JP2005310450A - Method of forming projection consisting of material containing carbon, plate board product having projection consisting of material containing carbon, and electron emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a projection consisting of a material containing carbon, a plate board product having a projection consisting of materials containing the carbon, and an electron emitting element. <P>SOLUTION: This is the method in which a mask 23 is formed having a plurality of patterns 23a arranged on a plate board 11 by respectively conducting etching 21 on a plurality of mask membranes formed on the plate board 11 having a region consisting of the material containing the carbon. Etching is conducted on the plate board 11 by using this mask 23 to form projections 11c respectively corresponding to a plurality of patterns 23a of the mask 23. Respective patterns 23a include a first mask layer 13a and a second mask layer 15a deployed in the direction to intersect with the main face 11a. Materials of the first mask layers 13a are different from those of the second mask layers 15a. In respective patterns 23a, size of the first mask layer 13a is different from that of the second mask layer 15a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for forming a protrusion made of a carbon-containing material, a substrate product having a protrusion made of a carbon-containing material, and an electron-emitting device.

  Reference 1 (for example, K. Okano, K. Hoshina, S. Koizumi and K. Nishimura, Diamond and Related Materials 5 (1996) pp19-24) describes forming a diamond protrusion structure. In the case of forming a diamond protrusion structure, polycrystalline diamond is formed in a recessed mold of a silicon region formed by anisotropic etching. Thereafter, the silicon region is removed to form a polycrystalline diamond pyramid.

  Reference 2 (Y. Nishibayashi, H. Saito, T. Imai and N. Fujimori; Diamond and Related Materials, 9 (2000) pp290-294) describes a method for forming a pyramid using a single crystal. . In this method, a minute cylinder is formed on the surface of diamond. Diamond is epitaxially grown on the cylinder while controlling the growth parameters. As a result, a pyramidal protrusion with a sharp tip is produced. Further, the minute cylindrical protrusions can be etched to further sharpen.

Reference 3 (Yoshiki Nishibayashi, Yutaka Ando, Hiroshi Furuta, Koji Kobashi, Kiichi Meguro, Takahiro Imai, Takashi Hirao, Kenjiro Oura; SEI Technical Review, August 2002 issue, or Yoshiki. Nishibayashi, Yutaka Ando, Hiroshi Furuta, Natsuo Tatsumi , Akihiko Namba and T. Imai; Sumitomo Electric Industries Technical Review, No. 57 (2004) 33-36.), A method of forming protrusions using a single layer Al mask is also reported. Among them, the candle-shaped protrusion has a high aspect ratio. In addition, it is possible to form a protrusion with a very high density and a very sharp tip.
K. Okano, K. Hoshina, S. Koizumi and K. Nishimura, Diamond and Related Materials 5 (1996) pp.19-24 Y. Nishibayashi, H. Saito, T. Imai and N. Fujimori; Diamond and Related Materials, 9 (2000) pp.290-294 Yoshiki Nishibayashi, Yutaka Ando, Hiroshi Furuta, Koji Kobashi, Kiichi Meguro, Takahiro Imai, Takashi Hirao, Kenjiro Oura; SEI Technical Review, August 2002, or Yoshiki. Nishibayashi, Yutaka Ando, Hiroshi Furuta, Natsuo Tatsumi, Akihiko Namba and T. Imai; Sumitomo Electric Industries Technical Review, No. 57 (2004) pp.33-36.

  However, in the method described in Document 1, when this method is used for an electron-emitting device, the protrusions are polycrystalline because it is necessary to reduce the tip particle size, and there are grain boundaries inside the protrusions. Is not smooth and electrons cannot be efficiently emitted from the NEA surface. Also, when used in a near-field optical probe, if it is polycrystalline, light propagation is not smooth due to light scattering due to grain boundaries and distortion of individual crystals. In Document 2, the variation in the size of the protrusion is not small. In Document 3, the size of one of these protrusions is about 1 micrometer, and it is impossible to accurately form a smaller protrusion using this method. For example, a method of forming four or more protrusions on a 1 μm square has not yet been proposed. That is, there is a demand for a method of forming protrusions arranged at high density.

  This invention is made in view of such a situation, and it is in providing a high-density protrusion structure, More specifically, the method of forming the protrusion which consists of material containing carbon, carbon is included. It is an object of the present invention to provide a substrate product having a protrusion made of a material, and an electron-emitting device.

