[DESCRIPTION] [Invention Title]

Nanodevice Structure and Fabricating Method Thereof [Technical Field]

<i> The present invention relates to a nanodevice structure and a fabricating method thereof and, in particular, to a nanodevice structure providing easy formation of. a nanomaterial pattern, and a fabricating method thereof. [Background Art]

<2> . Nanomaterial is a material with a size of less than 1 μm, and a typical example thereof is a carbon nanotube (CNT).

<3> The nanomaterial includes zero-dimensional structure such as nanoparticles and quantum dots, one-dimensional structure such as carbon nanotubes and nanowires, and two-dimensional structure such as nanodiscs.

<4> A nanomaterial such as a carbon nanotube generally shows semi- conductive or metallic properties during its manufacturing process, and these properties may be used for application to various sensors and electrical devices such as a field effect transistor (FET) and a single electron transistor (SET). Because of the feature that the nanomaterial emits electrons and x-rays by an electric current applied thereto, the nanomaterial is used for developing field emission displays and lamps.

<5> Such nanomaterials are generally less than lμm in size. Therefore, not only it is hard to place the nanomaterial to a required position, but also it is very difficult to grow the nanomaterial into a required shape.

<6> Various methods can be used for depositing the nanomaterial to a substrate. To name a few, a method of bonding the nanomaterial one by one by using an electron microscope, a method of growing the nanomaterial between electrodes, a method of patterning a thin layer by photolithography after shaping the nanomaterial into a thin layer, a method of using an atomic microscope or a dip pen, and a method of moving the nanomaterial contained in a solution by using an electrical or magnetic field can be used.

<7> In the method to grow the nanomaterial directly on the substrate, a catalyst for growing the nanomaterial is applied between two electrodes, and then the nanomaterial is guided to grow into a shape connecting two electrodes inside a reactor that is filled with an appropriate gas and is kept at an appropriate temperature.

<8> While the method has the advantage of mass-producing the nanomaterial in a large area, the method causes each nanomaterial to grow into a different shape and has difficulty in controlling the nanomaterial in terms of number and size. In addition, some electrodes may happen to not be connected to the nanomaterial, depending on the shape of the growing nanomaterial. <9> On the other hand, the nanodevice may be made by dripping a solution containing the nanomaterial between electrodes. In this method, firstly the nanomaterial is dispersed in a solution, and then the nanomaterial is dripped through a pipette or the like on electrodes that are already formed. In order to reduce contact resistance in this method, annealing may be carried out after forming the nanomaterial layer between the electrodes, or additional electrodes may be deposited.

<io> However, these previous methods have difficulties in making the property of the nanodevice uniform as well as in obtaining uniform nanodevices. Also, the non-uniform property of the nanodevice causes the problem of low productivity.

<π> Fig. 1 is a schematic diagram showing nanodevice structures according to the prior art, and Fig. 2 is a cross-sectional view of the nanodevice structure according to the prior art. Referring to Figs. 1 and 2, the nanodevice structure includes two electrodes 121, 122, both applied on a substrate 110, and nanodevice structures formed on the electrodes 121, 122 to connect the electrodes 121, 122 therewith. Each of the electrodes 121, 122 is connected electrically to respective power supplies.

<i2> In order to fabricate such a nanodevice structure, the electrodes 121, 122 are formed in a certain pattern on the substrate 110, and then a uniform amount of the nanomaterial 130 should be injected between the electrodes 121,

122. This process lowers productivity because the nanomaterial 130 is manually injected between the electrodes 121, 122.

<i3> Also, the above-mentioned structure causes large contact resistance between the electrodes 121, 122 and the nanomaterial 130. The fabricating process also becomes complicated with additional annealing or application of additional electrodes required for reducing the contact resistance. [Disclosure] [Technical Solution]

<14> The present invention intends to solve the above-mentioned problems, and therefore provides a nanodevice structure that may be easily fabricated and may reduce the contact resistance between electrodes and a nanomaterial.

<15> For the purpose, the nanodevice structure according to the present invention includes a substrate having alignment marks formed thereon, a plurality of nanomaterial layers applied on the substrate, and electrodes formed to be partially in contact with the upper surface of the nanomaterial 1ayer .

<i6> The alignment marks may be formed at plural and symmetrical locations.

