JP4414728B2 - Carbon processed body, manufacturing method thereof, and electron-emitting device - Google Patents

Description

  The present invention relates to a carbon processed body such as an electron-emitting device applicable to an electron gun, an electron tube, a vacuum tube, a field emission display (FED) and the like, a manufacturing method thereof, and an electron-emitting device.

  One of the conductive carbons is a carbon nanotube (hereinafter referred to as CNT). Since this CNT is very thin, an electric field is concentrated on the tip, and electrons can be emitted at a low voltage. It has also been reported that FEDs can be formed from CNTs using printing technology.

As such a carbon processed body made of CNT, for example, an electron-emitting device described in Non-Patent Document 1 is known. The electron-emitting device described in this document has a plurality of protrusions formed on a substrate by arranging a metal catalyst such as Ni or Fe in a dot shape on the substrate and growing CNT only on that portion. .
New Diamond and Frontier Carbon Technology, Vol. 11, No. 4 (2001), p235

  However, the following problems exist in the prior art. That is, since CNT is grown using a metal catalyst, the catalyst metal often remains inside the tip of the protrusion. Since this catalytic metal is embedded in the carbon having chemical resistance, it is very difficult to remove. In addition, since the growth is utilized, the side wall surface of the protrusion is a conductive layer in which the CNTs are closed and is electronically inactive. As a result, the electron emission characteristics of the electron-emitting device are lowered.

An object of the present invention is to provide a carbon processed body capable of improving electrical characteristics by electronically activating a protrusion on a substrate, a manufacturing method thereof, and an electron-emitting device.

The present invention is a carbon processed body formed by forming a protrusion made of conductive carbon on a substrate, wherein the substrate is a SiC substrate, and the protrusion has a six-membered ring of conductive carbon with respect to the upper surface of the SiC substrate. It has a structure that extends to the root in a substantially vertical state, forms a layer made of conductive carbon on the SiC substrate by pyrolysis , and then etches the layer made of conductive carbon machining der those formed by is, the side surface portion of the projection, and is characterized in that there exists a broken conductive carbon six-membered ring by an etching process.

In the case of forming such a carbon processed body, a conductive carbon layer is formed on at least the upper surface side of the substrate so that the six-membered ring of carbon stands on the upper surface of the substrate. Is etched to form protrusions on the substrate. At this time, since the conductive carbon layer having a structure in which the six-membered ring of carbon stands with respect to the upper surface of the substrate is etched, the broken (broken) conductive carbon of the six-membered ring is formed on the side surface of the protrusion. And the protrusion becomes electronically active. Further, unlike the case where the protrusion is formed by growing conductive carbon, the catalytic metal does not remain inside the tip of the protrusion. As described above, when the carbon processed body of the present invention is used as an electron-emitting device, the threshold voltage for emitting electrons from the protrusions can be lowered, so that the electron emission characteristics can be improved.
At this time, the substrate is made of SiC. In this case, an SiC substrate having a flat upper surface is prepared, and a conductive carbon layer made of carbon nanotubes is formed on the upper surface side of the SiC substrate by, for example, pyrolysis, so that the carbon six-membered ring is formed on the SiC substrate. A flat carbon-containing substrate having a structure standing with respect to the upper surface can be obtained. Thereby, when the conductive carbon layer of the carbon-containing substrate is etched to form a plurality of protrusions made of carbon nanotubes, the heights of the protrusions are almost uniform. Accordingly, when the carbon processed body is used as an electron-emitting device, an electron-emitting current can be effectively extracted from each protrusion, so that the electron-emitting characteristics can be further improved.

  Preferably, the tip of the protrusion is thin with respect to the root of the protrusion. The protrusion having such a shape can be formed by etching the conductive carbon layer, and it is extremely difficult to form the protrusion using the growth of the conductive carbon. By making the tip of the protrusion thin with respect to the base of the protrusion, a large electric field can be applied to the protrusion at a low voltage when the carbon processed body is used as an electron-emitting device, so that electrons are easily emitted from the protrusion. . Therefore, since the threshold voltage can be further lowered, the electron emission characteristics can be further improved.

  Preferably, the conductive carbon is a carbon nanotube. Since carbon nanotubes are very thin, when an electric field is applied to the protrusion, the electric field tends to concentrate on the tip of the protrusion. Therefore, when the carbon processed body is used as an electron-emitting device, electrons can be emitted at a very low voltage.

  Further, preferably, a plurality of protrusions are provided, and the plurality of protrusions are regularly arranged on the substrate. Accordingly, when the carbon processed body is used as an electron-emitting device, each projection is effectively used, and thus better electron-emitting characteristics can be obtained.

  Preferably, a plurality of protrusions are provided, and the height uniformity of each protrusion is 10% or less. By making the height uniformity of the protrusions in this way, an electron emission current is effectively drawn from each protrusion, so that even better electron emission characteristics can be obtained.