  One aspect of the invention relates to a method of forming a protrusion made of a carbon-containing material. The method includes (a) a step of sequentially forming a plurality of mask films on a main surface of a substrate having a region made of a material containing carbon, and (b) etching the plurality of mask films, respectively. Forming a mask having a plurality of patterns arranged on the main surface of the substrate, and (c) etching the substrate using the mask to form a protrusion corresponding to each of the plurality of patterns of the mask. Each pattern includes a group of layers arranged in a direction intersecting the main surface, and the group of layers includes a first layer closest to the main surface, and the main surface A second layer farthest from the first layer, wherein the material of the first layer is different from the material of the second layer, and in each pattern, the size of the first layer is the second layer. Different from layer size.

  According to this method, since the substrate is etched using the mask including the first and second layers, the substrate is first etched using the second layer farthest from the main surface as a mask, and then the main surface. Etching is performed using the first layer closest to the mask as a mask. Since the size of the first layer is different from the size of the second layer, the formed protrusion has a first portion and a second portion arranged in a direction intersecting the main surface. Since the first portion is formed using the first layer and the second portion is formed using the second layer, the size of the first portion is different from the size of the second portion. . Since the first and second portions are formed using the first layer and the second layer, respectively, the variation in the shape of the protrusion is small.

  In the method of the present invention, each of the patterns further includes a third layer, and the third layer is provided between the first layer and the second layer. Also good. According to this method, the protrusion further includes a third portion formed using the third layer, and the first to third portions are formed using the first to third layers, respectively. The variation in the shape of the protrusion is small.

  In the method of the present invention, the maximum size of each pattern is 300 nanometers or less, the second mask layer is provided on the first mask layer, and in each pattern, the second layer May be larger than the size of the first layer. According to this method, protrusions can be formed using a small pattern of about 300 nanometers. The substrate is etched using a second layer having a size that is larger than the size of the first layer, followed by etching using the first layer.

  In the method of the present invention, the first layer may be made of a metal containing aluminum or titanium nitride, and the second layer may be made of a metal containing titanium nitride or gold. However, according to this method, a combination of aluminum and a titanium nitride layer is preferable, and a combination of a metal layer containing aluminum and a metal layer containing titanium nitride is preferable.

  In the method of the present invention, the substrate may be a diamond substrate. According to this method, a projection made of diamond can be formed.

  Another aspect of the present invention relates to a substrate product having protrusions made of a carbon containing material. The substrate product includes (a) a supporting base, and (b) a plurality of protrusions made of a carbon-containing material arranged on the main surface of the supporting base, and each protrusion intersects the main surface. The first portion has a cross-sectional shape different from the cross-sectional shape of the second portion, and the first portion is a protrusion of the protrusion. The tip includes a tip, the second portion includes a root of the projection, the maximum size of the tip of each projection is 100 nanometers or less, and the maximum size of the base of each projection is 300 nanometers or less.

  According to this substrate product, since the base size of each protrusion is 300 nanometers or less, a protrusion structure having a high protrusion density is provided.

  In the substrate product of the present invention, it is preferable that the plurality of protrusions are arranged in an array, and the density of the protrusions is 4 or more per square micrometer. The substrate product includes four or more densely arranged protrusions per square micrometer.

  In the substrate product of the present invention, the support base and the protrusion may be made of diamond. According to this substrate product, a protruding structure made of diamond is provided.

  According to still another aspect of the present invention, an electron-emitting device is provided on at least one of (a) the substrate product described above and (b) the main surface and the back surface of the support base of the substrate product. Electrode.

  According to this electron-emitting device, the base size of each protrusion is 300 nanometers or less. For this reason, the electron-emitting device includes a protrusion structure having a high protrusion density. An electron-emitting device capable of realizing a high current density is provided.

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  As described above, according to the present invention, there are provided a method for forming a protrusion made of a carbon-containing material, a substrate product having a protrusion made of a carbon-containing material, and an electron-emitting device.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, embodiments of a method for forming a protrusion made of a carbon-containing material, a substrate product having a protrusion made of a carbon-containing material, and an electron-emitting device according to the present invention will be described with reference to the accompanying drawings. . Where possible, the same parts are denoted by the same reference numerals.

(First embodiment)
1A, FIG. 1B, FIG. 1C, FIG. 2A, FIG. 2B, and FIG. 2C are materials containing carbon according to the first embodiment. It is drawing which shows the method of forming protrusion which consists of.