<17> The nanomaterial may be made of zero-dimensional or one-dimensional structures.

<18> The substrate may be made of an insulant or a wafer having an insulation layer formed thereon.

<19> The substrate may be made of a polymer film, a glass insulant, or a silicon wafer of a semi-conductor.

<20> The electrodes may be positioned apart from each other with the nanomaterial placed therebetween.

<2i> The nanomaterial may be made of carbon nanotubes or nanowires.

<22> A fabrication method of the nanodevice structure according to the present invention includes a step of forming alignment marks on a substrate, a step of applying a solution containing a nanomaterial in a predetermined pattern on the substrate with reference to the alignment marks, and a step of applying electrodes on the nanomaterial pattern.

<23> The solution containing the nanomaterial may be applied by jetting it onto the substrate. <24> The fabrication method of the nanodevice structure may include a step of removing impurities after applying the nanomaterial. <25> The application of the electrode may be carried out by one method selected from chemical vapor deposition (CVD), sputtering, e-beam evaporation, and thermal evaporation. <26> A step of heating the substrate may be further included after applying the nanomaterial in order to prevent clustering of the nanomaterial. <27> The substrate includes a wafer and an insulation layer formed on top of the wafer. <28> A fabrication method of the nanodevice structure according to the present invention may include a step of forming alignment marks on a substrate, a step of forming metallic electrode layers on the substrate having the alignment marks formed thereon, and a step of forming a pattern of the nanomaterial with reference to the alignment marks. <29> The fabrication method of the nanodevice structure according to the present invention may further include a step of annealing the metallic electrode layer after forming the electrode layers on the substrate. <30> The fabrication method of the nanodevice structure according to the present invention may further include a step for surface treatment of the nanomaterial pattern in order to arrange at least some of the nanomaterial at a right angle after forming the nanomaterial pattern. <3i> The fabrication method of the nanodevice structure according to the present invention may further include a step of heating the substrate for better application of the nanomaterial thereon.

[Advantageous Effects] <33> The nanodevice structure may be easily fabricated according to the present invention, and therefore productivity is improved. <34> The nanodevice structure according to the present invention reduces the contact resistance significantly. Also, the nanodevice structure according to the present invention may be made in a high density so that it is possible to reduce both the size of the nanodevice structure and the production cost. <35> Although embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the present art will still fall within the spirit and scope of the present invention, as defined in the appended claims.

[Description of Drawings] <36> Fig. 1 is a schematic diagram showing nanodevice structures according to the prior art. <37> Fig. 2 is a partial cross-sectional view of the nanodevice structures according to the prior art. <38> Fig. 3 is a perspective view of nanomaterial layers formed on a substrate according to a first embodiment of the present invention. <39> Fig. 4 is a perspective view showing the forming process of the nanomaterial layers on the substrate according to the first embodiment of the present invention. <40> Fig. 5 is a photograph of the nanomaterial layers formed on the substrate according to the first embodiment of the present invention. <4i> Fig. 6 is a photograph showing the texture of the nanomaterial layers formed on the substrate according to the first embodiment of the present invention. <42> Fig. 7 is a perspective view of the nanodevice structures according to the first embodiment of the present invention. <43> Fig. 8 is a partial cross-sectional view of the nanodevice structures according to the first embodiment of the present invention.

<44> Fig. 9 is a partial cross-sectional view of the nanodevice structures according to a second embodiment of the present invention.

<45> Figs. 10 to 15 are diagrams showing the fabrication processes of the nanodevice structures according to the second embodiment of the present invention.

<46> Fig. 16 is a diagram showing a field emission display having nanodevice structures according to a third embodiment of the present invention.

<47> Fig. 17 is a diagram showing a field emission display having nanodevice structures according to a fourth embodiment of the present invention. [Mode for Invention]

<48> Hereinafter, with reference to the appended drawings, the embodiments of the present invention will be described in detail for enabling those skilled in the art to produce the invention. However, the present invention may have different forms and is not limited to these embodiments.

<49> Fig. 3 is a perspective view of nanomaterial layers formed on a substrate according to a first embodiment of the present invention, and Fig. 4 is a schematic diagram showing the forming process of the nanomaterial layers on the substrate.