The method for producing a carbon processed body of the present invention includes a step of forming a carbon-containing substrate provided with a layer made of conductive carbon on at least the upper surface side, a step of patterning a mask on the carbon-containing substrate, and conductive carbon. look including a step of forming a projection by etching a layer made of, by forming a layer of conductive carbon SiC substrate by thermal decomposition method, characterized in that to form a carbon-containing substrate is there.

  By producing the carbon processed body in this manner, the conductive carbon having a broken (cut) six-membered ring is present on the side surface portion of the protrusion, and the protrusion becomes electronically active. Further, unlike the case where the protrusion is formed by growing conductive carbon, the catalytic metal does not remain inside the tip of the protrusion. As described above, when the carbon processed body is used as an electron-emitting device, the threshold voltage for emitting electrons from the protrusion can be lowered, so that the electron emission characteristics can be improved.

Moreover , a carbon-containing substrate is formed by forming a layer made of conductive carbon on the SiC substrate by a thermal decomposition method. In this case, a flat carbon-containing substrate having a structure in which a carbon six-membered ring stands with respect to the upper surface of the SiC substrate can be obtained. Thus, when the conductive carbon layer on the carbon-containing substrate is etched to form a plurality of protrusions made of carbon nanotubes, the heights of the protrusions are almost uniform.

The present invention is also an electron-emitting device in which a plurality of protrusions made of conductive carbon are formed on a substrate , the substrate is a SiC substrate, and the protrusions are made of a six-membered ring of conductive carbon made of a SiC substrate. It has a structure extending to the base in a state of being substantially perpendicular to the upper surface, and after forming a layer made of conductive carbon on the SiC substrate by a thermal decomposition method, der those formed by etching a layer serving is, the side surface portion of the projection, and is characterized in that there exists a broken conductive carbon six-membered ring by an etching process.

  When forming such an electron-emitting device, a conductive carbon layer having a structure in which a carbon six-membered ring stands with respect to the upper surface of the substrate is formed on at least the upper surface side of the substrate. Is etched to form protrusions on the substrate. At this time, since the conductive carbon layer having a structure in which the six-membered ring of carbon stands with respect to the upper surface of the substrate is etched, the broken (broken) conductive carbon of the six-membered ring is formed on the side surface of the protrusion. And the protrusion becomes electronically active. Further, unlike the case where the protrusion is formed by growing conductive carbon, the catalytic metal does not remain inside the tip of the protrusion. As described above, the threshold voltage when electrons are emitted from the protrusions can be lowered, so that the electron emission characteristics can be improved.

According to the present invention, the collision force, which is formed on the substrate, the six-membered ring of the conductive carbon has a structure which extends up to the base in a state of standing substantially perpendicular to the upper surface of the substrate In addition, since a layer made of conductive carbon is formed on the substrate and then the layer made of conductive carbon is etched, the electrode is arranged in the vicinity of the protrusion, for example. When electrons are emitted from the electron emission characteristics, the electron emission characteristics can be improved.

  Hereinafter, preferred embodiments of a carbon processed body, a manufacturing method thereof, and an electron-emitting device according to the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view showing a first embodiment of an electron-emitting device as a carbon processed body according to the present invention. The electron-emitting device 1 of the present embodiment includes a substrate 2 and a plurality of columnar or prismatic protrusions 3 (columnar in the figure) formed on the substrate 2. In such an electron-emitting device 1, a gate electrode (not shown) is provided on the substrate 2 and an anode electrode (not shown) is disposed so as to face the upper surface of the substrate 2. When a voltage is applied between them, an electric field is applied to each protrusion 3, and electrons are emitted from the tip of each protrusion 3.

  Each protrusion 3 is regularly arranged on the substrate 2. The alignment form of the protrusions 3 may be a quadrangular shape as shown in FIG. 1, a triangular shape, or the like. In addition, it is possible to arrange the protrusions 3 at random, but it is advantageous to align the protrusions 3 in order to effectively use each protrusion 3 and to obtain highly efficient electron emission characteristics. It is. The diameter of each protrusion 3 is, for example, about 10 μm at the maximum, and the height of each protrusion 3 is, for example, about 3 μm at the maximum.

  The protrusion 3 is made of conductive carbon such as carbon nanotube (hereinafter referred to as CNT), highly oriented graphite (hereinafter referred to as HOPG), graphite, or the like. The protrusion 3 is formed by etching such a layer made of conductive carbon (hereinafter referred to as a conductive carbon layer).

  When the protrusion 3 is made of CNT, the substrate 2 is preferably a substrate made of SiC (hereinafter referred to as a SiC substrate). When the protrusion 3 is made of HOPG, the substrate 2 is preferably a highly oriented graphite substrate (hereinafter referred to as a HOPG substrate) made of HOPG.