(Mask film deposition)
On the main surface 11a of the substrate 11, a plurality of mask films are formed in order. The substrate 11 includes a region 11b made of a material containing carbon at least on the surface layer. In this embodiment, as shown in FIG. 1A, a first mask film 13 and a second mask film 15 are deposited on a substrate 11 such as a diamond substrate. The material of the first mask film 13 is different from the material of the second mask film 15. In a preferred embodiment, the first mask film 13 may be made of a metal containing aluminum or titanium nitride, and the second mask film 15 may be made of a metal containing titanium nitride or gold. In the case of using a plurality of mask films, a combination of a metal layer containing aluminum or titanium nitride and a titanium nitride layer is preferable, and a combination of a metal containing aluminum or titanium nitride and a metal layer containing gold (Au) is preferable. The substrate 11 can be a diamond substrate. According to this method, a projection made of diamond can be formed. In one example, a 30 nm thick titanium nitride film and a 60 nm thick aluminum film are grown by sputtering.

(Resist pattern formation)
A mask for forming a pattern on the mask film is formed on the plurality of mask films. In this embodiment, as shown in FIG. 1B, a photoresist mask is formed on the second mask film 15. More specifically, a resist is applied on the second mask film 15. Next, a resist mask 17 is formed by a photolithography method using a stepper or an electron beam lithography method using an electron beam drawing apparatus. The resist mask 17 has a plurality of patterns 17 a arranged on the second mask film 15. In the present embodiment, an electron beam drawing apparatus (for example, JXB-5D) suitable for microfabrication is used at an acceleration voltage of 50 kilovolts, and a pattern 17a with high accuracy is obtained. Each pattern 17a has a dot shape.

(Resist pattern reduction)
If necessary, the size of the pattern 17a of the resist mask 17 is reduced in order to form finer protrusions. As shown in FIG. 1C, the resist mask 17 is exposed to the plasma 19 to form a reduced pattern 17b from the pattern 17a. The plasma is generated using oxygen gas. For example, the flow rate of oxygen gas is 50 sccm, the pressure is 80 Pascal (0.6 Torr), the RF power is 140 watts, and the resist mask 17 is approximately Oxygen plasma treatment is performed for 40 seconds. Each pattern 17b has a dot shape.

(Mask formation)
Etching 21 of each of the plurality of mask films is performed to form a mask 23. This mask has a plurality of patterns arranged on the main surface 11 a of the substrate 11. In this embodiment, as shown in FIG. 2A, the second mask film (upper film) 15 is dry-etched using the resist mask 17. Thereafter, the first mask film 13 (lower film) is dry etched. As a result, a mask 23 is formed. Each pattern 23a of the mask 23 includes a group of layers (in this embodiment, mask layers 13a and 15a) arranged in a direction intersecting the main surface 11a. This group of layers includes a first layer closest to the main surface 11a (in this embodiment, the first mask layer 13a) and a second layer farthest from the main surface 11a (in this embodiment, the second layer). Mask layer 15a). In each pattern 23 a of the mask 23, the size D 1 of the first mask layer 13 a is different from the size D 2 of the second mask layer 15.

  Dry etching mainly proceeds in the film thickness direction. When over-etching occurs, side etching occurs and the pattern of the mask 23 is reduced in size. When the mask is formed by etching using an etching gas having a high etching rate for the first layer 13a, the diameter of the first mask layer 13a becomes smaller than the diameter of the second mask layer 15a. According to this method, each pattern 23a of the mask 23 extends along a certain axis Ax, and is excellent in symmetry with respect to the axis Ax appropriately.

  In one embodiment, when the first mask film 13 and the second mask film 15 are made of an aluminum metal film and a titanium nitride film, respectively, dry using a chlorine-based etching gas such as chlorine gas and / or boron trichloride. Etching can be performed. The titanium nitride film is on the top, and etching is started first. Since the etching rate of the titanium nitride film is smaller than the etching rate of the Al film, side etching proceeds faster in the Al film, and the pattern of the Al layer becomes smaller than the pattern of the TiN layer.

(Substrate etching)
The substrate is etched using the mask to form protrusions on the substrate. In this embodiment, as shown in FIG. 2B, when the substrate 11 is etched 25 using the mask 23, as shown in FIG. Corresponding protrusions 11c are formed. As a result of this etching 25, a substrate product 31 such as a protrusion structure having protrusions 11c arranged in an array is obtained. In order to perform the etching 25 on the region 11b made of a material containing carbon, an oxygen-based etching gas such as an oxygen gas or a gas obtained by adding a small amount of CF ₄ gas to the oxygen gas can be used. The region 11b made of a material containing carbon is etched by oxygen plasma. Referring to FIG. 2B again, the second mask layer 15a functions as a mask, and the region 11b made of a material containing carbon is etched to form a pillar made of the material containing carbon. Next, the first mask layer 13a serves as a mask, and the pillars and regions 11b made of a material containing carbon are etched.

