JP2006196364A - Field electron emission element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a field electron emission element, in which a large emission current is obtained at a low voltage, and to provide its manufacturing method. <P>SOLUTION: The field electron emission element is composed of a plurality of carbon nanotubes 3 formed on a catalyst film 2 on a glass substrate 1 for one side, and the other ends of the plurality of carbon nanotubes have a tip, respectively 4 assembled acutely. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a field electron emission device and a manufacturing method thereof.

  A needle-like conductive material having a large length to diameter ratio, such as a carbon nanotube, has a large electric field concentration at the tip because the radius of curvature at the tip is small in the electric field. Therefore, it can function as a field electron-emitting device that gives a large emission current under a relatively low electric field. Therefore, the development of field electron emission devices using carbon nanotubes is underway.

  In conventional gate electron emission devices using carbon nanotubes, there are multiple carbon nanotubes in the center of the gate hole and single carbon nanotubes in the center of the gate hole. It is known that

  When there are multiple carbon nanotubes in the center of the gate hole, there are many emission sites (positions where the field electron emitters emit electrons) compared to the size of the gate hole. It is considered that a large amount of emission current can be obtained at a lower voltage than when it does not exist. However, when a plurality of carbon nanotubes are present densely with no gap therebetween, electric field concentration at the tip of each carbon nanotube is hindered. Therefore, it is considered that more emission current can be obtained by adjusting the average interval between the carbon nanotubes.

  As a method for adjusting the average interval of carbon nanotubes in this way, a method of patterning a catalyst film by lithography using an electron beam is known (see Non-Patent Document 1). In this method, the dots of the catalyst film having a diameter of about 100 nm can be arranged so as to have the same spacing as the height of the grown carbon nanotubes. Thereafter, the carbon nanotubes can be grown in accordance with the catalyst dot pattern by CVD growth of the carbon nanotubes.

In addition, there is known a method using a carbon nanotube aggregate array film obtained in a self-organized state in which carbon nanotubes as a conical substance are densely grown and aggregated (see Patent Document 1).
JP 2003-277030 A L. Gangloff, E. Minoux, KBK Teo, P. Vincent, VT Semet, VT Binh, MH Yang, IYY Bu, RG Lacerda, G. Pirio, JP Schnell, D. Pribat, DG Hasko, GAJ Amaratunga, WI Milne, and P. Legagneux, Applied Physics Letters Volume 4, p.1575 (2004)

  However, the above-described electron beam exposure method is costly and has a limited dot size, and patterning with a diameter of 10 nm or less is difficult. The diameter of carbon nanotubes grown by CVD correlates with the size of catalyst dots, and carbon nanotubes having a diameter of 10 nm or less that are advantageous for electric field concentration cannot be used in this method. By vacuum-depositing the catalytic metal with a polystyrene sphere spread as a mask, patterning can be performed at a lower cost by controlling the average distance between the dots of the catalyst, but it is difficult to pattern dots with a small diameter.

  In the method disclosed in Patent Document 1, since the aggregate of carbon nanotubes is formed in a self-organized manner during the growth of carbon nanotubes, the bottom surface is determined by the growth conditions of the carbon nanotubes. Therefore, there is a drawback that the diameter of the carbon nanotube and the average distance between the tips of the tips serving as emission sites cannot be controlled independently.

  As described above, conventionally known methods cannot achieve both control of the average interval of the emission sites and obtaining an emitter tip having a sufficiently small radius of curvature at the emitter tip compared to the average interval. .

  The present invention has been made to solve the above-described problems. In a field electron emission device in which a needle-like conductor such as a carbon nanotube is arranged on a substrate, an electric field is effectively applied at the tip of each needle-like conductor. An object of the present invention is to provide a field electron emission device that obtains a large emission current at a low voltage by controlling the position and shape of carbon nanotubes and a bundle of carbon nanotubes so that concentration is performed, and a method for manufacturing the same. .