<50> As shown in the drawings, a plurality of nanomaterial layers 20 are applied at predetermined intervals on a substrate 10 having alignment marks 16 formed thereon. The nanomaterial according to the present embodiment may be made of zero-dimensional structures like nanoparticles and quantum dots, or one-dimensional structures including carbon nanotubes and nanowires.

<5i> The substrate 10 is a common substrate made of a silicon wafer or glass that is generally used in optical lithography, and it may be any substrate that can be used in optical lithography.

<52> The alignment mark 16 may be formed by engraving the substrate or by applying a specific material to the substrate. Such an alignment mark 16 is arranged at a plurality of locations that are symmetrical with respect to the center of the substrate.

<53> Nanomaterial layers 20 are formed by spraying the solution containing

the nanomaterial in a jetting method, as shown in Fig. 4, in which solution drops of a uniform size fall to the substrate 10 from a spraying nozzle 31 by heat or pressure so as to form the nanomaterial layers 20.

<54> The jetting method has the advantage of arbitrary shaping of the dot or the line by jetting the solution drop with the required size to the required position. The ink jet method is a typical example of the jetting method. It is possible in the ink jet method to decrease the size of the solution drop to less than several tens of μm and to realize the patterned dot or line to be as small as several tens of μm in size.

<55> An applying apparatus 30 for applying the nanomaterial to the substrate includes a spraying nozzle 31 to spray the nanomaterial solution 25 to the substrate 10, a transporting member 35 to move the spraying nozzle 31, a container 37 to contain the nanomaterial solution 25, a connecting hose to connect the container 37 to the spraying nozzle 31, and a sensor 36 to detect the alignment mark 16.

<56> The applying apparatus 30 works as follows. First, the sensor 36 detects the alignment mark 16, and the transporting member 35 moves the spraying nozzle 31 to the position directly above the alignment mark 16. With this position as a reference point, the transporting member 35 moves the spraying nozzle 31 by predetermined distances DX and DY. Then the spraying nozzle 31 jets the predetermined amount of nanomaterial solution 25 on the substrate 10. By repeating this process, the entire surface of the substrate 10 is evenly coated with the nanomaterial layer 20. Also, depending on the pattern of the electrode to be made, it is possible to apply the nanomaterial solution 25 irregularly.

<57> However, the above-mentioned transporting mechanism is merely one example of the present invention, and any mechanism is sufficient for the present invention as long as it changes the relative positions of the spraying nozzle 31 and the substrate 10. Therefore, the spraying nozzle 31 may be fixed, and the substrate 10 may move with respect to the fixed spraying nozzle 31.

<58> By forming the nanomaterial layer 20 with the spraying apparatus 30, it is possible to quickly and precisely form the very small nanomaterial layer 20 on the substrate 10. In addition, because the nanomaterial solution 25 may be controlled to have a certain concentration, it is possible to control the amount of the nanomaterial contained in the nanomaterial layer 20.

<59> Fig. 5 is a photograph showing the state of carbon nanotubes applied to the substrate by the spraying method according to the first embodiment of the present invention. As seen in Fig. 5, the nanomaterial layer 20 is formed in a shape close to a circle at predetermined intervals. Also, the photograph of the nanomaterial layer taken by a scanning electron microscope in Fig. 6 shows that the carbon nanotubes are evenly distributed.

<60> Fig. 7 is a perspective view of the nanodevice structure having electrodes formed at both edges of the nanomaterial layer formed according to the first embodiment of the present invention, and Fig. 8 is the partial cross-sectional view thereof.

<6i> Metallic electrodes 15 are applied at both edges of the nanomaterial layer 20, and the metallic electrodes 15 may be applied by various methods such as optical lithography or the like.

<62> The metallic electrode 15 is formed into a shape to partially covering one edge of the nanomaterial layer 20, and two metallic electrodes 15 are symmetrically located for one nanomaterial layer 20.

<63> The application of the metallic electrode 15 according to the present embodiment may be carried out by chemical vapor deposition (CVD), sputtering, e-beam evaporation, or thermal evaporation. These techniques are well known so a detailed explanation thereof is omitted.

<64> The above-mentioned application methods of the metallic electrode 15 are merely examples of the present embodiment and do not limit the scope of the present invention. Besides the above-mentioned application methods, therefore, various conventional methods may be used.