  According to this method, since the substrate 11 is etched using the mask 23 including the first and second mask layers 13a and 15a, the substrate 11 first masks the second mask layer 15a farthest from the main surface. Then, etching is performed using the first mask layer 13a closest to the main surface as a mask. Since the size of the second mask layer 15a is different from the size of the first mask layer 13a, the protrusion 11c has a tip portion and a root portion arranged in a direction intersecting the main surface 11a. The tip portion is formed using the first mask layer 15a, and the root portion is formed using the second mask layer 13a. Therefore, the size of the root portion is different from the size of the tip portion. Since the tip portion and the root portion are formed by using masks that are separately and precisely controlled, such as the first mask layer 13a and the second mask layer 15a, respectively, the variation in the shape of the protrusion 11c is small.

  The etching of the substrate will be described with reference to FIGS. As shown in FIG. 3A, the resist mask is completely removed by oxygen plasma. Further, when the etching of the substrate is advanced, the thickness of the pattern 23a is reduced by the etching, and the film thickness of the upper mask layer is reduced by the etching to be changed to the second mask layer 15b. By the etching using the second mask layers 15a and 15b, the pillar 11d having a width D3 corresponding to the width D2 of the second mask layers 15a and 15b is formed.

  As shown in FIG. 3B, when the etching of the substrate is advanced, the second mask layer disappears completely by etching, and the first mask layer 13a functions as a mask. As the etching of the substrate proceeds, the thickness of the first mask layer 13a is reduced by etching, and the thickness of the lower mask layer is changed to the first mask layer 13b reduced by etching. By the etching using the first mask layers 13a and 13b, a protrusion 11e having a width D4 corresponding to the width D1 of the first mask layers 13a and 13b is formed from the pillar 11d. By etching the substrate using the pattern 23a, the protrusion 11c is completed as shown in FIG.

  FIG. 4A shows a substrate product. FIG. 4B is a plan view showing the arrangement of the protrusions of the substrate product. The substrate product 31 includes a plurality of protrusions 33 made of a material containing carbon. The protrusions 33 are two-dimensionally arranged on the main surface 35 a of the support base 35. Each protrusion 35 has a first part and a second part arranged in order in a direction intersecting the main surface 33a, and forms a columnar shape.

  The protrusion 33 includes a first portion 33a corresponding to the first mask layer 13a and a second portion 33b corresponding to the second mask layer 15a. The cross-sectional shape of the first portion 33a is different from the cross-sectional shape of the second portion 33b. The first portion 33a includes the tip 33c of the protrusion 33, and the maximum size W1 of the tip 33c of each protrusion 33 is 100 nanometers or less. The first portion 33a includes the root 33d of the protrusion 11c, and the maximum size W2 of the root 33d of each protrusion 33 is 300 nanometers or less. According to this substrate product 31, since the base size of each protrusion is 300 nanometers or less, a protrusion structure having a high protrusion density is provided.

  Referring to FIG. 4B, in the substrate product 31, a plurality of protrusions are arranged in an array, and the density of the protrusions 33 is preferably 4 or more per square micrometer basic cell R. The substrate product 31 includes protrusions arranged at high density.

  In one embodiment, in the substrate product 31, the support base 35 and the protrusions 33 are made of diamond. According to this substrate product, a protruding structure made of diamond is provided. The above-described method is not limited to forming a protrusion using a diamond substrate, but a carbon-based material such as a diamond-like carbon (DLC) film, amorphous carbon nitride (a-CN), amorphous carbon It can be applied to (a-C) film, carbon nanotube (CNT) / SiC film, gufite / SiC film and the like. These surfaces preferably have high flatness (flatness of 100 nanometers or more, preferably 20 nanometers or more).

  In the above method, the mask for etching the substrate only needs to have at least a two-layer structure, and can further have a three-layer structure or a four-layer structure. FIG. 5A, FIG. 5B, and FIG. 5C are drawings showing various forms of masks. Referring to FIG. 5A, a pattern 23a of the mask 23 used in the first embodiment is shown. Referring to FIG. 5B, a pattern 24a of another mask 24 is shown. The pattern 24 a includes three mask layers 12 a, 14 a, and 16 a that are sequentially arranged in a direction intersecting the main surface 11 a of the substrate 11. The mask layer 14a is provided between the mask layer 12a and the mask layer 16a. The size of the mask layer 16a is larger than the size of the mask layer 14a, and the size of the mask layer 14a is larger than the size of the mask layer 12a. Referring to FIG. 5C, a pattern 26a of another mask 26 is shown. The pattern 26 a includes three mask layers 12 b, 14 b, and 16 b that are sequentially arranged in a direction intersecting the main surface 11 a of the substrate 11. The mask layer 14b is provided between the mask layer 12b and the mask layer 16b. The size of the mask layer 16b is larger than the size of the mask layer 12b, and the size of the mask layer 12b is larger than the size of the mask layer 14b.