  In order to solve the above problems, a field electron emission device of the present invention comprises a cathode wiring formed on a substrate, and a plurality of fibrous carbons formed so that one end of the cathode wiring adheres to the cathode wiring. And an anode disposed at a position facing the cathode wiring, and the other ends of the plurality of fibrous carbons are each sharply assembled.

  In order to solve the above problems, the field electron emission device manufacturing method of the present invention is such that the major axis direction is parallel to the direction perpendicular to the substrate on the cathode wiring formed on the substrate. The method includes a step of growing a plurality of carbon nanotubes, and a step of immersing tips of the plurality of carbon nanotubes in a hydrophobic solvent.

  According to another method of manufacturing a field electron emission device of the present invention, a plurality of carbon nanotubes are grown on a cathode wiring formed on a substrate so that a major axis direction thereof is parallel to a direction perpendicular to the substrate. And a step of immersing the tips of the plurality of carbon nanotubes in a liquid containing a binder containing silicon in a hydrophilic solvent.

  Since the bundle of carbon nanotubes having a sharp tip produced by the method of the present invention is microscopically a single carbon nanotube, the electric field concentration at the tip of each sharp carbon nanotube bundle is increased. Therefore, the characteristics of the carbon nanotube electron emitter using the sharp tip are not impaired.

  According to the present invention, it is possible to produce a field electron emission device capable of obtaining a high electric field concentration at the tip of the carbon nanotube and obtaining a large emission current at a low extraction voltage.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view of a field electron emission device according to an embodiment of the present invention. This element has a structure in which a plurality of chips that cause field emission are present in holes formed in a common gate electrode 7. In this structure, it is important not only to reduce the radius of curvature at the tip of the tip, but also to adjust the height of the tip and the average distance in the in-plane direction in order to increase the electric field concentration at the tip of the tip. is there. It will be described below that the element manufacturing method of the present invention can be manufactured while controlling the shape of an element that is optimal from these viewpoints.

  In FIG. 1, an insulating layer 6 having a thickness of 3 μm is formed on a substrate 1. In this example, a quartz glass substrate was used. In addition to other heat-resistant glass, a silicon single crystal substrate, a sapphire single crystal substrate, an MgO single crystal substrate, or the like may be used as the substrate. Any substrate having a smooth heat-resistant surface that can withstand the growth temperature of carbon nanotubes to be performed later can be used.

A part of the insulating layer 6 is opened, and a part of the surface of the glass substrate 1 is exposed. A metal cathode line 10 made of a titanium film having a thickness of about 100 nm shown in FIG. 1 is wired on the exposed glass substrate 1. On top of that, there is a catalyst film 2 made of a Co—Ni alloy with a thickness of about 50 nm, and a tip 4 composed of a bundle of carbon nanotubes with sharpened tips is formed on the catalyst film 2. Yes. As the carbon nanotubes constituting the tip 4 composed of the bundle of carbon nanotubes, multi-walled carbon nanotubes having a diameter of about 50 nm are used in this embodiment, but single-walled carbon nanotubes may be used. An electric field of 1 × 10 ⁹ V / m or more can be generated at the tip of these carbon nanotubes. A gate electrode 7 is formed on the oxide film 6 and is opened in the upper part of the plurality of emitter electrodes 4. The catalyst film 2 is a pattern having a size of about 1 to 2 μm square, and a plurality of patterns of these catalyst films are present in one opening.

  The region corresponding to the bottom side of the bundle of carbon nanotubes can be controlled by patterning the catalyst film. Therefore, by controlling the distance between adjacent catalyst films, the distance between the tips of the sharp carbon nanotube bundles can be moderately reduced. As a result, the electric field concentration at the tip of each carbon nanotube bundle is reduced. As a result, it is possible to increase the sum of the emission currents drawn from the tips of the bundles of a plurality of carbon nanotubes with a low extraction voltage.

  FIG. 2 is a scanning electron micrograph of the carbon nanotube bundle of FIG. As shown in FIG. 2, a plurality of bundles of carbon nanotubes having a sharp tip are formed. The diameter of one multi-walled carbon nanotube constituting the bundle of carbon nanotubes in the photograph is about 50 nm.

