type cold cathode is coated with a diamond film by electron cyclotron resonance plasma CVD according to the present invention. In the present embodiment, for example, a hydrocarbon-based source gas such as methane (CH ₄ ) is decomposed by plasma generated in a plasma generation chamber 8 (9 indicates a magnetic field coil for generating plasma), and is decomposed into a raw material. They are deposited as molecules on the cold cathode 1 (shown by broken lines). In the present embodiment, the cold cathode 1 is irradiated with carbon multivalent ions such as C ⁺⁴ and C ⁺⁵ simultaneously with the decomposed raw material (shown by a solid line).
The crystallization of the diamond film or the diamond-like carbon film is promoted. Note that the structure of the cold cathode 1 and that the cold cathode is negatively biased by the bias power supply 7 is the same as the case of the laser ablation method described with reference to FIG. .

Finally, according to the present invention, which is manufactured by using a method or an apparatus for forming a diamond film or a diamond-like carbon film according to the present invention, which is different from the above-mentioned Spindt cold cathode having a sharp tip cone shape. The cold cathode will be described.

FIGS. 4 (a) to 4 (d) are views showing a process of manufacturing the cold cathode, which are shown in a plan view (upper) and a cross-sectional view (lower) of the cold cathode array, respectively. However,
FIG. 4B does not have a plan view). First, a silicon substrate is selectively subjected to ion implantation and annealing to form a low-resistance stripe pattern used as a cathode line (FIG. 4).
(A)). Next, a high-resistance diamond-like carbon film is deposited by a laser ablation method (FIG. 4B). Thereafter, the portion where the cathode line is formed is locally irradiated from above the diamond-like carbon film by, for example, narrowing the beam spot of the polyvalent ion beam of the n-type impurity.
Then, an n-type low-resistance region indicated by, and a minute region having negative electron affinity characteristics (NEA) and emitting electrons well are formed (FIG. 4C). In forming the low-resistance region, it is necessary to supplementally heat the substrate obtained in the above manufacturing process. Finally, a gate electrode line (metal) is deposited in a direction orthogonal to the cathode line in a plane (FIG. 4D). The diameter of the opening of the gate electrode is shown in FIG.
The structure is such that the diameter of the high resistance diamond-like carbon film is larger than the diameter of the low resistance (NEA) region produced in the process shown in (c) and is sandwiched between the cathode (cathode line) and the gate electrode (gate electrode line). During which an electric field can act. In the above description, the process shown in FIG. 4B may, of course, use a CVD method instead of the laser ablation method.

It is generally said that it is difficult to add a large amount of n-type impurities (lower resistance) to diamond. It is considered that the reason why these impurities do not form a solid solution at the lattice positions is that the diffusion of atoms in diamond is extremely slow and the strain relaxation around the impurities is not sufficient.

However, the high-resistance diamond-like carbon film is irradiated with poly-charged ions of the n-type impurity shown in FIG. 4 (c), in particular, locally (FIG. 4 (c), (d)). The area with a small diameter in ()) and the area with low resistance (NEA) can be formed because the impurity itself to be added is a polyvalent ion, so that it has a high energy state including the atomic group around it. Therefore, it is considered that strain relaxation sufficiently progresses and electrical activation is easy.

[0032]

According to the present invention, a crystal of a diamond film or a diamond-like carbon film formed or being formed by a laser ablation method or a CVD method by irradiating a polyvalent ion beam of carbon or impurities. The proportion of the components in the whole can be increased.

In addition, a cold cathode capable of emitting good electrons can be obtained by incorporating a diamond film or a diamond-like carbon film having a large crystal component into the manufacturing process to form a cold cathode.

Further, the method or apparatus according to the present invention comprises:
Since local irradiation can be performed by narrowing the beam spot of the polyvalent ion beam, a cold cathode array can be manufactured without processing a polycrystalline diamond film by lithography or the like as in the related art.

The method and apparatus according to the present invention can be applied not only to cold cathodes but also to the production of diamond films as coating materials and diamond crystals for other electronic devices.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a state in which polyvalent ions of carbon are irradiated on a deposition surface of a diamond film or a diamond-like carbon film during laser ablation or CVD to promote crystallization of the diamond-like carbon film. FIG.

FIG. 2 is a diagram showing an embodiment in which the present invention is applied and a cathode tip is coated with a diamond-like carbon film by a laser ablation method when a Spindt-type cold cathode is manufactured.

FIG. 3 is a view showing an embodiment in which a Spindt-type cold cathode tip is coated with a diamond film by an electron cyclotron resonance plasma CVD method to which the present invention is applied.

FIG. 4 is a view showing a process in which a cold cathode that is not a Spindt type is produced by using the method or the apparatus for forming a diamond film or a diamond-like carbon film according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 cold cathode 2 cathode 3 insulating layer 4 gate electrode 5 diamond-like carbon film 6 graphite target 7 bias power supply 8 plasma generation chamber 9 magnetic field coil

Continuing from the front page (72) Inventor Hiroyuki Onishi 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Japan Broadcasting Research Institute (72) Inventor Kenkichi Tanioka 1-110 Kinuta, Setagaya-ku, Tokyo Japan Transmission Association, Broadcasting Technology Laboratory

Claims (7)

[Claims] In forming a diamond film or a diamond-like carbon film on a substrate by a laser ablation method or a CVD method, during or after the deposition of the diamond film or the diamond-like carbon film on the substrate, A method for forming a diamond film or a diamond-like carbon film, wherein a deposition surface is irradiated with a polyvalent ion beam of carbon or impurities. 2. The film forming method according to claim 1, wherein said carbon or impurity polyvalent ion beam is focused and said focused polyvalent ion beam is locally irradiated on said deposition surface. A method for forming a diamond film or a diamond-like carbon film. 3. The film forming method according to claim 2, wherein the local irradiation is performed by one-dimensional or two-dimensional scanning of an irradiation point of the focused multiply-charged ion beam. Characteristic method for forming a diamond film or a diamond-like carbon film. 4. A film forming apparatus for forming a diamond film or a diamond-like carbon film on a substrate by a laser ablation method or a CVD method. A method for forming a diamond film or a diamond-like carbon film, further comprising a means for irradiating a deposition surface of the films with a polyvalent ion beam of carbon or impurities after the deposition. 5. The film forming apparatus according to claim 4, wherein said apparatus further comprises means for supplementarily heating or cooling said substrate and / or applying a negative bias voltage. For forming a diamond film or a diamond-like carbon film. 6. A cold cathode, wherein a diamond film or a diamond-like carbon film formed by the film forming method according to claim 1 covers the cathode. 7. A low-resistance pattern to be used as a cathode is formed on a silicon substrate, and a laser ablation method or a CVD method is performed on the surface of the silicon substrate including the pattern.
A high-resistance diamond film or a diamond-like carbon film is deposited by a method, and the surface of the deposited film is locally irradiated with a polyvalent ion beam of impurities to thereby lower the irradiated portion of the film to a low-resistance film. A cold cathode formed through a process of forming a region in which electrons are easily emitted in place of a region, and arranging a gate electrode having a wide area opening including the region inside on the surface of the film. .