<65> Also, the present embodiment exemplifies the metallic electrode formed into a dot shape, but the present invention is not limited to this shape.

For effective contact of the metallic electrode 15 with the nanomaterial layer 20, the metallic electrode 15 may be formed into an alternate line shape as shown in Fig. 1. The alternate line shape for the electrode is well known so a detailed explanation thereof is omitted.

<66> For applying the nanomaterial in the jetting method, it is very important to enhance the bonding between the metallic electrode 15 and the nanomaterial layer 20 and to distribute the nanomaterial evenly within the nanomaterial layer 20. However, clustering of the nanomaterial may occur during the drying process of the nanomaterial solution 25. In order to prevent this clustering, the substrate 10 may be heated to quickly evaporate the nanomaterial solution 25 after the nanomaterial solution 25 is applied thereon.

<67> As described earlier, the fabrication method of the nanodevice structure according to the first embodiment of the present invention may include a step of applying the solution 25 containing the nanomaterial to the substrate 10 having the alignment marks formed thereon in the jetting method, and a step of applying the electrodes 15 on top of the nanomaterial layer 20.

<68> After the nanomaterial solution 25 is applied on the substrate, impurities included in the solution are removed, and the substrate is heated to evaporate the liquid of the solution so that the clustering of the nanomaterial is prevented.

<69> Fig. 9 is a partial cross-sectional view of the nanodevice structure according to a second embodiment of the present invention, and Figs. 10 to 15 are diagrams showing the fabrication processes of the nanodevice structure according to the second embodiment of the present invention.

<70> As shown in Fig. 9, the nanodevice structure according to the present embodiment includes a substrate 40 including a wafer 41 and an insulation layer 42 formed on top of the wafer 41; a nanomaterial layer 43 formed in the spraying method on the substrate 40; and electrodes 45 formed to be in contact with both edges of the nanomaterial layer 43.

<7i> The fabricating processes of the nanodevice structure are as follows.

As illustrated in Fig. 10, the insulation layer 42 is formed on the wafer 41 so as to form the substrate 40.

<72> Fig. 11 displays the nanomaterial layer 43, which is formed, in the same way as in the first embodiment of the present invention, by spraying the solution containing the nanomaterial on the substrate 40 having the alignment marks formed thereon by the ink jet method.

<73> As shown in Fig. 12, photoresist 44 is applied over the nanomaterial layer 45 and the substrate 40. Then, the photoresist 44 is removed into a predetermined pattern by exposing the area where the electrode is to be formed on the substrate 40 to light, as shown in Fig. 13. The metallic electrodes 45, 46 are applied to the substrate 40 where the photoresist 44 is removed to form the predetermined pattern, as shown in Fig. 14. The application of the metallic electrodes 45, 46 may be carried out by the various methods such as chemical vapor deposition (CVD), sputtering, e-beam evaporation, and thermal evaporation.

<74> Once the application of the metallic electrodes 45, 46 is completed, the photoresist 44 and the metallic electrode 46 on the photoresist 44 is removed by a lift-off method, as seen in Fig. 15.

<75> The nanodevice structure that is made by applying the electrodes in a predetermined pattern over the nanomaterial layer 43 formed on the substrate 40 consisting of the wafer 41 and the insulation layer 42 may be used as a field effect transistor (FET).

<76> Fig. 16 is a cross-sectional view of the nanodevice structure and an upper substrate responding thereto according to a third embodiment of the present invention, and shows a field effect display (FED) in a diode structure.

<77> As shown in the drawing, the nanodevice structure 50 according to the present embodiment includes a substrate 51 having alignment marks (not shown) formed thereon, a metallic layer 52 formed on top of the substrate 51, and nanomaterial layers 53 formed in a predetermined pattern on the metallic layer 52. Positioned above the nanodevice structure 50 is an upper substrate

60 that includes a transparent conducting layer 61 placed apart from the nanodevice structure 50, and phosphor layers 62 formed beneath the transparent conducting layer 61.