  Next, a manufacturing procedure of the three-terminal field electron emission device using the sharpened carbon nanotube bundle of FIG. 1 will be described with reference to FIG. FIG. 3 is a flowchart of the carbon nanotube production method of the present invention.

  First, as shown in S1 of FIG. 3, a catalyst film made of a carbon nanotube cathode line layer and a catalyst metal layer is formed on a substrate by sputtering. In this example, titanium having a thickness of about 100 nm was used as an adhesion layer also serving as a cathode wiring, and a Co—Ni alloy having a thickness of about 50 nm was used as a catalyst metal layer. In addition, you may utilize the other catalyst which can be used for the vapor phase growth of a carbon nanotube as a catalyst metal layer. For example, iron, Fe, Co, and Ni alloys, rare earths such as La and Y, noble metals such as Pt and Pd, and alloys thereof are known as substances that can be used as catalysts. Then, after film formation, as shown in S2 of FIG. 3, the catalyst film is patterned by photolithography or the like. Next, as shown in S3 of FIG. 3, vertically aligned carbon nanotubes are grown by microwave plasma CVD. Gases used for growth are methane and hydrogen, and growth is performed at 700 ° C. for 7 minutes. By this growth, carbon nanotubes having a length of 3 μm are formed.

  After the carbon nanotube growth, as shown in S4 of FIG. 3, the carbon nanotubes vertically aligned on the substrate are immersed in a toluene solution for 120 seconds, and then the substrate is pulled up and hot at 60 ° C. as shown in S5 of FIG. When the carbon nanotubes are dried on the plate, in the process, adjacent carbon nanotubes gather so as to come close to each other, and a carbon nanotube with sharp tips gathered as shown in FIG. 2 is formed.

  As shown in FIG. 3, even if a tip composed of a bundle of conical carbon nanotubes that has been dipped in toluene and then sharpened by drying is used, the tip of one carbon nanotube standing vertically on the substrate The fact that the same level of electric field concentration can occur will be described using the results of electric field simulation using a model.

  In the model shown in FIG. 4, the radius r1 represents the radius of curvature of the carbon nanotube located at the center of the conical tip, and B1-B2 represents the bottom surface of the tip composed of an aggregate of conical carbon nanotubes. Let H1 be the intersection of the perpendicular from A1 to the substrate surface and the substrate, and let α be the angle between B1-A1 and H1-A1. Here, it is assumed that there is only one conical tip on a flat cathode, the anode is parallel to the cathode, and the distance between the tip of the tip and the anode is d. Further, the potential difference between the anode and the cathode is V.

The relationship between the magnitude of the electric field at the position P of the tip of the carbon nanotube located at the center of the cone-shaped tip at various angles α from 0 degrees to 90 degrees under the conditions shown in Table 1 is shown. When the angle α is 0 degree, it represents a tip model in which a hemisphere with a radius r1 is placed on a cylinder with a radius r1 and a height h. This is regarded as a model of a single carbon nanotube standing vertically on the substrate. When the angle α is 90 degrees, a model in which a hemisphere having a radius r1 is directly mounted on a planar cathode.

  It can be seen from the graph of FIG. 5 that the magnitude of the electric field at the tip of the tip is the largest when the angle α is 0 degrees. When the angle α is less than 50 degrees, the magnitude of the electric field at the tip of the tip is almost the same as when it is 0 degrees, but when the angle α exceeds 50 degrees, the magnitude of the electric field may rapidly decrease. Recognize. Therefore, it is understood that the size of the bottom surface of the cone should be determined so that the angle α is less than 50 degrees. The size of the bottom surface of the cone can be controlled by patterning a portion where the catalyst exists on the substrate by means such as photolithography.

Next, the electric field at position P when the radius of curvature r1 of the tip of the tip located at the center of the cone-shaped tip is changed under the conditions shown in Table 2 with the angle α fixed at 45 degrees. FIG. 6 shows the relationship with the size of. It can be seen that the curvature radius r1 of the tip greatly affects the magnitude of the electric field at the tip position P.