  FIG. 6A is a drawing showing protrusions produced using the pattern 23a of the mask 23 shown in FIG. In the protrusion 33, the size of the second portion 33b is reduced along the axis Ax, and the size of the first portion 33a is substantially constant along the axis Ax. FIG. 6B is a drawing showing protrusions produced using the pattern 24a of the mask 24 shown in FIG. Referring to FIG. 6B, the protrusion 34 includes a second portion 34b corresponding to the mask layer 12a, a third portion 34c corresponding to the mask layer 14a, and a first portion 34a corresponding to the mask layer 16a. Including. In the protrusion 34, the size of the second portion 34b is reduced along the axis Ax, the size of the first portion 34a is substantially constant along the axis Ax, and the size of the third portion 34c is , Almost constant along the axis Ax. The cross-sectional shape of the second portion 34b is different from the cross-sectional shape of the first and third portions 34a and 34c. The second portion 34b includes the tip of the protrusion 34, and the maximum size W3 of the tip of the protrusion 34 is 100 nanometers or less. The first portion 34a includes the root of the protrusion 34, and the maximum size W4 of the root of the protrusion 34 is 300 nanometers or less. According to this substrate product 32, since the base size of each protrusion is 300 nanometers or less, a protrusion structure having a high protrusion density is provided. Also in the substrate product 32, the columnar protrusions 34 are two-dimensionally arranged on the main surface of the support base 35b.

  According to the experiments by the inventors, a mode in which the lower mask layer is smaller than the size of the upper mask layer is suitable for forming a highly accurate mask. The diameter of the lower mask layer is preferably 20% or more of the diameter of the upper mask layer. When this value is less than 20 percent, the upper mask layer cannot stand in some of the many patterns.

  When the lower mask layer has an aspect ratio (height / diameter ratio) of 3 or less, the mask layer stacks up to a size difference of about 50 percent between the upper mask layer and the lower mask layer. Can be produced. Furthermore, a second mask layer (upper layer) made of TiN and a first mask layer (lower layer) made of Al can be used. Au can be used instead of TiN. For the processing of Au, dry etching such as physical etching such as inert gas can be used. After processing Au, the lower layer is processed using chlorine-based gas. As the material for the lower layer, materials that can be processed using a chlorine-based gas (for example, Al, TiN) can also be used.

  When diamond is etched using such a mask, a candle-shaped column having a thin protrusion shape can be formed on the support base. Moreover, even though the maximum width of the protrusions is 300 nanometers or less, the sizes of the array-shaped protrusions are uniform and very accurate.

  According to the method described above, very fine protrusions of 300 nanometers or less can be formed. For example, when the tip of the protrusion is desired to be about 100 nanometers, the diameter of the lower mask layer is preferably about 200 nanometers in anticipation of side etch reduction of about 50 percent when the substrate is etched. If this method is used, the size of a candle-shaped projection having a large size can be accurately obtained.

  When the projections of minute size are actually formed, when the diamond projections are formed using a mask including an aluminum mask layer having a diameter of 80 nm and a titanium nitride mask layer having a diameter of 120 nm, the maximum size is about 120 nm. A candle-shaped or conical projection with a sharp tip can be formed. These microprotrusions can be dense up to a density of 25 protrusions per square micrometer.

  Since the mask of the lower mask layer is a mask for forming the tip, it is preferable to use a mask having an aspect ratio of the mask layer larger than that of the upper mask in order to form a sharp tip protrusion. According to the result of the experiment, the tip having an aspect ratio exceeding 1 can be sharpened at a very sharp tip. At this time, the tip of the protrusion formed by etching using the lower mask layer has an aspect ratio of 1 or more. Further, the enlargement ratio becomes 1 or more by the etching selection ratio. Even if the aspect ratio of the protrusion is 1 or less, the size of the mask layer is as small as 100 nanometers or less, so the size of the tip of the protrusion is equal to or less than the size of the mask layer, and the tip of the protrusion can be made very small.

Next, the reason why it is important to increase the emitter density will be described below. When a 1 micrometer-diameter projection array is formed, the emitter height is at least 2 micrometers or more. The emitter density of this protrusion array is at most 250,000 per square millimeter. In this projection array, if the current that can be stably output from one projection is estimated to be 0.1 microampere (μA), the emitter current density is 25 milliamperes per square millimeter (A / mm ² ). On the other hand, since the emission current density of a conventional emitter including a hot cathode material is about 100 milliamperes per square millimeter (A / mm ² ), the emitter current density of the protrusion array is smaller than this value. When protrusions having a diameter of 300 nanometers or less are formed, the protrusion interval can be reduced to about 500 nanometers. As a result, the emitter density is no less than 1,000,000 per square millimeter, and the current density is no less than 100 milliamperes (A / mm ² ) per square millimeter. Therefore, a technique capable of forming four or more emitter protrusions within one square micrometer is necessary to form a meaningful device. If the diameter of the protrusions is 200 nanometers or less, the protrusion density is 6.25 or more in one square micrometer. Further, the protrusions are arranged with regularity.