  In the structure in which the protrusions 3 are made of CNTs, as shown in FIG. 2A, a plurality of CNTs 4 forming the protrusions 3 are arranged in a bundle with almost no gap. At this time, the protrusion 3 has a structure in which the carbon six-membered ring forming the CNT 4 stands substantially perpendicular to the upper surface of the substrate 2. Here, “a structure in which a carbon six-membered ring stands substantially vertically” includes a six-membered ring that extends to the base of the protrusion 3 even if it is oblique to the upper surface of the substrate 2. Say.

  On the other hand, in the structure in which the protrusions 3 are made of HOPG, as shown in FIG. 2B, the plurality of graphite layers 5 forming the protrusions 3 are arranged in a bundle with almost no gap. At this time, the protrusion 3 has a structure in which the carbon six-membered ring forming the graphite layer 5 stands substantially perpendicular to the upper surface of the substrate 2.

  The protrusion 3 is formed by etching the conductive carbon layer as described above. When the conductive carbon layer having a structure in which the six-membered ring of carbon stands on the upper surface of the substrate 2 is etched, the protrusion 3 is formed. The six-membered ring is broken (destroyed) everywhere on the side surface. Further, in a structure in which a carbon six-membered ring stands, since the six-membered rings are difficult to be separated from each other, it is strong against an electric field and mechanical strength, and the durability of the protrusion 3 is increased.

  Next, a method for manufacturing the electron-emitting device 1 as described above will be described with reference to FIG.

First, as shown in FIG. 3A, a carbon-containing substrate 11 provided with a conductive carbon layer 11a on at least the upper surface side is formed. At this time, it is important that the upper surface of the carbon-containing substrate 11 (conductive carbon layer 11a) is flat. For example, the flatness R _max of the upper surface of the carbon-containing substrate 11 is 1 μm or less, preferably 0.1 μm or less in a glossy state.

  The preparation of the carbon-containing substrate 11 having good flatness in this way affects the uniformity of the height of the protrusion 3 to be formed later, and also contains carbon in a process using photolithography (utilizing ultraviolet light) to be described later. This is because it affects when the substrate 11 is processed. That is, if the unevenness of the upper surface of the carbon-containing substrate 11 is large, not only the height of the protrusion 3 varies, but also the pattern shape on the carbon-containing substrate 11 is blurred, and fine patterning becomes difficult.

For example, if the flatness R _max of the upper surface of the carbon-containing substrate 11 is larger than 1 μm, the non-uniformity of the size of the Al mask formed on the contact mask of photolithography becomes as large as 30% due to bleeding. Further, when the protrusion 3 having a height of 3 μm is formed, a height non-uniformity of about 30% occurs, and when the protrusion 3 having a height of 1 μm is formed, the height non-uniformity of about 50% is generated. Will occur. In this case, the electron emission characteristics vary by 1 to 3 digits, making it impossible to manufacture a homogeneous electron-emitting device. If the flatness R _max is 5 μm or more, patterning may be impossible. On the other hand, if the carbon-containing substrate 11 having an upper surface with a flatness R _max of 1 to 10 nm is used, for example, when the protrusion 3 having a height of 1 μm is formed, the height non-uniformity is set to 0.1 to 1%. Can be suppressed.

  Here, when forming the protrusions 3 made of CNTs, a carbon-containing substrate 11 having a flat upper surface is formed using a SiC substrate. Specifically, first, as shown in FIG. 4A, an SiC substrate 12 having a flat upper surface is prepared. Then, a layer (CNT layer) 13 made of CNT is formed on the upper surface side of the SiC substrate 12 by pyrolysis as shown in FIG. For example, when the SiC substrate 12 is heated at 1500 to 1700 ° C. for 6 to 10 hours in a vacuum, only the Si on the upper surface side of the SiC substrate 12 is selectively removed, and the remaining carbon self-organizes the nanotubes. Layer 13 is formed. As a result, a carbon-containing substrate 11 with good flatness having a structure in which a carbon six-membered ring stands substantially perpendicular to the upper surface is obtained.

  On the other hand, when forming the protrusion 3 made of HOPG, a carbon-containing substrate 11 having a flat upper surface is formed using a HOPG substrate. Specifically, a thick original HOPG substrate having a c-axis orientation or a plurality of thin original HOPG substrates are prepared. Then, as shown in FIG. 5A, the original HOPG substrates 14 are arranged in a vertical state, and in this state, the original HOPG substrate 14 is molded and solidified with a resin 15 to form the HOPG substrate 16. As a result, the c-axis direction of the graphite of the original HOPG substrate 14 is aligned along the substrate surface (upper surface) 16 a of the HOPG substrate 16. Subsequently, as shown in FIG. 5B, the upper surface 16 a of the HOPG substrate 16 is polished (flattened) in the c-axis direction of graphite so as to include the molded original HOPG substrate 14. As a result, a carbon-containing substrate 11 with good flatness having a structure in which a carbon six-membered ring stands substantially perpendicular to the upper surface is obtained. The fixing of the original HOPG substrate 14 is not limited to a resin mold, and may be joined with a metal or the like.