  From the above results, as a whole, the diameter of the carbon nanotube located at the center (approximately 2 of the radius of curvature r1 of the tip) is larger than the angle formed between the direction perpendicular to the substrate surface and the ridge line of the conical aggregate of carbon nanotubes. It can be seen that (times) greatly affects the magnitude of the electric field at the tip.

  As shown in FIG. 2, in the bundle of conical carbon nanotubes that has been dipped in toluene and then sharpened by drying, the spreading direction is rapidly increased near the substrate. That is, assuming that the substrate surface is on the lower side of the tip, the ridge line of the weight-like tip is convex downward. The reason why the ridge line of the weight-like tip is convex downward in the process of the present invention will be described below.

  FIG. 7 schematically shows a cross-sectional view of an array of carbon nanotubes grown while being oriented perpendicular to the substrate. In FIG. 7, A0-B0, A1-B1,..., An-Bn represent carbon nanotubes. Here, it is assumed that the lengths A0-B0, A1-B1,..., An-Bn of the carbon nanotubes are approximately aligned with a length of about 4 μm. It is known that when carbon nanotubes are grown by the plasma CVD method, carbon nanotubes with substantially uniform lengths aligned perpendicular to the substrate grow. It is considered that the length of carbon nanotubes that are aligned vertically on the substrate can be adjusted more precisely by means such as CMP (Chemical Mechanical Polishing) or plasma etch-back. .

  Further, it is assumed that the distances B0-B1, B1-B2,..., An-1-An at the base growth position of the carbon nanotubes on the substrate are several tens of nm to 0.5 μm. It is assumed that the diameter of each individual carbon nanotube is about 1 nm to several tens of nm and is very small compared to the length of the carbon nanotube and the interval between the growth positions at the root of the carbon nanotube.

  It is known that the diameter of carbon nanotubes grown by the CVD method has a positive correlation with the particle diameter of the catalyst used during growth. By spin-coating a liquid in which catalyst particles having a uniform size in an appropriate solvent are dispersed on a substrate, the catalyst particles having a diameter of 1 nm to several tens of nm can be arranged on the substrate. The average interval between the catalyst particles can be adjusted by adjusting the viscosity of the liquid, the concentration of the catalyst particles, the rotation speed of the substrate during spin coating, and the like.

When these carbon nanotube arrays are immersed in a hydrophobic solution and then dried, the vertically aligned carbon nanotubes adhere to each other by sticking. When a photoresist with a minute pattern is taken out of the solution and dried, the pattern collapses due to adhesion between the resists (Hideo Namatsu, Kenji Yamazaki, and Kenji Kurihara, Journal of Vacuum Science & Technology B18, p. 780 (2000)), it is known that structures fabricated after etching in the fabrication process of microelectromechanical systems (MEMS) adhere to each other (Bharat Bhushan, Journal of Vacuum Science & Technology B21, p.2262 (2003). )). The phenomenon that carbon nanotubes adhere to each other is considered to be a phenomenon similar to these. The cylindrical surface of the carbon nanotube forms a network by bonding of six-membered rings of carbon atoms, which is considered to be hydrophobic. Therefore, when immersed in a hydrophobic solution such as toluene, it is considered that carbon nanotubes adhere in the drying process.

  At this time, as shown in FIG. 8, the tip A1 of the carbon nanotube A1-B1 has a circle whose center is B1 and whose radius is equal to the length of the carbon nanotube | A1-B1 |, and a line segment A0-B0 (the middle carbon Move to the intersection C1 with the nanotube. Similarly, the tip A2 of the carbon nanotube A2-B2 moves to the intersection C2 of the circle whose center is B2 and whose radius is equal to the carbon nanotube length | A2-B2 | and the line segment B1-C1 (middle carbon nanotube) To do. In this way, the positions C1, C2,..., Cn of the tips of the carbon nanotubes after the tips of the individual carbon nanotubes adhere to each other by sticking are below the straight line A0-Bn and on the downwardly convex curve positioned. That is, it can be seen that the aggregate of carbon nanotubes obtained by dipping in a hydrophobic solution and then drying forms a cone-shaped tip whose ridgeline has a downwardly convex shape.