  Preferably, the emitter projection has an aspect ratio of 1 or more. If the aspect ratio is 1 or more, the substrate capacitance can be made relatively small in an electron-emitting device having a gate electrode, which is suitable for high-frequency operation of the electron-emitting device. Further, when the gate electrode is manufactured by self-alignment, it is difficult to make a hole around the emitter having a small protrusion height. Moreover, if the arrangement of the protrusions is uniform, the emitter current distribution can be made uniform, which is suitable for achieving a high current density. In order to obtain a sharp and sharp protrusion having a high aspect ratio, a protrusion structure having two or more steps is preferable.

  According to the manufacturing method of the present embodiment, in a plurality of emitter projections, the deviation between the central axis of the lower diameter of the projection and the central axis of the tip (projection) is aligned within approximately 20 percent of the emitter diameter. And even within 5 percent of the emitter diameter.

  The above-described projection array for the emitter can be obtained by processing diamond by dry etching with an etching gas containing oxygen using a multi-layered mask having an upper mask layer having ridges.

  If a substrate having very good flatness is used, fine protrusions can be realized. The flatness of the substrate is preferably less than 100 nanometers. When this flat substrate is used, protrusions having a size of 1 micrometer or less can be formed. More preferably, the flatness of the substrate is less than 20 nanometers. For example, protrusions having a size of 200 nanometers or less can be formed. Not only a single crystal substrate but also a polycrystalline substrate can be used. Since the protrusion itself needs to reach the tip without the carrier disappearing, it is preferably a single crystal. The reason why the single crystal is preferable to the polycrystal in the projection of the size so far is that the projection includes a grain boundary. Since the protrusions according to the present embodiment are very small, a polycrystalline substrate can be used. A polycrystal having a particle size larger than the size of the protrusion is more preferable. Highly oriented polycrystalline diamond is preferred over randomly oriented polycrystalline, and a heteroepitaxial substrate is even more preferred.

  FIG. 7A, FIG. 7B, and FIG. 7C are drawings showing some electron-emitting devices. Referring to FIG. 7A, an electron-emitting device 41 includes a substrate product 45 having protrusions 43 arranged in an array, and a main surface 45b and a back surface 45c of a conductive support base 45a of the substrate product 45. And a cathode electrode 47 provided on at least one of them (back surface 45c in this embodiment). Referring to FIG. 7B, the electron-emitting device 51 is provided on a substrate product 55 having protrusions 53 arranged in an array and a main surface 55b of an insulating support base 55a of the substrate product 55. A cathode electrode 57. Referring to FIG. 7C, an electron-emitting device 61 includes a substrate product 65 having protrusions 63 arranged in an array, and a main surface 65b and a back surface 65c of a conductive support base 65a of the substrate product 65. At least one of them (a surface 65b in this embodiment) is provided with a cathode electrode 67 and a gate electrode 69.

  According to this electron-emitting device, the base size of each protrusion is 300 nanometers or less. For this reason, the electron-emitting device includes a protrusion structure having a high protrusion density. An electron-emitting device capable of realizing a high current density is provided.

  As described above, according to the embodiments of the present invention, a high-density protrusion array is provided, and a method for forming protrusions made of a carbon-containing material, and a substrate production having protrusions made of a carbon-containing material. And an electron-emitting device are provided.

(Second Embodiment)
A high-pressure synthetic single crystal diamond substrate having a (100) plane and a CVD polycrystalline diamond wafer substrate are prepared. This substrate is flattened to a few nanometers (nm) or less by polishing. An Al film and a TiN film are formed on the substrate by sputtering. FIG. 8 is a drawing showing combinations of film thicknesses.

  Thereafter, a negative resist for electron beam exposure is applied on the TiN film, and dot patterning is performed by electron beam exposure. A positive resist can also be used. By using a negative resist, the drawing time can be shortened. The size of the resist pattern (dots) is slightly reduced by ashing. If it is reduced by 50% or less from the original resist size, the variation due to ashing is not so large.