<78> The nanodevice structure 50 and the upper substrate 60 are connected electrically to a power supply 58 in a manner such that the negative pole is connected to the nanodevice structure 50 and the positive pole is connected to the upper substrate 60. The electron beam from the nanomaterial layer 53 is emitted to the phosphor layers 62, and the phosphor layers 62 emit visible light. In this case, it is preferable for the nanomaterial 54 contained in the nanomaterial layer 53 to be positioned at a right angle toward the phosphor layers 62.

<79> The fabrication processes of the nanodevice structure are as follows. First, a metallic layer 52 such as indium tin oxide (ITO) is applied on a substrate 51, and then nanomaterial layers 53 are formed in a predetermined pattern on the metallic layer 52. The nanomaterial layers 53 are sprayed in the jetting method on the metallic layer 52 to form a predetermined pattern. The alignment marks (not shown) formed either on the substrate 51 or on the metallic layer 52 are used as reference points in this process. The jetting method used in this process is the same as that used in the first embodiment so a detailed explanation thereof is omitted.

<80> In order to obtain appropriate characteristics of field emission, the nanomaterial layer 53 and the metallic layer 52 should be bonded securely to each other. For this purpose, various adhesives may be added to the solution of the nanomaterial 54, and the bonding strength may be improved by high temperature heat treatment.

<8i> Also, in order to emit the electron beam from the nanomaterial layer 53 toward the phosphor layers 62, the nanomaterial 54 should be positioned at a right angle. For this purpose, the surface treatment of the nanomaterial layer may be carried out by various methods such as attaching/detaching adhesive tape, laser irradiation, ion beam irradiation, milling, and microwave irradiation.

<82> Fig. 17 is a cross-sectional view of the nanodevice structure and an upper substrate responding thereto according to a fourth embodiment of the present invention, and shows a field effect display (FED) in a triode structure.

<83> The nanodevice structure 70 according to the present embodiment includes a conducting substrate 71, an insulation layer 72 formed on top of the conducting substrate 71, and gate electrodes 73 formed on the insulation layer 72. In addition, an emitter hole 76 of which the bottom has a cathode electrode 77 made of the same transparent conducting layer as the ITO layer formed thereon is formed inside the insulation layer 72.

<84> A nanomaterial layer 74 is formed on the cathode electrode 77. It is preferable for the nanomaterial 75 contained in the nanomaterial layer 74 to be positioned at a right angle.

<85> Further, positioned above the nanodevice structure 70 is an upper substrate 80 that includes a transparent conducting layer 81 placed apart from the nanodevice structure 70 and a phosphor layer 82 formed beneath the transparent conducting layer 81.

<86> In the triode field effect display (FED), a gate voltage 79 is applied to the gate electrode 73, and a main voltage 78 is applied to the upper substrate 80. The cathode electrode 77 beneath the nanomaterial layer 74 is electrically connected to the negative pole. Therefore, an electron beam is emitted from the nanomaterial 75 by the gate voltage 79, and the electron beam is deflected toward the upper substrate 80 by the main voltage 78. As a result, the electron beam collides with the phosphor layer 82 to generate light.

<87> The fabrication process of the nanodevice structure according to the present embodiment includes a step of forming the insulation layer 72 on the substrate 71, a step of applying the gate electrode 73 on the insulation layer 72, a step of forming the emitter hole 76 and forming the cathode electrode 77 in the emitter hole 76, a step of forming the nanomaterial layer 74 on the cathode electrode 77 by jetting the nanomaterial solution, and a

step of arranging the nanomaterial 75 at a right angle

<88> The substrate 71 may be made of glass, and the gate electrode 73 may be formed through deposition by sputtering a metallic material with high electrical conductivity. The emitter hole 76 is made by etching or the like, and the cathode electrode is made of ITO or the like. Also, the nanomaterial layer 74 is formed by jetting the solution containing the nanomaterial 75 into the emitter hole 76. The jetting is carried out with the alignment mark formed on the substrate as a reference point.

<89> Thus, the nanomaterial layer is easily formed, the contact resistance between the nanomaterial layer and the electrodes may be lowered because the alignment marks are formed on the substrate, and the solution containing the nanomaterial is applied on the substrate by jetting with the alignment mark as a reference point .

<90> The present embodiment exemplifies the nanodevice structure applied to the field emission display, but does not limit the scope of the present invention. The nanodevice structure of the present invention may be applied to an X-ray source and a cold cathode source used for a microwave amplifier and so on.