Next, the ridge line of the bottom of the cone-shaped tip composed of the aggregate of carbon nanotubes produced by the method of the present invention as described above becomes a downwardly convex curve. Compared with the convex case, the fact that the electric field is more easily concentrated and the magnitude of the electric field at the tip end is increased will be described below using electric field simulation.

  In the model shown in FIG. 9, the radius r1 represents the radius of curvature of the tip of the carbon nanotube located at the center of the conical tip, and B1-B2 represents the bottom surface of the tip composed of an aggregate of conical carbon nanotubes. . The intersection α between the perpendicular line from A1 to the substrate surface and the substrate is H1, and the angle α formed by B1-A1 and H1-A1 is 45 degrees. The ridge line is convex downward, and is an arc A1-D1-B1 of radius r2 centered on a straight line passing through the midpoint of the line segment A1-B1 and perpendicular to A1-B1. However, the radius r2 is equal to the length of the line segment A1-H1 and the length of the line segment B1-H1. Here, it is assumed that there is only one conical tip on a planar cathode, the anode is parallel to the cathode, and the distance between the tip of the tip and the anode is d. Thus, the system considered here is symmetric about rotation around the OP axis. Further, the potential difference between the anode and the cathode is V.

  In the model shown in FIG. 10, the radius r1 represents the radius of curvature of the tip of the carbon nanotube located at the center of the conical tip, and B1-B2 represents the bottom surface of the tip composed of an aggregate of conical carbon nanotubes. . The intersection α between the perpendicular line from A1 to the substrate surface and the substrate is H1, and the angle α formed by B1-A1 and H1-A1 is 45 degrees. The ridge line is convex upward, and is an arc A1-D1-B1 centered on a straight line passing through the midpoint of the line segment A1-B1 and perpendicular to A1-B1. However, the radius of the arc A1-D1-B1 is equal to the length of the line segment A1-H1 and the length of the line segment B1-H1. Here, for convenience, r2 is negative and the radius of the arc A1-D1-B1 is represented by -r2. It is assumed that there is only one cone-shaped tip on a flat cathode, the anode is parallel to the cathode, and the distance between the tip of the tip and the anode is d. Thus, the system considered here is symmetric about rotation around the OP axis. Further, the potential difference between the anode and the cathode is V.

FIG. 11 shows the result of the numerical calculation of the relationship between the curvature 1 / r2 of the ridge line and the magnitude of the electric field at the tip of the tip in the models of FIGS. 9 and 10 with the parameter values shown in Table 3. However, r2 <0 is the case where the tip ridge is convex downward as shown in FIG. 10, and r2> is the case where the tip ridge is convex upward as shown in FIG. 1 / r2 = 0 (r2 → ∞) represents a case where the tip edge is a straight line as shown in FIG. As shown in FIG. 11, the magnitude of the electric field at the tip of the tip is larger when the curvature 1 / r2 is negative than when it is positive. That is, it can be seen that the ridgeline of the cone-shaped tip is more convex as an electron-emitting device because it tends to concentrate the electric field more easily than when it is convex upward.

Therefore, as shown in FIG. 3, in the bundle of cone-shaped carbon nanotubes that have been dipped in toluene and then sharpened by drying, the carbon nanotubes that expand rapidly in the vicinity of the substrate are in the center of the tip. It can be seen that this is excellent as an electron-emitting device because the electric field concentration at the tip of the carbon nanotube in the portion increases.