Next, as shown in FIG. 3B, a metal such as Al, an oxide such as SiO ₂ or a nitride such as TiN is formed on the carbon-containing substrate 11 as described above, and a photolithography technique or an electron beam is used. Patterning of the micro-aligned mask 17 is performed using an exposure technique. As a material for the mask 17, a material that does not react as much as possible with CNT or HOPG is used, but Al is desirable for ease of patterning. In addition, SiO ₂ and TiN are difficult to react with CNT and HOPG, and are suitable for forming a desired shape and characteristics.

  The shape of the mask 17 may be a round shape as shown in the figure, or may be a polygon such as a quadrangle, a triangle, or a hexagon. The round shape has a good shape after that, and is suitable for manufacturing an element. The polygon is an advantageous shape when a photolithography mask is formed.

Thereafter, as shown in FIG. 3C, the conductive carbon layer 11a of the carbon-containing substrate 11 with the patterned mask 17 is dry-etched in plasma. At this time, since carbon is easily etched with oxygen, it is desirable to dry-etch the conductive carbon layer 11a in a gas containing a large amount of oxygen (oxygen may be 100%). Furthermore, when the gas contains 0.5 to 5% of CF ₄ , it can be processed vertically and is suitable as an electron-emitting device. Here, if the etching is completed before the mask 17 disappears, the conductive carbon layer 11a becomes a cylinder or a polygonal column corresponding to the shape of the mask 17.

  Finally, by removing the mask 17, a plurality of protrusions 3 made of conductive carbon are arranged on the substrate 2 as shown in FIG.

  As described above, when electrons are emitted from the protrusion 3, an electric field is applied to the edge of the protrusion 3, and the electrons are likely to be emitted. If there are many edges of this protrusion 3, since the electron emission effect is large, it is desirable that the size (diameter, etc.) of the protrusion 3 is small.

  By the way, as a method of forming protrusions made of CNTs on a substrate, there is a method in which a catalytic metal is patterned on a substrate and CNTs are grown only on that portion. However, the catalyst metal often remains at the tip of the protrusion formed by the growth. Since the catalyst metal is embedded in the CNT, it is protected by carbon having chemical resistance. For this reason, it is very difficult to remove the catalytic metal even if chemicals are used. Even if the catalyst metal remains at the root portion instead of the tip portion of the projection, the CNT (six-membered ring) is closed and inactive at the tip portion of the projection, so that the electron emission characteristic is low. turn into.

  The catalytic metal present on the protrusion may be removed by physical impact, but in this case, there is a disadvantage that the height of the protrusion is not uniform. It is also conceivable to etch the catalyst metal with oxygen plasma. However, the catalyst metal cannot be removed well, and the height of the projections becomes poor.

  There is also a method in which a conical tip portion made of Si is formed on a substrate, a catalytic metal is formed around the tip portion, and CNT is grown along the tip portion therefrom. However, since the CNT is grown after the formation of the chip portion, the height changes due to the addition of high-temperature treatment or the growth, and it becomes difficult to ensure the uniformity of the height of the protrusions. Further, since the protrusions extend along the chip portion, there is a disadvantage that the protrusions must be inclined with respect to the gate electrode, and the electric field is not easily applied to the protrusions.

  On the other hand, in this embodiment, the carbon-containing substrate 11 having the conductive carbon layer 11a having a structure in which a carbon six-membered ring stands is prepared, and the conductive carbon layer 11a is etched to form the protrusions 3. During the etching process, the carbon six-membered ring is scraped. For this reason, the side surface portion of the protrusion 3 formed on the substrate 2 is in a state in which the carbon six-membered ring is cut (opened) in the middle. That is, each protrusion 3 has many broken six-membered rings. Thereby, the protrusion 3 becomes electronically active. In addition, since the metal catalyst is not grown to form a protrusion, a metal that is difficult to remove does not exist inside the tip portion of the protrusion 3. Therefore, when an electric field is applied to the protrusion 3 to emit electrons from the protrusion 3, the threshold voltage can be lowered, so that the electron emission characteristics can be improved.

  In addition, since the conductive carbon layer 11a having a flat upper surface is etched, the heights of the protrusions 3 are aligned. As a result, when electrons are emitted from each protrusion 3, current can be effectively drawn from each protrusion 3 via a gate electrode (not shown), so that a large current can be obtained as a whole. . Also in this respect, the electron emission characteristics can be improved.

  At this time, the height uniformity of each protrusion 3 is desirably 10% or less. Here, “the uniformity of the height of each protrusion 3” refers to a variation in height with respect to the average value of the height of each protrusion 3. “The uniformity of the height of each protrusion is 10%” means, for example, 10 nm when the average height of each protrusion 3 is 1 μm, and when the average height of each protrusion 3 is 3 μm. Is 30 nm.