After forming a resist pattern of a desired size, a mask film is patterned by etching using a chlorine-based gas (mixed gas of Cl ₂ and BCl ₃ ). The TiN film is on the top, and the etching of the TiN film is started first. Since the TiN film has higher etching resistance to the above etching gas than the Al film, the side etching proceeds faster in the Al film, and the size of the Al film is smaller than that of the TiN film by etching for a certain time or longer. Become. After the etching is completed, the resist is removed if necessary. The resist is not necessarily removed. Since the process of etching the next diamond is a process of removing the carbon material, the resist is also removed.

  The diamond substrate is etched using this laminated mask film. Since the diamond substrate is first etched using the TiN mask layer, the thicker base protrusion is formed. When the TiN mask layer is removed, etching is performed using an Al mask layer having a small diameter, so that the tip portion of the base protrusion becomes thin. The diamond protrusion formed in this way has a candle shape.

  FIGS. 9A and 9B are SEM photographs in which a mask including an Al layer of 60 nm and a TiN layer of 30 nm is formed. Referring to FIG. 9A, the Al mask layer has a diameter of 80 nanometers, and the TiN mask layer has a diameter of 120 nanometers. Referring to FIG. 9B, the Al mask layer has a diameter of 110 nanometers, and the TiN mask layer has a diameter of 140 nanometers.

  FIGS. 10A and 10B are diagrams showing diamond protrusion arrays formed using the masks shown in FIGS. 9A and 9B, respectively. Referring to FIG. 10A, a candle-shaped protrusion is shown. The distance between the protrusions in the array is about 300 nanometers. Referring to FIG. 10B, a candle-type protrusion is shown, and the distance between the protrusions in the array is about 200 nanometers. In the 200 nanometer array and the 300 nanometer array, the shapes of the individual protrusions are uniform, and the protrusions are regularly arranged. The root size of the protrusion is 100 nanometers, and the tip of the protrusion is smaller than 80 nanometers and 50 nanometers or less. The protrusion density for the emitter is 25 million per square millimeter and 9 million per square millimeter, respectively. Further, the protrusion is columnar and the side wall of the column is substantially vertical. The tip is substantially conical. The difference between the central axis of the lower cylinder and the central axis of the protrusion tip is within 5 percent of the size of the root, and is approximately the same for each protrusion array. Individual protrusions are almost the same height. The variation in the height of the protrusion is 5% or less of the total height according to the rough measurement. According to the estimates of the inventors, when the size of the mask layer (lower layer) for the tip is 80 nanometers and the etching is stopped when the film is reduced by about 50 percent during etching, the diameter of the tip of the projection is The variation in height at the tip corresponds to the flatness of the substrate. In the case where a protrusion having a height of 600 nanometers is formed using a flat substrate having a maximum thickness of 2 nanometers, the height variation of the protrusion is about 0.3%. As described above, it is possible to form a candle-shaped projection having a nanometer size and a very high accuracy.

  In the single crystal substrate and the polycrystalline wafer substrate, there is no particular difference in the formed protrusions, but the flatness of the etched surface is flatter in the single crystal substrate than in the polycrystalline wafer substrate.

  As described above, according to the embodiments of the present invention, a high-density protrusion array is provided, and a method for forming protrusions made of a carbon-containing material, and a substrate production having protrusions made of a carbon-containing material. And an electron-emitting device are provided.

(Third embodiment)
A high-pressure synthetic single crystal diamond substrate having a (100) plane and a CVD polycrystalline diamond wafer substrate are prepared. This substrate is flattened to a few nanometers (nm) or less by polishing. An Au film and a TiN film are formed on the substrate by sputtering.
The combinations of film thicknesses of the respective films are shown in FIG. As in the second embodiment, a resist having a desired size is formed. Thereafter, the Au film mask is patterned with Ar gas. After the Au film is etched, the TiN film and the Al film are etched using a chlorine-based gas. Since the Au film cannot be etched with a chlorine-based gas, a mask (mushroom type mask) having the same shape as that of the second embodiment is formed. The diamond substrate is etched using this mask. Similar to the second embodiment, a fine protrusion array (candle-shaped protrusion) is formed. The features, advantages, etc. of the array have already been described in the second embodiment.

  As described above, according to the embodiments of the present invention, a high-density protrusion array is provided, and a method for forming protrusions made of a carbon-containing material, and a substrate production having protrusions made of a carbon-containing material. And an electron-emitting device are provided.