  FIG. 12 is a cross-sectional view of a field electron emission device according to an embodiment of the present invention. Example 2 differs from Example 1 in that the tip of the carbon nanotube bundle of the emitter electrode 4 in FIG. 1 is not sharpened by dipping in a hydrophobic solution, but in a hydrophilic solvent such as silicon. This is performed by immersing in a liquid containing a binder containing silicon. As the polymer containing silicon, a material generally used for an interlayer insulating film material of a semiconductor element such as SOG (Spin on Glass) can be used. The silicon-based polymer can reduce degassing in a vacuum by chemically changing to silicon dioxide at a high temperature. Other steps are the same as in Example 1.

  A part of the insulating layer 6 is opened, and a part of the surface of the glass substrate 1 is exposed. A metal cathode line 10 shown in FIG. 12 is wired on the exposed glass substrate 1. On top of this, there is a catalyst film 2 made of a titanium film with a thickness of about 10 nm and a Co—Ni alloy with a thickness of about 50 nm, and from a bundle of carbon nanotubes whose tip is sharpened over the catalyst film 2. A configured tip 4 is formed. As the carbon nanotubes constituting the tip 4 composed of the bundle of carbon nanotubes, multi-walled carbon nanotubes having a diameter of about 50 nm are used in this embodiment, but single-walled carbon nanotubes may be used. The tip 4 is composed of a bundle of carbon nanotubes, and a gap between the carbon nanotubes is filled with a silicon-based polymer 9 such as SOG. The surface of the tip composed of a bundle of carbon nanotubes containing SOG is covered with a conductive layer 8 composed of a TiC film having a thickness of 10 nm. TiC is used to impart electrical conductivity to the surface because the silicon-based polymer is an insulator. An electric field of 1 × 10 9 V / m or more can be generated at the tip of a bundle of carbon nanotubes coated with TiC.

  A gate electrode 7 is formed on the insulating layer 6 made of SiO 2, and is opened in the upper part of the plurality of tips 4. The catalyst film 2 is a pattern having a size of about 1 to 2 μm square, and a plurality of patterns of these catalyst films are present in one opening.

  Next, a manufacturing procedure of the three-terminal field electron emission device using the sharpened carbon nanotube bundle in FIG. 12 will be described with reference to FIG. FIG. 13 is a flowchart of the carbon nanotube production method of the present invention.

  First, as shown in S21 of FIG. 13, a catalyst film comprising a cathode line layer of carbon nanotubes and a catalyst metal layer is formed on a substrate by sputtering. In this embodiment, titanium having a thickness of about 100 nm was used as the cathode line layer, and a Co—Ni alloy having a thickness of about 50 nm was used as the catalyst metal layer. In addition, you may utilize the other catalyst which can be used for the vapor phase growth of a carbon nanotube as a catalyst metal layer. For example, iron, Fe, Co, and Ni alloys, rare earths such as La and Y, noble metals such as Pt and Pd, and alloys thereof are known as substances that can be used as catalysts. After film formation, as shown in S22 of FIG. 13, the catalyst film is patterned by photolithography or the like.

  Next, as shown in S23 of FIG. 13, vertically aligned carbon nanotubes are grown by microwave plasma CVD. Gases used for growth are methane and hydrogen, and growth is performed at 700 ° C. for 7 minutes. By this growth, carbon nanotubes having a length of 3 μm are formed.

  After the carbon nanotube growth, as shown in S24 of FIG. 13, a solution obtained by diluting SOG 1: 4 with ethyl acetate is coated on the carbon nanotube vertically aligned on the substrate by spin coating, and atmospheric pressure is applied as in S25. Vacuum deaeration is performed by reducing the pressure to 0.2 atm and maintaining for 60 seconds. As shown in S26 of FIG. 13, the adjacent carbon nanotubes are gathered so as to come close to each other in the process of drying SOG on a hot plate at 60 ° C., so that the carbon nanotubes whose tips are sharply gathered as shown in FIG. Is formed. The mechanism for adhering the carbon nanotubes so that the tips are sharp is slightly different from that shown in Example 1, and since the binder (binder) is contained in the soaked solvent, the solvent is removed during the drying process. Although it evaporates, it is considered that the binder remains and the carbon nanotubes adhere to the binder. The surface of the bundle of carbon nanotubes to which the SOG with the sharp tips at the end is attached as in S27 is coated with TiC having metallic conductivity by a sputtering method to obtain a field electron emission device.