  Furthermore, the degree of freedom of the protrusion shape is increased as compared with a structure in which the metal catalyst is grown to form the protrusion. Also, starting from dense conductive carbon, the etched surface remains flat, so there is almost no gas adsorption, and even during vacuum operation, the gas is discharged during operation and does not damage the tip of the projection 3. . Further, unlike the case of using the growth of the metal catalyst, it is not necessary to set the protrusion 3 at a high temperature.

  FIG. 6 is a perspective view showing a second embodiment of the electron-emitting device as the carbon processed body according to the present invention. In the figure, the same or equivalent members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the figure, an electron-emitting device 20 of the present embodiment includes a plurality of tapered protrusions 21 formed on a substrate 2. The protrusions 21 may have a conical shape as illustrated, or may have a triangular pyramid shape, a quadrangular pyramid shape, or the like.

  The protrusion 21 is formed by etching a conductive carbon layer made of CNT, HOPG, or the like, like the protrusion 3 in the first embodiment. In the structure in which the protrusions 21 are made of CNTs, as shown in FIG. 7A, a plurality of CNTs 4 forming the protrusions 21 are arranged in a bundle with almost no gap. On the other hand, in the structure in which the protrusions 21 are made of HOPG, as shown in FIG. 7B, the plurality of graphite layers 5 forming the protrusions 21 are arranged in a bundle with almost no gap. At this time, the protrusion 21 has a structure in which the six-membered ring of carbon stands substantially perpendicular to the upper surface of the substrate 2. Then, the number of layers of the six-membered ring at the tip portion of the protrusion 21 is smaller than the number of layers of the six-membered ring at the root portion of the protrusion 21.

  Next, a method for manufacturing the electron-emitting device 20 as described above will be described with reference to FIG.

  First, as shown in FIG. 8A, a carbon-containing substrate 11 having a conductive carbon layer 11a provided at least on the upper surface side is prepared. This manufacturing method is the same as that shown in FIG. Next, as shown in FIG. 8B, the mask 17 is patterned on the carbon-containing substrate 11 using photolithography or the like. This patterning method is the same as that shown in FIG.

  Subsequently, as shown in FIG. 8C, the conductive carbon layer 11a of the carbon-containing substrate 11 with the patterned mask 17 is dry-etched to form the conductive carbon layer 11a in a protruding shape. The gas used in this dry etching is the same as that shown in FIG.

  If etching is performed until the mask 17 becomes small in this etching step, the tip of the protruding conductive carbon layer 11a becomes thin. At this time, etching may be stopped when the tip diameter of the conductive carbon layer 11a becomes a desired diameter. For example, the conductive carbon layer 11a can be tapered until the tip diameter of the conductive carbon layer 11a is reduced to 2 nm or less.

As another method, the tip of the protruding conductive carbon layer 11a can be thinned by processing in the microwave plasma from the middle. As the plasma at this time, it is preferable to mainly use hydrogen gas. In particular, it is more preferable that a small amount of oxygen atom is added to hydrogen gas because it is easy to process. Oxygen atoms may be introduced in the form of O ₂ , CO, CO ₂ , NO, NO ₂ or the like. In that case, the effect is 10 times or more that in the absence of oxygen.

  Finally, if the mask 17 remains, the mask 17 is removed. As a result, as shown in FIG. 6, a plurality of protrusions 21 having pointed tips made of conductive carbon are arranged on the substrate 2.

  In the present embodiment as described above, since the shape of the protrusion 21 is tapered, when an electric field is applied to the protrusion 21 to emit electrons from the protrusion 21, a large electric field is generated even at a very low voltage, and the protrusion 21 It will be in the state where an electron comes out easily from. Therefore, the threshold voltage can be further reduced. Further, since the resistance of the entire protrusion 21 becomes low when a current is passed through the protrusion 21, the protrusion 21 hardly generates heat and the thermal conductivity increases, so that heat can be efficiently radiated. For this reason, a large current can flow through the protrusion 21. As described above, the electron emission characteristics can be improved as compared with the electron-emitting device 1 in the first embodiment.

  In addition, since the protrusion 21 has a tapered structure, the protrusion 21 can stand firmly without falling down, and thus the electron-emitting device can be effectively manufactured with good yield without damaging the protrusion 21 in the process of manufacturing the gate electrode and the like. Can be produced. In addition, since graphite has good thermal conductivity in the in-plane direction of the six-membered ring, it conducts heat and electricity well in the height direction of the protrusion 21. For this reason, the protrusion 21 having a diverging structure further helps the conduction of heat and electricity, which is very effective.

  Further, since the size of the tip portion of the protrusion 21 can be reduced, there is an advantage that when the electron-emitting device having the gate electrode is formed, the gate electrode can be formed after the protrusion 21 is formed.

  In addition, as a protrusion whose front-end | tip is thin with respect to the root, it is not restricted to said protrusion 21, Various deformation | transformation is possible. A specific example of such a protrusion is shown in FIG.