  As described in several embodiments, the fine candle-shaped sharp protrusion has very good height uniformity. Since the protrusion has a small size, a high-density emitter can be manufactured, and the current density can be increased. It is possible to increase the aspect ratio of the protrusion and increase the density of the protrusion. The accuracy of the central axis at the tip of the protrusion and the height variation of the protrusion are extremely small. The protrusion array can be useful for electron-emitting devices. Such uniform protrusions can be an important component for devices such as electron-emitting devices and near-field optical probes. In addition, the projection array can be applied to, for example, electron emission devices applicable to electron guns, electron tubes, vacuum tubes, field emission displays (FEDs), etc., and STM, AFM, SNOM, and electronic devices using these principles. It can be used for a simple atomic probe and a near-field optical probe.

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configuration disclosed in the present embodiment. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

FIG. 1A, FIG. 1B, and FIG. 1C are drawings showing a method of forming a protrusion made of a material containing carbon according to the first embodiment. 2A, 2B, and 2C are views showing a method of forming a protrusion made of a material containing carbon according to the first embodiment. 3A and 3B are drawings showing etching of a substrate. FIG. 4A shows a substrate product. FIG. 4B is a plan view showing the arrangement of the protrusions of the substrate product. FIG. 5A, FIG. 5B, and FIG. 5C are drawings showing various forms of masks. FIG. 6A is a drawing showing protrusions produced using the mask pattern shown in FIG. FIG. 6B is a drawing showing protrusions produced using the mask pattern shown in FIG. FIG. 7 is a view showing an electron-emitting device. FIG. 8 is a drawing showing combinations of film thicknesses. FIGS. 9A and 9B are SEM photographs in which a mask including an Al layer of 60 nm and a TiN layer of 30 nm is formed. 10 (A) and 10 (B) are diagrams showing diamond protrusion arrays formed using the masks shown in FIGS. 9 (A) and 9 (B), respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Board | substrate, 11c ... Protrusion, 11d ... Pillar, 11e ... Protrusion, 12a, 14a, 16a, 12b, 14b, 16b ... Mask layer, 13 ... 1st mask film | membrane, 13a, 13b ... 1st mask layer, 15 ... second mask film, 15a, 15b ... second mask layer, 17 ... resist mask, 17a, 17b ... pattern, 19 ... plasma, 21 ... etching, 23 ... mask, 23a ... pattern, D1, D2, D3, D4 ... Size, 24 ... Mask, 24a ... Pattern, 25 ... Etching, 26 ... Mask, 26a ... Pattern, 31, 32 ... Substrate product, 33 ... Projection, 33a ... First part, 33b ... Second part, 33c: tip of protrusion, 33d: root of protrusion, W1, W2 ... maximum size, 34 ... protrusion, 34a ... first part, 34b ... second part, 34c ... third part, 35, 3 a, 35b ... the support base

Claims (9)

A method of forming a protrusion made of a carbon-containing material,
A step of sequentially forming a plurality of mask films on a main surface of a substrate having a region made of a material containing carbon;
Etching each of the plurality of mask films to form a mask having a plurality of patterns arranged on the main surface of the substrate;
Etching the substrate using the mask to form a protrusion corresponding to each of the plurality of patterns of the mask,
Each of the patterns includes a group of layers arranged in a direction intersecting the main surface,
The group of layers includes a first layer closest to the main surface and a second layer farthest from the main surface;
The material of the first layer is different from the material of the second layer,
In each pattern, the size of the first layer is different from the size of the second layer. Each of the patterns further includes a third layer;
The method according to claim 1, wherein the third layer is provided between the first layer and the second layer. The maximum size of each pattern is 300 nanometers or less,
The second layer is provided on the first layer;
The method according to claim 1 or 2, wherein in each pattern, the size of the second layer is larger than the size of the first layer.   The said 1st layer consists of a metal containing aluminum or titanium nitride, and the said 2nd layer consists of titanium nitride or gold | metal | money characterized by the above-mentioned. Way.   The method according to any one of claims 1 to 4, wherein the substrate is a diamond substrate. A substrate product having protrusions made of a carbon-containing material,
A support substrate;
A plurality of protrusions made of a carbon-containing material arranged on the main surface of the support base,
Each protrusion has first and second portions arranged in order in a direction intersecting the main surface,
The cross-sectional shape of the first portion is different from the cross-sectional shape of the second portion;
The first portion includes a tip of a protrusion;
The second part includes the root of the protrusion;
The maximum size of the tip of each protrusion is 100 nanometers or less,
A substrate product characterized in that the maximum size of the base of each protrusion is 300 nanometers or less. The plurality of protrusions are arranged in an array,
The substrate product according to claim 6, wherein the density of the protrusions is 4 or more per square micrometer. 8. The substrate product according to claim 6, wherein the supporting base and the protrusion are made of diamond. A substrate product according to any one of claims 6 to 8,
An electron-emitting device comprising: an electrode provided on at least one of a main surface and a back surface of the support base of the substrate product.

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