  Next, a method for manufacturing a field electron emission device with a gate electrode using a tip prepared by sharpening a bundle of multi-walled carbon nanotubes grown vertically oriented on a substrate in the present invention will be described.

  The production procedure is shown in the schematic diagrams shown in FIGS.

  First, as shown in FIG. 14, Ta (thickness: 50 nm) serving as a cathode wire material is deposited on a quartz substrate 101 by sputtering. This is processed into a cathode wiring pattern 102 by reactive ion etching using CF4. After processing, in the novolak photoresist diluted with PGMEA (propyleneglycol monomethyl ether acetate), particles of Pd having a diameter of 2 nm to 5 nm prepared by the reverse micelle method are dispersed, and this is applied by the spin coat method, and the underlayer 104 is formed. Form.

  Next, as shown in FIG. 15, the underlayer 104 is patterned by photolithography exposure / development to form a 5 μm × 5 μm region pattern made of a resist in which Pd particles are dispersed on the cathode wiring pattern 102. . Thereafter, as shown in FIG. 16, the quartz substrate 101 is plasma heated in oxygen to 600 ° C. to oxidatively decompose the resist of the underlayer 104, and the catalyst film 103 made of only Pd particles is formed on the quartz substrate 101. Form.

  Next, as shown in FIG. 17, carbon nanotubes 105 oriented perpendicular to the substrate are grown on the catalyst film 103 by high-frequency plasma CVD. In this process using the high-frequency plasma CVD method, hydrogen gas and methane gas were supplied into the CVD chamber as source gases, and the flow ratio was 82.5: 17.5. Carbon nanotubes were grown for 20 minutes at a plasma input power of 200 W and a pressure of 230 Pa. The grown carbon nanotube 105 had a length of about 5 μm and a diameter (outer shape) of about 20 nm.

  Next, the tip of the grown carbon nanotube 105 is immersed in toluene for 1 minute and then dried for 10 minutes on a hot plate heated to 60 ° C., thereby sharpening the tip of the bundle of carbon nanotubes 105 as shown in FIG. To form an emitter tip.

Next, as shown in FIG. 19, SiO ₂ is deposited by sputtering on the cathode wiring pattern 102 including the tip of the emitter and the quartz substrate 101 to form an insulating layer 106. After that, as shown in FIG. 20, the unevenness on the surface of the insulating layer 106 due to the emitter tip being the base is planarized by CMP (Chemical Mechanical Polishing).

  Next, as shown in FIG. 21, Ta as a gate electrode material is deposited by sputtering to form a Ta layer 107 having a thickness of about 150 nm. Thereafter, the gate electrode is patterned to form a resist pattern 110 in order to expose the tip of the emitter tip.

Thereafter, as shown in FIG. 22, the Ta layer 107 and the underlying insulating layer 106 are etched by reactive ion etching (RIE) using CF ₄ to expose the tip of the emitter tip. At this time, the RIE is controlled so as to stop when the tip of the emitter tip is exposed. FIG. 23 is a top view of the field electron emission device after completion of the step of FIG. As shown in FIG. 23, the external contact holes are also etched at the same time in the process of FIG.

  Thereafter, as shown in FIG. 24, the resist pattern 110 is removed, the portion other than the external contact hole is covered with a mask for electrical connection with the cathode wiring pattern 102, and the external contact hole is vacuum-deposited on the external contact hole. Is filled with gold to form a contact electrode 108. The contact electrode 108 is connected to a ground electrode (not shown) by a bonding wire 109.

  The field electron emission device manufactured by the above process can obtain a large current at a lower gate voltage than when the tip of the carbon nanotube is not sharpened.