  The protrusion 30 shown in FIG. 9A has a columnar base 31 and a columnar electron emission portion 32 provided on the base 31 and having a diameter smaller than the diameter of the base 31. . The projection 34 shown in FIG. 9B has a columnar base 35 and a substantially conical electron emission portion 36 that is provided on the base 35 and tapers from the root toward the tip. The protrusion 38 shown in FIG. 9C has a substantially trapezoidal cross section that tapers from the root toward the tip.

  In addition, this invention is not limited to the said embodiment. For example, in the above-described embodiment, the entire projection formed on the substrate 2 has a structure in which the carbon six-membered ring stands with respect to the upper surface of the substrate 2, but at least the tip of the projection has a six-membered ring. May stand up to the upper surface of the substrate 2, and a six-membered ring does not necessarily stand at the base of the protrusion.

  In the above-described embodiment, the carbon processed body is applied to an electron-emitting device. However, the carbon processed body according to the present invention includes a scanning tunnel microscope (STM), an atomic force microscope (Atomic Force microscope). It can also be applied to atomic probes applicable to electronic devices using these principles, such as Microscope (AFM), Scanning Near-field Optical Microscope (SNOM), and the like. In this case, an atomic probe with good probe characteristics can be obtained.

[Example 1]
Five commercially available original HOPG substrates (1 cm square, 1 mm thick) were laminated and bonded with resin, and the end surfaces thereof were polished so that the flatness R _max was 0.1 μm or less. At this time, the entire original HOPG substrate was buried in resin and hardened. As a result, a carbon-containing substrate having a structure in which a 1 cm × 6 mm substrate surface (end surface) was an upper surface and a carbon six-membered ring stood with respect to the upper surface was prepared.

  Subsequently, an Al mask was patterned into dots on the carbon-containing substrate by photolithography. The diameter of the Al mask was 0.3 μm to 5 μm. The diameter of the Al mask can be changed depending on the size design of the photomask for photolithography, and can also be adjusted by adjusting the etching time of Al.

Subsequently, using an Al mask, HOPG is etched in an oxygen gas containing a small amount (1%) of CF ₄ gas to remove HOPG in a portion without the Al mask, thereby forming a projection made of HOPG. did. At this time, there were prepared one in which the etching was stopped before the Al mask disappeared, one that was etched until immediately before the Al mask disappeared, and one that was etched until just after the Al mask disappeared. Under the condition that the CF ₄ gas concentration was 0.5% to 3%, the protrusion could be finished in the same shape.

  FIG. 10 shows the shape of a HOPG protrusion obtained in such an experiment. Since HOPG can set the substrate to be thick, if the etching time is increased according to the thickness of the Al mask, the tip of the protrusion could be sharpened.

FIG. 11 shows the yield and electron emission characteristics of the protrusions formed in this way. In the table of the figure, “vertical HOPG” refers to a protrusion having a structure in which a carbon six-membered ring stands perpendicular to the upper surface of the substrate, and indicates the performance of the protrusion formed in this example. Yes. As can be seen from this table, it was confirmed that when the protrusions were formed as in this example, the electron emission characteristics were improved. It was also clear that the formation yield of the protrusions was good.
[Comparative Example 1]
The commercially available original HOPG substrate (1 cm square, 1 mm thickness) used in Example 1 was used while the c-axis direction of the graphite was perpendicular to the substrate surface (upper surface). Then, the substrate surface of the original HOPG substrate was polished flat. At this time, since layered peeling occurred, it was difficult to cleanly polish. Subsequently, protrusions were formed on the polished HOPG substrate by the same process as in Example 1. However, since it was difficult to polish the substrate flatly, the protrusions could not be formed cleanly on the entire surface of the substrate. In addition, even in a flat part, the protrusion was easily broken, and the durability was poor. However, when the substrate was polished obliquely close to the vertical, the state and characteristics of the protrusions were good as in Example 1.

FIG. 11 shows the yield and electron emission characteristics of the protrusions formed in this way. In the table of the figure, “horizontal HOPG” is a projection having a structure in which a carbon six-membered ring is parallel to the substrate surface of the HOPG substrate, and indicates the performance of the projection formed in this comparative example. Yes. As can be seen from this table, the electron emission characteristics were not good as compared with the case of Example 1.
[Example 2]
A single-crystal SiC (111) substrate having a mirror surface by single-side polishing is heated at a high temperature of 1700 ° C. for 2 to 20 hours in a vacuum of 1 × 10 ⁻² Pa, and a carbon six-membered ring (CNT) standing upright on the SiC substrate is obtained. A CNT layer having high density was formed. Next, an Al mask was patterned in a dot shape on the CNT layer by photolithography. The diameter of the Al mask was 0.3 μm to 5 μm. The diameter of the Al mask can be changed depending on the size design of the photomask for photolithography, and can also be adjusted by adjusting the etching time of Al.

Next, by using the Al mask, the CNTs were etched in oxygen gas containing a small amount (1%) of CF ₄ gas to remove the CNTs without the Al mask, thereby forming protrusions made of CNTs. . At this time, there were prepared one in which the etching was stopped before the Al mask disappeared, one that was etched until immediately before the Al mask disappeared, and one that was etched until just after the Al mask disappeared. Under the condition that the CF ₄ gas concentration was 0.5% to 3%, the protrusion could be finished in the same shape.

  The shape of the CNT projections obtained in such an experiment is shown in FIG. FIG. 12 shows the experimental results when the thickness of the CNT layer is as thin as about 1 μm. At this time, when the Al mask was as thin as 0.3 μm, the tip of the protrusion became thinner than the base under various conditions such as etching time. However, if the Al mask was too thin and the etching time was too long, the CNT layer would disappear, so care was required. When the thickness of the Al mask was as thick as 0.5 μm, the CNT protrusions also became cylindrical when the etching time was short, and the tips of the protrusions were not sharp. However, even if the Al mask was thick, the tip of the protrusion could be sharpened if the etching time was increased.

  The above is the result when the thickness of the CNT layer is about 1 μm. When the CNT layer was thickened to 2 μm, the tendency of the shape shifted in the direction of increasing the thickness of the Al mask. That is, the shape of the protrusion made from an Al mask having a thickness of 0.1 μm and a diameter of 0.5 μm was obtained from an Al mask having a thickness of 0.3 μm and a diameter of 1 μm by setting the thickness of the CNT layer to 2 μm. .

The CNT layer could be formed at atmospheric pressure of 100 Pa to 10 ⁻⁹ Pa and temperature of 1400 ° C. to 1900 ° C. The film thickness of the formed CNT layer increased in proportion to the square root of time, and was thicker as time was spent.

FIG. 11 shows the yield and electron emission characteristics of the protrusions formed in this way. In the table of the figure, “CNT” indicates the performance of the protrusions formed in this example. As can be seen from this table, it was confirmed that when the protrusions were formed as in this example, the electron emission characteristics were improved. It was also clear that the formation yield of the protrusions was good.
[Comparative Example 2]
A conductive substrate (Si) was prepared and formed by aligning fine dot patterns of Fe (metal) by photolithography. Then, this was put in a reaction vessel, and a mixed gas of methane gas and hydrogen gas was flowed into the reaction vessel at a methane gas / hydrogen gas concentration of 10% to grow CNTs at a temperature of 900 ° C. At this time, the generation of plasma in the reaction vessel promoted the decomposition of methane gas and increased the growth rate. As described above, CNT protrusions were formed only on the portions where Fe was present. The diameter of the protrusion was 300 to 500 nm.

FIG. 11 shows the yield and electron emission characteristics of the protrusions formed in this way. As can be seen from the table in the figure, the electron emission characteristics of the electron-emitting device were not good as compared with the cases of Examples 1 and 2.
[Example 3]
The conductive graphite was processed in the same manner as in Examples 1 and 2, and an attempt was made to produce a graphite projection. However, the processing was stopped before the Al mask was etched, and cylindrical and prismatic protrusions were formed. At this time, since round, square, triangular, and star-shaped dot patterns were used, corresponding columnar bodies were formed.

FIG. 13 shows the electron emission characteristics of the protrusions thus formed. As can be seen from the table in the figure, when the protrusions are formed as in this example, the electron emission characteristics are better than when the metal catalyst is grown and the protrusions made of CNT are formed as in Comparative Example 2. I was able to confirm. At this time, the shape with a lot of acute angles such as a star shape had relatively good characteristics. Further, in the columnar protrusion as in the present embodiment, the threshold electric field (threshold voltage) tended to be larger than the protrusion having a tapered tip as in the first and second embodiments.
[Example 4]
Randomly arranged protrusions were formed by the same method as in Examples 1 and 2. Comparing the electron emission characteristics with the aligned protrusions, although the threshold voltage and current density differ depending on the protrusion interval, the distribution of characteristics at which electrons start to be emitted is very close. Very uniform electron emission characteristics were obtained. On the other hand, with randomly arranged protrusions, electrons are often emitted from one of a plurality of closely arranged protrusions, and as a whole, the number of protrusions is not sufficient to obtain an electron emission point. The current density was about 30 to 50% smaller than the arranged one. This revealed that the electron emission characteristics are better when the protrusions are aligned.
[Example 5]
In Example 1 or Example 2, instead of the Al mask, an SiO ₂ mask or a TiN mask was formed, and the mask was used for forming the protrusions. At this time, it was confirmed that protrusions were formed as in the case of the Al mask. In the case of the Al mask, only Al was selectively etched by semi-cocrine wet etching or BCl ₃ dry etching. However, in the case of the SiO ₂ mask, selective etching was performed by BHF wet etching or CF ₄ gas dry etching. In the case of a TiN mask, etching was performed by dry etching of BCl ₃ . The protrusion formed by etching the conductive carbon film with the SiO ₂ mask had an electron emission current density about twice as large as that of the Al mask. Further, the protrusion formed by etching the conductive carbon film with a TiN mask had an electron emission current density about three times higher than that of the Al mask. This seems to be because a metal that is oxidized or nitrided is better than a single metal such as Al because carbon reacts slightly with the mask material.
[Example 6]
Providing a same substrate as in Example 1 or Example 2, flatness R _max of the substrate surface (upper surface) is finished to be 10nm or less. A fine Al mask having a diameter of 300 nm or less was formed on the substrate by electron beam lithography, and the conductive carbon film was etched to form protrusions. When the protrusions were formed with the Al mask having this diameter, the protrusions having a lower tip and a pointed shape could be formed than when photolithography was used.