  Each of the above-described embodiments exemplifies an apparatus and a method for embodying the technical idea of the present invention. The technical idea of the present invention is based on the material, shape, structure, and arrangement of components. Etc. are not limited only to those disclosed in the embodiments. The present invention can be variously modified and implemented without departing from the spirit of the present invention.

It is sectional drawing of the field electron emission element which is an Example of this invention. 2 is a scanning electron micrograph of a bundle of carbon nanotubes of FIG. It is a flowchart of the manufacturing method of the carbon nanotube of Example 1 of this invention. It is a conceptual diagram of the electric field simulation model of a carbon nanotube. It is a figure which shows the result of the electric field simulation using the model of FIG. FIG. 5 is a diagram showing the relationship between the radius of curvature of the tip end when the angle α in FIG. 4 is 45 degrees and the magnitude of the electric field at P in FIG. 4. It is sectional drawing of the arrangement | sequence of the carbon nanotube grown by aligning perpendicularly | vertically to a board | substrate. It is sectional drawing which shows the adhesion shape of the front-end | tip of the carbon nanotube grown by aligning perpendicularly | vertically to a board | substrate. It is a cross-sectional model figure which shows one shape of a carbon nanotube. It is a cross-sectional model figure which shows the other shape of a carbon nanotube. FIG. 11 is a diagram illustrating a relationship between the curvature 1 / r2 of the ridge line and the magnitude of the electric field at the tip end in the models of FIGS. It is sectional drawing of the field electron emission element of Example 2 of this invention. It is a flowchart of the manufacturing method of the field electron emission element of Example 1 of the present invention. It is a manufacturing process figure of the field electron emission element of Example 3 of the present invention. It is a manufacturing process figure of the field electron emission element of Example 3 of the present invention. It is a manufacturing process figure of the field electron emission element of Example 3 of the present invention. It is a manufacturing process figure of the field electron emission element of Example 3 of the present invention. It is a manufacturing process figure of the field electron emission element of Example 3 of the present invention. It is a manufacturing process figure of the field electron emission element of Example 3 of the present invention. It is a manufacturing process figure of the field electron emission element of Example 3 of the present invention. It is a manufacturing process figure of the field electron emission element of Example 3 of the present invention. It is a manufacturing process figure of the field electron emission element of Example 3 of the present invention. It is a manufacturing process figure of the field electron emission element of Example 3 of the present invention. It is a manufacturing process figure of the field electron emission element of Example 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Glass substrate 2 ... Catalyst film 4 ... Tip 6 ... Insulating layer 7 ... Gate electrode 8 ... Conductive layer 9 ... SOG
DESCRIPTION OF SYMBOLS 10 ... Cathode electrode 101 ... Quartz glass substrate 102 ... Cathode wiring pattern 103 ... Catalyst film 104 ... Underlayer 105 ... Carbon nanotube 106 ... Insulating layer 107 ... Ta layer 108 ... Contact electrode 109 ... Bonding wire 110 ... Resist pattern

Claims (5)

A cathode wiring formed on the substrate;
A plurality of fibrous carbons formed so that one end thereof adheres to the cathode wiring;
An anode disposed at a position facing the cathode wiring;
A field electron-emitting device, wherein the other ends of the plurality of fibrous carbons are each sharply assembled.   The field electron-emitting device according to claim 1, wherein an angle formed between the one end of the fibrous carbon and the other end with respect to the vertical direction of the substrate is less than 50 degrees.   The field electron-emitting device according to claim 1, wherein a distance between each of the one ends of the plurality of fibrous carbons is several hundred nm to 0.5 nm. A step of growing a plurality of carbon nanotubes on a cathode wiring formed on a substrate so that the major axis direction thereof is parallel to a direction perpendicular to the substrate;
And a step of immersing the tip portions of the plurality of carbon nanotubes in a hydrophobic solvent. A step of growing a plurality of carbon nanotubes on a cathode wiring formed on a substrate so that the major axis direction thereof is parallel to a direction perpendicular to the substrate;
A step of immersing the tips of the plurality of carbon nanotubes in a liquid containing a binder containing silicon in a hydrophilic solvent.