  The shape of such a protrusion is shown in FIG. As can be seen from this figure, even when the size of the Al mask is small, a pointed protrusion, a cylindrical protrusion, or the like could be formed. Also, the electron emission characteristics were good.

1 is a perspective view showing a first embodiment of a carbon processed body (electron-emitting device) according to the present invention. It is a conceptual diagram which shows the carbon structure of the processus | protrusion shown in FIG. It is a figure which shows the manufacturing process of the electron-emitting element shown in FIG. It is a figure which shows an example of the method of making the flat carbon containing board | substrate shown to Fig.3 (a). It is a figure which shows the other example of the method of making the flat carbon containing board | substrate shown to Fig.3 (a). It is a perspective view which shows 2nd Embodiment of the carbon processed body (electron emission element) which concerns on this invention. It is a conceptual diagram which shows the carbon structure of the processus | protrusion shown in FIG. It is a figure which shows the manufacturing process of the electron-emitting element shown in FIG. It is a figure which shows the protrusion with another shape formed on the board | substrate shown in FIG. FIG. 3 is a diagram showing the shape of a HOPG protrusion obtained in Example 1. It is a table | surface which shows the yield and the electron emission characteristic of the processus | protrusion formed in Example 1, 2 and Comparative Example 1,2. 6 is a view showing the shape of a CNT protrusion obtained in Example 2. FIG. 6 is a table showing electron emission characteristics of protrusions formed in Example 3 and Comparative Example 2. It is a figure which shows the shape of the processus | protrusion obtained by Example 6. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electron emission element (carbon processed body), 2 ... board | substrate, 3 ... protrusion, 4 ... carbon nanotube (CNT), 5 ... graphite layer, 11 ... carbon containing board | substrate, 11a ... conductive carbon layer (it consists of conductive carbon) Layer), 12 ... SiC substrate, 13 ... CNT layer (layer made of conductive carbon), 14 ... original HOPG substrate (layer made of conductive carbon), 16 ... HOPG substrate (highly oriented graphite substrate), 16a ... substrate surface (Upper surface), 17 ... mask, 20 ... electron-emitting device (carbon processed body), 21 ... projection, 30 ... projection, 34 ... projection, 38 ... projection.

Claims (7)

A carbon processed body formed by forming protrusions made of conductive carbon on a substrate,
The substrate is a SiC substrate;
The projection has a structure in which the six-membered ring of the conductive carbon extends to the root in a state of being substantially perpendicular to the upper surface of the SiC substrate, and the SiC substrate by a thermal decomposition method. after forming a layer composed of the conductive carbon on state, and are not formed by etching a layer made of the conductive carbon,
The carbon processed body , wherein the conductive carbon in which the six-membered ring is broken by the etching process is present on a side surface portion of the protrusion .   The carbon processed body according to claim 1, wherein a tip of the protrusion is thinner than a base of the protrusion.   The carbon processed body according to claim 1, wherein the conductive carbon is a carbon nanotube. A plurality of protrusions;
The carbon workpiece according to any one of claims 1 to 3 , wherein the plurality of protrusions are regularly arranged on the substrate. The projection includes a plurality of carbon processed body of any one of claims 1 to 3 in which uniformity of the height of each projection is equal to or less than 10%. Forming a carbon-containing substrate provided with a layer made of conductive carbon at least on the upper surface side;
Patterning a mask on the carbon-containing substrate;
Look including a step of forming a projection by etching a layer consisting of the conductive carbon,
A method for producing a carbon workpiece , wherein the carbon-containing substrate is formed by forming a layer made of the conductive carbon on a SiC substrate by a thermal decomposition method. An electron-emitting device formed by forming a plurality of protrusions made of conductive carbon on a substrate,
The substrate is a SiC substrate;
The projection has a structure in which the six-membered ring of the conductive carbon extends to the root in a state of being substantially perpendicular to the upper surface of the SiC substrate, and the SiC substrate by a thermal decomposition method. after forming a layer composed of the conductive carbon on state, and are not formed by etching a layer made of the conductive carbon,
The electron-emitting device according to claim 1, wherein the conductive carbon having the six-membered ring broken by the etching process is present on a side surface of the protrusion .

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